Hydrofoil Questions

[tiller98]

I wonder if anybody on this site has done any work with hydrofoils. I have been designing and building two person hydrofoil sailboats for a couple of years and was wondering if anybody had experience using push-pull cables or some other method of controlling the "ailerons" on the foils. On my design the skipper controls the roll, pitch, and yaw much like an airplane with stick and rudder but rigging this system has proven to be one of the most difficult aspects of the build. Any thoughts on a good interface between skipper and ailerons? To see what I'm talking about, check out my boats at:

http://corycraft.blogspot.com

[Submarine Tom]

Cory,

I use two hand levers to independently control the ailerons and a centre pivoting foot platform (a mechanical mixer) to control the elevators and rudders simultaneously on my micro subs.

Works great!

-Tom

[Tim B]

That's a mechanical mixer, Tom, not a swash plate. A swash plate is used to mix cyclic and collective control inputs on helicopter rotors. Google for details.

Control rods spring to mind; just make them stiff. Servos and direct connections are good if you can make it watertight. You might also want to run the hydrofoils from an autopilot to simplify the controls, in which case the latter is probably the best solution.

Tim B.

[daiquiri]

How come Doug Lord didn't jump in yet?

[Doug Lord]

Originally Posted by tiller98

I wonder if anybody on this site has done any work with hydrofoils. I have been designing and building two person hydrofoil sailboats for a couple of years and was wondering if anybody had experience using push-pull cables or some other method of controlling the "ailerons" on the foils. On my design the skipper controls the roll, pitch, and yaw much like an airplane with stick and rudder but rigging this system has proven to be one of the most difficult aspects of the build. Any thoughts on a good interface between skipper and ailerons? To see what I'm talking about, check out my boats at:

http://corycraft.blogspot.com

===============
Cory, very interesting stuff! Don't hesitate to post under "sailboats" or "multihulls". There is a wealth of hydrofoil related info here: check out "Foiler Design" and "Moth on Foils" under sailboats.
I used a push-pull cable on my first full size foiler and have switched to using carbon tube pushrods which are easier to eliminate play.
Check out the various topics on different foilers in "multihulls". You will run across the modifications a couple of Rave owners did to their boats by eliminating the wand altitude control system and replacing it with a set-up very similar to yours.
Best of luck-and have fun!
PS- if you don't have it already you might want to invest in Ray Vellingas new book "Hydrofoils Design Build Fly" which is filled with excellent reference material for any small hydrofoil designer. Also,if you haven't already check out
www.foils.org and this site-it is in French but you can read it fairly well using google translate: http://foils.wordpress.com/

[Submarine Tom]

Tim B,

I am well familiar with what a swash plate is, I don't need to Google it, that's why I put it in quotation marks, it wasn't a literal meaning.

You are correct however, it does not rotate nor does it move "up and down" (in this case fore and aft).

It's the closest I could get to describe what I've made. Is my edit more to your liking? If not, then I suspect you simply don't understand what I mean.

-Tom

[tiller98]

Thank you all for the quick and helpful responses. Tim, the boat is too small to use an autopilot and one of the design goals is to have the operator in full control of the boats attitude, but interesting idea. Doug, thank you for the suggestions. I will spend some time researching them. I really like the carbon pushrods idea. In fact, I think I have to run out to my shop right now...

[Doug Lord]

Originally Posted by tiller98

Thank you all for the quick and helpful responses. Tim, the boat is too small to use an autopilot and one of the design goals is to have the operator in full control of the boats attitude, but interesting idea. Doug, thank you for the suggestions. I will spend some time researching them. I really like the carbon pushrods idea. In fact, I think I have to run out to my shop right now...

=====================
Cory, found the Rave mod pdf-take a look:

[Tim B]

Tom,

Much appreciated. I think one of the biggest problems we have these days is the use of the wrong terms to describe what we mean.

Cheers,

Tim B.

[tiller98]

Thank you Doug. The PDF showing the Rave conversion was one of the most helpful articles I have seen on the subject of manual hydrofoil control. Pictures really are worth a thousand words and the close ups in that article were particularly helpful. I am going to incorporate several of the ideas. Time to pull the boat out of the water and fiddle with it for a week or two!