Steering foil craft

We have few foil craft in New Zealand and the ferries we had were in constant trouble damaging foils.Which system is most favoured to steer foilcraft?

 

steering foilcraft

There does not seem to be much information about steering foilcraft other than conventional steering by outboard equiped foilcraft which is not as simple as it may appear as the foils have a mind of their own when it comes to directional control. Rudders don`t give good control of foilcraft either.Does anyone know of any other systems.

 

The most common method of steering hydrofoil craft is to have trailing edge flaps on the aft foil support struts. By themselves, the directional control from vertical flaps can be marginal; slaved to/with bank/roll control flaps on the main lifting foil and the directional control is just fine (making huge assumption, of course, that the overall craft design is properly done to start with). Same problem with trying to steer a foil-borne craft with only the outboards; it can be ugly if the craft cannot also be banked at the same time.

We've also built hydrofoils that use steerable nozzles on waterjets. Again, the directional control is good as long as turn and banking angles are fully and properly coordinated.

 

I believe the russian surface piercing hydrofoil ferries are steered by rotation of the aft ladder foil. The foil dehideral resists for the outward roll in the turns. Of the US military fully submerged hydrofoils, didn't only the Flagstaff (Grumman) and Plainview (Lockheed) 2-1 foilers have a steerable aft foil? All the others (Boeing 1-2 designs) and the Boeing Jetfoils had fixed foils and were "flown" by banking into the turns.

Anyway, open ocean hydrofoils have proven fairly fragile, with a lot of object damage over the years. So whatever method you use, it has to be strong.

 

I left out the PHM/Boeings...the OP seemed to be focusing more on the larger population of craft with simpler foil systems and not including/requirin full fly-by-wire flight control. That said, our last foil demonstrator craft (all of 43 ft LOA and 9 mtons) required fly-by-wire and full 3-axis computer stabilization to operate; manual attitude and steering control was flat impossible.

Rodriguez and several of the Russian surface-piercing foil designs used aft strut flap plus bank angle control; that was probably the best 'simple' solution I had seen in my years of working with foils.

 

The most current information for power or sailing hydrofoils with loads of detail is here:
"Hydrofoils Design Build Fly" by Ray Vellinga, Peacock Hill Publishing, ISBN # 9780982236116 avail at Amazon, I think....
Kotaro Horiuchi designed many powered foilers and he seems to have preferred bow steering-at least on small boats.
Most sailing hydrofoils are steered with an aft rudder/foil combination-both multifoilers and monofoilers.

 

Our demonstrator (fully submerged foils), the Rodriquez foils, Supramar, nearly all of the Russian designs, etc etc are all 'tail draggers' with the main foil just forward of CG and smaller balance-foil all the way aft. Hard to steer them from the bow.. That said, the old design in the OP pic could/would be a good candidate for bow steering; though still requiring some means of controling bank angle during a turn

 

Heres a video of Horiuchi's Yamaha foiler -bow steered:

http://www.youtube.com/watch?v=wObflyTPLvM

 

What's amazing to me is...it appears he is managing to fly that craft manually?? I tried to fly our 43-foot waterjet hydrofoil manually...managed about 1/2-mile of teeth-grinding extreme tension flight and did keep her more or less flying straight and level...before crashing by laying her over on her beam.


That video very clearly shows the critical requirement to correctly couple turn and bank angles too.

Neat stuff

 

---------------------
Horiuchi has got a great book out-lots of neat stuff! I think that boat had an altitude control surface sensor on the forward foil-I'll have to check later.
Several sailboats have been sailed manually on two foils-my first 16 footer, an International 14 in 1999, Mirabaud(26') 2010 and a couple of Rave(three foils) multifoilers.

 

But I'm quite certainyou are not going to a) tell me it is 'easy' nor b) just let me hop in one and give it a go.

I suppose that the manual flight control of our craft could have been masterd over time...but since the computer took care of it all, little practice in manual flight ever happened. It was so much nicer to sit back in my comfy Recaro seat and nudge one of the joysticks every once in a while.

Taking the control of height out of the man-in-loop control part would have made manual flight of our craft much easier..so I can see that being the key to flying the one in the video. Makes perfect sense then.

(Under auto flight control, we used a microwave bow height radar unit to feed the flight computer.)

 

If you look closely at the front strut, there appears to be a black colored surface sensor of some kind, maybe speed linked. IIRC, several of the sailing and HPV foilers out there have mechanical float type sensors linked into the foils to handle ride altitude so this may be what is going on.

I designed a couple of manual linked heave and pitch controlers for HPV subs, of course they wern't going as fast as this. The control yoke on SUBHUMAN II (she's in the Undersea Warfare Museum at Keyport) has full 4 axis (heave[depth], pitch, yaw, and roll) control by independent control of the 4 dive planes and vectored thrust. By pushing/pulling the yoke handles, she changed depth on an even keel, by rotating the yoke handles, you pitched her up or down. I think a little more though to the control set up and you could make it fairly intuitive for a foiler in manual control.

 

I don't doubt that..but we've reduced the computer-based fly-by-wire servo-operated flight (or motion) control systems down so far in cost and weight over the last couple of decades that we even deliver and install them in unmanned tank models these days...

But that does not mean I'm not completely fascinated by all the sailing foils and alos the personal foilcraft in that video.

 

===============
Actually, it is easy: On my boat it was easy except for foul ups that had nothing to do with manual control-like slack in the system(poor design), and I've talked to the guys involved with the Rave, Mirabaud(one man assigned to altitude control in rough water-far better than a wand). The I-14 guy said "it was a handfull" but he had manual control of the rudder foil only-all the others are manual control of the main foil flap(s).
I will use the Mirabaud system to some extent in the future: you can switch between manual and wand....

 

I suppose it does not realy matter if you have to remove the human pilot from control of even recreational foil craft. If we want a foil craft we have to learn to "fly". What does it matter when a few electronic controls will do the work much better. Thank`s for the info. We seem to be having a lot of crashes with small aircraft in New Zealand over the last few years and the craft are pretty sophisticated. We do not need a pilots license to fly a ground effect vehicle.