Foiler 2 seat hydrofoil

Hi,
My name is ryan archer and i have designed a 2 seat hydrofoil called the foiler. I plan on building it out of fiberglass with a direct drive steering system on the canard foil. The mold for the boat will be made from plywood, i've attached pictures, i plan on running a 40hp evinrude motor, i have not mounted the motor to the cad model yet as i'm still figuring out CG,
i'm trying to figure out how to mount the steering system, my father thinks that the front foil will be ripped form the vessel as soon as it goes past 5mph, i could make a sweeping system, say it pivots on one rod, and then the controls are from another rod in a sweeping unit, i'll post pics in a bit, but anyways, here it is, the foiler. a Ryan Archer design.



Ryan

 

You might get some design cues from this:
http://au.youtube.com/watch?v=wObflyTPLvM&feature=related

I think pitch control is an important issues. Your renderings do not indicate how this will be achieved.

Bicycles that have rear wheel steering are hard to impossible to ride as they are inherently unstable. I expect you will find a similar instability with a rudder at the front of a water craft.

If you compare the foil area you have with the one in the video you seem to have an extremely large area.

You could also look at air chairs to get proportions and foil shapes. They seem to give away a lot of efficiency to gain maneuverability. There are benefits in a single strut to reduce strut drag. Also foils suffer wave drag. It becomes significant when the foil is within 3 chord lengths of the surface. So this tends to push towards shorter, deeper foils.

Rick W

 

the reason i went with a larger area is:

so it would be foilborne at around 20 mph, I've seen the video before and i really didn't like how the craft would not remain foilborne when turning, because either he didn't have enough lifting surface when he was turning or he did not have enough power to maintain his speed during the turns.
i don't want to go that fast, so i added more wing area, i know it causes more drag aswell, but i think the trade off's are how i want,
as for the stability of pitch,
i've read that a surface piercing foil is inevitably stable in roll and pitch, the back foil is surface piercing to aid in stability and the front has dihedral in order to aid in stability aswell there are tiplets on both foils adding to the stability even further. as for the bycycle reference i think you are correct.
i will probably need to mount the front foil completely stable and add a rudder in the back, if needed i could put a gyro with a servo on the front canard and add control surfaces, the reason i have such a big vertical stab for the canard was to have it mount strong enough, but i can change this now because i am going to add a rudder, also i can now run a pull pull linkage to the rudder which will be a lot easier to steer with no dead zone.

what do you guys think?
Ryan






>edit<
here is an updated picture.

 

I think your renderings look nice, elegant even, but maybe impractical.
The technology to build wings like that could be expensive (could be more than the cost of a regular boat or jet ski!).
The youtube video above can teach much.
What Yamaha did, with expert engineers and big budgets, is shown on the video. Only short wings made of regular metal and fiberglass were needed, so that is what they used.
To use low horsepower, you could use bigger wings, but not as big as your pictures. The reason the boat in the video sinks a bit in turns is centrifgual force -video claims 1.4g in turns! Surface piercing foils would sink too, if you turn hard. Foils that are too big make a boat uncontrollable.

The Japanese designer Horiuchi also made simpler versions shown in the video at 7:30. If you followed the principle of the outboard skiff version it would probably work and be affordable.
40hp is probably more than enough motor, and it might weigh too much. The more weight, the more stress on the foils, the more expensive construction to build them, etc.

If I were trying to make a foil motor boat of a new design I would definitely try a radio controlled working model first.
And do a lot of math.
I would also make the hull of plywood, which would be cheaper lighter and stronger than fiberglass.

 

I have a couple questions on your design. Not from an engineering standpoint, but from a guy who's had some run-in's with submerged objects.

I'm complete agreement with your Dad. That Cunard is too 'futuristic' to be practical. There aren't any exotic materials in this world that will survive an impact of 40Mph and survive with that single-point suspension cunard design you have.

What if you made your Cunard the steering device using a 'rudder' theory, like turning the Cunard from side to side and also the elevators would be in the Cunard to aide in steering.
You could make the Cunard stronger and the little wings shorter and much sturdier.
Then move the weight bearing wing further forward and the Cunard a little rearward or at least extend the hull forward a bit so that if you did have an impact with a submerged object, the ship wouldnt dive straight into the water at such a steep angle. AKA Suicide dive at 40Mph.

How about this idea? Put the Evinrude up front and mount the Cunard on the lower unit of the Evinrude.
You'd have steering from the front and if you made the elevators in the Cunard you'd have some Porpoising control by tipping the Evinrude a little bit Fwd or aft.