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WakeWorld Discussion Board » >> Boats, Accessories & Tow Vehicles Archive » Archive through November 17, 2003 » custom aluminum diesel twin-prop wakeboard boat??? « Previous Next »
By Doug Triebelhorn (beginpend) on Friday, September 05, 2003 - 4:08 pm:    Edit Post Delete Post
I am a metal fabricator and intermediate boarder. I currently own a 93 reinell 18' boat with a 205hp V6, tower, and 600# ballast. The wake is not that great and with an aggressive rider the speed is hard to maintain. I am considering a real wakeboard boat, but I love the look of the aluminum jet sleds (Duckworth). I was considering having a 21' bare hull out of aluminum by NW Jet Boats and then adding something like a Duramax or new Cummins diesel engine and a hydrostatic pump/tranny out of a combine (large farm implement) turning two hydraulic motors attached to seperate counter-rotating props. With 300 hp, 500+# torque this would give AWESOME pulling power regardless of boat loading!!!! Also, 3000# welded-in auto-ballast system, Perfect Pass, single pylon (like a flagpole), centered drivers cockpit. What do you think. I would like to find the ultimate hull shape/size and clone it in alum. Since I will be doing most of the work,I figure this whole project will cost in the neighborhood of 30,000$. It's not so much about the $, but I love uniqueness and building stuff. What do you think? Am I crazy?
 
By Salmon Tacos (salmon_tacos) on Friday, September 05, 2003 - 4:40 pm:    Edit Post Delete Post
1. I'd go with a single prop for a cleaner wake.

2. Why at pylon instead of a tower? Towers are much nicer and if you can weld up your own...

3. Make the ballast system like the Calabria Pure-Vert system. fast fast fast

4. I'm not sure what you are talking about with the powertrain but it certainly sounds adequate.

 
By Doug Triebelhorn (beginpend) on Friday, September 05, 2003 - 5:07 pm:    Edit Post Delete Post
The diesel engine would be attached to the hydrostatic drive (which is basically a variable speed oil pump that converts rotation to oil pressure). That is how they get the diesels to adjust speed and maintain a constant speed in their peak torque range. The pump would then send the oil through high-pressure hoses to the hydraulic motors (which convert oil pressure back to rotational motion) attached to the prop shafts.

Why would two props harm the wake?

I was also thinking of polishing the whole thing and painting it to resemble a Coors Light can.

 
By walt leonard (walt) on Friday, September 05, 2003 - 6:21 pm:    Edit Post Delete Post
It sounds like you want to pull stumps not wake boarders !
 
By Salmon Tacos (salmon_tacos) on Saturday, September 06, 2003 - 3:42 pm:    Edit Post Delete Post
Two props would muck up the wake a bit because of the prop wash. When you have one prop in the middle, it's not too bad. Imagine, instead, two props with their wash going right into the already-formed area of the wake.

Why do you want two props?

 
By Kirk (kirk) on Saturday, September 06, 2003 - 6:08 pm:    Edit Post Delete Post
Doug,
Where you located? NW Jet makes a great boat...
I have fished the Reach in one, but wakeboard?

Kirk
Tri-cities Wa.

 
By Kirk (kirk) on Sunday, September 07, 2003 - 1:19 am:    Edit Post Delete Post
I think CC already owns the patent on this idea...
 
By Doug Triebelhorn (beginpend) on Sunday, September 07, 2003 - 9:40 am:    Edit Post Delete Post
Kirk,

I'm in Pendleton. I talked to the NW Jet Boats owner and he said he could sell me the hull in any stage of completion I wanted. I was going to take measurements and pictures and have NW Jet Boats clone the actual hull shape of a good wakeboard boat. I guess two props is not a good idea.



 
By Wake Products (tahoe) on Sunday, September 07, 2003 - 11:04 am:    Edit Post Delete Post
If you polish it to look like a Coor Light Can, will you be using beer for ballast ? hahahaha

Seriously though, I think the diesel exhaust will be kinda rough on your riders. Also with an aluminum hull your gonna need to add a buttload of weight to make up for this lightweight hull. Twin props aren't needed unless you plan on going 100mph.

I think you would be better off spending the 30K on a real wakeboard boat & use your time boarding, instead of being in the garage. Just my opinion!

 
By wakeman (skihardkore) on Sunday, September 07, 2003 - 5:29 pm:    Edit Post Delete Post
I think it's an amazing idea. The hydrostatic would be awesome for a boat! I've never thought of that before. Should be an absolute breeze and pleasure to drive. It will hold any speed! and pulling riders (and any islands in your way) out will be a cinch. Diesel exhaust would be the only concern....but, the newer engines are pretty clean....what about getting diesel on the water? Is that a problem in your area? If you could, the calabria N-vert system would be and awesome system. Are you familiar with it? Anyway, it sounds like an awesome boat, and you should definatley build a tower on it
 
By Doug Triebelhorn (beginpend) on Sunday, September 07, 2003 - 9:33 pm:    Edit Post Delete Post
Thanks for all the input. I mentioned before about a + - 3000# ballast. The reason for the alum. boat is empty it would be a breeze to tow being so light but loaded with a ton and a half of water, and beer, it should throw a good wake.

Wakeman is right, the new generation of diesel engines are much cleaner and quieter. I'm sure all of you have seen a older dodge or ford pulling out of a intersection spewing black smoke. Not so with the newer engines.

I think single prop is the best way. Just a large diameter. Large diameters are more efficient at pulling that a smaller diameter one.

A polished alum. tower would be pretty sweet.

Not familiar with the calabria ballast system. Have only been in a few actual wakeboard boats. Only two people in my city one one. One MC X-star and a Centurion.

(Message edited by Beginpend on September 07, 2003)

 
By Greg Hodgin (eccpaint) on Monday, September 08, 2003 - 6:29 am:    Edit Post Delete Post
I think this is a kick ass idea. You should definately go for it. You may start the next big thing! Your boat could be to wakeboard boats, as the H1 Hummer is to SUV's.
 
By derek boyer (toyotafreak) on Monday, September 08, 2003 - 6:48 am:    Edit Post Delete Post
Agree that the best approach would be to buy one and go ride. However...

With hotboats, you can buy a blank, just like the mfr. you've mentioned, just so you can mount your own powertrain. See if you can get a towboat mfr. to sell you a blank and then make it diesel.

One of the reasons they do this hybrid propulsion scheme in ships is to give flexibility in the drivetrain (what you've described is not much different than diesel-electric or nuke/diesel electric. The thing that would send you over the top would be if you mounted the drive motor & prop in a swiveling pod. This would give some real control in the marina.

And to take it one step further, adding a little up/down adjustment to the pod would allow for some pitch control for ride or wake tuning.

 
By Salmon Tacos (salmon_tacos) on Monday, September 08, 2003 - 7:40 am:    Edit Post Delete Post
Doug,

The Calabria ballast system uses most of the space under the floor as a tank. They have two big gate valves on the bottom of the transom which one can open at rest to fill the tanks or open at speed to empty them...simple and fast.

You can go to www.uspto.gov and search for patent # 6,234,099 if you want a better description.

 
By Ryan Bush (ryanbush11) on Monday, September 08, 2003 - 8:25 am:    Edit Post Delete Post
i think the idea is cool but what if you spend 30 grand on this boat, and then the wake sucks? then you've got a hudge piece of metal that you will never sell. anybody agree?

 
By Salmon Tacos (salmon_tacos) on Monday, September 08, 2003 - 9:13 am:    Edit Post Delete Post
I think he could be pretty safe there if he copies the hull of a wakeboard boat as he was thinking of doing.
 
By Jeff Guilford (fogey) on Monday, September 08, 2003 - 9:46 am:    Edit Post Delete Post
It sounds like a really interesting project. However, it's worth remembering that engineers with years of experience in designing wakeboard boats for a living don't get it right the first time with a new hull. That's why the manufacturers have R&D sections and spend many months of trial-and-error in development.

My guess is that getting a great wake the first time out is very remote, even using a proven fiberglass hull as a pattern. Too many variables are being changed, and we all know how much difference 100# here or there can make.

The PureVert system is elegant, but you would be building a prototype, for all intents and purposes. You will want flexibility and adjustability--i.e., the ability to move ballast wherever it's needed, and you definitely will need to control how much ballast is in each location. You cannot do either of these things with a PureVert arrangement. (By the way, using a PureVert system--even for personal use--would infringe the patent, but I guess we really don't want to go there).

Someone mentioned that the hydrostatic drive should have no problem with holding speed. But speed control issues arise from the hull's planing characteristics, drag, and load, right? I don't see how it will be any better than an engine with a gear-reduction transmission--and my guess is that PP is out of the question. For $30K, I'd sure want PP.

Finally, Ryan raises an issue that occurred to me, too. If you build a boat with a wake that clearly is superior to anything out there, you may be able to sell it when you're through with it. But if it is only as good as (or not as good as) production boats, why would a prospective buyer even bother to look at it?


 
By Doug Triebelhorn (beginpend) on Monday, September 08, 2003 - 1:54 pm:    Edit Post Delete Post
More very good points from everyone.

Greg, I agree with you. I don't want something that is extremely high maintenance fiberglass (even though the H1 is VERY high maintenance)and metal would solve that. It would be a multi-purpose boat that I could do other things in (occasional fishing). No ballast and you could ski or fish. How many of you wakeboarders EVER fish out of your boat during the off season. My guess is not many.

Derek, I've tossed around the propuslsion pod idea for a while, including all day today driving around at work. Hydraulic motors are small and that would definitely be possible. My only concern would be the thrust loading on the shaft bearings. I will have to get some specs. from mfg.s

Salmon tacos, That system sounds very efficient since there is wasted time anyway getting the board on and line etc. ready to go and also while waiting for someone to get the truck/trailer.

Ryan, Why would the wake suck if the hull had the same shape and size as a proven design?????It shouldn't.

Jeff, I mentioned already of cloning a proven design. I wouldn't even consider this project if I had to design the hull from scratch. I'll let the big mfg. pay their R&D teams for that. You're right, the Calabria system would be hard to get the weighting correct on the first try with a single tank. Wouldn't two ballast tanks (one in back, the other in front) work? You could install a fuel tank sender/guage in each one to monitor/measure ballast amounts. This way you could open/close the valves to get the front/back weight distribution you wanted and with the "gas" guages, you could repeat it very accurately.

As far as pulling, I saw a cruise control (I think PP) that used a servo-motor attached to a drum/cord that constantly varied the throttle setting to maintain a speed the speed sender unit provided. Since this would be an automobile engine, the same as all other inboards, the PP should hook up to the throttle body the same way. The hydrostat would be to fine tune speed and then PP would maintain that. Also, a hydrostatic system is self-lubricating and infinetely adjustable. This project is doable, but I'll have to sack up to start over the winter.

As far as resale, I'm not even thinking about it. This boat couldn't be horrible and chances are it will be better than by 18' Reinell.

 
By Rod McInnis (rodmcinnis) on Monday, September 08, 2003 - 3:05 pm:    Edit Post Delete Post
Doug:

I am a little confused by what you meant by a "3000 pound welded in auto ballast system". If this means ballast tanks, OK. If this means welding in fixed ballast, then that is not such a good idea.....

As for the separate props: first question is WHY? The most common reason for using dual props is so that you can have dual engines, and twice the HP. Your application shares the output of one engine to two props, and I don't see the advantage.

I would be concerned about the shape of the wake with dual props. In a standard inboard, the prop creates a bit of a rooster tail directly behind the boat, and all of the turbulance and unsteady water is there. A typical dual engine boat is pretty wide, much wider than your typical wakeboard boat. You wouldn't be able to get the props too close together without the tip turbulance interferring with each other, so your choices are to have a wide boat or the props well to the side of the boat.

A wide boat is going to give you a wide wake, plus the extra planing surface will cut the size of the wake considerably (for a given amount of weight).

A narrow boat with the props close to the sides is going to put the rooster tails and turbulance right on top of the wake. Depending on the direction of rotation, the torque put into the water is going to make the wakes either curl into breaking wave or flatten out. Either way it might destroy the shape of the wake for wakeboarding.

I have my doubts about a pair of hydraulic motors dealing with 150 HP each and turning 4000 RPMs. The only experience I have had with hydraulic motors has been with high torque, low RPM applications: Winches, post hole augers, fork lifts, etc. Efficiency has never been their strong suit, and they always seem to leak oil.

I wouldn't expect there to be any trouble adapting the Perfect Pass to control the diesel engine. Getting the desired speed regulation out of a diesel engine in general is another issue. The industrial diesel engines generally have a rather narrow RPM operating range. A typical gasoline engine, as used in a boat, will have a usable RPM range from about 1500 RPM to over 5000 RPMs, and wakeboarding typically at 2000 to 2500 RPM. This provides a usable range, with control at the desired speed while maintaining top end for the ride home.

An industrial diesel engine likes to run, what, 2000 RPM? Red line at 2200 RPM? I suppose you could plumb your hydraulic motors so that you had a parallel connection of low speed and series for high speed.

This would certainly be an interesting project, if you were willing to take the risk that when you were done you had something that simply didn't work. I wouldn't suggest selling your Reinell until you were satisfied with this boat, however.

 
By Doug Triebelhorn (beginpend) on Monday, September 08, 2003 - 4:20 pm:    Edit Post Delete Post
Does anyone read previous posts??????

Rod, what I mean by welded in tanks is they would be of metal and permanent. They could be the bases of the bench seats or under the hull as in the Calabria system.

Your typical inboard prop is no larger than 15" diameter. I was thinking about dual 13". 13" X 2 = 26" width plus an inch or two between. Because your typical wakeboard boat has nearly a 100" beam, that leaves 72+" (3' each side) outside the props and wouldn't have to be "close to the sides". Each prop centerline would be 7.5" off center.

I have pretty much ruled out twin props. The reason I thought about them is that with 205 horse in my boat and 6-7 people and 600# ballast, it is relatively slow getting on plane. Twin props would have twice as much disc area and hence twice the "traction". If they were counter-rotating, in theory they would affect both wakes the same, either positively or negatively. Reg and rev. rotation props could be switched to change the effect.

If you had paid attention, I mentioned an AUTOMOTIVE diesel engine, not an industrial engine designed for constant rpm output. AUTOMOTIVE diesels' throttle characteristics are similar to gas' but with much better torque and fuel economy. I realize that a Duramax or Cummins redlines at 3300 rpm but right now I pull boarders at 2800 and I could prop/gear it to run at any rpm I wanted. More like 1600-1800 would be ideal for both economy and peak engine torque.

You mention hydraulic motors leaking. That is a real concern. But look at the environment most run in. Dusty, hot, constant binding (winches, augers, lifts). If they were kept cool and virtually dirt free, all you would have to fight is water/seal integrity and actual frictional wear.

Snap-out carpeting is a must along with numerous cup holders.

All these questions are awesome and help in determining if I will tackle this project. They also help uncover any problems I haven't thought about, such as the twin prop/wake integrity. Keep 'em coming.

 
By Rod McInnis (rodmcinnis) on Monday, September 08, 2003 - 5:46 pm:    Edit Post Delete Post
Doug:
Have you run any calculations on the hydraulics for this idea? I am not a hydraulic engineer, but my quick calculations just don't add up to being close to what you need.

I can't get 300 HP into a hydraulic motor at any reasonable flow rate (gallons per minute) or pressure. For safety reasons I wouldn't want to operate at more than a few hundred PSI, and at those pressures you need thousands of gallons per minute of flow. That means enormous hoses/pipes.

Efficiency loss would also be significant. Since the efficiency loss usually goes into heat, most of which ends up in the oil, you will need a rather large oil cooler.

I would be interested in the pump/motor that would provide this kind of operation at the shaft RPMs that you would need.

 
By Doug Triebelhorn (beginpend) on Monday, September 08, 2003 - 9:09 pm:    Edit Post Delete Post
Rod,

You bring up a good point about the efficiency loss. I am not sure this is the best way. I will have to pick the brains of implement dealers/mechanics. I just know on our ranch our 15+ ton combines run off of hydrostatic pumps and motors up and down steep hills. Thats just for the movement of the machine not to mention all of the threshing power required (that is also hydraulic). I have no doubt that the pump is workable, just not a "single" motor. That is why I was floating the twin prop idea. Divide 300 hp = 150 hp each. Much more managable. I could also gang 2 motors to one shaft.

About the hydraulic pressure. They operate in the multiple thousands of psi, not hundreds. That is how a small (relatively) pump can provide so much motion to different locations all over the combine. They don't rely on volume, mostly psi.

If this idea doesn't pan out, I may have to use a conventional drive.

 
By YellowDog (yellowdog) on Tuesday, September 09, 2003 - 2:11 pm:    Edit Post Delete Post
Doug,

As for the wake, it should have a pretty good shape. My last boat was a North River and it had a nice wake. The only problem I had was keeping the correct speed. The hull of a jet boat is built to plane at slow speeds so that you still run the shallow water but you can also slow down enough to read the rapids. However, with enough ballast, you shouldn't have a problem keeping the back of the boat in the water.

 
By Tony Neal (aneal000) on Wednesday, September 10, 2003 - 7:55 am:    Edit Post Delete Post
You had me interested until you said Coors Light can, now if you had said Bud Light I might of followed you!

Actually I think it is a great idea.

Suggestions:

Tower not pylon.

Would attemp to make the exhaust come out under the water.

Check with PP for use on diesel. I don't know if they are compatable... might be, might not be, would just check into it.

If you are going from scratch you might as well build a hydrofoil (like the wedge) for the rear and one for the front, make them both hydrauically retractable and be able to remotly adjust their angle.

 
By Richard G (rich_g) on Wednesday, September 10, 2003 - 8:51 am:    Edit Post Delete Post
I say Go For It. You will get $30K worth of satisfaction just from building it. You'll be like Kevin Costner in "Field of Dreams". There is a custom boat mfg called Ski Pro www.extremeskiboats.com that uses a dual prop setup on an I/O. You could do some research on how it affects wake characteristics.

There are alot of variables. You could copy a classic hull design, but the weight distribution will be different. Make your ballast fine-tunable, and I would try to get it as low in the hull as possible (below floorline). You may also need trim tabs to eliminate porpoising.

 
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