Concept Boat Design Need Help

[Jus10]

Hello, I'm new to this forum. A bit of my background. I'm a deticated rc enthusiast with a lot of experience with scale and sport planes, helicopters, cars, and a little with boats. I've been wanting to take on a new project. Something different. I came up with many ideas but I'm fond of the one I'm pitching now hehe. I got some flack on another forum for my idea but some support. I know this isn't going to be some revolution of the boat industry, but just a fun project for me, if I give it the all "GO". Below is a quick sketch of what I was thinking. A somewhat scale looking craft powered by a ducted fan. Most likely a OS .91 with a 5" dynamax fan. I think this would be a unique project. I drew a more scale drawing on some graph paper. It ended up being suprizing close to the size of a 1/8 scale unlimited. I have not got to the point of putting it in CAD yet. I am looking for some construction ideas. I have not built a boat from scratch but I have built several planes. I've been reading as much as possible about boat construction, which information is hard to find. I'm trying to figure out if I do this what to use to build it. I am not fond of fiberglass and would prefer wood construction. I seen some designs are WOF. Is there a particular plywood that is used? (online source?) I am also unsure what type of finishing is used on these boats. Many have awsome paint and looks like glass. How is this done? Thanks for the help. If you have any question or ideas construction or on the concept please post them.

http://static.rcgroups.com/gallery/data/500/16899Sketch-med.jpg

 

[myrcbud]

It might work with a ducted fan engine, Iwouldn't use ajet engine though. I here jet engines don't take well to water and I pesonally would use water type rudder instead of a thrust type rudder for better control BTW cool concept

 

[izitbrokeyet?]

Good looking idea, but I have some bad news: It’s been my experience that small fans don’t produce enough thrust to get hulls up on step; they are limited to about 2/3 hull displacement speed. A fan drive units has lots of slip on the low end and won’t engage enough in the air to bring your hull up on step.

 

[Jus10]

I expect to get 10 lbs of trust from the engine and fan I would use. I've seen people state up to 15 lbs with that setup. Seems to high to me so I'll stay on the conservative side of the thrust numbers. I figure if those small airboats they sell could get on plane with a airplane prop I wouldn't have a problem.

 

[izitbrokeyet?]

It’s your money.....hope you have fun

I think you may have forgotten to mention how much thrust it takes for your hull to get on step.

How much were you thinking?

 

[Jus10]

You have any sudgestions to over come getting the boat on plane? Your saying the boat would just push water? I wonder if if changing the angle of the trust while moving would make it get on plane. I'm not suggesting thrust vectoring by any means. Just a way to change the attitude of the boat in the water.

 

[piper_chuck]

Good looking idea, but I have some bad news:  It’s been my experience that small fans don’t produce enough thrust to get hulls up on step; they are limited to about 2/3 hull displacement speed.  A fan drive units has lots of slip on the low end and won’t engage enough in the air to bring your hull up on step.

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Why does this sound familiar?

 

[izitbrokeyet?]

My apologies if the reality check seems harsh….don’t forget that your CL of thrust is above the waterline and will actually cause more hull drag as you add throttle.

I dont have any really good suggestions

 

[Jus10]

LOL, piper_chuck I knew you'd chime in... good to see you.

 

[AndyBrown]

It will work!

Built it simple first, because you'll need to make angle of attack, sponson width, C.G. location, and other ajustments until it's just right.

Build a good strong servicable center hull to support your power unit, radio, rudder along with strong mounting support for the sponsons.

Start with a 50% CG location on the afterplane. (back of front sponson to back of rear sponson)

Front sponsons - 5 dgree AOA 3" wide bottoms

Rear sponsons - 3 degree AOA 1 1/2" bottoms

Thrust line _ Zero degrees.

Keep deck lift neutral. High speed down force will need to be built into the hull.

This will take some trial and error considering you have no hull design experience.

Unless you're just building something to look at, forget the nice paint. Build it with foam and plywood.

Once you are happy with running performance then go for the fancy paint.

Don't go to CMDRACING.COM for a prop....cause you won't need one! LOL

But if we can help with anything else drop us a note.

 

[Mark]

Wow AB, sounds like you've built one before. Would be a great test bed for someone wanting to put a jet engine in an R/C boat some day. Who knows maybe this will be the beginning of the end for prop drive!

 

[John Finch]

The Navy did some tests on a model similar to this back in the 60s in a wind tunnel. It was powered like yours but the sponsons were in the rear like a cat boat. It did 72 mph if I remember correctly. Problem with turbines is sucking water and they blow up. Stay with the ducted fan.

John

 

[VansRacing]

Some of these type boats have already been built and tested around 12 years ago. You can contact Joe Momohan at 707 Specialties to find out who was building these and what kind of problems they had with this concept.

If I remember correctly, once they took a bad hit of water, they would almost start flying. Using air for thrust, the boat would not sit back down as quickly as a prop driven boat will.

Joe can tell you more about these boats. Hope it helps.

-Carl,

 

[John Finch]

Some of these type boats have already been built and tested around 12 years ago. You can contact Joe Momohan at 707 Specialties to find out who was building these and what kind of problems they had with this concept.
If I remember correctly, once they took a bad hit of water, they would almost start flying. Using air for thrust, the boat would not sit back down as quickly as a prop driven boat will.

Joe can tell you more about these boats. Hope it helps.

-Carl,

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Have you seen the new model boat that is also an airplane. Kind of the same concept except they took it a lot further. A video was on this site a month or so ago. Awesome boat/plane.

 

[Joe_Knesek]

Have you seen the new model boat that is also an airplane. Kind of the same concept except they took it a lot further. A video was on this site a month or so ago. Awesome boat/plane.

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We should start a new IMPBA class for the boat/planes. Just think...3D lane infractions. Going to be over on the start, just do a loop!

 

[Jus10]

Have you seen the new model boat that is also an airplane. Kind of the same concept except they took it a lot further. A video was on this site a month or so ago. Awesome boat/plane.

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We should start a new IMPBA class for the boat/planes. Just think...3D lane infractions. Going to be over on the start, just do a loop!

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Funny you guys mention that... I'm waiting on my kit to arrive... It is a awsome and orginal concept...

 

[Tofastformellow]

i have been caught out thinking of this general idea, everytime im at the hobby shop looking at the ducted fans

you could use a fairly conventional

looking hydro and mount 2 or 4 ducted fan engines and a large rudder that would also direct the thrust aswell as hanging down in the water..

flaps and elevators would be a must, but aerilons would just be for trim.

if using 4 thrust units the possibily of using throttle variation to improve turning stability etc...

go for it. just remember that the record potential would be limited to 'non shaft driven ' type speeds..

jason

 

[Jus10]

i have been caught out  thinking of this general idea, everytime im at the hobby shop looking at the ducted fansyou could  use a fairly conventional

looking hydro and mount 2 or 4 ducted fan engines and a large rudder that would also direct the thrust aswell as hanging down in the water..

flaps and elevators would be a must, but aerilons would just be for trim.

if using 4 thrust units the  possibily of using throttle variation to improve turning stability etc...

go for it. just remember that the record potential would be limited to 'non shaft driven ' type speeds..

jason

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I'm not intending to break any records... but that would be a cool if it did work...

 

[Jus10]

I need construction materials. Where would be a good place to buy them? Perferably online. I can't make it to the not so local "LHS" for a week or two.

 

[Jus10]

I need construction materials. Where would be a good place to buy them? Perferably online. I can't make it to the not so local "LHS" for a week or two.

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The OS .91, Dynamax fan, JMP tuned pipe, Header, and starter probe are on the way! Also got a bvm "inflight" (lets hope not) mixture control hehe. Still looking for material source!