Tunnel Plate Question...

[WheelerDealer]

I was thinking about trying to come up with some type of system that would tell you at what speed your tunnel plates came out of the water. Can anyone think of a simple way to install some kind of sensor/pick-up type system that could somehow be mounted temporarily to one of the tunnel plates and connected by impact tube or electrics up to a gauge in the cockpit. Could it be as simple as using a plain old speedo pick-up mounted somehow on top of the plate to where the pick up hole was slightley lower than the bottom of the plate and then whenever the plates came out of the water the gauge would drop to zero???? Let's put our heads together and come up with a way to best do this and I will try it on my Southwind Tunnel Dragster. I think it might be another good tuning instrument. I guess it would only apply to a few different hulls though..SWTD, Placecraft, Bahner, Crusader, Mach One????

[steelcomp]

I was thinking about trying to come up with some type of system that would tell you at what speed your tunnel plates came out of the water. Can anyone think of a simple way to install some kind of sensor/pick-up type system that could somehow be mounted temporarily to one of the tunnel plates and connected by impact tube or electrics up to a gauge in the cockpit. Could it be as simple as using a plain old speedo pick-up mounted somehow on top of the plate to where the pick up hole was slightley lower than the bottom of the plate and then whenever the plates came out of the water the gauge would drop to zero???? Let's put our heads together and come up with a way to best do this and I will try it on my Southwind Tunnel Dragster. I think it might be another good tuning instrument. I guess it would only apply to a few different hulls though..SWTD, Placecraft, Bahner, Crusader, Mach One????
I've thought about the same thing. How 'bout a video cam mounted on the back somehow?

[WheelerDealer]

The video cam might be a bit exspensive since I'm thinking it would have to be in a water proof housing unless you built a big ole' boom arm and stuck it back there , then you would have to have a remote monitor in the dash to watch it and the speedo :D I have thought about having a drunk friend hang off the back with a rope running up front and they could yank it when the plates came up but with the delayed reaction time due to level of intoxication in said individual you probably wouldn't get an accurate reading. :D

[Bob Hostetter]

How about a depth finder like the ones the fishing guys use? Since they measure changes in density if you mounted one on the trailing edge of the plate it would read the depth of the water until it came out of the water. Then it would read something less then a foot because it would be reading the distance from the sensor to the surface of the water.

[Squirtin Thunder]

What about a water presure gage ????

[bp]

if you had a data collection system of some type, you could install a pressure sensor on the tunnel plate. if pressure is 0, it's not riding on the water.

[WheelerDealer]

Hey ST, either idea could probably be made to work, but i would think you would need some type of gauge that would function like a recall or tattle tale tach does so that you wouldn't have to stare at the speedo and the tunnel plate gauge...know what I mean?

[WheelerDealer]

Hey bp, would the data collection system like MPD sells be able to tell you at what speed the plate lifted? I am trying to figure out a way to do this without having to watch two gauges while running wide open since that probably isn't a good idea. Do you know at about what speed your TD plates come up off the water, and if so would you care to share? Also, with experience have you found that you can "feel" when this happens or not, thanks.

[Squirtin Thunder]

Like BP said if you had some sort of data system it would store the info. Or you could run a air/water presure gage up to the dash. Simple install.

[Squirtin Thunder]

My question is why ??? If you are running over 70mph maybe less they should be out of the water or you would only be plowing along.

[WheelerDealer]

Squirtin Thunder originally posted...
My question is why ??? If you are running over 70mph maybe less they should be out of the water or you would only be plowing along.
To see if and how set up changes made a difference in the time it took for the boat to start packing air and doing it's thing as a tunnel, as I said, just another tuning tool to have at the track. How did you come up with the 70mph or maybe less figure, what makes you think this is when it happens?

[Squirtin Thunder]

From looking at Steelcomps and Jeanyuses boat in action.
What kind of boat do you have which plays an important part in the way it acts also.
Some true tunnels are strieght and some are taperd.
A strieght tunnel needs more mph to lift the traperd tunnel packs air for you lifts alot erlier.
Jim

[steelcomp]

The video cam might be a bit exspensive since I'm thinking it would have to be in a water proof housing unless you built a big ole' boom arm and stuck it back there , then you would have to have a remote monitor in the dash to watch it and the speedo :D I have thought about having a drunk friend hang off the back with a rope running up front and they could yank it when the plates came up but with the delayed reaction time due to level of intoxication in said individual you probably wouldn't get an accurate reading. :D
The video cam idea was more of a joke...but the drunk friend...now I'm LMAO!!
You could put just about anything on the plate that would indicate pressure, and it wouldn't necessarily have to hang down under the plate, or below the running surface. You could drill a hole straight through the plate, say 1/8", epoxy or otherwise fasten a small piece of tube, and hook it up to a guage. I'd start with a low press. gauge since being square to the plate might not show much, but the needle would move. You aren't trying to measure the pressure, just find out when the plate is out of the water. If you had something like a speedo pitot hanging down even the slightest, you wouldn't geet a true lifting point of the plate. You could hand hold the gauge or temporarily mount it to your dash right next to your speedo, and it might take a half dozen runs or so, but you could get a pretty darn accurate idea of when the plate was lifting as compared to speed.
I've talked to a dozen people about plate settings and get a dozen different answers. Some say drop them slightly so they help trap air in the tunnel. Some say to raise them a little to get them out of the way. I haven't had any luck determaining if mine make any difference one way or the other, but I haven't gotten my basic set up right yet, let alone worry about my plates. They're up for now, about 1 1/2 - 2 deg. There, they may not be helping, but I know they're not hurting. Upon thinking about it, pointing them down might help lift the back of the boat upon initial launch, and they'll be out of the water at speed. Hmmm.

[WheelerDealer]

I plan on trying different settings with the plates as well as everything else, and I know what you mean about asking twelve different people and getting twelve different answers. Hell, the way I see it they put the plates there for a reason, and they put turnbuckles on them for a reason(adjustability) so why not try and optimize that part of your set up as well??

[LVjetboy]

"Hell, the way I see it they put the plates there for a reason, and they put turnbuckles on them for a reason"
Ya but did "they" truly know what they were doing at the time and sometime later, does anyone really know why "they" did it? Same confusion if you ask, "What's the purpose of a ride plate?" Our hobby seems to have a huge lack of recorded data and technical information on these seemingly simple questions. A bit of continuity other than word-of-mouth would be helpful.
Oh ya and I've wondered the same thing...when are they out? Let me know what you find.
jer

[FOURQ]

Ya but did "they" truly know what they were doing at the time and sometime later, does anyone really know why "they" did it?
jer
thats a stupid statment...and yes we know why we put them there....

[LVjetboy]

"thats a stupid statment...and yes we know why we put them there..."
Not as stupid as you may think. And not a statement but a question. So who is the "we" you mention and why did you working with others decide to put them there? WheelerDealer has a valid question, but his question assumes tunnel plates have a well-defined and tested function. Anytime I see that, I question, especially if nobody seems to know or supply a good answer. I'm not saying they don't work, just that his question is worth a serious answer that doesn't assume they do. If you and yours decided to put trim tabs there and verified their benefit, please share the technical details with us.
jer

[comin' unscrewed]

The camera thing's not that silly. I could be really interesting to see what's going on back there. Doesn't have to be expensive or complicated either. Hell a USB web cam a laptop would work. A little duct tape and a ziploc should seal it well enough for a few passes. Just leave the lens exposed.

[bp]

Hey bp, would the data collection system like MPD sells be able to tell you at what speed the plate lifted? I am trying to figure out a way to do this without having to watch two gauges while running wide open since that probably isn't a good idea. Do you know at about what speed your TD plates come up off the water, and if so would you care to share? Also, with experience have you found that you can "feel" when this happens or not, thanks.
quikdata or racepak data collection can be used. either way, you'd run a speed pickup as well as many other data collection points. you could mount pressure sensors on the keel, the tunnel plates as well as the tunnels. you can also mount pressure sensors on the ride plate. pressure data can be collected from pretty much anywhere on the hull, and correlated to whatever speed you can generate. for value, you will also want to have spotters that can accurately record the water and weather conditions at the time of the pass.
there are other things to play with besides these plates that will have more of an effect on performance.

[bp]

thats a stupid statment...and yes we know why we put them there....
"we know why we put them on there"????? were you involved in the original design and installation of the tunnel plates?

[WheelerDealer]

bp originally posted...
there are other things to play with besides these plates that will have more of an effect on performance.
I totally agree bp, but I don't think that means I should disregard the plates as a tuning tool as well unless I found that they really didn't have very much real effect on the boats performance, but the only way I am going to know that is to experiment right?? It is very hard for me to ask a question on these forums and have it actually be read and interpreted the way I meant it. I am very interested in the tunnel plates because I see them on several boats, but I have never really heard why they are there. I have heard several peoples ideas as to why they are there, some of which are quite detailed and they may be right, but the reasons I get have varied widely and are often contradicting, so I thought it was a rather valid question and a subject worth researching and experimenting with first hand to see what effect the plates have. Of the people I have heard give explainations as to why they are there, none of them have ever actually done any testing to prove their theories, or at least they can't or won't share it with you.
bp, I know that you have your boat dialed in on the money for what you do, and I have no doubt that you know how to make a Southwind haul ass. I can say that everything you have told me you can and have also backed up with data and real world testing, you are one of the few who can or will do that. You have helped me a bunch already and the boat hasn't even gotten wet yet. I guess you could say I am an information junkie and I like to have as much hard data as I can, so I see this as a wide open area to be studied, however I certainly agree you have to get the boat dialed in in all other areas as well if not more so. The plates as I see them are just another piece of the puzzle.
FOURQ originally posted...
thats a stupid statment...and yes we know why we put them there....
Who is "we" and please share the answer with us, why are they there and what do they do? Do you know who designed them into the SWTDs/Placecrafts/Bahners or any others that have them and why they felt like any of those particular hulls need them? Finally, have you done any testing that showed when the plates come out of the water and what effect overall boat set up has to do with it? If you have or know someone that has, how did they set up sensors and what not for the tests? These are the questions I am trying to answer, if you can help then by all means please do.

[Jake W2]

We is his grandpa.
Dragboats , all though a Youngblood 18 tunnel is not a Daytona they may or may no have a recessed place for plates in the tunnels so they run them(YB 18) both ways.and it is a true tunnel with forkes.
Jake

[WheelerDealer]

Jake W2, Is his Grandpa's name Percival or something like that? I think the guy that designed the original SWTDs like I have was named Phil Percival or something like that, or at least that is what Jack at MPD told me I think?????

[steelcomp]

From what I can tell, the plates are mainly installed on Mod V's. True entrapment hulls don't have them. The most comon denominator I can see is the pump extension or "pod", and I think this was an attempt to extentd the bottom somewhat to make up for a condition caused by the difference in length between the transom and the pump extension. I was told from the beginning that the plates were a "bandaid" of sorts. You seldom see them properly attached to the bottom by being let in, more, they're just hung off the back as an add-on. They're not intended to be adjustable while running, therefore I'm guessing thery're more for correcting a condition than a runing trim device. Having said thet, I have seen several set ups where they ARE driver adjustable, and it would be interesting to have that set up to see what the effects are while running at different speeds at different settings under different conditions. I know that my boat, without a PD, has a terrible porpoise below 50 or so. It's set up for top speed, and I was wondering if controllable cav's, like in a flat, would be cool for the exact same result. I know there's a lot of flexability with the PD...I'm not dismissing that at all, just wonder about the addition of another triming option. My Bahner may just end up with somethning like that. Hey, if for nothing else, it looks cool!!
ForQ...we're all waiting. That was a BIG statement, and I, for one, am really interested in hearing the FIRST actual factually based reason as to why they are there. Just the facts, man, just the facts. Was that one of those comments that seemed simple enough to say, but now you're finding out it's not as clear as you thought? Uh oh!! I've asked everyone I know that might know someone thet knows for 5 yrs, and still haven't gotten a clear answer, so you da' man!!

[WheelerDealer]

steelcomp originally posted...
ForQ...we're all waiting. That was a BIG statement, and I, for one, am really interested in hearing the FIRST actual factually based reason as to why they are there. Just the facts, man, just the facts. Was that one of those comments that seemed simple enough to say, but now you're finding out it's not as clear as you thought? Uh oh!! I've asked everyone I know that might know someone thet knows for 5 yrs, and still haven't gotten a clear answer, so you da' man!!
Ditto!

[djdtpr]

I have no idea why they were put there but i can say that on my placecraft they made a hell of a diference in performance as to where they were set.I noticed more from adjusting those than a rideplate adjustment.I dont think mine ever came out of the water even at top speed i think the ends were still in the water.The only reason i say that is because the atitude of the boat was different on the top end and changed with every adjustment.All the adjustments were also done at the track so we could see actual changes in speed and atitude.But like you said ask 10 people and get 10 different answers.I would also guess that diferent boats with diferent setups and hardware will react completely diferent.

[Nucking futs]

WEll phill had no intrest nor did he design the tunnel.Phill built the inserts for the mold on the SWTD.The tunnel is the same bottom as the sw18 with some inserts in the mold and then some testing to the boat and then the mold was made.As for the plates, The reason they are there is to give lift. They will hold the air in longer and gives the boat more lift.You go up on the plates and it will exhaust the air faster and let the boat fall. They way i understood it and i was young then,but you are squeezing the air to make the boat lift.The pod is there only as a cover for the pump.It is a setback pump and the pod covers it to give it more support and cover the pump just to look pretty :D The plates will aid in some of the set up and is a big factor for the other things that need to be set up as well.The plates on a dialed in boat should be out of the water when it takes a set.I don't think anyone knows "when" they are out of the water, but on all the pics we have all of the race boats the plates are out of the water.I know of a few that have taken them off and there boat rides flat and it is real squirrly on the big end and they were reinstalled.So no they are not a band aid and that is the reasoning why they are there. Oh and here is the very first tunnel made....Timhttp://www.***boat.com/forums/attachment.php?attachmentid=8329&stc=1

[steelcomp]

WEll phill had no intrest nor did he design the tunnel.Phill built the inserts for the mold on the SWTD.The tunnel is the same bottom as the sw18 with some inserts in the mold and then some testing to the boat and then the mold was made.As for the plates, The reason they are there is to give lift. They will hold the air in longer and gives the boat more lift.You go up on the plates and it will exhaust the air faster and let the boat fall. They way i understood it and i was young then,but you are squeezing the air to make the boat lift.The pod is there only as a cover for the pump.It is a setback pump and the pod covers it to give it more support and cover the pump just to look pretty :D The plates will aid in some of the set up and is a big factor for the other things that need to be set up as well.The plates on a dialed in boat should be out of the water when it takes a set.I don't think anyone knows "when" they are out of the water, but on all the pics we have all of the race boats the plates are out of the water.I know of a few that have taken them off and there boat rides flat and it is real squirrly on the big end and they were reinstalled.So no they are not a band aid and that is the reasoning why they are there. Oh and here is the very first tunnel made....Timhttp://www.***boat.com/forums/attachment.php?attachmentid=8329&stc=1
Thanks Tim...so where should they be "theoretically" set?
Then the question is why don't other "true" tunnels have them, and not just the mod v's?

[Nucking futs]

I can't say were they "should be set" as each boat is different.but on mine i would start at 2* up and tune as needed.
As for other boats i could not tell you why the don't or if they should.I also have trim tabs on my cruiser only to adjust on the fly for water conditions that the p/d won't help.I also think the plates help with attitude just like the ride plate. I have seen different length plates on different boats so it also could stand to reason that a longer or shorter plate will do different things.Place crafts have shorter plates then the SW and that could be as the P/C have bottom mods made into the hull already.To bad Bill PLace isnt around anymore to ask him why they made them shorter.I have seen also on the crusader and bakers have shorter plates too but i cant answer why.
Tim

[TRG]

good explanation!
now if you look at the hull of a true tunnel (daytona or stealth)are the sponsons totally parallel to each other or the center pod?
i guess what im saying is,...is there even the slightest angle inward the further back the sponson's go?...kind of like a pinching effect.
now that im thinking about it, it might be a dangerous scenerio if there was a loss of power and the whole right/left deal, but if you could look past that, that would definitly trap some air?

[Jake W2]

Nucking Futs can you make that pic bigger?
Jake

[FOURQ]

Thanks Tim...so where should they be "theoretically" set?
Then the question is why don't other "true" tunnels have them, and not just the mod v's?
the setting is all relevent to all the other settings thrust angle, rideplate, hp and things of that nature.. we set all ours at about 3* up to start then come down as needed .. lots of pepole have blown the plates off as they think they are not needed and set them at 0* and the boat dont do to good..if you look at most of the other tunnel boats the outsides are deeper giving it more lift ....the idea behind the outsides being only 2 1/2 inches was to try to get as much of the boat out of the water giving it less drag but as WE found out later they wernt deep enough the plates were there from the start and aided in adjusting the exaust air fine tuning the ride. if you look at the place craft the outsides are deeper and in some cases the plates are shorter that was their fix to the problem we had but all in all it seems to work about the same... the swtd the first prototype swtd was started in 1974 and wasnt put out to race maket till 1976 and to the public in 1977..
4Q

[Jake W2]

Todd yes they taper on a Daytona CP even its not a pickel,Stealth.Cheyenne ect.
Jake

[Cs19]

So you run the plates down to keep air in the tunnells longer, generating lift.Makes sence.
But aernt those plates still really wet till say 85-90. Gotta wonder if its a fair trade off.Youll get the lift on the big end, but excessive drag through acceleration since the plates are at a negative angle.
Could it be possile that running some down in those plates could generate some lift much like a backcut does? I realize it wouldnt be generating lift directly under the boat like the BC does, but who knows, maybe get the ass out a little bit? Probably not. Just a thought.
Jer, Bp what do you think?

[FOURQ]

Nucking Futs can you make that pic bigger?
Jake
i can http://www.***boat.com/forums/attachment.php?attachmentid=8332&stc=1
4Q

[FOURQ]

Todd I have had mine shut down on a wfo pass and it set down so sweet and went straight
thank god..
4Q

[Jake W2]

It looks like the hull was cut down even more after that one was made.
Jake

[TRG]

i remember us talking about that in your front yard a few weeks ago, but my concern was the daytona and stealth, not that its a concern but ive noticed it when ive done some work on the cp tunnels,...they are not parallel at all, so would that be a good reason why they are not good lake boats (cptunnels) never mind, i dont want to get off your guys topic with cav plates!

[LVjetboy]

Tim, could you make that picture a bit bigger? Oh geez, I'm slow never mind Jake beat me to it. :frown:
On the plates...
"They will hold the air in longer and gives the boat more lift.You go up on the plates and it will exhaust the air faster and let the boat fall."
That was one of the ideas floated :wink: on RJB-II awhile back. Among others. If air dam was the original intent, the plates do not function in that role until the back of the tunnels exhausted. Prior to that speed, the back of the tunnels are the air dam. Curiously, no one seems to know the critical speed or even if exhausting happens? And the difference in hull attitude and lift would be considerable depending on whether hydrodynamic or aerodynamic forces are acting on those plates. So you'd think the transition point important?
Once exhausting, the plates could function as an air dam, but not a very good one. At least for the PlaceCraft, the inboard side of the dam is partially backed up by the pod (with an 1/8" gap) but the outboard side open to release air.
In the early 90's(?) PlaceCraft went to a recessed plate which seems to make more sense in an air dam function. My 91 PC has the older extended plates and MikeC's 96 PC had the recessed.
Without a clear purpose or benefit, any extention's just more drag. But they do look cool and work great for a swim step.
jer

[Nucking futs]

The SWTD was built for safty at "HIGH" speeds.Would'nt catch me in a cp tunnel at 115-160 MPH.
Come on BP, i know you have some input on this.
Jer, all the SW have resecced plates.Also on the pod length , if you cut the pod that will affect the relaese of air quicker on all sides. See, Bill Place put alot of time in his boats,not to say frank didnt, but i think Bill had a working knowlage of what was happening on the first going places (swtd) and did alot of R&D on the SW before he made the placecraft.So i think alot of the info on this topic has all past away with the people that made it what it is and i really am no expert on this stuff and am still learning as well. Ron hamilton might be able to defighn this alittle better as he did all the hardware on both the going places boats.Someone should call him and pick his brain.......Tim

[LVjetboy]

"So i think alot of the info on this topic has all past away with the people that made it"
Yep. That continuity thing. Unless recorded and published, lost or distorted by word-of-mouth.
By recessed plate I meant nothing sticking out past the transom...the newer PC plates were actually moved forward and tucked completely into the tunnels. No more turnbuckles, no more swim step. :(
jer

[LVjetboy]

"But aernt those plates still really wet till say 85-90. Gotta wonder if its a fair trade off.Youll get the lift on the big end, but excessive drag through acceleration since the plates are at a negative angle."
My thought too, that's why transition may be important. Then there's launch...where they function as a trim tab?
jer

[Mrs CP 19]

The SWTD was built for safty at "HIGH" speeds.Would'nt catch me in a cp tunnel at 115-160 MPH.
Don't even go there.

[FOURQ]

Don't even go there.
have you ever seen a blown fuel cp? not I..

[LVjetboy]

http://members.cox.net/lvjetboy/TunnelPlates.jpg
:D :D :D !
jer

[steelcomp]

So you run the plates down to keep air in the tunnells longer, generating lift.Makes sence.
But aernt those plates still really wet till say 85-90. Gotta wonder if its a fair trade off.Youll get the lift on the big end, but excessive drag through acceleration since the plates are at a negative angle.
Could it be possile that running some down in those plates could generate some lift much like a backcut does? I realize it wouldnt be generating lift directly under the boat like the BC does, but who knows, maybe get the ass out a little bit? Probably not. Just a thought.
Jer, Bp what do you think?
Chris, I don't see anywhere here where they said they run the plates down. I read anywhere from 2 to 3 deg. up, and start from there. I read that zero didn't work.
What kinds of speeds are we talking about here?
Why would the down plate be excessive drag if a back cut shoe is doing the same thing? I would think the further back you can create the lift, the better. It's why pumps get set back and droops or just snoots are installed. I would think that if the plate is aiding in getting the back of the boat out of the water AS SOON AS POSSIBLE, it would be more effective then a back cut shoe by say, 200%. By the time the boat is out of the water, the plate is acting like the dam it was intended to be, not slowing anything down.
Was the first SWTD built with the plates right off the drwg board. or were they added later because of a certain condition? I'm betting on the latter, which, IMO, makes them a bandaid. An effective one, yes, but still an after thought. Especially since they're not controllable. I think if they were controllable, they could and would serve exactly the same putpose as a cav plate. Down on the start to keep the nose down and create forward movement instead of upward, adn when under way, bring 'em up, out of the way.
Great input here, but it seems like everyone is still guessing.
I was also told by Jack McClure that untill a mod v is running well over 90 that it's acting like a v bottom anyway, so the packing air effect below that speed seems irrelevant. This thing (tunnel plate) isn't like the elevator on an airplane...or is it?
If the plate is down, at what speed will it actualluy create life via deflection of air? Or will it? How much pressure needs to be trapped in the tunnels in order for the boat to actiually start "lifting"? Is the pressure more at the back of the tunnels than at the front?
Did anyone here see unchained's "box" under his pick up? I wonder if, in the same fashion, if one was to fabricate a true three-sided tunnel extension, instead of just a plate for the roof of the tunnel, what the effects would be.

[steelcomp]

I have no idea why they were put there but i can say that on my placecraft they made a hell of a diference in performance as to where they were set.I noticed more from adjusting those than a rideplate adjustment.I dont think mine ever came out of the water even at top speed i think the ends were still in the water.The only reason i say that is because the atitude of the boat was different on the top end and changed with every adjustment.All the adjustments were also done at the track so we could see actual changes in speed and atitude.But like you said ask 10 people and get 10 different answers.I would also guess that diferent boats with diferent setups and hardware will react completely diferent.
DJ...what were the settings you worked with?

[WheelerDealer]

LVjetboy originally posted...
So you'd think the transition point important?
I certainly think it would be important, and that is the reason I started this thread as to the best way to devise a system to accurately measure the moment when it occurs. I am headed out to the garage right now to measure the size of the tunnels, depth of the center sponson, depth of the outer sponsons, and the size of the plates on my SWTD. Do you have these measurements on your Placecraft jer, if so I would like to compare. How about you Bahner tunnel owners, do any of y'all have these measurements?

[steelcomp]

My outer sponsons at the transom are 8" wide. The tunnels are parallel at 16" wide, and the center sponson is 16" wide as well. The outer tunnel wall is 3 3/4" deep at the transom, and the inner wall is 4 1/2" deep at the transom. The tunnel is 15 3/4" wide at the top, giving the outside wall of the tunnel a slight angle outward. Someone can trig out the number...Hey Jer, what's the angle when the hippopotomus is 3 3/4" and the short leg is 1/4"? That's the angle on the out side wall of the tunnel. I'm guessing about 2-3 deg.The outer sponsons are about 145" long. My plates are 15" wide by 8" deep.
My thought is that unless you're runing at 100, these plates aren't doing anything when they're out of the water. Below that speed, even if they're out of the water, they're ineffective, and only working when in the water. Then they're acting like any other trim device.

[steelcomp]

have you ever seen a blown fuel cp? not I..
There's a BIG differnece between a CP gullwing, and a CP tunnel.

[Nucking futs]

Don't even go there.
Like i said i won't. I love the cp's but after a certain point i would not push it.Not saying they suck or nothing im saying that the SW was built for "safe" handling over a 100 mph thats all............... :cool:
Just my opinion, but they get alittle loose at speeds over 100 on the river for "me"..................Tim

[Old Guy]

Not one of the above mentioned hulls.......however just for reference.
http://files.triton.net/old1/tunnel.jpg
'76 Sleek Craft Aristocrat

[WheelerDealer]

My tunnels are about 17.25 wide, my outer sponsons are about 2.25 deep, and my center sponson is 4.25 deep. I forgot that my plates are at the powder coaters.

[steelcomp]

Not one of the above mentioned hulls.......however just for reference.
http://files.triton.net/old1/tunnel.jpg
'76 Sleek Craft Aristocrat
Wish I had a CAD...I would love to be able to whip that out like that :cool:

[Old Guy]

LOL........actually I "whipped it out" on 6/24/03 and posted it on the RJB board. I was lookin for info on tunnel plates.
Mine have no plates. I couldn't get any info.
You are doing way better. Keep goin!!!!!

[steelcomp]

LOL........actually I "whipped it out" on 6/24/03 and posted it on the RJB board. I was lookin for info on tunnel plates.
Mine have no plates. I couldn't get any info.
You are doing way better. Keep goin!!!!!
Is there something about your hull that makes you think you need them? Does your hull have a pump extension? I'm assuming it's a mod v.

[sanger rat]

Not one of the above mentioned hulls.......however just for reference.
http://files.triton.net/old1/tunnel.jpg
'76 Sleek Craft Aristocrat
Looks like my boat. http://www.***boat.com/image_center/data/500/1937pic006.jpg

[LVjetboy]

"Do you have these measurements on your Placecraft jer, if so I would like to compare."
Sure no problem...
http://members.cox.net/lvjetboy/PCProfile.jpg
Also posted on RJB-II long gone.
Here's a computer generated shot...
http://members.cox.net/lvjetboy/Tunnel3D.jpg
Here's the real thing...
http://members.cox.net/lvjetboy/TrimPlate.jpg
I have mine set at zero now, baseline and because I have no better idea of what they really should be. When I get bored with 100 mph, maybe I'll tweak them. :D
jer

[Jeanyus]

I had my plates set at 0, the boat was real flat in the water. I moved them to 3 degrees up, and the nose rides up, which works a whole lot better.
My best top speed has been 78, and the plates have a big effect on how the boat rides.
Here is a shot of the bahner hull.
http://www.hotboatpics.com/pics/data/500/5859stern.jpg
http://www.hotboatpics.com/pics/data/500/5859bahnerback.jpg

[Old Guy]

Is there something about your hull that makes you think you need them? Does your hull have a pump extension? I'm assuming it's a mod v.
That kind of gets us back where this started doesn't it. What do the plates do? How do they work? Who needs them?
I have come to the conclusion that ANY air trapped under the hull will put force upward on the hull and lift it out of the water. Maybe only 1/16th of an inch.......but it will be upward. With less boat in the water, the boat can go faster with the same amount of power. I expect that if too much air is trapped under the hull, it will become very unstable. It will also (probably) be going quite fast at the time.
This is the rear (stern for those who are pure) of my boat.
http://files.triton.net/old1/new_pump.jpg
Roger

[steelcomp]

Here's my Bahner. Tops of tunnels are not flat with lateral c/l of boat.
http://www.***boat.com/forums/attachment.php?attachmentid=8335&stc=1

[steelcomp]

That kind of gets us back where this started doesn't it. What do the plates do? How do they work? Who needs them?
I have come to the conclusion that ANY air trapped under the hull will put force upward on the hull and lift it out of the water. Maybe only 1/16th of an inch.......but it will be upward. With less boat in the water, the boat can go faster with the same amount of power. I expect that if too much air is trapped under the hull, it will become very unstable. It will also (probably) be going quite fast at the time.
This is the rear (stern for those who are pure) of my boat.
http://files.triton.net/old1/new_pump.jpg
Roger
Thanks Roger. No pod, no plates. The more and more I see these examples, I see the one common denominator of the boats with plates is the pump extension, or "pod". I'm wondering if they're not meant to get the air from under the tunnel past the pod because of some kind of turbulance there. Pod on one side of the tunnel, no pod on the other. Air can't escape the tunnel equally, and needs to be carried out past the pod.

[LVjetboy]

Oh ya almost forgot...
"Hey Jer, what's the angle when the hippopotomus is 3 3/4" and the short leg is 1/4"? That's the angle on the out side wall of the tunnel. I'm guessing about 2-3 deg."
The hippo with the short leg looses and the other two dominate the swamp, wallow over the women and drink all the beer.
3.8
jer

[steelcomp]

Oh ya almost forgot...
"Hey Jer, what's the angle when the hippopotomus is 3 3/4" and the short leg is 1/4"? That's the angle on the out side wall of the tunnel. I'm guessing about 2-3 deg."
The hippo with the short leg looses and the other two dominate the swamp, wallow over the women and drink all the beer.
3.8
jer
LMAO!! You crack me up!! Thanks Jer! :D

[Squirtin Thunder]

I had my plates set at 0, the boat was real flat in the water. I moved them to 3 degrees up, and the nose rides up, which works a whole lot better.
My best top speed has been 78, and the plates have a big effect on how the boat rides.
Here is a shot of the bahner hull.
http://www.hotboatpics.com/pics/data/500/5859stern.jpg
http://www.hotboatpics.com/pics/data/500/5859bahnerback.jpg
Ron,
Did you check them after I, we moved them at Ming ???

[Cs19]

they didnt mention zero. I was ASSuming that, my bad.
Say you run the plates at 3 deg up from the tops of the tunnells. Is that still preventing air from exhausting the rear of the boat?

[Squirtin Thunder]

We set Rons (Jeanyus) the same as Dannys (DJDPlacecrafts). It was easy to copy because he was right next to us @ Ming.
Jim

[Cs19]

Why would the down plate be excessive drag if a back cut shoe is doing the same thing? .
the actual Back cut area on a shoe is probably not even 7 inches wide. Those plates combined are probably 18 inches wide.Almost triple the size.
This inst about back cut, but I look at it as a trade off. You can only get so much lift out of a backcut, plate,shoe whatever. Once your no longer benefiting from it, it turns into drag, and youd be better backing off the angle once you reached the point where the boat is no longer responding to it.
I saw some things first hand and learned a little about drag and the losses you see at firebird last race. I say its for real.

[steelcomp]

the actual Back cut area on a shoe is probably not even 7 inches wide. Those plates combined are probably 18 inches wide.Almost triple the size.
This inst about back cut, but I look at it as a trade off. You can only get so much lift out of a backcut, plate,shoe whatever. Once your no longer benefiting from it, it turns into drag, and youd be better backing off the angle once you reached the point where the boat is no longer responding to it.
I saw some things first hand and learned a little about drag and the losses you see at firebird last race. I say its for real.
CS, the lifting capability of the backcut shoe is limited by it's size. If you had a shoe under the boat with the same square inches of area as the plates, how much lift do you think that would generate vs/ drag??

[steelcomp]

they didnt mention zero. I was ASSuming that, my bad.
Say you run the plates at 3 deg up from the tops of the tunnells. Is that still preventing air from exhausting the rear of the boat?
If the plates are set at zero, and the boat runs at say 3 deg up, then the plates are pointing down 3 deg relative to the air flow. When the plates are up a few degrees, they are more parallel with the water nad air flow. I have no idea what this means, just an observation.

[Jeanyus]

Jim I still have my plates set a 3 degrees up. I only used it one time since Ming, that was at Rollins Lake when I raced a v-drive with a 427 tunnel ram engine, and beat him. OK now I'm gonna get flamed.
Hey Old Guy what is that extra piece on yuor PD, the metal rod near the ram?
Is it a stop? This is what I use. It stops me from being able to make big roosters, but I can find the sweet spot without thinking about it.
http://www.hotboatpics.com/pics/data/500/5859diverterstop-thumb.jpg

[Old Guy]

It's not a stop. It's probably the linkage that operates my home made trim indicator sending unit.
Roger

[bp]

the idea behind the outsides being only 2 1/2 inches was to try to get as much of the boat out of the water giving it less drag but as WE found out later they wernt deep enough the plates were there from the start and aided in adjusting the exaust air fine tuning the ride. if you look at the place craft the outsides are deeper and in some cases the plates are shorter that was their fix to the problem we had but all in all it seems to work about the same... the swtd the first prototype swtd was started in 1974 and wasnt put out to race maket till 1976 and to the public in 1977..
4Q
not to belabor the point, but this "we" thing is still confusing to me, in that you seem to be personally taking credit for being directly involved with the development and tuning of this hull during the late '70s, involved with analysis, evaluation, and decision making processes in how to tune it. you're at least, what, 30ish? so, i'm somewhat confused as to how much direct involvement you could have had??? if you were not involved in the first person, but it was your father/grandfather, you should make that clear.
don't have time to talk about tunnel plates again..

[djdtpr]

DJ...what were the settings you worked with?
Scott we started my plates at 4* then we went down to 3* it rode with the nose over pretty heavy.After that we set them at 4.5 then ended up at 4.9.After that i started to drop the rideplate and shoe for the final adjustments.But the setup is not something i would run as a pleasure boat at the river or on rough water cause it is pretty loose.
CS do you remember this summer when we were at big river and i tried to run the plates at o* andd the boat nosed over real bad and broke water at the back seat area?It rode like a dream but set real heavy.I think some boats will take that adjustment different though due to hardware and setup.Just my thought though.

[FOURQ]

not to belabor the point, but this "we" thing is still confusing to me, in that you seem to be personally taking credit for being directly involved with the development and tuning of this hull during the late '70s, involved with analysis, evaluation, and decision making processes in how to tune it. you're at least, what, 30ish? so, i'm somewhat confused as to how much direct involvement you could have had??? if you were not involved in the first person, but it was your father/grandfather, you should make that clear.
don't have time to talk about tunnel plates again..
yes BP you are corect it was my grandfather and father it was a family run company and alot of the knowlage has been passed down.. there for 99% of my information comes direct from the horses mouth.there is alot of information i still have about this subject that i dont post cause its not worth it in my mind to sit there and argue about it for those of them that have their own opinion and are to closed minded to listen and try to understand it with out getting into a pissing contest.i mean dont get my wrong I am by no means an expert and there is alot of good valid points and I am not bashing anyone. BP if you want more info go ask Buzz on my board he will explane all the r&d THEY did on the swtd and the reasoning for them and the reasoning of the settings...
4Q

[WheelerDealer]

Jeanyus originally posted...
I had my plates set at 0, the boat was real flat in the water. I moved them to 3 degrees up, and the nose rides up, which works a whole lot better.
I am thinking if the plate settings have this much effect on a boat going 78mph that they would have even more effect on a boat going 100+.

[moneysucker]

Thanks Tim...so where should they be "theoretically" set?
Then the question is why don't other "true" tunnels have them, and not just the mod v's?
I set mine at 0. I did set them down once and it made a huge diference (bad) it bow steered bad and drove the nose into the water. The southwinds do have let ins for the plates and I have seen and driven one that did not use them and it handled very well, Better than mine. But Petrofied had air entrapment and may not have needed the plates for additional lift area. These are both SWDT's and most I have seen haqve the plates. Out of the mold they are let in for the plates.

[moneysucker]

I am thinking if the plate settings have this much effect on a boat going 78mph that they would have even more effect on a boat going 100+.
If you have seen the pix of mine at 100 I caught a lot of crap for being too nose high and mostly the ride plate will set where the nose rides. The tunnel tabs will only work to a certain extent. at some point the outer sponsons come out of the water also and the nose starts to dance. This happens at 98mph on both mine and Rubber Ducks boat. When the outer sponsons break contact with the water there is not too much more air pack to be had no matter where the plates are set.The speed at which a DT is packing air properly is wher it stops hopping up and down at low speed.

[WheelerDealer]

hey sucker, are you saying that petrofied took off the plates after he added the air entrapment?

[Norseman]

Hey ST, either idea could probably be made to work, but i would think you would need some type of gauge that would function like a recall or tattle tale tach does so that you wouldn't have to stare at the speedo and the tunnel plate gauge...know what I mean?
Use a pressure sensor and have it light a light on the dash when the plate is out of the water.

[moneysucker]

hey sucker, are you saying that petrofied took off the plates after he added the air entrapment?
He actually never had any with the boat. He purchased a 1982 SWDT un rigged 4-6 years ago. It didn't have a hole cut in it but the intake and the bottom had already been done with air entrapment added. He ran 112 with out tunnel tabs and I drove it and it sold me on blown injected motors. I also noticed an extreme diference in handling at high speed. I am adding air entrapment on mine. I enjoyed the stability of Petrofied. I curse Skee every day for letting me drive. I was almost content being carbureted tunnel ram. Curse you devil boy!

[WheelerDealer]

I have my SWTD completely stripped right now sanding it all down, and when we flip it upside down I paln on adding to the outside sponsons for a little air-entrapment action myself, just not sure how much to add or the best way to go about doing it. I am thinking about taking the outsides from 2.25 deep to 3.75... :confused: :confused:

[moneysucker]

I have my SWTD completely stripped right now sanding it all down, and when we flip it upside down I paln on adding to the outside sponsons for a little air-entrapment action myself, just not sure how much to add or the best way to go about doing it. I am thinking about taking the outsides from 2.25 deep to 3.75... :confused: :confused:
Go over on the petrofied Moneysucker quack attack thread and ask Psycho Squid, formerly Petrofied how far his were down. My memory says basically 1.5" x 3.5" was added to the outside sponsons. He probably has pix too.

[LVjetboy]

"...at some point the outer sponsons come out of the water also and the nose starts to dance. This happens at 98mph on both mine and Rubber Ducks boat."
My nose doesn't dance at 98 or 100. A very slight porposed but no dance or floaty feeling. But then I'm riding way stuck to the water. Good for lake running...maybe not best for top speed. A good example of a different setup and how each part can interact with another...so no magic tunnel plate trim angle. Anyway I'm still wondering, are the tunnels exhausted at that speed? Does anyone know?
jer

[Cs19]

CS, the lifting capability of the backcut shoe is limited by it's size. If you had a shoe under the boat with the same square inches of area as the plates, how much lift do you think that would generate vs/ drag??
Steel i cant answer that, only "imagine " what it would be like. I will say Ive ran a flat shoe and a back cut shoe back to back at ming and I know what that did for me.
Steel, if you like the idea of having a large surface thats shaped in a backcut like angle, you could add that right into the hull itself with glass. One of my old race jetskis had that feature.. The last 4 inches of the hull were at a 2-3 Bc angle..Fastest hull I ever had, 74 mph with a mild motor.
Steel you dont buy the whole drag thing do you? :D

[PC Rat]

if you like the idea of having a large surface thats shaped in a backcut like angle, you could add that right into the hull itself with glass. One of my old race jetskis had that feature.. The last 4 inches of the hull were at a 2-3 Bc angle..Fastest hull I ever had, 74 mph with a mild motor.
Wow, and people spend so much time removing hook. :cry:
.

[steelcomp]

Steel i cant answer that, only "imagine " what it would be like. I will say Ive ran a flat shoe and a back cut shoe back to back at ming and I know what that did for me.
Steel, if you like the idea of having a large surface thats shaped in a backcut like angle, you could add that right into the hull itself with glass. One of my old race jetskis had that feature.. The last 4 inches of the hull were at a 2-3 Bc angle..Fastest hull I ever had, 74 mph with a mild motor.
Steel you dont buy the whole drag thing do you? :D
My question was only theoretical. If the idea was worth expanding on, it would have been tried by now. So far what I have learned here is that every improvement gained by tunnel plates was in the up position, relative to keel.
I've dealt with drag issues in ways you probably wouldn't understand, Chris. Drag is a trade off in any event that causes a reaction with the water or air. If you want more of a reaction, you're going to cause more drag. Your hull with the back cut bottom was causing drag, but you compliment it's effect. Way more drag than a back cut shoe. Drag vs. effect is completely relative.
Quote, CS 19: You can only get so much lift out of a backcut, plate,shoe whatever. Once your no longer benefiting from it, it turns into drag, and youd be better backing off the angle once you reached the point where the boat is no longer responding to it.
What about increasing speed?
The issues about tunnel plates are still a mystery here. I haven't heard anything that tells me WHY they were added, or that they were added as a result of...??? in any solid data form, just a lot of supposition. It's clear they have an effect, both positive and potentially negative.

[LVjetboy]

"Wow, and people spend so much time removing hook."
Did they have a tunnel? Apples to oranges.
"I haven't heard anything that tells me WHY they were added, or that they were added as a result of...??? in any solid data form, just a lot of supposition."
You're right Steel. But that seems to be the norm for our sport. Trial and error, supposition and maybe even superstition. Facts or data hard to come by.
jer

[steelcomp]

Wow, and people spend so much time removing hook. :cry:
.
Hook is a different issue. What we're talking about here is mostly mechanical deflection. Hook, which is more of a countour shape than a sharp break, causes a pressure differential under the boat and want's to suck the boat down. The back of CS's hull acted like a trim device that causes deflection forcing the surface away from the water.

[Cs19]

If the plates are set at zero, and the boat runs at say 3 deg up, then the plates are pointing down 3 deg relative to the air flow. When the plates are up a few degrees, they are more parallel with the water nad air flow. I have no idea what this means, just an observation.
Ok i follow you.. I was thinking the same thing last night, but I had a hard time putting what i was thinking into text..
Ya if the boat runs nose high, then a plate at 0 deg. will pinch off the air on the outlets, makes sence. If you run your boat flat, not gonna see a whole lot of pinch though. ?? If you look at it that way, plate length might be something to play with?
I still think the plates have way more affect on the way the boat rides or attitude than the idea of the plates keeping air in the tunnells longer.

[steelcomp]

Ok i follow you.. I was thinking the same thing last night, but I had a hard time putting what i was thinking into text..
Ya if the boat runs nose high, then a plate at 0 deg. will pinch off the air on the outlets, makes sence. If you run your boat flat, not gonna see a whole lot of pinch though. ?? If you look at it that way, plate length might be something to play with?
I still think the plates have way more affect on the way the boat rides or attitude than the air dam thing does.
I'm not following the air dam thing??? I read about "entrapment"??? Maybe I'm just slow here.

[Cs19]

Quote, CS 19: Once your no longer benefiting from it, it turns into drag, and youd be better backing off the angle once you reached the point where the boat is no longer responding to it.
[QUOTE=steelcomp]What about increasing speed?
Isnt increased speed a response from the boat?
I said... Once the boat stops responding to it, its pointless to keep adding backcut.
You said in one of the posts its a deflection force, you dont think that can result in drag?

[Cs19]

edited the post ,maybe you will understand it now.

[steelcomp]

Isnt increased speed a response from the boat?
I said... Once the boat stops responding to it, its pointless to keep adding backcut.
You said in one of the posts its like deflection, you dont think that can result in drag?
Deflection always results in drag. Weather or not it is giving the results you want. The effect of the backcut shoe is more relative to the speed of the boat than the angle of the shoe. A slower boat like mine will require more backcut than yours. (Not taking into consideration hull differences) If the boat quits responding to angle changes, it's because there's not enough deflection, which is directly related to the speed of the boat or water "hitting" or "pushing" the shoe. Add ten mph and change the angle and see what happens. Just adding ten mph without changing the angle will create more deflection, (and more drag) causing more lift. This is why the faster a boat goes, the less back cut it needs, ultimately ending up with a flat or even tapered shoe, trying to keep the boat stuck.

[LVjetboy]

"Hook is a different issue. What we're talking about here is mostly mechanical deflection."
Hook is also mechanical deflection or a hydrodymamic force pushing the nose down. My point was, hook in a shallow v is different than negative-angle tunnel plates on a mod-v depending on speed. Why? Not because they work different than a hook, just because they work over a different speed range. A hook on a riding surface will always produce a hydrodynamic down force on the nose no matter the speed. A negative angle tunnel plate will produce a down force on the nose until the speed where the tunnel exhausts. After that, all bets off. Sure there's still aerodynamic forces, but not nearly as significant as hydrodynamic forces. Copy?
That's why hook not exactly the same as tunnel plate.
jer

[moneysucker]

I'm not following the air dam thing??? I read about "entrapment"??? Maybe I'm just slow here.
Air entrapment (adding to the outside sponsons running parallel with the tunnels) is used to increase the lift on the boat with less HP. Air dam would be a section that angles down in the tunnels creating a "dam" in the air flow which will add to the lift of the rear of the boat. The air entrapment lifts the boat uniformly and air dam will lift the rear to a point befour driving the nose down. Maybe this will clear things up a little.

[steelcomp]

Ok i follow you.. I was thinking the same thing last night, but I had a hard time putting what i was thinking into text..
Ya if the boat runs nose high, then a plate at 0 deg. will pinch off the air on the outlets, makes sence. If you run your boat flat, not gonna see a whole lot of pinch though. ?? If you look at it that way, plate length might be something to play with?
I still think the plates have way more affect on the way the boat rides or attitude than the idea of the plates keeping air in the tunnells longer. I read your edit...are you referring to them when cruising, and they're in the water, or at speed? If they're out of the water, the air through the tunnels is the only thing they have to react with.
Think about this. The air coming out of the back of those tunnels is accelerating, being compressed and forced through those tunnels. Just like the water going through your jet. When the air comes out of the tunnel, it is expanding, and pushes against the back of your boat, just like the water coming out of the nozzle of your jet. This action has an opposite reaction of pushing your boat forward, in both cases. NOt only does the air cause a high pressure under the boat lifting it, but also pushes it to a certain extent. Now think of tunnel plates in that respect, along with, or without a pump extension pod. :idea:

[steelcomp]

"Hook is a different issue. What we're talking about here is mostly mechanical deflection."
Hook is also mechanical deflection or a hydrodymamic force pushing the nose down. My point was, hook in a shallow v is different than negative-angle tunnel plates on a mod-v depending on speed. Why? Not because they work different than a hook, just because they work over a different speed range. A hook on a riding surface will always produce a hydrodynamic down force on the nose no matter the speed. A negative angle tunnel plate will produce a down force on the nose until the speed where the tunnel exhausts. After that, all bets off. Sure there's still aerodynamic forces, but not nearly as significant as hydrodynamic forces. Copy?
That's why hook not exactly the same as tunnel plate.
jer
10-4, c'mon!

[Cs19]

Upon thinking about it, pointing them down might help lift the back of the boat upon initial launch, and they'll be out of the water at speed. Hmmm.
Chris, I don't see anywhere here where they said they run the plates down.
i knew someone mentioned running the plates down, thats what got me going on all this steel. :rollside:
Deflection always results in drag. Weather or not it is giving the results you want.
and the whole time i thought you were debating it.
as far as the speed increasing, yes i agree, but you dont just see a 10 mph increase without major changes, best to compare to just one boat with the same hp so we can actually get somewhere with this topic.

[Cs19]

"Hook is a different issue. What we're talking about here is mostly mechanical deflection."
Hook is also mechanical deflection or a hydrodymamic force pushing the nose down. My point was, hook in a shallow v is different than negative-angle tunnel plates on a mod-v depending on speed. Why? Not because they work different than a hook, just because they work over a different speed range. A hook on a riding surface will always produce a hydrodynamic down force on the nose no matter the speed. A negative angle tunnel plate will produce a down force on the nose until the speed where the tunnel exhausts. After that, all bets off. Sure there's still aerodynamic forces, but not nearly as significant as hydrodynamic forces. Copy?
That's why hook not exactly the same as tunnel plate.
jer
copy.

[LVjetboy]

"This action has an opposite reaction of pushing your boat forward, in both cases. NOt only does the air cause a high pressure under the boat lifting it, but also pushes it to a certain extent. Now think of tunnel plates in that respect, along with, or without a pump extension pod."
Huh?
jer

[Cs19]

I read your edit...are you referring to them when cruising, and they're in the water, or at speed?
Whos to say they are ever out of the water? On a Pc, yeah ill buy they are dry, with a SWTD with the average river engine, maybe they never dry out..
We own a 1980 19' SWTD wth 600 HP,MPD stage 2 pump,Backcut shoe and loader grate, and Ive watched it blow by me at WOT while i was on a jetskii at WOT, I have my opinions on how much they get up on top based on what Ive seen with that boat in the 20 plus years Ive watched it run.
Im saying when they are in the water.

[Cs19]

When the air comes out of the tunnel, it is expanding, and pushes against the back of your boat, just like the water coming out of the nozzle of your jet.
Steel, put the crack pipe down. :cool: J/K
Interesting thought..

[steelcomp]

"This action has an opposite reaction of pushing your boat forward, in both cases. NOt only does the air cause a high pressure under the boat lifting it, but also pushes it to a certain extent. Now think of tunnel plates in that respect, along with, or without a pump extension pod."
Huh?
jer
read what I said a couple of times and think about it.

[moneysucker]

I read your edit...are you referring to them when cruising, and they're in the water, or at speed? If they're out of the water, the air through the tunnels is the only thing they have to react with.
Think about this. The air coming out of the back of those tunnels is accelerating, being compressed and forced through those tunnels. Just like the water going through your jet. When the air comes out of the tunnel, it is expanding, and pushes against the back of your boat, just like the water coming out of the nozzle of your jet. This action has an opposite reaction of pushing your boat forward, in both cases. NOt only does the air cause a high pressure under the boat lifting it, but also pushes it to a certain extent. Now think of tunnel plates in that respect, along with, or without a pump extension pod. :idea:
I am agreeing with this one, though I never thought about it this way, with a slight up angle in the plates as the compressed air will expand to equalize its density with the surrounding atmosphere and as it expands upon exiting it can exert a little force to the plates (if angled correctly) and actually create a forward thrust. The plates realistically just create a little extra surface area for the compressed air to push against the more they are angled down the more compressed the air in the tunnels,. The more up angle, the less compression in the tunnels. I will spend a day with the same set up making diferent adjustments utilizing a gps, video cam, and a radar gun and we will get a decent amount of research done. I may go to the river as soon as new years and we can help this argument a little.

[LVjetboy]

"read what I said a couple of times and think about it."
I only had to read it once to know the air expanding pushing thing was bullsh*t.
jer

[LVjetboy]

"I am agreeing with this one, though I never thought about it this way, with a slight up angle in the plates as the compressed air will expand to equalize its density with the surrounding atmosphere and as it expands upon exiting it can exert a little force to the plates (if angled correctly) and actually create a forward thrust. The plates realistically just create a little extra surface area for the compressed air to push against the more they are angled down the more compressed the air in the tunnels,. The more up angle, the less compression in the tunnels. I will spend a day with the same set up making diferent adjustments utilizing a gps, video cam, and a radar gun and we will get a decent amount of research done. I may go to the river as soon as new years and we can help this argument a little.
Are you freakin' serious???
jer

[LVjetboy]

Who posting here understands the difference between air drag and water drag?
jer

[moneysucker]

"I am agreeing with this one, though I never thought about it this way, with a slight up angle in the plates as the compressed air will expand to equalize its density with the surrounding atmosphere and as it expands upon exiting it can exert a little force to the plates (if angled correctly) and actually create a forward thrust. The plates realistically just create a little extra surface area for the compressed air to push against the more they are angled down the more compressed the air in the tunnels,. The more up angle, the less compression in the tunnels. I will spend a day with the same set up making diferent adjustments utilizing a gps, video cam, and a radar gun and we will get a decent amount of research done. I may go to the river as soon as new years and we can help this argument a little.
Are you freakin' serious???
jerYep. It is theoretically possible. Any proof it isn't? A substance under pressure will try to equalize itself in all directions unless impeaded.

[moneysucker]

Who posting here understands the difference between air drag and water drag?
jer
Uh, water creates more drag than air. It may have something to do with surface tension. Maybe we should present this thread in the physics chat room.

[Cs19]

Who posting here understands the difference between air drag and water drag?
jer
im always up for a lesson Jer. im sure youve been educted on this, i know i havent.

[LVjetboy]

"Yep. It is theoretically possible. Any proof it isn't? A substance under pressure will try to equalize itself in all directions unless impeaded."
A substance under pressure will try to equalize itself? So what. How does that lead to Steel's conclusion that air exhausting out the tunnels is providing significant thrust?
jer

[Cs19]

Lv, id like to hear the differences in drag if you have time.

[LVjetboy]

"...water creates more drag than air. It may have something to do with surface tension."
Yes water does create more drag than air. And it does depend on surface area in contact with water. That's why lift can have a HUGE affect on jet speed. That's why you can actually go faster into the wind on the lake than with the wind. Unlike a car. In fact, how much hp does it take to go 100 mph in a car compared to 100 mph in a jet?
jer

[moneysucker]

"Yep. It is theoretically possible. Any proof it isn't? A substance under pressure will try to equalize itself in all directions unless impeaded."
A substance under pressure will try to equalize itself? So what. How does that lead to Steel's conclusion that air exhausting out the tunnels is providing significant thrust?
jer
Significant; No. Slight forward thrust, provided that the plates are set at the correct angle to match the expansion rate of the air and maximizing its potential energy; Yes. I was agreeing to the fact that escaping air has the potential to create forward thrust you would see a better result reducing drag by shaving your arms most likely, but it can create thrust.

[Cs19]

i dont know, maybe 125 in a car and maybe 750 in a jet

[LVjetboy]

"Significant; No"
As in no significance. Don't we want to focus on what makes a difference?
jer

[moneysucker]

"...water creates more drag than air. It may have something to do with surface tension."
Yes water does create more drag than air. And it does depend on surface area in contact with water. That's why lift can have a HUGE affect on jet speed. That's why you can actually go faster into the wind on the lake than with the wind. Unlike a car. In fact, how much hp does it take to go 100 mph in a car compared to 100 mph in a jet?
jer
The density of a substance dictates a lot of the drag (resistance) when an object is passing through it water is more dense than air, sand is more dense than water thus creating more friction on the object passing through it. The benifit you have in a car hitting 100 also is down grades. There aren't too many of those in boating. The closest thing we have is current. Down hill, I can get a geo metro to go 100 mph and it has probably 85 hp. Good night. I will see how this turns out in the morning.

[moneysucker]

"Significant; No"
As in no significance. Don't we want to focus on what makes a difference?
jer
Combine about 20 of these little things and I may gain a mile per hour. I have bigger fish to fry than this, you are right. If I was going for some kind of speed record I would be all over it.

[LVjetboy]

"Lv, id like to hear the differences in drag if you have time."
Sure no problem. Give me a bit and I'll post details. From my background I can tell you there's a huge difference. Consider a Vette with 300 hp will run 150 mph mostly limited by air drag with somewhat less wheel bearing drag. A jet with 600 hp will run 90 mph mostly limited by water drag and somewhat less air drag. That's twice the hp for only 60% of the speed. What's up with that? Should the Vette focus on wheel bearing drag? Should the jet focus on air drag? I think not.
jer

[LVjetboy]

"Combine about 20 of these little things and I may gain a mile per hour."
That's not the question here. The question here is a trade-off, not combining 20 little things. Sure combining 20 little things if all positive add up. But what if you change a supposidely "little" thing and trade air drag for water drag...then what? Do you know or understand? Do you appreciate the difference between air and water drag?
jer

[djdtpr]

I think that everyone is missing the point made by everyoe that has posted on this!DIFFERENT SETUP DIFFERENT HARDWARE makes a difference.Lets take for instance JER's ride it runs 100 on a seriously conservitive setup.Now look at Moneysucker's ride everyone said that the nose was to high but they run the same speed but completely diferent setups.So the point is where is the sweet spot for the plates?Its gonna depend on what ya got.

[LVjetboy]

djd, I agree. But that "sweet spot" is what we (at least me) are trying to define in terms that fit more than one hull or engine. I truly believe there are guiding principles that can be known to achieve the best performance from our jets. Those principles based on science and the physics of how things work. Do we know them? No. Should we try to understand and know them...YES!. Can we know everything. No. But there are some general principles here that we can know and if we did know would help us make our jet faster. That's what it's all about.
What makes tunnel plates work and if they work...why? It's a simple question. But not so simple answer? Is it a water or air force? If both water and air then where's the transition? If you don't know that then what's the point? Do they benefit more on initial acceleration or top speed? Etc.
jer

[Cs19]

I think that everyone is missing the point made by everyoe that has posted on this!DIFFERENT SETUP DIFFERENT HARDWARE makes a difference.Lets take for instance JER's ride it runs 100 on a seriously conservitive setup.Now look at Moneysucker's ride everyone said that the nose was to high but they run the same speed but completely diferent setups.So the point is where is the sweet spot for the plates?Its gonna depend on what ya got.
we always miss the point, thats just ***boat forum for ya.

[PC Rat]

"Wow, and people spend so much time removing hook."
Did they have a tunnel? Apples to oranges.
Geez, I guess I'll take my sarcasm elsewhere. BTW what happened to the hippopotomus?
.

[LVjetboy]

That dog already barked. 3.8.
jer

[steelcomp]

wow...a guy gets a little sleep and look what happens.
Jer...I never said how significant the "thrust" was. It just hit me while I was thinking about all this. The aeordynamics of the boat are all related, and the way the air exits the tunnels is as much a part of the equation as anything. Weather or not it's measurable is moot. I'm not going to argue the significance of the fact, but the fact remains. What I stated is a fact, and since no one can say exactly "how' or "what" the tunnels are doing, no one can say that my observation is insignificant.
Water vs. air CD? (coefficient of drag) I'll find out, but it's a simple ratio. What's your point??

[WheelerDealer]

I have another question about some plates I saw on a Placecraft that a guy in Houston has. The plates on his boat have been dimpled on the bottom side like a golf ball, each dimple is about 1/2" in diameter. I asked the guy about it and he said that he didn't know why they were like that but that is how they were when he bought the boat. He bought the boat at a bankruptcy auction and says he doesn't know who it's previous owners were, but it was a center steer race boat. Anybody got a thought on the dimples??

[djdtpr]

djd, I agree. But that "sweet spot" is what we (at least me) are trying to define in terms that fit more than one hull or engine. I truly believe there are guiding principles that can be known to achieve the best performance from our jets. Those principles based on science and the physics of how things work. Do we know them? No. Should we try to understand and know them...YES!. Can we know everything. No. But there are some general principles here that we can know and if we did know would help us make our jet faster. That's what it's all about.
What makes tunnel plates work and if they work...why? It's a simple question. But not so simple answer? Is it a water or air force? If both water and air then where's the transition? If you don't know that then what's the point? Do they benefit more on initial acceleration or top speed? Etc.
jer
Jer i agree with you that there is a common baseline to start from.I dont think that the sweet spot will be the same setup on two seperate boats though especaily different type hulls.I would bet that if i put my plates where yours are and set my rideplate the same and the shoe the same i probably wouldnt run close to what you are and they are basicaly the same hulls.I always thought that the plate were an extension of the bottom and gave the boat a little extra to set back on and get alittle more lift.

[djdtpr]

I have another question about some plates I saw on a Placecraft that a guy in Houston has. The plates on his boat have been dimpled on the bottom side like a golf ball, each dimple is about 1/2" in diameter. I asked the guy about it and he said that he didn't know why they were like that but that is how they were when he bought the boat. He bought the boat at a bankruptcy auction and says he doesn't know who it's previous owners were, but it was a center steer race boat. Anybody got a thought on the dimples??
They do that so there isnt as much drag on the plates.If you look at the bottom of a rideplate you can see where the water almost kinda burns it or leaves friction marks.Its cause its flat.That is why the sell beveled rideplates.It is the same thing with the cav plates.

[Bob Hostetter]

Just a couple of thoughts regarding tunnels on boat hulls and water vs air drag..........
Water drag has a much higher effect on the performance of a boat then air drag for several reasons. The reason is that there is greater contact area, and greater forces pushing them together, which in turn results in maintaining greater contact area. The main advantage of tunnels in the hull is the reduction of that contact area by lifting the hull out of the water which causes a reduction in surface area contact volume on the bottom of the boat. You also reduce water drag because as the boat planes it is pushed upward by the water which reduces the wetted surface area.
Tunnel designs cause the front of the boat to lift which transfers the weight or roll center of the boat to move backwards to the transom, which is what helps keep the jet intake in the water. The only way to left the transom with air would be to control and compress the air trapped in the tunnels as they near the transom. This would require a tunnel shape that decreases in volume as it nears the transom which would cause an increase in air pressure in the tunnel which would work to push the hull upward. This is easy to measure by installing pressure sensors in the tunnels, one about midship, and the other say 10" in from the transom. The effectiveness of this would depend on the overall weight of the boat and the air speed/volume (boat speed) of the air moving thru the tunnel.
Using a plate at the exit of the tunnel to control or direct the flow of air exiting the tunnel is questionable at speeds normally seen in jet boats or any boat for that matter. In order for it to provide a measurable amount of thrust the air exiting the tunnel would have to be under a pressure equaling or exceeding the weight of the boat, and have an exit velocity exceeding the velocity of the boat. Since the air velocity will be a function of the speed of the air entering the tunnel (boat speed) and the pressure will be a function of the compression provided by the tunnel design it is unlikely that you would every be able to meet that requirement. However you could control the direction of the exiting air and use it to fill the low pressure area immeadiately behind the boat caused by the transom moving thru the air thus reducing aero drag. The effectiveness of this would be directly related to the speed of the boat, the faster, the greater the effect. You could also use plates to create an extension of the tunnels to further reduce the volume of the exit port, creating a ventura effect which would create an increase of available pressure increasing the lifting abilty of the tunnel. By controlling the overal shape of the tunnel extension you could route the air into the low pressure area at the transom, creating a benefit in both reduced water drag (lifting the hull, creating less contact area) and aero drag, reduction or elimination of the low pressure area at the transom. Keep in mind as you create more lift at the transom, you are raising the jet intake and at some point will start introducing air into the intake.
Aero drag over the top of the hull in most boats is a non issue. 1st we don't normally run the boats at speeds which create a measurable amount of drag (over say 150-170mph), and 2nd boats don't present a large enough profile to the air to generate large aero numbers. An area where we can work with the air in our speed ranges (up to say 110 mph) is in external air dams or wings. You see a lot of this in the upper drag boat classes such as the BAF where the wing is used to help the transom take and hold a set. But the same thing, in reverse, could be done to create lift................
Someone spoke about dimpling on a plate. Dimpling is done to reduce the total contact area between the plate or surface and the meduim it is in contact with. The concept is the same as a golf ball. By dimpling the surface you disrupte the air flow on the surface of the ball reducing the the total amount of surface contact area, and thus aero drag. It is a principle that works equally well with aero and water drag. However, just like steps in the bottom of a 'v' hull, it can have a destabilizing effect on the hull which increases as speed increases.

[cyclone]

Bob and DJD- it makes me wonder why the last few feet of the boat arent dimpled? I read about the golf ball thing before but never thought to apply it to a ride plate. I'd like to try that and see if there is a measureable difference in acceleration or top speed.

[WheelerDealer]

I would think it would be hard to do the dimple thing to the bottom of a boat unles they were real shallow, and can't you just imagine what that bottom job would cost. On the rideplate I don't guess it would be that hard to do, or for that matter the tunnel plates.
Cyclone, my guess is that if did the dimpled rideplate thing on a boat that ran as loose as yours did it might be too unstable, be hell, what do I know? I wish we could get one of the pros in here to see if any of them have tried any of the stuff mentioned in this thread.

[cyclone]

You're right. The dimple thing would be much easier to implement in the mold rather than afterwards.
I'm still curious as to what effect it would have. I'm going to try and find the correct mill tool to dimple my ride plate and see what happens.

[Lake Ape]

Just use a ball end-mill, I can set that up for you in a matter of seconds in Mastercam.

[cyclone]

I dont own a mill but I'm thinking that if I bring SuperDave the tool, mabye he'd be willing to dimple my ride plate for me. All in the name of science! :D

[Bob Hostetter]

Actually a 1/4" ball end mill and a CNC mill is what we used to use........

[cyclone]

Actually a 1/4" ball end mill and a CNC mill is what we used to use........
So you've dimpled a ride plate before? did you get any comparative data on a boat afterwards?

[moneysucker]

"Combine about 20 of these little things and I may gain a mile per hour."
That's not the question here. The question here is a trade-off, not combining 20 little things. Sure combining 20 little things if all positive add up. But what if you change a supposidely "little" thing and trade air drag for water drag...then what? Do you know or understand? Do you appreciate the difference between air and water drag?
jer
I have been right in every post and, "Do you know or understand? Do you appreciate the difference between air and water drag?" is BS. Obvoiusly I do know the difference and I do understand, otherwise I would be posting statements that are incorrect. I do not "appreciate" the difference between air and water drag, I acknowledge there is a significant difference but for you to talk to me like I am a retard is BS.
Your quote:
djd, I agree. But that "sweet spot" is what we (at least me) are trying to define in terms that fit more than one hull or engine. I truly believe there are guiding principles that can be known to achieve the best performance from our jets. Those principles based on science and the physics of how things work. Do we know them? No. Should we try to understand and know them...YES!. Can we know everything. No. But there are some general principles here that we can know and if we did know would help us make our jet faster. That's what it's all about.
There is no sweet spot for any two boats. Unless they are identical: hulls, bottom work, placement of and angle of intake,weight distribution, Hp, Fuel, Pump, thrust angle, Nozzle size, Identical boats and driver weight. No two boats will be the same optimum set up. There may be a "good enough" for two identical set ups in different boats but no ideal set up.

[bottom feeder]

Looks like were hitting PAR :D
Done the ball mill thing, slots, V slots, I can tell you one shape works better than all the others.

[Nucking futs]

WEll phill had no intrest nor did he design the tunnel.Phill built the inserts for the mold on the SWTD.The tunnel is the same bottom as the sw18 with some inserts in the mold and then some testing to the boat and then the mold was made.As for the plates, The reason they are there is to give lift. They will hold the air in longer and gives the boat more lift.You go up on the plates and it will exhaust the air faster and let the boat fall. They way i understood it and i was young then,but you are squeezing the air to make the boat lift.The pod is there only as a cover for the pump.It is a setback pump and the pod covers it to give it more support and cover the pump just to look pretty :D The plates will aid in some of the set up and is a big factor for the other things that need to be set up as well.The plates on a dialed in boat should be out of the water when it takes a set.I don't think anyone knows "when" they are out of the water, but on all the pics we have all of the race boats the plates are out of the water.I know of a few that have taken them off and there boat rides flat and it is real squirrly on the big end and they were reinstalled.So no they are not a band aid and that is the reasoning why they are there. Oh and here is the very first tunnel made....Timhttp://www.***boat.com/forums/attachment.php?attachmentid=8329&stc=1
[QUOTE]
I can't say were they "should be set" as each boat is different.but on mine i would start at 2* up and tune as needed.
As for other boats i could not tell you why the don't or if they should.I also have trim tabs on my cruiser only to adjust on the fly for water conditions that the p/d won't help.I also think the plates help with attitude just like the ride plate. I have seen different length plates on different boats so it also could stand to reason that a longer or shorter plate will do different things.Place crafts have shorter plates then the SW and that could be as the P/C have bottom mods made into the hull already.To bad Bill PLace isnt around anymore to ask him why they made them shorter.I have seen also on the crusader and bakers have shorter plates too but i cant answer why.
Tim
[QUOTE]
Did'nt i say all this way back when?I made it simple and to the point so everyone could come up with an "IDEA" why they were there.Im no rocket scientist, but that is how i remember it being described when they were building them.
TIm

[Bob Hostetter]

Cyclone,
The couple of times we tried it was on cav plates for flatbottoms. Never tried it on ride or tunnel plates for a jet but the principle would be the same. Didn't do any before and after testing so I couldn't give you any hard data. But as someone else has already stated if you can find 20 different areas to gain a small advantage in, it starts adding up.
Dimpling the last couple of feet of the hull would be interesting to test but difficult to do. If you tried to do with the mold you would have to make sure you had equal pressure across the mold when laying the glass in or you might end up with unequal dimples which could cause differnces in drag across the transom causing the hull to track crooked in the yaw axis. I would instead like to try small steps across the width of the hull, say about 1/4" deep probably starting mid point in the jet intake. This should provide excellent aireation of the hull, breaking the surface tension, and reducing drag. They could be cut with a router and be keep equal across the hull fairly easily. You could leave the strates intact to maintain directional stabilty which as surface tension is decreased may become a problem.
LVjet, at the speeds we run boats at trading water drag for air drag will always be a good thing. For one, the CD of air is much lower and two, much easier to manage. Air can be compressed and as such can be controlled and used to our benefit, water won't compress, at least not at the pressures we are discussing here, and as such is the largest hinderance to speed we encounter. Well that and adapting circular horsepower to forward motion using water as the medium.
There are a lot of things that could be tried to improve the performance of tunnels hulls, and I think a lot of them would show benefits. The problem is the market for these types of hulls is very, very small, the R&D would be expensive, and no one I know is willing to step up and finance it.
Moneysucker, if I am the one who pissed you off, sorry, it wasn't on purpose.
Back to lurking mode.....................

[Jeanyus]

I have had a boat with tunnel plates on it for a year , and thier is one thing that I learned about them that eveyone has in common.
Everyone have a differing opinon of them.
Ok. Carry on with the debate. I'm triying to learn. :) :rollside:

[Cs19]

In order for it to provide a measurable amount of thrust the air exiting the tunnel would have to be under a pressure equaling or exceeding the weight of the boat, and have an exit velocity exceeding the velocity of the boat..
Bob,Same goes for the water exiting the nozzle, Right? Once the nozzle cant keep up with or exceed the speed of the boat, you are no longer accelerating. Is this right ?
That would require some serious velocity coming off the tunnels to actually make the boat move faster than it already going.
I think this myth has been busted.

[steelcomp]

If I can say something about dimpling the plates...don't do it. I have to disagree with Bob on this one. The effect the dimples have on a golf ball are because the ball is traveling through air. In regard to that type of surface condition, you can NOT make the comparison between air and water. They aren't anything like eachother in those conditions. The small dimples only serve to cause more wetted surface area in water, and a terribly irregular one at that. The water will try and follow those irregularities and cause turbulance and drag. With the golf ball they're actually trying to ATTRACT the air as to create laminar air flow over the ball instead of turbulence. They want the air to stick to the ball and follow it's contour rather than have the ball force it's way through the air. The coefficient of drag in the air is so much less than in the water, they can afford the added drag which if FAR outweighed by the laminar airflow. A golf ball, or any sphere for that matter, isn't very aerodynamic at all, especially at the velocities of a hard driven golf ball. There was a post here earlier that stated how negative the effect a dimpled bottom of a boat had. No need to make the same mistake someone has already made, or repeat an experiment that was conclusive. Just because some guy with an expensive race boat had it done to his plates, dosen't mean it was right, or effective. But you guys already know that. These are some of the sharper minds here in this discussion, AFAIC.
The issue of water drag vs air drag is irrelevant here, because they don't have anything to do with eachother. The added air drag by changing the plate settings is probably immeasurable, where as the added water drag is I think a factor of four (for the CD of H20) for every knot increase in speed. Once the plates are out of the water, the drag is a non issue. In the water, big issue.

[steelcomp]

Quote moneysucker:
"There is no sweet spot for any two boats. Unless they are identical: hulls, bottom work, placement of and angle of intake,weight distribution, Hp, Fuel, Pump, thrust angle, Nozzle size, Identical boats and driver weight. No two boats will be the same optimum set up. There may be a "good enough" for two identical set ups in different boats but no ideal set up."
To me, the most important part of what moneysucker posted is the first sentence ... "There is no sweet spot for any two boats" ... I say this because it is physically impossible to layup and rig two absolutely "Identical" boats. I'd go a little further based on our drag racing experience and say that there is no one "Sweet Spot" for any one given boat for all ET's &/or Speeds as the quicker and/or faster any boat goes, the more things change ... in particular the longitudinal and (hopefully not as much) the transverse dynamic CG's and its interaction with the aero/hydrodynamics of a given hull.
I guess what I'm saying is that I feel we all have to Understand and "Tune" our boats to the purpose we wish to accomplish with them ... Sharing information between each other, no matter what types of boats each of us has, will help each of us individually ... Just a thought.
Bear, I think you hit the nail on the head by saying basically that there are no ideal sweet spots even on the same boat. Add 200 hp or 10 mph, and just about everytihgn goes out the window. The theories still apply, but the application is different. That is true for almost anything that functions in a dynamic state. Heck, just a change in the weather, and last weeks sweet spot is now a sour stain!
This is great forumatization at its best!
Now I have a BIG idea that I need to follow up on. Sorry...can't tell ya!!

[steelcomp]

Bob,Same goes for the water exiting the nozzle, Right? Once the nozzle cant keep up with or exceed the speed of the boat, you are no longer accelerating. Is this right ?
That would require some serious velocity coming off the tunnels to actually make the boat move faster than it already going.
I think this myth has been busted.
I disagree. I never said it was a measurable force, I was only analyzing the air coming out of the tunnels and it's reaction and relation to the back of the boat. If the air comes in the tunnel at the same speed of the boat, and is compressed to create higher pressure, it's going to exit the tunnel under higher pressure, and at greater speed then when it went in, therefore faster than the speed of the boat. It can't not. If the air is exiting at a higher pressure than it went in, especially into a low pressure area behind the boat, it's going to expand, and it can only expand in every direction equally, which includes toward the back of the boat, the side of the pod, etc. If the air is expanding against the back of the boat, it is, by definition, "pushing" on the back of the boat. Is it measurable? Probably not. Is it beneficial? It can't be anything but beneficial. To what degree? More than if it wasn't pushing. More than if there was a vacuum behind the boat trying to suck it backwards!!

[moneysucker]

Dimpling the bottom, at speed creates pockets of less resistance I have a couple of wake boards that are dimpled on the bottom. I would dimple anywhere but on the main pod, in front of the intake. The turbulence and possible air pockets could cause some cavitation. I like the idea of dimpling the plates. I will have a second set built and dimpled. I can always use one set on the boat I am building. My polisher won't like them but it is in the name of science.
For the water pushing the boat forward, I am sure you all have seen the spray and or a surfer at the end of a barrel ride where they are blown out of the tube.

[steelcomp]

Pops1 posted earlier...
We did a lot of testing between Deep Well (water) & Bench Air flow and learned a lot. I know we were told by those to be, that we were not testing apples & apples. yet both provided us juice.
A true but funny story- A custom boat builder in local HB who calls himself a design engineer holding over 40 patients, asked me to come see him. He had a problem-New 502 Motor- Jet Drive- in his custom looking 20' car boat which would only run 37 MPH. He was convinced it was another manufacture's pump causing him the problem.
A good friend of mine had a large business next door to him so I was some what aware of what was going on inside and for that reason I never called on them. Well any way I stop by as asked to meet him. Come to find out he was the one that had used my niece's 2 jet ski's to mock up his fire boat.
He tells me he had a new Patent pending bottom on this boat and it would run with the right drive in it. I look at the boat and then crawl under to look at the bottom. He dimpled the bottom with Golf Balls-The dimples were concave into the hull. I told him he had created the safest boat ever produced as it shure would not ever get on plaine. I gave him a phone number to get the bottom re-done and later heard the hull ran in the upper 50MPH range ,as it should stock. So watch your dimples!
I rest my case.

[Bob Hostetter]

Steelcomp,
Disagreeing is cool, however, dimpling should be move effective with water as a medium then with air. Water is heavier and can't react as fast to the changing surfaces that dimples would create. As a result there would be a separation between the surface of the plate and the surface of the water where the dimples were forming a depression, reducing the wetted surface, which would reduce the amount of drag. That turbulence that you spoke of is what you are looking for. Is causes a separation of the air from the water, allowing the air to get between the water and the plate surface. It is this principle that makes steps in 'v' bottom boats faster. Aero drag is lower then water drag.
Regarding the air exiting the tunnels, the air must be exhausted into the area directly behind the transom, and within the low pressure pocket. By using a standard tunnel plate you are creating a longer tunnel which moves the release point of the high pressure air further behind the transom. If it is moved too far back it will exit outside of the low pressure pocket and be of little use. However if you use the tunnel plate to direct the high pressure air directly into the low pressure pocket, yes you would effectively reduce the aero drag of the boat, possibly increasing the speed potential. You would not be actually pushing the boat but instead reducing the drag. In order to push the boat, the high pressure air would have to have a pressure higher then the weight of the boat. It would have to be a lot higher then the weight of the boat to compensate for the fact that as soon as exiting the tunnel there would be close to a 100% pressure drop because there is nothing to contain the escaping air and maintain the pressure. This would difficult to create and direct, but does not negate the advantages of reducing or eliminating the low pressure area behind the transom. A certain NASCAR car builder used to like to run the exhaust pipes from the motor and have them dump directly above the rear bumper and below the rear spoiler. It took everyone else a while to figure out why his cars were a couple of mph faster on the superspeedways, and nobody could draft on them.
CS-19,
yes you have the same problem with the water exiting the jet nozzle, once the boat velocity equals the exit water velocity you balance out and there is no extra thrust to push the boat faster. The problem with jet pumps is that the total amount of water you can force thru the pump is limited. Since the internal size of the pump is static, as you increase volume you must also increase velocity, which means you increase pressure. At some point you exceed the pressure capability of the housing and have a housing failure. Now if can could increase the volume and the velocity without increasing the pressure, you could increase the speed of the boat without blowing the pump. But this would mean increasing the internal volume of the bowl and the nozzle. You could also get a pressure drop if you reduced the internal friction of the water passing their the pump. This would require reducing the amount of contact that the water has with the pump walls (surface tension) and the only thing that comes to mind at the moment, dare I say it, is to dimple the inside of the pump.
Sorry, I couldn't help myself...................
For what it's worth, I have been out of racing for a long time, but this discussion reminds me of many a night I spent 15-30 years ago with hard core racers who would take these conversation's to the mill and make them happen. I miss those days....

[steelcomp]

Steelcomp,
Disagreeing is cool, however, dimpling should be move effective with water as a medium then with air. Water is heavier and can't react as fast to the changing surfaces that dimples would create. As a result there would be a separation between the surface of the plate and the surface of the water where the dimples were forming a depression, reducing the wetted surface, which would reduce the amount of drag. That turbulence that you spoke of is what you are looking for. Is causes a separation of the air from the water, allowing the air to get between the water and the plate surface. It is this principle that makes steps in 'v' bottom boats faster. Aero drag is lower then water drag.
Regarding the air exiting the tunnels, the air must be exhausted into the area directly behind the transom, and within the low pressure pocket. By using a standard tunnel plate you are creating a longer tunnel which moves the release point of the high pressure air further behind the transom. If it is moved too far back it will exit outside of the low pressure pocket and be of little use. However if you use the tunnel plate to direct the high pressure air directly into the low pressure pocket, yes you would effectively reduce the aero drag of the boat, possibly increasing the speed potential. You would not be actually pushing the boat but instead reducing the drag. In order to push the boat, the high pressure air would have to have a pressure higher then the weight of the boat. It would have to be a lot higher then the weight of the boat to compensate for the fact that as soon as exiting the tunnel there would be close to a 100% pressure drop because there is nothing to contain the escaping air and maintain the pressure. This would difficult to create and direct, but does not negate the advantages of reducing or eliminating the low pressure area behind the transom. A certain NASCAR car builder used to like to run the exhaust pipes from the motor and have them dump directly above the rear bumper and below the rear spoiler. It took everyone else a while to figure out why his cars were a couple of mph faster on the superspeedways, and nobody could draft on them.
CS-19,
yes you have the same problem with the water exiting the jet nozzle, once the boat velocity equals the exit water velocity you balance out and there is no extra thrust to push the boat faster. The problem with jet pumps is that the total amount of water you can force thru the pump is limited. Since the internal size of the pump is static, as you increase volume you must also increase velocity, which means you increase pressure. At some point you exceed the pressure capability of the housing and have a housing failure. Now if can could increase the volume and the velocity without increasing the pressure, you could increase the speed of the boat without blowing the pump. But this would mean increasing the internal volume of the bowl and the nozzle. You could also get a pressure drop if you reduced the internal friction of the water passing their the pump. This would require reducing the amount of contact that the water has with the pump walls (surface tension) and the only thing that comes to mind at the moment, dare I say it, is to dimple the inside of the pump.
Sorry, I couldn't help myself...................
For what it's worth, I have been out of racing for a long time, but this discussion reminds me of many a night I spent 15-30 years ago with hard core racers who would take these conversation's to the mill and make them happen. I miss those days....
That makes sense!! :D

[moneysucker]

. A certain NASCAR car builder used to like to run the exhaust pipes from the motor and have them dump directly above the rear bumper and below the rear spoiler. It took everyone else a while to figure out why his cars were a couple of mph faster on the superspeedways, and nobody could draft on them.
I have a friend who ran NASCAR a long time ago. He has told me all sorts of stories of ways to go faster. The shape of the bottom of the car, Washing the car, Clear coating over all the vinyl decals and a coat of wax actually made the difference between qualifying and not and was found in a wind tunnel. Little things do make a difference.
To reduce pressure you would have to reduce contact and/or friction in the pump on the high pressure side. I am leaning toward teflon coating the impeller, Bowl, droop and nozzle. I will let someone else try to dimple it all.
[QUOTE=Bob Hostetter]
For what it's worth, I have been out of racing for a long time, but this discussion reminds me of many a night I spent 15-30 years ago with hard core racers who would take these conversation's to the mill and make them happen. I miss those days....
Don't worry, there still are people on here that will do things just to prove everyone who said, "it will never work." wrong. There are a lot who don't think that graphite coating the ride surface makes a diference either.

[WheelerDealer]

I think I am going to give the dimpled ride plate deal a try myself. after I get a decent baseline on the boat, I will swap out ride plates and see what happens........hopefully I will not get wet.. :smile: :smile:

[Cs19]

bob, thanks for the reply.
Lets get ***boat to do a story on it (dimpling).. I know of a boat thats ready for the scrap yard, but still has a little life left in it and its a tunnel botttom. You could make a fixture and use a hand drill and dimple the whole running surface, other than the entry and see what happens.

[LVjetboy]

"Jer...I never said how significant the "thrust" was. Aeordynamics of the boat are all related, and the way the air exits the tunnels is as much a part of the equation as anything. Weather or not it's measurable is moot."
Not moot but debatable. I'm not convinced air exiting the tunnels gives any thrust but you stated...
"I'm not going to argue the significance of the fact, but the fact remains. What I stated is a fact"
How is that? How does air exiting the tunnels give thrust and why is what you posted a fact?
"Water vs. air CD? (coefficient of drag) I'll find out, but it's a simple ratio. What's your point??
Find out and post. Yes I know what CD is. My point is simple. Water drag is way more important that air drag and the purpose of the tunnels is to use aerodymanic forces to lift and reduce water drag. Not to provide some bogus air thrust with tunnel plates.
jer

[LVjetboy]

"I do not "appreciate" the difference between air and water drag, I acknowledge there is a significant difference but for you to talk to me like I am a retard is BS."
Didn't intend the retard thing. I was focusing on your 20 different things comment. I fully understand how 20 different positive changes can add up. But what if just one of those changes cancels out 18 of the others? Not so unlikely if you're dealing with water drag. And we are talking tunnel plates...not a guaranteed performance enhancement.
You may read, add this intake and increase you performance by 15%. Then buy this or that filter and gain 10 hp. Add a turbo swirl carb spacer and boost your power even more. But wait, our headers will give you 25 hp more! Proven on the dyno. How about a new computer ignition chip? You'll get 10-15 more hp, ETC. If you add up 20 alledged performance hop ups and claimed gains, you'll have an 800 hp engine you think? No. Seen the same in the aircraft industry btw.
My only point was, there's a huge difference in changes that affect hydrodynamic vs aerodynamic drag. And us regular jet boaters don't always appeciate or understand that.
jer

[LVjetboy]

"Just because some guy with an expensive race boat had it done to his plates, dosen't mean it was right, or effective."
Yes, yes yes!! I was going to post that point but you beat me to it SteelComp.
jer

[LVjetboy]

"There is no sweet spot for any two boats. Unless they are identical: hulls, bottom work, placement of and angle of intake,weight distribution, Hp, Fuel, Pump, thrust angle, Nozzle size, Identical boats and driver weight. No two boats will be the same optimum set up. There may be a "good enough" for two identical set ups in different boats but no ideal set up."
Of course not. And understand, my posts or others are not implying we expect one size fits all. BUT there ARE guiding principles. And there are things that can be known about how our boats work...some of those things not yet known. And there are basic physics about how air drag and water drag affect our hulls. In fact, enough can be known to give basic guidance to how we tune even though our hulls and setups are different. And that's what we are talking about here and trying to understand more. Not implying that one size fits all copy?
jer

[LVjetboy]

"Little things do make a difference."
Yes they can. But only if those little things all add in the right direction not subtract.
So let's talk about dimpling...that seems to be the interest here now. Does anyone know how dimpling affects a golf ball and are we going to assume that applies to water drag on a hull? Be careful...apples to apples. What about laminar vs turbulent flow transition and drag? What about dimple size and speed? If dimpling is gauranteed to reduce drag then why aren't submarines dimpled?
I'm all for new ideas and experiment, but don't jump to conclusions.
jer

[LVjetboy]

"dimpling should be move effective with water as a medium then with air."
Don't know about that. I question the "should be more effective" The Navy's done quite a few test with different surface treatments (groove, dimples, orientation, etc) in contact with water. Read those then explain to me way dimples should(?) be more effective.
I suggested another approach to reducing water hull friction long ago on RJB-I. That was air injection. Instead of creating a vacuum like a dimple in hopes of cutting drag, injection would create a positive force and air cushion...absolutely reducing water drag. Think air table hocky puck. The pressure would not have to be that much. So far, not much interest.
jer

[Old Guy]

I suggested another approach to reducing water hull friction long ago on RJB-I. That was air injection. Instead of creating a vacuum like a dimple in hopes of cutting drag, injection would create a positive force and air cushion...absolutely reducing water drag. Think air table hocky puck. The pressure would not have to be that much. So far, not much interest.
jer
Hey jer,
I've wanted to do the "air injection" program for quite a while. However I have a tunnel hull and it's hard to imagine where to introduce the air so as to be effective but not cause cavitation in the pump.
How about "air washed" tunnel plates. Plates installed in the tunnels slightly back from the c/g. The plates would be movable under way.
I first thought of this as a frictionless trim tab. Lift without the "hook" effect.
Roger

[bottom feeder]

FYI,
The dimples are on a golf ball to make it stay in the air longer :cry:
"Just because some guy with an expensive race boat had it done to his plates, dosen't mean it was right, or effective."
Who was it and how have you proved them wrong?
When was it stated the dimple was best?

[Bob Hostetter]

Lvjetboy,
Submarines don't have any kind of surface irregularlity because the turbulence that reduces drag also causes noise. Submarines by design are supposed to be sleathy, and noise is a very bad thing...................
Actually dimples probably would not be the best shape, micro grooves cut at 90 degrees to the direction of travel would probably be better.
Air injection under the hull should create the same effect if you could figure out how to do in a controllable and repeatable manner. Thats basicially what you are doing by having a tunnel hull in the 1st place. Since you already have a trapped source of high pressure air you could probably cut bleeder veins at about a 45 degree angle to the tunnel that gently taper out to feed the air to the ride surface. But if the boat started to walk around on the transom you might have a problem with the edge of the vein catching the water, like a chime, and causing a rapid change of direction. We had the same problem when we tried adding skirts to the rear of a hydro to trap the air under the tail. I will have to think about that one. Gee, something else I can spend time on instead of making money.....lol

[WheelerDealer]

Has anyone one noticed that all of the "pros" are staying away from this thread? I wonder why? There is a lot of good information here, keep it coming!

[moneysucker]

Has anyone one noticed that all of the "pros" are staying away from this thread? I wonder why? There is a lot of good information here, keep it coming!
All the "pros" will stay out because they are just like all of us they got where they are today by experimenting and learning from others.
Dimpling only works at a certain speed. Low speeds will allow the water to follow it and does create more surface area for drag. At high speed these dimples will work the way they are intended breaking contact with the water. I hate to admit it but the benifits may only be useful for top speed not ET.

[WheelerDealer]

Your probably right moneysucker, but wouldn't it be cool to be different? I am thinking more along the lines of experimenting more with plate lengths than dimpling, who knows, it might be fast enough to scare me and I won't want to find any more speed.

[moneysucker]

Your probably right moneysucker, but wouldn't it be cool to be different? I am thinking more along the lines of experimenting more with plate lengths than dimpling, who knows, it might be fast enough to scare me and I won't want to find any more speed.
Problem is you have a lot of experimenting to do. You have to try different lengths but you have to adjust the plates to see where they are best at each length. That is a lot of time to spend on the water in one day to get accurate results. The rule in boating is to only change one thing at a time. Otherwise you can negate a change and not realize the gain and change direction and do the wrong thing.

[WheelerDealer]

I definitely have a huge learning curve going from the Youngblood TX-19 to the SWTD. And I know you are right about the one thing at a time thing.

[moneysucker]

I definitely have a huge learning curve going from the Youngblood TX-19 to the SWTD. And I know you are right about the one thing at a time thing.
If you have any questions me, rubber duck or Psycho squid, AKA Petrofied.will be glad to help you.

[Nucking futs]

If you have any questions me, rubber duck or Psycho squid, AKA Petrofied.will be glad to help you.
And you guys know What?? How to go a hundred with 1200 H.P. Thats not difficult......oops wrong thread sorry.... :D

[WheelerDealer]

Thanks, I appreciate it and I will need it I'm sure.

[steelcomp]

AAhhh...the submarine example...I wondered when someone would bring that one up. Bob stated that subs don't have any type of surface treatment because they want to be silent. Well, the one treatment they do use is air bubbles, and for that very reason. The noise vibrations won't travel through the air as it does the water when it surrounds the sub. Noises inside the sub are insulated by this cushion of air bubbles.
I've also thought about the air injection idea, and even thought of a way to do it. Lets face it, the CD of air is immeasurable as compared to the CD of water. For example, to illustrate how low the CD of air is, take an unloaded lightly oiled ball brg. Riding on a film of oil, let's say the ball brg's CD is .001. An air bearing of the same size would have a CD of .000001. (there are such things as air bearings. LV mentioned one earlier, the "bearing" that an air hockey puck rides on) Taking bleed air off the pump is too complicated. Using a small CO2 bottle like what activetes shifters would work, especially for drag racing. So you use a whole cyl in a run? Swap it out for a full one. No big. I know how to plumb it as well. What I'm in the process of figureing out is the best pattern of air. We'll see.
AFA dimpling your cav plates...have at it. I doubt if you could measure the difference even if you reduced the friction to zero. Also, like moneysucker said, it's most likely to only work at speeds where the water and air will seperate, and if your set up is right, the plates will be out of the water at that speed. Below that speed they will only create more drag, which could definately be measured. Remember...the CD of water increases dramatically with speed and/or surface area. I think it's a factor of four with every knot. I still think the dimpling is a mistake on the bottom of the boat.
If you guys really want to know who has the ultimate in reduced drag on a boat hull, talk to the guys that run the World Cup Sail Boats. They're on the leading edge of every applicable technology there is for gaining speed in the water with very limited power.

[steelcomp]

There is an excellent example of a perfect underwater design that an ingenious designer came up with. It's called an Albacore tuna. A lot caould be learned from one, if you were to look closely. Having cought quite a few, I have spent considerable time looking at one. First thing you'll notice, is there's no surface irregularities on one. Smooth as glass. Their fins fold in flush with their bodies. Even their eyes are flush as can be. There are few fish that can move through the water like an Albacore, and they are clearly designed with one thing in mind. Speed.

[steelcomp]

And you guys know What?? How to go a hundred with 1200 H.P. Thats not difficult......oops wrong thread sorry.... :D
Don't be a dick.

[PC Rat]

Looks like were hitting PAR :D
Done the ball mill thing, slots, V slots, I can tell you one shape works better than all the others.
Please do.
-

[steelcomp]

"Little things do make a difference."
Yes they can. But only if those little things all add in the right direction not subtract.
So let's talk about dimpling...that seems to be the interest here now. Does anyone know how dimpling affects a golf ball and are we going to assume that applies to water drag on a hull? Be careful...apples to apples. What about laminar vs turbulent flow transition and drag? What about dimple size and speed? If dimpling is gauranteed to reduce drag then why aren't submarines dimpled?
I'm all for new ideas and experiment, but don't jump to conclusions.
jer
Jer...I tried to explain golf ball dimpling earlier, but maybe it wasn't clear. Maybe this will help. This is from Bob Thurman, an aerospace engineer that designs golf balls for Wilson Sporting Goods.
The dimples, those little indentations on the surface of a golf ball, help it in its flight from tee to hole.
"With a golf ball, the dimples actually create turbulence, which keeps the airflow attached to the ball, producing a smaller wake and reduced aerodynamic drag," said Thurman. "With a smooth ball the wake separates much earlier from the ball, creating a large wake and tremendous drag forces."
He added that three primary factors determine the performance of a golf ball-the amount of surface covered by dimples, the angle that a dimple breaks from the surface of the ball, and dimple depth.
"The maximum amount of the surface that can be covered with dimples is about 80 percent," he explains. "Changes in how sharp the angle is where the dimple breaks from the surface of the ball and dimple depth provide room for the most variables."
As a general rule of thumb, deeper dimples produce lower, flatter trajectories. Shallow dimples produce higher, ballooning trajectories. The key, Thurman says, is to create a dimple with enough depth to produce air turbulence around the ball as it rotates in flight. That helps the ball penetrate what engineers call "the force barrier"-the resistance that builds up as the ball moves through the air.
Jer...I think it's safe to say that this isn't the result we're looking for in the design of the bottom of a boat. I also think it's safe to say that the comparison between dimples on the bottom of a boat reacting to water can not be compared to dimples on a golf ball reacting to air .

[WheelerDealer]

[i]steelcomp originally posted...[i]
There is an excellent example of a perfect underwater design that an ingenious designer came up with. It's called an Albacore tuna. A lot caould be learned from one, if you were to look closely. Having cought quite a few, I have spent considerable time looking at one. First thing you'll notice, is there's no surface irregularities on one. Smooth as glass. Their fins fold in flush with their bodies. Even their eyes are flush as can be. There are few fish that can move through the water like an Albacore, and they are clearly designed with one thing in mind. Speed
I've got it, I will have some plates made that look like Albacore Tuna fish, yeah that's the ticket!
They are some seriously fast fish, and although my comment was meant to be humorous, we could all learn a lot by studying the designs in nature.

[steelcomp]

There is an excellent example of a perfect underwater design that an ingenious designer came up with. It's called an Albacore tuna. A lot caould be learned from one, if you were to look closely. Having cought quite a few, I have spent considerable time looking at one. First thing you'll notice, is there's no surface irregularities on one. Smooth as glass. Their fins fold in flush with their bodies. Even their eyes are flush as can be. There are few fish that can move through the water like an Albacore, and they are clearly designed with one thing in mind. Speed.
I've got it, I will have some plates made that look like Albacore Tuna fish, yeah that's the ticket!
They are some seriously fast fish, and although my comment was meant to be humorous, we could all learn a lot by studying the designs in nature.
Nature is the perfect design. :D :rolleyes:

[WheelerDealer]

Amen brother!

[Mr.&Mrs.Budlight]

A couple of yrs ago I read an article where Reggie Fountain set a new speed record for powerboats by using air vents on the deck to pack extra air under the hull thru hoses routed thru the interior of the boat! The deck vents were shapped by that nasa design that has no drag as air passes over it. Nascar uses it to vent air into car with no drag. Why wouldn't that work for a jetboat? Budlight :idea: :confused:

[steelcomp]

A couple of yrs ago I read an article where Reggie Fountain set a new speed record for powerboats by using air vents on the deck to pack extra air under the hull thru hoses routed thru the interior of the boat! The deck vents were shapped by that nasa design that has no drag as air passes over it. Nascar uses it to vent air into car with no drag. Why wouldn't that work for a jetboat? Budlight :idea: :confused:
It certainly would work!! It's called an NACA duct, or "nacka" duct. Reggie has a lot more boat to work with, as far as installing something like that, but the principle is definately applicable. Introducing the air into the bottom is the trick. I think he used his steps as places to introduce the air. It's a little more difficult on a flat surface.

[Mr.&Mrs.Budlight]

maybe if you turned the duct backwards on the outlet? :confused: Budlight

[steelcomp]

maybe if you turned the duct backwards on the outlet? :confused: Budlight
Ummmmm..............no. :D

[Nucking futs]

Don't be a dick.
Take a chill pill, Trying to lighten the mood.That coment had nothing to do with you......

[steelcomp]

Take a chill pill, Trying to lighten the mood.That coment had nothing to do with you......
Me take a chill...I was just messin witcha. :frown:

[Cs19]

Steel, Futs is homies with moneysuck.. dont worry about it.
Lv, Factory Kawasaki watercraft racing dumps their exhaust out of the bottom of the hull, in 3 different places, in attempt to get lift..At least they did when i was a fanatic and used to drool over their stuff..It may be wishful thinking since the 3 cylinder 2 strokes dont pump all that much air, but they do ok..Nothing like a big block though..
Reggie fountains idea..Well theres no way i would be interested in introducing more air underneath my boat than it already gets..Plennnty for me.
Not trying to bash your post Bl, thanks for the post, interesting idea for sure.

[moneysucker]

No, It had to do with me. Futz, you are the reason I polish my motor.
So you can see the look on your face while M$ is in front of you.
Can we get back to arguing... er, debating about tunnel plates and dimples.

[steelcomp]

Steel, Futs is homies with moneysuck.. dont worry about it.
Lv, Factory Kawasaki watercraft racing dumps their exhaust out of the bottom of the hull, in 3 different places, in attempt to get lift..At least they did when i was a fanatic and used to drool over their stuff..It may be wishful thinking since the 3 cylinder 2 strokes dont pump all that much air, but they do ok..Nothing like a big block though..
Reggie fountains idea..Well theres no way i would be interested in introducing more air underneath my boat than it already gets..Plennnty for me.
Not trying to bash your post Bl, thanks for the post, interesting idea for sure.
I'm not worried. Didn't mean anything by it.
CS...the kind of air we're talking about isn't more air in the tunnels, it's just enough air to create a bubble stream under the running surfaces. This would essentially put the boat on little air ball bearings. VERRRRRRY slippery. :idea:

[WheelerDealer]

I'm thinking that boat Reggie was driving weighed a little bit more than the average 18-20ft low-pro jetboat does and needed all the lift it could get.. Damn, I sure wish I had Reggie's budget!

[Cs19]

I'm not worried. Didn't mean anything by it.
CS...the kind of air we're talking about isn't morte air in the tunnels
i fully understand the concept ..Budlights post about fountains air ducts didnt mention where it was being released,in the tunnells or under the running surface.
I like the idea.

[steelcomp]

i fully understand the concept ..Budlights post about fountains air ducts didnt mention where it was being released,in the tunnells or under the running surface.
I like the idea.
I'm not sure that Fountain makes a tunnel. Thats why I was thinking they were releasing the air into the steps on the bottom. I'm working on this one.

[steelcomp]

I'm thinking that boat Reggie was driving weighed a little bit more than the average 18-20ft low-pro jetboat does and needed all the lift it could get.. Damn, I sure wish I had Reggie's budget!
I'd like to have the spare change at the end of Reggie's day!!

[Squirtin Thunder]

This tread is closed !!!!

[Cas]

ok, I haven't read through all the posts, just the first couple of pages. Why not just get a piece of clear tubing about 15' long, drill a hole into the plate, insert tube and run it forward to your seat. When you get to the point the plate is out of the water, you stop getting wet :D
oh yea, then look at your tach to see what rpms you're at, convert it to mph and you've got your answer ;)

[LVjetboy]

"Hey jer, I've wanted to do the "air injection" program for quite a while. However I have a tunnel hull and it's hard to imagine where to introduce the air so as to be effective but not cause cavitation in the pump."
Inject it lateral, outboard from the pump intake. With my tunnel you could inject on the outer sponsons and outboard of the fins on the center pod...etc. There are lots of places no matter the hull design that can benefit from friction reduction not in direct path of pump intake.
The biggest challenge I see is someone willing to butcher their hull to try this idea. With an aluminum hull easier. With fiberglass? Donno.
But the payoff? How about 10 mph more top end with no more hp? Think supercavitation. All it would take is someone brave enough to take the first step. And the pressure required not that much...means not that exotic of a delivery system and a whole lot longer lasting supply. I think I calculated less than 5 psi way back when.
jer

[LVjetboy]

"Actually dimples probably would not be the best shape, micro grooves cut at 90 degrees to the direction of travel would probably be better."
That's my point. Dimples may if fact not be best for our application and may actually increase drag. With a golf ball they encourage BL transition to turbulant flow (not good by itself) but also reduce BL separation (better than turbulant flow losses) So they appear to work in that application. But in a tunnel plate?
A tunnel plate is not a golf ball excuse me.
So let's talk micro grooves. At what height and width? Are you sure about 90 degrees? More importantly, does that Navy research on micro grooves really apply to our jet boats? What speed and hull design tested. You know what I'm talking about. Yes those Navy studies speak a lot more towards our application than say, comparing a golf ball to a jet hull. But still, they fall short of our typical application.
jer

[LVjetboy]

"Has anyone one noticed that all of the "pros" are staying away from this thread? I wonder why? There is a lot of good information here, keep it coming!"
Are you saying we're not pros? :D j/k
Seriously...I do not care. Realistically, I think pros have reputation at stake so carefully pick their posts and battles. A "pro" will understand their knowledge limit and not blatantly make that known. If you were they wouldn't you? If I was them I'd do the same. But do you really think they know all the answers to these questions? I think not. If so you're mistaken.
So if someone assumes a "pro" does not post to a controversial thread just because they don't like the challenging or controversial theme? Then maybe they should consider that forum Ghandi opposes the exchange of new ideas...some with potential to break out of the status quo.
And "pro" status can be overrated.
jer

[LVjetboy]

On the subjet of Cd. I'd say Cd's a lot less influence on water drag than density and viscous effects. After all, how much does Cd change? How much density? The different between air and water density about 1 to 1000. What is the difference between Cd air and Cd water?
jer

[kojac]

"Has anyone one noticed that all of the "pros" are staying away from this thread? I wonder why? There is a lot of good information here, keep it coming!"
Are you saying we're not pros? :D j/k
Seriously...I do not care. Realistically, I think pros have reputation at stake so carefully pick their posts and battles. A "pro" will understand their knowledge limit and not blatantly make that known. If you were they wouldn't you? If I was them I'd do the same. But do you really think they know all the answers to these questions? I think not. If so you're mistaken.
So if someone assumes a "pro" does not post to a controversial thread just because they don't like the challenging or controversial theme? Then maybe they should consider that forum Ghandi opposes the exchange of new ideas...some with potential to break out of the status quo.
And "pro" status can be overrated.
jer
You got that right.
If a pro knew and understood the principles they would have tried them and you would probably be hearing from them now to instill new confidence in their knowledge and therefore assuring renewed business.
Very interesting and enjoyable thread.
Kojac

[Bob Hostetter]

Actually the mirco grooves idea came from one of the engineers that does some consulting work for me. I described what we were talking about here and his comment was, "oh we already tried that, mirco grooves work better". Of course he also suggested we convert the plates to adjustable and use a fly-by-wire system to control them using a gyro to drive the mircoprocessor to maintain the angle of attack and yaw angle. He works at JPL for his day job and is pretty sharp so he may be right. Of course I recently decided to never ride in a van with him again.......
I am not sure that creating more 'lift' in a tunnel hull is a good thing. At least it wasn't in my old Eliminator Daytona. You need to make sure it was transom lift and not bow lift, and if it was transom lift at some point you would have a problem with lifting the jet intake out of contact with the water surface. I would stay with the idea of reducing drag instead.
I think improvements in jet performance in the future will be found in two areas. Drag reduction and increasing the water flow and flow velocity thru the pump itsself.
I have always wanted to try a variable flow nozzle that was controlled by either boat speed and/or engine rpm with a driver override. It should allow you to run a larger impeller which should equal more top end. All you would need to do is......but thats another story.

[WheelerDealer]

LVjetboy originally posted...
Realistically, I think pros have reputation at stake so carefully pick their posts and battles. A "pro" will understand their knowledge limit and not blatantly make that known. If you were they wouldn't you? If I was them I'd do the same.
I probably would. I think you read a little more into my post about "pros" than I had intended. Just because someone is in the business doesn't automatically give them the answers to all the questions, however I do think that some of the pros have probably tried some of this stuff but are not willing to share the information they have obtained, and I completely understand that. They are the ones who spent the time, blood, sweat and tears so why should they divuldge ever little secret they know?
The only thing that technically makes a pro a pro is the fact that they do it for a living. Just because you charge someone to do something for them doesn't give you infinite knowledge and make you a guru. That being said though, when you do something for a living for a long time you tend to learn quite a bit, and the more you things you attempt to do the more you will learn, that is why the "pros" are usually the go to guys in the jet boat business in my opinion.

[moneysucker]

I thought a Pro was someone who used other peoples stuff and money to experiment with and do R&D.

[WheelerDealer]

moneysucker originally posted...
I thought a Pro was someone who used other peoples stuff and money to experiment with and do R&D.
Yes, your definition is much better than mine, my bad!

[UBFJ #454]

Been watching this thread when I've had time (Mike & I have been taking our boat totally apart and redoing everything for next yeat ... new nuts, bolts, wiring, all the etc.'s plus pump teardown/refurb., next phase bottom work, loader construction, etc. ... Refiting for next year will be done, except for the motor, by the end of next week).
A couple of comments:
1st - Anyone ever consider that these "Pro's" y'all seem so willing to put down (for no constructive reason that I can see) may have no other reason for posting other than they have Businesses to Run ... Families To Be With (after boat work) ... Some More Important "Other Things" to do other than sit and read whatever is posted on the Internet and respond?
2nd - You want a "Dimpled" Ride Plate??? ... Run it a few seasons and you'll have a caviation pitted pattern on the bottom of it "Custom Fit" to your particular boat (Fit by The Natural Laws of The Universe) ... Don't mean to belittle what you guys are asking questions about, but, I think they, your questions, have to do with speeds far beyond what is Safe on our lakes and rivers ... above say, 130 -140mph ... And, far beyond where you really want to go ... Unless, your Racing.
Just some comments before taking a shower and getting all this Itchy fiberglass off me.

[WheelerDealer]

I wasn't meaning to put any of the pros down Bear, you know me better than that. My post to moneysucker was meant in fun.
PS. I tried to call you yesterday

[UBFJ #454]

Wheeler-
I Know That ... My comments weren't directed at you, or, for that matter anyone else ... Just commenting that a lot of people have other lives than boats though boats and the improvement of boating ... be it recreational or racing ... may be an integral part.
Re .. Call ... Musta been somewhere under, over, or, back of the boat ... or ... dealing with a part in hand ..... Sorry, I didn't hear the shop phone.

[steelcomp]

Wow, Jack, what on earth would we "amateurs" have done without that piece of wonderfully constructive criticizm!! :sleeping: Been watching this thread when I've had time (Mike & I have been taking our boat totally apart and redoing everything for next yeat ... new nuts, bolts, wiring, all the etc.'s plus pump teardown/refurb., next phase bottom work, loader construction, etc. ... Refiting for next year will be done, except for the motor, by the end of next week).
A couple of comments:
1st - Anyone ever consider that these "Pro's" y'all seem so willing to put down (for no constructive reason that I can see) may have no other reason for posting other than they have Businesses to Run ... Families To Be With (after boat work) ... Some More Important "Other Things" to do other than sit and read whatever is posted on the Internet and respond?
2nd - You want a "Dimpled" Ride Plate??? ... Run it a few seasons and you'll have a caviation pitted pattern on the bottom of it "Custom Fit" to your particular boat (Fit by The Natural Laws of The Universe) ... Don't mean to belittle what you guys are asking questions about, but, I think they, your questions, have to do with speeds far beyond what is Safe on our lakes and rivers ... above say, 130 -140mph ... And, far beyond where you really want to go ... Unless, your Racing.
Just some comments before taking a shower and getting all this Itchy fiberglass off me.

[moneysucker]

Wheeler-
I Know That ... My comments weren't directed at you, or, for that matter anyone else ... Just commenting that a lot of people have other lives than boats though boats and the improvement of boating ... be it recreational or racing ... may be an integral part.
Re .. Call ... Musta been somewhere under, over, or, back of the boat ... or ... dealing with a part in hand ..... Sorry, I didn't hear the shop phone.
That and most of the "Pros" who posess a lot of knowledge don't do computers. They build boats

[Cs19]

... Just commenting that a lot of people have other lives than boats
Must suck to be one of those people. :)
Its like a lifestyle for some of us.

[moneysucker]

.".. Just commenting that a lot of people have other lives than boats"
People like that don't like me.

[LVjetboy]

"Actually the mirco grooves idea came from one of the engineers that does some consulting work for me. I described what we were talking about here and his comment was, "oh we already tried that, mirco grooves work better"
I read a Navy study on hull micro grooves and orientation. Now I can't find it. If I remember right, groove orientation was a factor as well as geometry. And of course Reynolds number comes into play so I'm not sure if their test results have anything to do with our jet boat performance. That's a huge difference overlooked in the simple golf-ball-dimple-reduces-drag theory.
"Of course he also suggested we convert the plates to adjustable and use a fly-by-wire system to control them using a gyro to drive the mircoprocessor to maintain the angle of attack and yaw angle."
That's where I draw the line. Adjustable plates...sure, but a gyro? No. I may go with some automation, but stop way short of space shuttle mentality. :) I think you have the right focus though. Drag reduction and pump efficiency.
Did anyone check out supercavition? With an aluminum hull you could hog out recesses for aluminum plates with angled injection holes and try these ideas.
Why does a bullet travel a few feet in water and thousands of feet in air? Could there be a huge difference in drag between water and air you think?
jer

[LVjetboy]

"They (pros) are the ones who spent the time, blood, sweat and tears so why should they divuldge ever little secret they know?"
I'm sure some won't. Does that mean we shouldn't challenge a pro to reveal? Or question alleged secrets no matter the poster? If they choose not to back up their knowledge or experience that's their business. I respect those who do post yet acknowledge their limits. But I'll always challenge an idea I think questionable no matter the source, newbie or pro.
Then let the chips fall.
jer

[LVjetboy]

"1st - Anyone ever consider that these "Pro's" y'all seem so willing to put down (for no constructive reason that I can see) may have no other reason for posting other than they have Businesses to Run"
Some challenge a pro, some consider pro posts gospel. If you're talking to me Bear, you know where I stand. Yes most pros have a business to run. Yes they have experience in testing some of us jetters don't have. But everyone posting has different experience and knowledge to share. If a pro is intimidated by posters, and decides not to post...their loss in my opinion.
I will challenge any pro; JackMc, Dave Ebbert or Duane if I have a different opinion. Even though the've all contributed to the performance of my jet. You copy? That's me and you should know me by now. The true value of the internet is information. If I challege a pro and they prove me an idiot with their experience...then those reading the post will understand I'm an idiot.
Or we could all just sing along cum-by-ya with the alleged pros.
jer

[UBFJ #454]

Jer -
My post wasn't directed toward anyone in particular ... Just a general comment, that's all. I think everyone should ask questions of everyone posting ideas ...
What I don't care for though is what I perceive to be a "Negative Context" attributed to people who make their living working with and/or racing boats ... Like the only reason they post is to "Blow Their Own Horn".
Maybe it's just me.

[UBFJ #454]

Oh Yeah, Forgot to mention Mike & I put "Dimples" on the back/intake side of our boats keel bubble ... Think it's going to help us get water into the intake and pump and, make us go faster?

[WheelerDealer]

BEAR_454PE originally posted...
Oh Yeah, Forgot to mention Mike & I put "Dimples" on the back/intake side of our boats keel bubble ... Think it's going to help us get water into the intake and pump and, make us go faster?
:D, Hey Bear, I hope y'all got the angle of the dangle right!

[djdtpr]

Oh Yeah, Forgot to mention Mike & I put "Dimples" on the back/intake side of our boats keel bubble ... Think it's going to help us get water into the intake and pump and, make us go faster?
Air bearings may cause the water to be so fast it bypasses the intake.But dont worry the thrust of the air exiting the tunnels will have a thrust afect and may create a greater push than the jet. :D

[LVjetboy]

"Oh Yeah, Forgot to mention Mike & I put "Dimples" on the back/intake side of our boats keel bubble ... Think it's going to help us get water into the intake and pump and, make us go faster?"
No. But then if you subscribe to dimples on everything no matter the physics makes you go faster then maybe you'll think so.
jer

[Cs19]

Oh Yeah, Forgot to mention Mike & I put "Dimples" on the back/intake side of our boats keel bubble ... Think it's going to help us get water into the intake and pump and, make us go faster?
Nope.
Jak, your kidding right?

[UBFJ #454]

Chris - Yeah.

[Squirtin Thunder]

I was thinking about trying to come up with some type of system that would tell you at what speed your tunnel plates came out of the water. Can anyone think of a simple way to install some kind of sensor/pick-up type system that could somehow be mounted temporarily to one of the tunnel plates and connected by impact tube or electrics up to a gauge in the cockpit. Could it be as simple as using a plain old speedo pick-up mounted somehow on top of the plate to where the pick up hole was slightley lower than the bottom of the plate and then whenever the plates came out of the water the gauge would drop to zero???? Let's put our heads together and come up with a way to best do this and I will try it on my Southwind Tunnel Dragster. I think it might be another good tuning instrument. I guess it would only apply to a few different hulls though..SWTD, Placecraft, Bahner, Crusader, Mach One????
Anything this guy says is bullshit !!!!

[sanger rat]

Don't hold back Jim. Tell us how you really feel.