Shoe angle

[bo brown]

I have just recently purchased a 75 18ft Rodgers boat w/ LS7, Berkley pump. I am somewhat new to the jet boat world but eager to play. A friend of mine that has been around jet boats for a while was telling me something about setting the angle on the shoe to get maximum speed from my boat. Can anyone enlighten me on the subject and how and why this needs to be set? I am somewhat familiar where the shoe and diverter plate is located, I just need to know how to set it all up.
Thanks in advance for any comments.
Bo

[bp]

do you have any pics of the transom and pump? does your boat have a shoe/rideplate installed??
go to this site: http://home.pacbell.net/jmcclure/ShoePlate.html, and look at the third pic down. it gives an example of what is termed a "tapered" shoe, which is thicker toward the biting edge than at the back (i.e., angled "up" at the rear), and a "backcut" shoe which, from the biting edge back, is angled downward (as installed).
the "depth of the biting edge" below the intake, or shoe mounting pad, is critical in maintaining adequate suction pressure to the pump. if the depth is too shallow the pump can run out of water at higher speeds; excessive depth can result in overloading, causing other problems to the point of being unsafe. each boat is different, but in general, keep the biting edge above keel centerline (straight edge down the centerline of the keel, the biting edge should be above it).
in general, a "backcut" shoe will provide greater keel lift than a "tapered" or "flat" shoe. in other words, at a given speed (say 40), with a backcut shoe the hull will be riding somewhat "higher" on the water than the same hull with a tapered shoe; more lift = less drag = more efficient ride. less drag also equals quicker and faster.
in a faster and lighter hull, say a 400lb air entrapment hull over 110, it's likely that "more lift" is undesirable, in that the keel can be riding so lightly on the water that it can lose suction pressure - undesireable condition. or, the hull just gets too flighty at elevated speeds, dancing from side to side. in those cases, a flat or tapered shoe is desired to help keep the keel down on the water.
as a boat goes faster and faster, a low pressure area develops behind the intake opening, which results from water being vacuumed out of the lake/river. the pressure becomes so low that water molecules turn into gaseous form. the ride plate (or suction plate) provides an extended platform to stabilize the hull while the vapor condense back to liquid. without a plate to provide this stability, the hull could become unstable at higher speeds, trying to ride on vapor.
this kind of gives you an idea of what they are and what they do.

[Elimin8Jet71]

bp
That was very informative... nice right-up thanks

[bp]

bp
That was very informative... nice right-up thanks
you're welcome. i tried to stay generic because, at least to me, it's just as (if not more) important to understand concepts then it is to just hear "do this, do that".

[Cas]

you're welcome. i tried to stay generic because, at least to me, it's just as (if not more) important to understand concepts then it is to just hear "do this, do that".
kudo's to you Bob, that was one of the best explanations I've read in a long time. I'm really tired of the "do this do that" thing or the pm me, call me thing that is posted so often these days.

[hkunz]

Thanks for the post. I don't have a shoe, but this helps me undestand what one might do for me. Right now we occasianally get airborne at speed and then the motor over-revs, so a shoe that makes the keel "lighter" might not be the best idea, is my understanding.
I guess I just have to get it running with the new motor first, then dial in the other stuff.

[Cas]

I can explain it to ya better. PM or call me. 805-466-4719 :D :D :D
I wasn't pointing fingers, it happens a lot these days by many....professionals or not. Hell, you can ask bp, I kind of slammed him a few years ago because he would always refer people to MPD and DNE without adding much to the discussion. As shown above, bp has a sh*tload of knowledge to share from personal experiences from lake boating to a very successful racing career.

[bp]

Thanks for the post. I don't have a shoe, but this helps me undestand what one might do for me. Right now we occasianally get airborne at speed and then the motor over-revs, so a shoe that makes the keel "lighter" might not be the best idea, is my understanding.
I guess I just have to get it running with the new motor first, then dial in the other stuff.
h, shoe design make any difference when running over rollers or chop:) i've had my 23' hallett catch air, and it doesn't have any shoe at all...

[bp]

I wasn't pointing fingers, it happens a lot these days by many....professionals or not. Hell, you can ask bp, I kind of slammed him a few years ago because he would always refer people to MPD and DNE without adding much to the discussion. As shown above, bp has a sh*tload of knowledge to share from personal experiences from lake boating to a very successful racing career.
so that was you using an aliazz about 9 years ago??? i see the same things, but i'm not gonna comment - i already got one guy all fluffed up just from suggesting he get his own box in the "manufacturers" section, rather than multiple intermittent spam threads that just get lost in space.
i'll still refer people to mpd or dne when the question warrants it. in my view, they're the best out there at what they do, and my feeling about that won't change. but most questions don't need to be referred. on the other hand, i see plenty of people reference cstraub for a cam design - dne has been designing his own cams for well over a decade, and has 30 years of daily experience building some of the baddest jetboat engines around; but i'll defer from spamming him:D

[Cas]

so that was you using an aliazz about 9 years ago??? i see the same things, but i'm not gonna comment - i already got one guy all fluffed up just from suggesting he get his own box in the "manufacturers" section, rather than multiple intermittent spam threads that just get lost in space.
i'll still refer people to mpd or dne when the question warrants it. in my view, they're the best out there at what they do, and my feeling about that won't change. but most questions don't need to be referred. on the other hand, i see plenty of people reference cstraub for a cam design - dne has been designing his own cams for well over a decade, and has 30 years of daily experience building some of the baddest jetboat engines around; but i'll defer from spamming him:D
There's no doubt mpd is arguably the best in the biz when it comes to pumps...it's pretty damn hard to beat Jack's track record. As far as dne, based on what I've read, Dave builds excellent engines that last a long time.
Geez, we been around these boards for a long time and nope, I've always been Cas although my original screen name here was Cas42. I only used that for a very few posts in early '99 though. I think we had a bit of a run in when I quoted this-
Cavitation means that cavities or bubbles are forming in the liquid that we're pumping. These cavities form at the low pressure or suction side of the pump, causing several things to happen all at once:
* The cavities or bubbles will collapse when they pass into the higher regions of pressure, causing noise, vibration, and damage to many of the components.
* We experience a loss in capacity.
* The pump can no longer build the same head (pressure)
* The pump's efficiency drops.
The cavities form for five basic reasons and it's common practice to lump all of them into the general classification of cavitation. This is an error because we'll learn that to correct each of these conditions, we must understand why they occur and how to fix them. Here they are in no particular order :
* Vaporization
* Air ingestion (Not really cavitation, but has similar symptoms)
* Internal recirculation
* Flow turbulence
* The Vane Passing Syndrome
you got on me because of the referrence to cavities :D
Ahhh, the good ole days of the RJB board! I definitely learned a lot from that board....Jack and a couple of other pros answering questions and giving excellent tips.
You still using that LBBA t-shirt to polish your boat with? :D

[bp]

i still have it. i even have an old norcal ***boat t-shirt somebody, i think al, gave me about 8 years ago...
cavities... :rolleyes: no, i'm not gonna start rolling on fluid flow and thermodynamics again...

[bo brown]

Bp thanks for the information on the shoe angle. The boat does have a ride plate. I do not have any pictures of the bottom of the boat right now, but , I will have this afternoon. Sorry about not responding sooner, I'm a field service tech and have been out of town the last few days. This boat is a lot of fun. However it seems to have a little drag getting out of the hole. Once the boat is on top of the water it does great. From 20 or 30 mph it very strong. A friend of mine that plays with these boats a little was telling me to check the shoe angle. It sounds like the shoe angle has more to do with getting water in the pump. I just have a lot to learn about working on this boat and the do's and don'ts. thanks for your help I will go and look at the website you gave me. Thanks again.
Bo

[Cas]

what kind/style of loader does it have? The loader the the thing that is installed into the intake which is on the bottom of the boat. If you can get a picture of the loader also, it would be very helpful for people to help out.

[jetboatperformance]

I can explain it to ya better. PM or call me. 805-466-4719 :D :D :D
Hey Jon Am I missing something here ? do you not think some polite friendly tech help and explanation is appropriate Tom

[bp]

Bp thanks for the information on the shoe angle. The boat does have a ride plate. I do not have any pictures of the bottom of the boat right now, but , I will have this afternoon. Sorry about not responding sooner, I'm a field service tech and have been out of town the last few days. This boat is a lot of fun. However it seems to have a little drag getting out of the hole. Once the boat is on top of the water it does great. From 20 or 30 mph it very strong. A friend of mine that plays with these boats a little was telling me to check the shoe angle. It sounds like the shoe angle has more to do with getting water in the pump. I just have a lot to learn about working on this boat and the do's and don'ts. thanks for your help I will go and look at the website you gave me. Thanks again.
Bo
bo, shoe angle doesn't have an impact on launch out of the hole. shoe angle will make a difference in acceleration from 20 to 60, and on up.
talk more about what it does out of the hole - rpm, etc.

[bo brown]

The boat is a 17 ft Rogers. The engine is LS7 bored .030. It is making about 550 Hp. I don't know the exact speed yet but will put a GPS on it this week to see. However the boat has plenty of horsepower, it just hesitates out of the hole from dead stop. Once the boat planes it's great. The boat, if I had to guess, will run out at about 8o to 85mph. The guy I bought the boat from said he built the engine to push 100 mph. Don't know that it'll do that or not. It appears to be bringing in plenty of water through the pump. The boat is really quick once it's on plane. I have noticed that there is slack in the flap over the shoot of the pump. I guess that's the right terminology. I may need to try and adjust the cable in the shifting part to make sure it's not covering the hole on the pump when I'm taking off?
Thanks again for your help and explanations.
Bo

[bp]

flap = "reverse bucket", or "bucket"
shoot = "nozzle"
you say it "hesitates"; does the engine rpm hesitate, i.e., you hit the gas and it stumbles a bit? or does engine rpm climb to the moon without the boat moving??? two very different things.
with 550hp in a vintage rogers, i'd guess you'll top out somewhere around 75-80, which is really pretty good. you could always take it to bakersfield, put it on the track in their river racer deal and find out for sure.

[bo brown]

Thanks bp for the help. To answer your question, it stumbles for a split second and then accelerates fine. It's not like a cough or anything it stumbles a little. I guess after I think about it enough this would not be anything to do with the angle of the shoe. It may have something to do with carburation. The engine has (2) 750 holley's on it. Or I guess it could be the timing.
Bringing it to Bakersfield would be next to impossible as I live in Willis, Texas
That does sound like fun though. Not many jets around here, that I've found yet anyway.
Thanks again
Bo

[bp]

definately carburation - not timing. has nothing to do with main jetting, but is all about the idle and transition circuit, and possibly accelerator pumps, but more likely fine tuning is needed in idle/transition.
there are tons of jetboats in texas. southern dragboat association (sdba) is in texas.. http://www.sdbaracing.com/
also, ihba is in marble falls august 8-10.
however, their river racer programs are compitition, where the njba's is a get acquainted, make some laps kind of thing. if you're so inclined.

[bo brown]

Thanks for the help. This has been very informative. I have a lot to learn about these boats. I have been running a pontoon boat last several years, just trying to get some fishing in. Anyway I really appreciate your help with this. Obviously I'll have to do some studying. I have a tendancy not try and fix what ain't broke. But I do want to learn how to work on my own boat, if I can. Maybe with a little help from this forum I can do that.
Thanks again
Bo