Burning ride plate

[Squirtin Thunder]

OK here it is with out pics as of yet. I some how broke the bolts that hold the turnbuckles to the transom. I also have pitting and the speed coating has come off the center of the ride plate right behind, about 2" back, the apex of the shoe area !!! It looks to me to be cavitation burns !!! Why would this happen ??? Now my ride plate is adjustable by turnbuckles and the pillow block that holds to the transom has broke off. Now would this be like a week spring in a V-Drive and sucking the plate ???
Any help or ideas would be nice !!!
Jim

[Ken F]

Jim you are right, it is cavitation burns. Very common.
I don't think there is anyway around it.
Ken F

[UBFJ #454]

Jim - Cavitation burns on the bottom of ride plates is quite common ... It is a result of water coming off the keel and 'blowing' by the intake. If the pitting is very severe, it means that a lot of water is not going into the intake.
For a Dropped Race Keel the degree and position(s) of the pitting is one way we tell how well we have the shape of the keel 'Tuned' to the intake. All last year, as I continually refined the shape of the 'Mamba's' keel (ever so slightly at a time), the pitting deminished a considerable amount ... now to a point where there is very little ... want to get to where there is almost none, but, that may never happen as different water conditions could cause some at any time ... it's when severe pitting occurs that you know the keel is not being totally efficient in terms of delivering the water to the intake.
Note that the above refers to tuning a high speed 1/4 miler not a lake or river boat ... Variable water and running conditions on lakes or rivers means cavitation pitting will occur no matter how good the keel tuning..

[moneysucker]

First, jim, WTF are you doing posting about a ride plate at 1 am? and second, The bolts broke due to the screwed up angle that they are at going to the transom. I have a wedge with ears on it that the turn buckles attach to between the bowl and the droop, that way the turnbuccles are strait up. Cav burns are common, that means the plate is doing its job. Have a good day.
Cy

[pops1]

OK here it is with out pics as of yet. I some how broke the bolts that hold the turnbuckles to the transom. I also have pitting and the speed coating has come off the center of the ride plate right behind, about 2" back, the apex of the shoe area !!! It looks to me to be cavitation burns !!! Why would this happen ??? Now my ride plate is adjustable by turnbuckles and the pillow block that holds to the transom has broke off. Now would this be like a week spring in a V-Drive and sucking the plate ???
Any help or ideas would be nice !!!
JimYou will get burns on higher speeds. The plate tends to warp and pull down causing a forced pressure vs a more flowed pressure. We came out with a Racer Ride Plate which is braced (extrusion) and step machined on the bottom @ .050 to aid in laminar flow.Brace your ride plate so it will not bend or pull by suction which becomes heat.Get you plate thich enough to step machine across the bottom. This will help.Dave aggressor

[Squirtin Thunder]

Jim - Cavitation burns on the bottom of ride plates is quite common ... It is a result of water coming off the keel and 'blowing' by the intake. If the pitting is very severe, it means that a lot of water is not going into the intake.
For a Dropped Race Keel the degree and position(s) of the pitting is one way we tell how well we have the shape of the keel 'Tuned' to the intake. All last year, as I continually refined the shape of the 'Mamba's' keel (ever so slightly at a time), the pitting deminished a considerable amount ... now to a point where there is very little ... want to get to where there is almost none, but, that may never happen as different water conditions could cause some at any time ... it's when severe pitting occurs that you know the keel is not being totally efficient in terms of delivering the water to the intake.
Note that the above refers to tuning a high speed 1/4 miler not a lake or river boat ... Variable water and running conditions on lakes or rivers means cavitation pitting will occur no matter how good the keel tuning..
So Jak, Being I changed the keel a bit, smoothed the entry to the intake & caried the bubble back about an 1/8", this could be why it is happening now or the increase in speed ???
Thanks
Jim

[UBFJ #454]

Jim - The slight move back of the keel release pt. (bubble) with increased speed could very well be causing more water to 'blow' by the hole pitting the ride plate more ... but, I couldn't tell you definatively ... ??? Welcome to the "Black Art" of Jet Boat Bottoms.

[Squirtin Thunder]

Jim - The slight move back of the keel release pt. (bubble) with increased speed could very well be causing more water to 'blow' by the hole pitting the ride plate more ... but, I couldn't tell you definatively ... ??? Welcome to the "Black Art" of Jet Boat Bottoms.
So Jak what would you do now ??? To fix the cav burns and keep them from happining again or more.

[Squirtin Thunder]

You will get burns on higher speeds. The plate tends to warp and pull down causing a forced pressure vs a more flowed pressure. We came out with a Racer Ride Plate which is braced (extrusion) and step machined on the bottom @ .050 to aid in laminar flow.Brace your ride plate so it will not bend or pull by suction which becomes heat.Get you plate thich enough to step machine across the bottom. This will help.Dave aggressor
Dave do you have a pic of that ride plate ???
The warping or forced presure is what caused the bolts to sheer I believe now.

[UBFJ #454]

Jim -
Before doing anything more to the keel, if I were you I'd install a good & solid (reinforced) ride plate ... loose the turn-buckles and install the ride plate with a cradle. If you'd like, you can give me a call and I'll explain how we have our ride plate installed and some other things regarding ride plates and keels ... best time to catch me at the house today would be after 2 PM.
Jak

[flat broke]

I agree with Bear. Since your intake is already setup for a ride plate, it looks like you could 1. get a slightly longer plate in there. 2. get a better mounting setup (I.E. cradle mount, or at least ears off the bowl) 3. move up to some channel on supporting your ride plate. Do a quick search on the forums and there are pictures of various reinforced plates. I'm pretty sure Squirtcha did his own, so he might even be able to walk you through the procedure to keep costs down.
As for why the bolts broke, look at the direction the force is being loaded against them. As that plate sees force applied to it, the linkage to the transom is being pushed up and in. If it were me, I'd tie the plate off to the pump just so if this happened again you didn't damage the gel on your transom.
Now for why it seems like its doing this all of the sudden, could it be that you didn't pay that close of attention before? Maybe as others have said, your bottom work is allowing more water to slip past the intake, and as it does so it becomes airated and now you're seeing it on the plate? If you speed coated the plate, it's gonna show the cavitation in black and white. Where as before if your plate wasn't coated, you might not have noticed the difference in the texture of the metal?
Chris

[pops1]

Welcome to the "Black Art" of Jet Boat Bottoms.Its not a black art- its just not defined yet!I will note that what you said indicates "REVERSION", Known by most heavy drinkers as "UP CHUCK"!

[pops1]

Dave do you have a pic of that ride plate ???
The warping or forced presure is what caused the bolts to sheer I believe now.Had a real hard problem getting material. Should have some in two to three weeks, machined & done. All went quick and did not think the demand would be there. I owe several out to dealers now. Will post when I have in stock. The problem most do not understand is the plate gets very hot, combined with great pressure's on plate pull. This warps the plate. The plate is always cool when you touch it, as water surrounds and cools it.
All we did was take what Ross (Pappy) Wilder learned and we combined it with a what one of our Racers (Phil Roshiem)was using for a ride plate assembly, a large extrusion. We had to order a larger extrusion to provide us with material to step cut the groves in the bottom and remachine to match up @ the shoe. 8-10 are in Drag Boats now and we have had very good comments on them. I have seen several plates made by Locals and fill that just structual support will not overcome all the problems. The Black Art of set-up, Reversion & Impeller Pull.

[Squirtin Thunder]

As for why the bolts broke, look at the direction the force is being loaded against them. As that plate sees force applied to it, the linkage to the transom is being pushed up and in. If it were me, I'd tie the plate off to the pump just so if this happened again you didn't damage the gel on your transom.
Now for why it seems like its doing this all of the sudden, could it be that you didn't pay that close of attention before? Maybe as others have said, your bottom work is allowing more water to slip past the intake, and as it does so it becomes airated and now you're seeing it on the plate? If you speed coated the plate, it's gonna show the cavitation in black and white. Where as before if your plate wasn't coated, you might not have noticed the difference in the texture of the metal?
Chris
Before doing anything more to the keel, if I were you I'd install a good & solid (reinforced) ride plate ... loose the turn-buckles and install the ride plate with a cradle. If you'd like, you can give me a call and I'll explain how we have our ride plate installed and some other things regarding ride plates and keels ... best time to catch me at the house today would be after 2 PM.
Jak
Chris,
So your talking about the way most of the SWTDs have it right. As for the cav burns, I had a very small amout before the changes over a long period of time, about 2" wide and about 4" long. Now it is about 4" wide and 8" long. This time it was quick and pronounced. Yes much more noticable with the black and white.
Jak,
I am sure that it is flexing at speed. And it needs some sort of suport. So I will make some rails for now. The Sanger intake is not machined for a ride plate it is added after the intake. Being that the intake is flat and goes in form the bottom. I do have another intake that I will have machined for a standard style or stepped style ride plate and switch down the road. This change will also allow more water to be forced into the intake from the angle of the shoe and creat more lift. And hoping that it will aid in more speed and ride quality.
Pops1,
The stepped style ride plate sounds interesting. Would sure like to see pics !!!
Jim - The slight move back of the keel release pt. (bubble) with increased speed could very well be causing more water to 'blow' by the hole pitting the ride plate more ... but, I couldn't tell you definatively ... ??? Welcome to the "Black Art" of Jet Boat Bottoms.
Jak
Does your race boat get cav burns on the ride plate ???
Thank you
Jim

[HBjet]

Here is my rideplate designed and made by the one and only...
http://www2.***boat.com/image_center/data/500/20rideplate.jpg
Using C channels, the angle they are in, and the # and spacing of the bolts are all calculated to correct the problem I was having before with the plate flexing. No more flex now (front to back or side to side)
HBjet :rollside:

[flat broke]

Here is my rideplate designed and made by the one and only...
http://www2.***boat.com/image_center/data/500/20rideplate.jpg
Using C channels, the angle they are in, and the # and spacing of the bolts are all calculated to correct the problem I was having before with the plate flexing. No more flex now (front to back or side to side)
HBjet :rollside:
Man, If you ever want to run BIG numbers, make sure all of your screw slots are going the same way!!!! that will really have you haulin the mail :D
Hows stuff? you get that rig all buffed out yet? Got your call the other day, but I've been laid up on the couch popin pills. I'll know more on dates at the River after tomorrow. ;)
Chris

[HBjet]

well, my boat is a v-bottom hull, so that's why we run the C-channel at a V :idea:
(that was a joke)
Yeah, I heard about you... sorry your going through that! Boat is all clean, new tires on the trailer, I have the spacer off at DNE to get O-ringed. Going to swap headers with Cyclone so those are off my boat now and it makes it much easier to clean the motor/rail kit. Fresh oil is all in and I'm going to get the new valve springs in 2 weeks. Just about done!
HBjet

[LVjetboy]

"The problem most do not understand is the plate gets very hot, combined with great pressure's on plate pull. This warps the plate. The plate is always cool when you touch it, as water surrounds and cools it."
What leads you to believe the plate gets very hot? Or that that's the reason for plate warp? I think the term "cavitation burn" is misleading...better might be "cavitation errosion"
jer

[steelcomp]

"The problem most do not understand is the plate gets very hot, combined with great pressure's on plate pull. This warps the plate. The plate is always cool when you touch it, as water surrounds and cools it."
What leads you to believe the plate gets very hot? Or that that's the reason for plate warp? I think the term "cavitation burn" is misleading...better might be "cavitation errosion"
jer
Funny...I was wondering the same thing. :coffeycup

[Jake W2]

Coolest ride plate I have ever seen was on Duanes (HTPs) FLASHBACK it was a solid billet alum milled out so it had its own support nothing bolted on (kinda of like the new Aggressor plates)now the part that was really cool to me was it had a half moon or curve from nothing to someting milled in the bottom of it.
(pressure relief)
Ken or Duane you guys have a pic of it?I think Duane said when he sold FLASHBACK the plate went with it.
My ride plate stiffners are solid inch by inch billet drilled and tapped no bolts and then drilled on the sides to lighten them up.http://www.hotboatpics.com/pics/data/500/4324rps.jpg
Jake

[Squirtin Thunder]

"The problem most do not understand is the plate gets very hot, combined with great pressure's on plate pull. This warps the plate. The plate is always cool when you touch it, as water surrounds and cools it."
What leads you to believe the plate gets very hot? Or that that's the reason for plate warp? I think the term "cavitation burn" is misleading...better might be "cavitation errosion"
jer
Funny...I was wondering the same thing.
Well on a prop a cav burn is the water & air getting so hot it explodes the little mixed molecules. Am I right ???

[UBFJ #454]

Jim -
Yes, our ride plate has shown cavitation scarring ("errosion", if you like) at times, the degree and positioning of it I attribute to the depth of the keel and shape of the its release/inlet area ... as I've gotten the keel 'tuned' better and more water has gone into the intake, the scarring has diminished greatly.
Before every run I spray the shoe, loader and ride plate with graphite and 'read' them right after the boat returns to the pit to determine 'wear patterns'. Doing this and reviewing the intake and bowl pressures (along with other data) from our data acquisition system helps us determine whether or not we're going in the right direction with our bottom hardware setup relative to the keel ...
Realize that our boat is a 1/4 Miler and only a 1/4 Miler and we are still 'Dialing' her in to make her as Quick as we can in the quarter so it's a continual, tedious process and if we change any one thing ... Everything can change. 'Tuning' to that degree really isn't necessary and is a waste of time and effort with a lake or river boat once you get them setup for general, Safe recreational use.

[Duane HTP]

You can see one of his billet ride plates on the intake set up on my site. Sorry I don't have a picture of the bottom of it.
http://www.hi-techperformance.com/Parts.HTM

[bp]

jim, on the sw, i don't have a lot of room under the pod for stiffeners, so we just made a new plate out of half inch aluminum, since the old 3/16 was warped all to hell. this one doesn't doesn't flex. you need a cradle.

[steelcomp]

Here is my rideplate designed and made by the one and only...
http://www2.***boat.com/image_center/data/500/20rideplate.jpg
Using C channels, the angle they are in, and the # and spacing of the bolts are all calculated to correct the problem I was having before with the plate flexing. No more flex now (front to back or side to side)
HBjet :rollside:
I'm curious as to what you used to calculate the angles of the c channels and the bolt spacing?
Nice looking piece. :coffeycup

[Jeanyus]

Jim put in stiffeners and get a cradle. I was also told to use grade 8 bolts in the cradle.
http://www.hotboatpics.com/pics/data/500/5859rideplate.jpg
I need bolts in the ends of my stiffener, they used to go under the cradle, but I had to cut them off to raise the ride plate. I cut the cradle down a lot so now I have a shim under it. So I can adjust it, at ming.

[pops1]

"The problem most do not understand is the plate gets very hot, combined with great pressure's on plate pull. This warps the plate. The plate is always cool when you touch it, as water surrounds and cools it."
What leads you to believe the plate gets very hot? Or that that's the reason for plate warp? I think the term "cavitation burn" is misleading...better might be "cavitation errosion"
jer :crossx:
All I can do here is go thru an experience I had working with one of the best. Boat had an inherent problem of scrapping out ride plates in short periods. The cure was solid sides on oversize billet plate, machined with .050 groves to create surface diversion. IT WORKED!
An IMPELLER ALSO HAS FORWARD PULL MOTION! Just to add fun back into the game.

[LVjetboy]

"Well on a prop a cav burn is the water & air getting so hot it explodes the little mixed molecules. Am I right?"
No.
"...now the part that was really cool to me was it had a half moon or curve from nothing to someting milled in the bottom of it. (pressure relief) Ken or Duane you guys have a pic of it?"
I do...
http://members.cox.net/lvjetboy/DuanesRide1.jpg
http://members.cox.net/lvjetboy/DuanesRide2.jpg
Here's another idea, a step design with very stiff side rails...
http://members.cox.net/lvjetboy/PumpSide.jpg
http://members.cox.net/lvjetboy/BottomView.jpg
http://members.cox.net/lvjetboy/PumpSidePhoto.jpg
Maybe good, maybe bad. At a certain level, only DA can decide regardless of personal seat-of-the-pants bias.
Learn what's tried. Question everything. Innovate. But in all things, strive towards a better understanding of the natural laws...the physics of what really happens. Not accepted or often repeated myths, even tho respected.
What's the purpose of a ride plate?
jer

[Jake W2]

Jer is that an Aggressor ride plate?Because that would be the type of plate that was on Flashback but that was like 3 years ago.
Jake

[Ken F]

Jer,
Maybe I've missed it on the boards, but curious as to how your new rideplate design works? You happy with it?
Ken

[Duane HTP]

The ride plate that we developed for Hi-Tech Express, Black-n-Blue, Flashback, and R & D Express is the one in the picture. We felt that it freed the boat up quite a bit. Seemed like the measurable difference was small, but there. One other thing that you are missing here, is the hole drilled through the plate at a 45 degree angle up at the front of the parabolic curve. This relieved the drag associated with the burn spot that we had had before. It also cools down the plate and injects air bubbles for the rest of the plate to run on. Seemed like the boat tracked like a slot car with the effect of the two side rails. We have made and used them on several of our sponsored boats, but we never put them on the market because of the cost involved in making them. We were afraid that Chet would not approve of the HYPE or COST. HA HA! I even went so far as to have some of them cast, but was afraid of the strenght of cast in that application, so they are still lying here in the back room.

[LVjetboy]

"Maybe I've missed it on the boards, but curious as to how your new rideplate design works? You happy with it?"
I've run it to mid 90's with no structural or handling problems. The idea behind a step design was to improve low speed pitch control (anti-porpoising) by effectively lengthening the plate, and low speed drag reduction by deflecting more water away from the pump and linkages, all without adversely affecting the high speed drag or pitch control of a standard plate.
With the flexibility to vary both primary and secondary plate lengths and/or vertical height, I think this design has a lot of tuning potential. But ride improvement is subjective and dependent on conditions. Performance improvement, acceleration (drag reduction) and top speed need to be measured in a controlled environment...the track. So w/o racing tests and data aquisition I can't tell you if this is a better performing design.
But it looks cool. :D
jer

[Squirtin Thunder]

LVjetboy
But it looks cool. :D
jer
Yes it does !!!

[LVjetboy]

Thanks Thunder.
One thing I'm not happy with is the plate supports. Although adjustable links are easily varied (unlike the cradle and spacers) they do have "slop" or pin-to-hole clearance. I'm not sure if this's important but it could be as speed goes up.
Let me expand on my short "no" answer to your cavitation question.
Cavitation occurs when water pressure is lower than the water vapor point. When that happens, water vaporizes and forms a cavity or bubble. That bubble has no "air" or ability to "explode" with heat...just water vapor and trace amounts of gasses. Cavitation can occur at a very low water temperature...in fact at normal lake water temperature. When cavitation bubbles reach a higher pressure than vapor pressure they implode (not explode) The damage to the surface it's attached to, be that a propeller, impeller or ride plate is caused by the imploding bubble shock wave and the extreme pressure generated as it impacts the surface, not the temperature that impact induces. Similar to a shaped charge I suppose.
This is a mechanical stress, deformation and failure caused by material fatigue...not temperature "burn" or melting. As with any material deformation there will be localized heating but think of hitting an aluminum plate with a ball peen hammer. Eventually you're gonna remove material. Is that plate significantly hotter? No. If that plate was hit repeatably along with water cooling what do you think? No.
Cavitation pitting or errosion is primarily a mechanical not temperature driven failure. Plate becoming hot? Or even warm? I think not. I'm sure a materials expert could correct me if I'm wrong. SteveM?
jer

[pops1]

Thanks Thunder.
Cavitation pitting or errosion is primarily a mechanical not temperature driven failure. Plate becoming hot? Or even warm? I think not. I'm sure a materials expert could correct me if I'm wrong. SteveM?
jeri THINK SO! 1ST YOU ARE NOT GOING TO REMOVE MATERIAL WITHOUT TEMP. IS CAVATATION NOT ALSO CALLED A STEAM VENT.

[jweeks123]

i THINK SO! 1ST YOU ARE NOT GOING TO REMOVE MATERIAL WITHOUT TEMP. IS CAVATATION NOT ALSO CALLED A STEAM VENT.
very good pops1.
what field did you say your degree was in?
jw

[LVjetboy]

”1ST YOU ARE NOT GOING TO REMOVE MATERIAL WITHOUT TEMP.”
I'd agree. You can't remove material without some change in temperature no matter how slight. But is that removal caused by temperature or mechanical force? In a cooled environment with a material that conducts heat readily, a change in temperature with impact even smaller. But the mechanical force produced by the implosion shock wave WILL generate local heating as material is deformed.
From my post above: "As with any material deformation there will be localized heating..."
My point was, I don't think temperature or material melting is the primary cause of material failure on a ride plate and the pitting some call “burn marks” I think the resulting localized heat or material temperature rise is not as significant to surface pitting as is the repeated mechanical force of the imploding bubble shock wave causing material fatigue, fracture and eventually pitting of the surface.
From my understanding, there is a difference in the failure modes. And I think the term "burn marks" is misleading.
But I'm no material expert…SteveM? Anyone out there know the true failure mode behind cavitation pitting? Is it primarily temperature melting the surface as in a blow torch or mechanical fatigue as with a hammer blow? Both of course heat and can fail the surface...one heats less than the other.
You second point? "IS CAVATATION NOT ALSO CALLED A STEAM VENT."
I haven't heard that term but no big deal. I'd ask, is steam always hot?
jer

[LVjetboy]

"very good pops1. what field did you say your degree was in?"
Does a degree have anything to do with it? Or the implied status of someone "in the business?" Maybe more important an understanding of what's already known combined with the knowledge of what has been done and a healthy respect for what can be done.
jer

[pops1]

very good pops1.
what field did you say your degree was in?
jwJUST ONE OF THEM DROP OUTS! Yet most any racer will tell you his ride plate gets hot in cold water after making a 120 mph pass. That must be that inverted vapor lock of chill doing it. So get the slide rule out something is going on in the heat department. On Apollo I got the degree bit and ring on the finger with a lot of schoolboys and told them to redesign parts all the time. In the end it was done, because it was the right way, not the degree way. So can we move on!

[pops1]

[i
You second point? [i I'd ask, is steam always hot?
jerIs it! What is funny, One of the racers dropped by last week. Said he seen the string and was taken back by the response. Said his plate has been so hot you could not touch it! Jer on the ride plate shown: Why the concave which creates a suction action.

[miketsouth]

An IMPELLER ALSO HAS FORWARD PULL MOTION! Just to add fun back into the game.
Guess no one saw this one. I did. I used an open mind, realizing y'all got lots of experience and i got none.
If one was to make the monsterous assumption that one could PULL water then the calculation would be (area x pressure). At 5" diameter and 15psi atmospheric pressure this would be about 90 lbs, a consideration.
Yet most any racer will tell you his ride plate gets hot in cold water after making a 120 mph pass....something is going on in the heat department.
You mean he got back there and actually touched it while it was running at 120, or that it just was so hot it did not have time to cool that much by the time he touched it. Dont sound right to me, but i have been very wrong before.
[QUOTE=pops1]Is it!
It aint. I run steam at 42F and millions of BTU/hr all day/year long. BUT in turning back into water steam does produce 980btu/lb (remember this, it is temperature independant, heat specific)
One of the racers dropped by last week. Said his plate has been so hot you could not touch it! .you did say it was funny.
Jer, you know my take on this, Pops1 i know you know some stuff that i will never know, so dont take this as an affront.
Aside from that, the cavitation burns on the ride plate (no, no one posted a single pic for me to see such an unbelievable thing) is bona fide such that i got to believe it and i wonder about it.
I'm with you on this one Jer. If it gets hot, you would have to have a temp sensor on it as it skims over the water because in a second it would be cool again, an your erosion example fits all that i have experienced in working with many types of pumps and piping.
I am still trying to figure out what rideplate depth and angle has to do with pump loading. I have the directive: "get a intake pressure gauge, foo..."

[Cs19]

Im having a hard time with this "ride plate getting hot" thing.Theres ALOT of cooling around that plate.
How are the "racers" checking their plates after a 120 mph run? Its usually atleast a 2-3 minute wait to get your boat back on the trailer after a run, no doubt the heat would be long gone by then.

[Squirtin Thunder]

Im having a hard time with this "ride plate getting hot" thing.Theres ALOT of cooling around that plate.
How are the "racers" checking their plates after a 120 mph run? Its usually atleast a 2-3 minute wait to get you boat back on the trailer after a run, no doubt the heat would be long gone by then, since its underwater.
There is no Flippin way the plate is even thinking of getting hot !!!
The day it happend the river was like 30*, Flippin Ice Cold !!!!!
OK there are explosion errosion marks on my ride plate !!!

[TRG]

well if everyone is worried about heat being the issue here, why dont they make a ride plate out of glass and gel, seems to work out quite well for boats, they dont seem to be having any problems with water eroding the bottoms out from them? Then you could just reinforce it with the 1" angle like you guys are donig now!
then again!...what would i know?
i'm doing ok with my G.E.D though! lol
Todd

[Cs19]

well if everyone is worried about heat being the issue
I dont think everyone is worried about heat, only a few.Ill be sure to check mine after a run this weekend at the races.
One of these days im gonna get my rideplate hard anodized, thats gotta help some.

[Squirtin Thunder]

I dont think everyone is worried about heat, only a few.Ill be sure to check mine after a run this weekend at the races.
One of these days im gonna get my rideplate hard anodized, thats gotta help some.
The original one from Sanger was and it had less burns or markings on it !!!
Opps the boat wasn't fast enough yet to creat friction burns !!!
But it was Anodized Gold and is very hard !!!

[Bense468]

Chris- I think you should make a pass, jump in right after and see if its hot. :D

[LVjetboy]

Pops don't get me wrong, I have no more respect for degrees than experience. I could care less about titles or position. Either is fine, either can be BS. I do favor experience if true and objective. But history shows both schooling and living may lead to wrong conclusions.
What I value is the truth. And the search for truth can at times appear, well...a bit anal?
jer

[LVjetboy]

"Jer on the ride plate shown: Why the concave which creates a suction action."
I think you're refering to my pic of Duane's modified ride plate. Since that's his plate design, ask him. My guess the concave design was an attempt to relieve suction losses with a pressure relief port (hole at the apex.) The value of that design may go back to my question in that post (#27)...
"What's the purpose of a ride plate?"
jer

[bp]

i THINK SO! 1ST YOU ARE NOT GOING TO REMOVE MATERIAL WITHOUT TEMP. IS CAVATATION NOT ALSO CALLED A STEAM VENT.
it's not the change in temperature, but the change in phase or state of h20 that causes the problem. jer explained it very well. the change in phase from a vapor bubble to a liquid, at the same temp, releases a tremendous amount of energy in btu. this occurs at saturation tempurature.
however, if you place an aluminum plate in a bead blaster, and just keep beating on it, the plate will warm up just from the friction.

[steelcomp]

it's not the change in temperature, but the change in phase or state of h20 that causes the problem. jer explained it very well. the change in phase from a vapor bubble to a liquid, at the same temp, releases a tremendous amount of energy in btu. this occurs at saturation tempurature.
however, if you place an aluminum plate in a bead blaster, and just keep beating on it, the plate will warm up just from the friction.
To take your glass beading example a step further...lay the plate in water and bead blast it. Will it get hot then? Not likely.
Water has some neat properties. It's interesting that water can be used to cut titanium several inches thick, will wear granite stone to nothing, yet we stand under it in the shower and wash our delicate clothes in it. Hit it at 100 MPH, and you think you're on pavement, but tip over a glass of it, and you have a mess, or refresh your thirst! :D

[kojac]

it's not the change in temperature, but the change in phase or state of h20 that causes the problem. jer explained it very well. the change in phase from a vapor bubble to a liquid, at the same temp, releases a tremendous amount of energy in btu. this occurs at saturation tempurature.
however, if you place an aluminum plate in a bead blaster, and just keep beating on it, the plate will warm up just from the friction.
It take 970.3 btu's to change one pound of water (h20) from a liquid state to a vapor 212 degrees at atmospheric pressure and the same 970.3 btu's to change it back into a liquid again. (latent heat of vaporation)Are we postulating that the water temperatures raises from about 70 degrees (lake water) another 142 degrees to get to 212 degrees and then add's another 970.3 btu's to change it to a gaseous vapor? Not to mention there is a whole lot more than one pound of water being effected??
Is the pressure rising or dropping on the plate area which has a instant bearing on when the water changes state?
I have used a torch on steel to bring it to a molten hot metal and dipped it into a bucket of water and could touch it in about ten seconds. I wonder how anyone can get out of there boat fast enough to get back to the ride plate and touch it to determine if it is hot or not when it is sitting in 75 degree water?
This is interesting but I'm really confused??? I think there is some thing else going on besides heat.
Kojac

[pops1]

it's not the change in temperature, but the change in phase or state of h20 that causes the problem. jer explained it very well. the change in phase from a vapor bubble to a liquid, at the same temp, releases a tremendous amount of energy in btu. this occurs at saturation tempurature.
however, if you place an aluminum plate in a bead blaster, and just keep beating on it, the plate will warm up just from the friction.
Is BTU not Temp. What i do know is I have seen sound engineered ride plates warped, and cav burned or that which resembles cav burns (if you say its not so) distroyed in a very limited # of runs.
A ride plate that is maintaining the attitude of the hull is seeing a high amount of pressure or resistance in doing so. Compound this by speeds of 120 MPH and so far you have not convinced me "it is anything less then pressure's and some form of Temp distorting the plate" What was used to correct the condition I stated for those that want to try it, and input back to myself from those that are running our this way has been very good. Good Luck to you on resolving this matter.

[pops1]

It take 970.3 btu's to change one pound of water (h20) from a liquid state to a vapor 212 degrees at atmospheric pressure and the same 970.3 btu's to change it back into a liquid again. (latent heat of vaporation)Are we postulating that the water temperatures raises from about 70 degrees (lake water) another 142 degrees to get to 212 degrees and then add's another 970.3 btu's to change it to a gaseous vapor? Not to mention there is a whole lot more than one pound of water being effected??
Is the pressure rising or dropping on the plate area which has a instant bearing on when the water changes state?
I have used a torch on steel to bring it to a molten hot metal and dipped it into a bucket of water and could touch it in about ten seconds. I wonder how anyone can get out of there boat fast enough to get back to the ride plate and touch it to determine if it is hot or not when it is sitting in 75 degree water?
This is interesting but I'm really confused??? I think there is some thing else going on besides heat.
Kojac Just seen this one. Lets suppose you have a 8"x18" plate in the Water running 125 MPH pushing the nose of a boat down, each & every time the nose wants to come up too high. Do we not have friction here. If the answer is yes, We have heat. If you have air bubbles further getting entrapped will you not end up with a form of burning also. If so I say you have heat within the metal or item receiving the force of the friction.
You further have negative forces trying to pull and distort that 8x18 plate passing under the full flat surface of it. Any distortion which occurrs will only further compound the the existing condition. Warp becomes a concave which becomes a suction which further try's to distort. Someone above talked about water in a glass spilling and making a mess running all over vs water at 100 MPH being a resistive barrier.(my words but I thing he was saying the same) You also have a laminar flow barrier which can assist in transfer or eliminate some or all of the temp being generated in this condition.
Im not a Engineer, just a guy that grew up in the Manufacturing world, so my terms may not be exact yet I think my conclusion is, based on a past resolution to the problem. What we did was step cut the plate every 1/4" to a depth of .060th to increase the barrier flow on the bottom side of the plate.
We also had special extruded stock made for us to allow for the machining and provide side walls of 2" stock as a U channel. This thing is getting beyound what I was trying to help with and I don't see any + being added beyound Calc's and hell I still use my toe's to get my numbers so any over 20 kills me unless I use my ear's which takes me to 10+10=20 + 2= 23 see ya.

[LVjetboy]

"I wonder how anyone can get out of there boat fast enough to get back to the ride plate and touch it to determine if it is hot or not when it is sitting in 75 degree water?"
I'm no racer but if my plate felt warm in the pit I'd guess the heat came from above...engine, driveshaft spline friction, bearing, etc. conducted through the pump housing and suction piece to the plate.
jer

[bp]

It take 970.3 btu's to change one pound of water (h20) from a liquid state to a vapor 212 degrees at atmospheric pressure and the same 970.3 btu's to change it back into a liquid again. (latent heat of vaporation)Are we postulating that the water temperatures raises from about 70 degrees (lake water) another 142 degrees to get to 212 degrees and then add's another 970.3 btu's to change it to a gaseous vapor? Not to mention there is a whole lot more than one pound of water being effected??
Is the pressure rising or dropping on the plate area which has a instant bearing on when the water changes state?
I have used a torch on steel to bring it to a molten hot metal and dipped it into a bucket of water and could touch it in about ten seconds. I wonder how anyone can get out of there boat fast enough to get back to the ride plate and touch it to determine if it is hot or not when it is sitting in 75 degree water?
This is interesting but I'm really confused??? I think there is some thing else going on besides heat.
Kojac
ving, you are solely relating the amount of energy required to change phase at a specific temp and specific atmospheric pressure. however, if the psat is much lower, as jer mentioned, the temp does not have to be 212. you can (and do) have saturation conditions well below that temp, in low pressure conditions, which is a condition that could exist just before the location discussed here. pressure changes can result in phase changes at lower pressure.
BTU is not a temperature measurement. a british thermal unit is heat energy defined as "the amount of heat" required to raise one pound of 60 degree water one degree farenheit. you can superheat steam by adding a lot of it, and you can freeze water by removing a lot of it. the temperature of either is only relevant to the pressure of the system or surroundings.

[miketsouth]

Are we postulating that the water temperatures raises from about 70 degrees (lake water) another 142 degrees to get to 212 degrees and then add's another 970.3 btu's to change it to a gaseous vapor? Kojac
I dont think so. It is about the same btu at any pressure. It just boils at a lower temperature at reduced pressure. At some rather low pressure, water will actually freeze if you dont add some heat.
Pops solution appears to be that he saw that low pressure was what was causing working rideplates to self destruct, figure out a solution and correct the problem without changing the desireable properties of the rideplate. No further analysis necessary, done, next problem.
120mph water causing friction enough to heat? maybe not. Just dont seem fast enough. If the boat is doing 120mph then the water leaving the nozzle has to be faster than that, and i dont think that the nozzles burn off, and does the bottom of the boat burn too?
BUT, in thinking of this, if somehow the plate is experienceing a negative pressure in the middle of it because of a slight concavity, or even from a slight up angle or from whatever, then the water is not cooling it, yet it evaporates from the water surface and condenses on the rideplate, causing erosion, and increased temperature. while the boat is running. So, why dont the bottom of the boat burn up (or does it?)
Sure would like a picture of what this looks like on a rideplate. I aint got a snowballs chance in hell of ever seeing it on my boat.
Kojak, I look to see you at Lake Anna sometime this summer. I would really like to see the Sterling P/F too.

[kojac]

I dont think so. It is about the same btu at any pressure. It just boils at a lower temperature at reduced pressure. At some rather low pressure, water will actually freeze if you dont add some heat.
Pops solution appears to be that he saw that low pressure was what was causing working rideplates to self destruct, figure out a solution and correct the problem without changing the desireable properties of the rideplate. No further analysis necessary, done, next problem.
120mph water causing friction enough to heat? maybe not. Just dont seem fast enough. If the boat is doing 120mph then the water leaving the nozzle has to be faster than that, and i dont think that the nozzles burn off, and does the bottom of the boat burn too?
BUT, in thinking of this, if somehow the plate is experienceing a negative pressure in the middle of it because of a slight concavity, or even from a slight up angle or from whatever, then the water is not cooling it, yet it evaporates from the water surface and condenses on the rideplate, causing erosion, and increased temperature. while the boat is running. So, why dont the bottom of the boat burn up (or does it?)
Sure would like a picture of what this looks like on a rideplate. I aint got a snowballs chance in hell of ever seeing it on my boat.
Kojak, I look to see you at Lake Anna sometime this summer. I would really like to see the Sterling P/F too.
I was thinking that the cavitating burns might be from the oxygen scavenging in the water causing a form of pitting and scaling more than just heat.
When I used to work on boilers we had to add chemicals to prevent the scaling and pitting on the metals due to oxygen scavenging. Of coarse that was steel not alluminum and I don't know what oxygen does to the alluminum.
I agree that the fiberglass bottom of the boat does not seem to warp and I would think that would be more emeniable to warping than alluminum due to the heat process. I have never seen a fiberglass jetboat bottom blistered from heat.
Maybe some one who has experience in the faster flatbottom, or hydro boats could elaborate more on the experience of heat on their equipment. The top alchohol flatbottoms, and hydros certainly run faster than the jets and I wonder if they see similair results. But then they tend to just be set up for the quarter mile and might not see the same as a jetboat that spends a lot more of time at the lake cruising.
I was wondering if anyone had experimented with inverting the rideplate so that it would concave out rather than in so as to lift the stern of the boat and free it up. It might cut down on the radical shutdowns of the tunnels and allow more speed and efficiency to the boat.
Dunno just a thought.
I'm getting ready to put nitrous on the sterling. Bought the 400hp plates and selenoids last week. I want to test the rideplate with the water nozzles some more before I use the nitrous. Waiting for the edelbrock aquisition system to arrive and then Need some good weather to test.
Kojac

[Unchained]

With the reference to water jet cutting machines there is not JUST water doing the cutting.
There is an abrasive mixed in with the water at the cutting tip.
The water pressure can be over 50,000 psi to cut some metals.
Nozzle diameter is about .100

[miketsouth]

I'm getting ready to put nitrous on the sterling. Bought the 400hp plates and selenoids last week. I want to test the rideplate with the water nozzles some more before I use the nitrous. Waiting for the edelbrock aquisition system to arrive and then Need some good weather to test.
Kojac
I was gonna ask "Can i borrow it"? I know someone who needs a good ass-whoopin. I wont say his name but his initials are MIKE JANSON. But i got to thinkin' he is gonna have enough trouble with the mouse. :D :D :D

[Squirtin Thunder]

OK here it is with out pics as of yet. I some how broke the bolts that hold the turnbuckles to the transom. I also have pitting and the speed coating has come off the center of the ride plate right behind, about 2" back, the apex of the shoe area !!! It looks to me to be cavitation burns !!! Why would this happen ??? Now my ride plate is adjustable by turnbuckles and the pillow block that holds to the transom has broke off. Now would this be like a week spring in a V-Drive and sucking the plate ???
Any help or ideas would be nice !!!
Jim
I forgot to mention that it occured from about a 5 - 10 mile run at 75mph+ !!!
Not sure how fast but we were rollin !!!

[fakethis]

Its play time again Mr MiKe T
I see its time for beer & BS............ :cool
Wayne lookin for a race not me...Mine is slow :cry:

[Duane HTP]

I don't care to get involved in the argument of what is for sure causing the erroding, pitting or cavitation burn, but I just wanted to add that I have seen it eat up the fiber glass behind the intake opening of several fast boats that did not have ride plates. In fact the bottom of the boat Mellow Yellow, that we set the Comp Jet records with in the 70's was erroding, or burning up so bad, that we put a ride plate on it just for the purpose of stopping the damage to the figer glass behind the pump. We were running 114 mph in a V-Bottom boat that didn't even have a shoed intake. (Man! Were we crazy, or what?)
Just thought this imformation might help some of you engineers in your thinking of what is going on.

[kojac]

I was gonna ask "Can i borrow it"? I know someone who needs a good ass-whoopin. I wont say his name but his initials are MIKE JANSON. But i got to thinkin' he is gonna have enough trouble with the mouse. :D :D :D
Mike,
Do you want to borrow the data aquisition or the plates. Either or but I think the plates will be too big for your application. They go under two 1050's on a sheet metal manifold on top of a 572.
Got to use the data stuff on Ronnie' Tommy's and mine of course but your welcome to use it and any of my boathouse load of stuff to try to improve your setup.
Duane,
No arguement about any of pitting,burning, etc. Just trying to get some insight into what's really happening.
Years ago I used to hear that any jet boat going over 100mph would have pitting on the fiberglass bottom from the heat. I would run my boat up to 104 in those days and when I was through I would check the bottom for the pits or bubbles. Never found any.
Afew years ago I had the bottom of the sterling redone with the bubble and setback pump. In doing so we found the old bottom was just about to crack and come apart at various points. Probably did it just in time. I thought that probably the next run or so would be the kicker.
Here again I think that it is due to the repeated friction of the water bubble's acting like sandpaper or a grinder. (I know they produce heat when they are used) But with all that cool water volume I seriously wonder about a heat buildup.
I used to hear in bench racing circles from the outlaw racers that some race cars had there bodies replaced not because of denting or abuse but just because the wind put so much stress on them at continued high speed that they were thought to be unsafe and come apart. Don't know have personal knowledge on that maybe some of our race car guru's could comment.
You have more experience than most of us with the fast boats, What do you think is happening?
Kojac

[miketsouth]

Mike,
Do you want to borrow the data aquisition or the plates.
I meant the whole Sterling, but i was only kidding. I play around with Mike and Ray alot, they are very good to me and i have fun when i am with them. What i do remember is meeting you last year and finding you such a gentleman (not to depreciate any of the other fine people i met at Jacks).
Like i said, hope to see you this year. Before i met you Mike had shown me a pic of the Sterling Pickle...i liked it... I had a Sterling V and did not know they made Pickles. He told me 'Kojak' has it. Well, i did not know who you were at that time, so it was a double pleasure meeting you.
I had the yellow pickle with the small block...dont need (wont afford) any more. Realisticly and truthfully i am too scared to drive one much faster anyway. If i get 80mph this year i will be satisfied. I know i can do it, but i need to understand the relationship of the pump loading as regards shoe and loader (i had all kinds of 'big plans' last year to test and tune but got lost in just the driving of it).
I saw 74 last year, once, but usually it was around 63 to 68 and that after an extended WOT. I have some headers this year that should do the cam i put in it more justice (did not quite get the scavenging right, and the trumpets burned me anyway).
The lighter weight of the SB made the boat get great gas mileage and a really fine ride (as compared to the sterling V) Did hundreds of miles thru water that would have beat up either me or the Sterling V (and Mikeys BBC :wink: )

[fakethis]

Let's put that 572 in my boat. :idea:

[kojac]

Let's put that 572 in my boat. :idea:
It's available.
kojac

[fakethis]

I would love 2 try it, but it would probably scare the crap out of me. Anytime you're up this way bring the boat and stop in. I would love 2 see Wayne's face if you were sitting on our ramp when he showed up.I think I am in the low 90's on the juice with my 30 over 54 with a 175 shot. Are you going to run at Harrisburg this year? I am trying to get pops to come to Anna this year but he's into the damn ski boats now and its no fun doing 48 and I am no skier. Take care, see you at Anna

[LVjetboy]

Anna...seems I remember that lake. This shot at Anna...
http://members.cox.net/lvjetboy/Anna.jpg
Maybe I still got a few of the nuc(?) plant.
jer

[Duane HTP]

Kojac, I really don't know for sure. If there is heat involved, it would be hard to measure it because it would always be cooled down by the time you could check it. On the other hand it kind of seems like the metal is being shot peened with water dropletts re-entering from a viod. More like an abrasion thing to me. But like I say I really don't know. I used to think I did until this thread started. HA!

[bp]

Anna...seems I remember that lake. This shot at Anna...
http://members.cox.net/lvjetboy/Anna.jpg
Maybe I still got a few of the nuc(?) plant.
jer
that would be north anna... :cool:

[sanger rat]

Couldn't a passenger shoot the ride plate with a handheld I.R. temp gun? And I'm not saying to do it at 100mph!

[Duane HTP]

Let me bring up another point here. It seems to me that BP is in the right area when he says'
the temp does not have to be 212. you can (and do) have saturation conditions well below that temp, in low pressure conditions, which is a condition that could exist just before the location discussed here.
Correct me if I'm wrong here, but I don't believe I've ever seen this "Pitting", "Burning" or "whatever it is", on a ride plate that was running at a down degree from the shoe. It has always been on a plate that is running pretty close to parallel or more than likely a degree or so up from the shoe surface. This slight bend in the running surface at this point would for sure create a low pressure area in the pitted spot. This low pressure area is what helps lift the nose of the boat. Right? It helps in pulling the plate down by suction created from the water going straight off of the shoe and leaving a void, (vacumn), right at the bend.
The pitted area is at the point of the water regaining contact with the plate. Wheather it's hot or not, I don't know. Don't one of you engineers have a way of hooking up some kind of a heat sensor to answer our question about heat here? Now. When we find out if it's hot or cold, Where do we go from there? As mentioned earlier, the hole we drilled in the concave area of our plate, (pictured above-post # 13) stopped the pitting. So, that leads me to believe it has to do with suction, and water re-entry.This is just my uneducated guess as to what is going on. It also leads me to believe the suction theroy of lifting the nose by suction there, because we had to go up another degree on our plate to maintain attitude when we drilled the hole. All of this seemed to free the boat up a bit. But, like I said before, "seemed" because we did not really have an accurate means of measurement.

[Ken F]

Duane,
I think you have it nailed here, but I have a couple of questions.
You wrote:>This slight bend in the water at this point would for sure create a low pressure area in the pitted spot. This low pressure area is what helps lift the nose of the boat. Right? It helps in pulling the plate down by suction created from the water going straight off of the shoe and leaving a void, (vacumn), right at the bend. <
On my rideplate, there is evidence of what looks to me like a "cavitation burn". however, it starts on the outside edges of the plate, and goes to a point at center (about 2/3 of the length of the plate). I had always been under the impression that it was caused by a vacume created at the bend of the angle between the back of the shoe and the rideplate, causing the water to "implode", (possibly not the right term) much like on the back of an impeller, where cavitation occurs.
You stated that it occurs where the water regains contact with the plate.
Mine seems to happen where there would be a vacume created in the middle of the plate.
Second, I don't understand how that small amount of vacume would help lift the nose. I would tend to think that the boat is setting back on the rideplate, and the vacume is formed due strictly to the change in angle from the shoe to the rideplate.
Ken

[Duane HTP]

Ken, My termonology might not be right, but I didn't intend to say anything different than you just did. I agree 100 percent. If you'll notice, I corrected the word "water" to "running surface". Maybe that will clearify my meaning some.
The boat is riding back on the plate, After, or behind, the area we are discussing here. The suction helps in keeping it to ride on the plate. On the plate pictured above, we felt it was riding on the outside 2" rails on each side of the concave area. I have one of those plates here on the shelf. I'll bring it to Table Rock next time I come and you can try it. You can see what you think. Send me your old ride plate right now while your motor is down, and I can match it up to this one here and make sure we have a perfect fit. Okay?

[Ken F]

Duane,
Thanks I'd love to give it a try, but the boat is still at Ervins getting my "trailer Ding" touched up. In process right now of getting my shortblock assembled, and as soon as the engine is together, I'm headed down to get the boat. I'll send it then.
Ken

[steelcomp]

Duane,
If the supposed purpose of a ride plate is to create that low pressure area under the plate, helping to raise the nose of the boat, then why would you drill a hole in it to relieve the pressure?? Wouldn't this contradict the purpose of the plate? Who cares if there are "cav burns" on the plate? If they are just a result of the plate doing what it's supposed to do, then I would thing this is a good sign. I don't understand all the fuss about the wear. It's really not a very "technical" part...if it wears out while doing it's job, make another one!
So what am I missing here? :idea:

[LVjetboy]

"So what am I missing here?"
Nothing.
Consider...THE PURPOSE OF A RIDE PLATE? The question I posted on the second page of this thread. Yes, the mechanism for plate errosion may not be all important. Although knowing that may lead to understanding. And the truth in all things is why some question for better understanding. Question everything.
The truth: Pitting is not from high temperature or "burning." Trust me. Beyond that?
From my understanding, a ride plate has more than one purpose. If that's true, plate pitting may or may not be good depending on application. I'm no racer. And I'm not saying plate pitting is good or bad. Just commenting on the real reason for pitting and wondering what design makes the ideal ride plate for a given application.
jer

[LVjetboy]

"that would be north anna..."
The nuc...I think yes. My shot...more to the west/southwest if I remember. Here's another...
http://members.cox.net/lvjetboy/AnnaAir.jpg
jer

[Ken F]

I remember reading a really good post, or an article on what causes "cavitation burns" on the back of an impeller. Maybe it was from Jack Mc.....my memory is getting bad with old age! lol
Can anyone post a good explination of what actually causes cavitation burning on the back of an impeller? I think that would solve the question about what is going on with the bottom of rideplates.
Jer?
Ken F

[miketsouth]

all you ever wanted to know and more than you can understand about cavitation (http://caltechbook.library.caltech.edu/1/00/content.htm)
just too much information and WAY too much math.
There are some nice pics of the bubbles though
and and easier one on the mind (http://www.cheresources.com/centrifugalpumps3b.shtml)
[

[Duane HTP]

Steelcomp, I agree with you 100%. No fuss at all from me about the pitting. Just trying to always learn more about jet boats and how to improve them. Drilling the hole was just an expirment. I expirment on this stuff all the time. I have several different projects going on right now. Drilling the hole may have been the wrong thing to do, but by putting the results of what it did here, maybe you or someone else will pick will on a new idea from it that will help all of us at some point and time.
Mike, thanks for the interesting reading. That is fantastic material.
I was going to work in the yard today, but now I'm hooked on it. Thanks!

[LVjetboy]

"So the fluid comes in from the opposite side at this high velocity and bangs against the metal creating the impression that the metal was hit with a "ball pin hammer"
Mike, good link. I thought my hammer analogy was original. :hammerhea Also liked this...
"Cavitation erosion from bubble collapse occurs primarily by fatigue fracture due to repeated bubble implosions on the cavitating surface, if the implosions have sufficient impact force. The erosion or pitting effect is quite similar to sand blasting."
My point, cavitation damage primarily fatigue failure not temperature driven. Thus cavitation erosion or pitting...not burn. Whatever. Purpose of a ride plate? Who cares. Nobody took the bait so carry on. I'm done with this thread.
jer

[miketsouth]

taken from this site (http://www.key-to-metals.com/PrintArticle.asp?ID=14)
Abstract:
Aluminum owes its excellent corrosion resistance and its usage as one of the primary metals of commerce to the barrier oxide film that is bonded strongly to its surface and, that if damaged, re-forms immediately in most environments. On a surface freshly abraded and then exposed to air, the barrier oxide film is only 1 nm thick but is highly effective in protecting the aluminum from corrosion....
cavitation easily strips this layer, i suppose. The relatively high energy oxygen liberated from the caviatating water binds with new aluminum. equals heat. promotes temperature .
Pops seems to have the solution for a rideplate. Wonder if it would work on an impeller?

[Ken F]

Mike,
Thanks for the links, even though the first one really hurt my head!
This is definatly what is happening to the bottom of the rideplates.
Duane,
I kind of doubted that there would be ENOUGH vacume created under the rideplate to raise the nose, but you stated that it was necessary to raise the angle a degree or two to make the boat ride correctly after drilling your hole.
This would indicate that there is in fact enough vacume created to raise the nose.
Was there less evidence of cavitation after drilling the hole in the rideplate?
Did the size of the hole need to be increased to compensate for the vacume created under the rideplate, or would any sized hole relieve the vacume?
Ken F

[Duane HTP]

I kind of doubted that there would be ENOUGH vacume created under the rideplate to raise the nose, but you stated that it was necessary to raise the angle a degree or two to make the boat ride correctly after drilling your hole.
That's true Ken, BUT, not scientific. Maybe we had to raise the plate because of less surface now running on the water??? I just know what happened, not why it happened. However, vacumn is what causes the low pressure area that creates the bigger bubbles.
Was there less evidence of cavitation after drilling the hole in the rideplate?
It eliminated it altogether on this particular application. Now, was that because of a cooling effect from letting the air in, did it add more bubbles that were of the type that were not collapsing, did it remove the higher pressure area that causes bubble collapse, or did it remove the wall effect that the bubbles had been collapsing against???? This thread has brought more questions to me than is has answers.
Did the size of the hole need to be increased to compensate for the vacume created under the rideplate, or would any sized hole relieve the vacume?
I can't answer that question. The findings on this phenonenia were strictly accidental. ( just like so many other things). We were just making the hole big enough, (approx. 3/8"), to get an allen wrench to the bolt that holds the back of the toploader down to the pump throat.
Once again, Mike thanks for the excellent reading. I read every word of it, and am picking up some of the mentioned books from the WSU physics library Monday. Very interesting stuff here.

[HoffmanEagleMarine]

CBR, your ride plate is done! Let us know when you receive it.... Doug

[bp]

[QUOTE=Ken F
Can anyone post a good explination of what actually causes cavitation burning on the back of an impeller? I think that would solve the question about what is going on with the bottom of rideplates.
Jer?
Ken F[/QUOTE]
it's not easy to provide a simple explanation of the cause of cavitation. first, there are some physical concepts that need to be accepted or understood. these concepts may seem simple, but they really need to be understood. simply taking a couple of excerpts out of a lengthy text doesn't describe what's really happening, and since jer's done with this thread, i'll give it a shot.
first, water changes phase to a gas at 212F at atmospheric pressure, 14.6psi. the gas is the same 212F as the water; there is no difference in temp.
if you reduce the pressure to, say, 0.25 psi, water at 60F will change phase to a gas. this is a physical law.
now, here is the key that is also a physical law, but that is very difficult to comprehend without the math and the physics classes. the energy, measured in btu's, in 1 pound of 60 degree liquid is approximately 28 btu. when that liquid converts to a vapor, at 60 degrees, it contains 1059 btu. when that vapor condenses back to liquid, that energy must be released (conserved).
psat refers to saturation pressure, or (simply) the pressure at which water will change phase to a gas (and vice versa) without changing temperature.
the cavitation you see on an impeller occurs when the pressure at the eye of the impeller is significantly reduced to psat, or below, and the liquid converts to a vapor, generally seen as small bubbles. the bubbles don't travel far before finding a higher pressure location, where the psat is higher and the water cannot exist as a vapor and must condense. the "marks" left on the vanes are from the vapor bubbles giving up their energy as they condense back to a liquid. this energy can do ALOT of damage. an electric driven cavitating pump sounds like it is pumping rocks, and can destroy an impeller if not quickly corrected. the type of cavitation we see is generally minor as these pumps are designed to operate with very low net positive suction head.
regarding the plate, think about the fact that you have a speeding boat with a big hole in the bottom sucking a hole in the water, and basically, that hole is "sealed" by all sides of the keel. as the hole moves behind the shoe, atmospheric pressure refills it, but if the boat is running fast enough, how long does it take for atmospheric pressure to refil the hole? in other words, there is a negative pressure somewhere behind the shoe biting edge that drops to a low enough level, at some location, that some liquid is vaporized. as the boat moves forward, the vapor that contacts the plate condenses, giving up its energy at that point. if the engine was silent, you would hear it. the vapor bubbles that do not give up their energy to the plate escape, and condense in air, or simply condense in the water. in any case, energy is conserved and is given up to the medium in which the condensation occurs.
duane's "hole" is acting as a "vacuum breaker", in that it is allowing atmospheric pressure to enter the area below the plate which raises the pressure there so the water cannot exist in a vapor state, and must condense before contact.
in both cases, temperature of the liquid/vapor/liquid transition is the same, no change. this does not mean that no temperature increase is transferred to the medium (impeller/plate) that the vapor bubble condenses against. energy is given up as the bubble collapses, and part of that energy can be seen as heat energy, part of the energy is given up to the passing liquid. but it would take a whole lot more instrumentation to determine how much, than it's really worth.
think about it this way.. if you took a torch and heated a 2lb nut to 1000 degrees, and dropped it in firebird lake, how many degreesF would firebird lake rise? :cool:
hope this helps

[miketsouth]

.....since jer's done with this thread....
....think about it this way.. if you took a torch and heated a 2lb nut to 1000 degrees, and dropped it in firebird lake, how many degreesF would firebird lake rise?... :cool:
:D

[Duane HTP]

That's a pretty good answer BP.

[Ken F]

BP,
Thanks for taking the time. I have read enough on the internet to basicly understand what causes cavitation, though I've never had enough physics to really have a good understanding, but I'm able to grasp the concept.
from what I've read I'm in agreement that heat has very little (or nothing) to do with the pitting which occurs on both an impeller or rideplate, rather a mechanical (?) damage is occuring as the implosions take place near a solid surface.
I feel certain that your explination will help many understand what is happening to their rideplates.
Thanks again,
Ken F

[Squirtin Thunder]

Burned Ride Plate Pic;
http://www2.***boat.com/image_center/data/520/2311Burning_Ride_Plate_0001.JPG

[Cs19]

Thats not bad ST. IVe seen some that are REAL bad, wheret the plate is warped and pited to death.
Ive got Cyclones old plate off the Rogers, its pretty bad!

[miketsouth]

Burned Ride Plate Pic;
http://www2.***boat.com/image_center/data/520/2311Burning_Ride_Plate_0001.JPG
thank you. Now i have a better idea of what it looks like (since i probably will never see it).
That looks like it was caused by shoe/rideplate angle. I would guess the rideplate was not parallel to the shoe (a little up)?
Maybe caused by the intake grate? Did it exist on the shoe too?
I have looked at a couple of shoe/rideplate angles. I usually see some up angle to the rideplate, compared to the shoe.

[NELSON#109]

Holly Split.....no Wonder Engineers Dont Want Anything To Do W/ Squirt Boats... By The Way, Thanks For The Help Duane, The Cp Should Get Wet At Fbc, N Should See The May Race.... Cross My Fingers... Thanks Again.... Nelson....

[bp]

one more (little) thing. the "bubbles" talked about when we talk about vaporization are very small. they are actually water molecules exploding to approximately 26 times their size. looks more like steam or vapor than foamed up bubbles.