Austin and I toyed with the idea of putting a small hydrofoil fin on the nose of a longboard. When you were back on the tail it would be totally out of the water but when you walked forward out on the nose the fin would make contact with the water and provide lift at the nose. We never got around to making the prototype.
I'd be keen to try out those hydroboards as well..... i just think it would be wierd to have the foil underneath you when your paddling....
One idea i thought of, was a retractable hydrofoil, for paddle in surfboards.
The aim is that when your paddling the foil is lifted, say between your feet for easy paddling.
Then once up, you stomp down with your backfoot.... and push the foil down once on the wave.
Here's some professional graphics I laboured over for around 3 hours.
Please excuse my 'cutoff' surfer.... but this is the paddling stage with foil up...
And you definately gain muscles like this mad ass surfer...... surfing along without even needing a wave!
Well all average drawings aside, what do you guys think about the idea of a retractable foil?
I think forces generated would be pretty stiff on the thing, so to keep it down, it could have a locking mechanism once pushed down, and one to keep it up when not in use, but easy to push down and lock....
Wrap your head around that for a minute..... or just dont bother and save yourself the time ;)
p.s - i do characateurs, special mates rates if you mention this swaylocks post!
"Well all average drawings aside, what do you guys think..."
I think hicksy got it right .."wozzies do strange things !"
welcome mate !
sydneysiders do strange things too ! [I know , I lived there for 20 years]
definately keep the photos and experimenting coming ,
"Turns like a skateboard" Will you please/You must please/Please won't you post more pics of your current set-up, mounts, how-tos
Too bad about the chop thing--was thinking it would be less affected by chop since youre planing on water under the surface bumps, but I wa thinking the foils were deeper than I guess they really are
Now I see what you mean by concave and convex foils. I thought you meant the foil cross section. What type of foil cross section do you use? something like an aircraft wing, symmetrical, flat bottom, etc? Do you find that the foils are very sensitive about pitch (nose up and down) changes, or is that why you have 2 foils, one front, one rear?
Interesting stuff, tell us more when you can.
Could I do this to an old body board I have? it's pretty stiff, and I could cut out a chunk and glass it where the foil goes or something like that. I've always liked hydrofoils, they just look cool to me. (I still remember the videos of the old navy boats that had them, I thought they were the coolest!)
After all that research, you still want some input. I am no aero/hydrodynamicist, but have you played with switching the canard out to the rear, like most conventional aircraft? I remember reading that canards are more susceptible to front foil/canard stalling due to their CG being forward, between the center of lift of the main foil (what you call the slave foil) and the canard, hence the stubby shape of most canard aircraft and their fully floating control surfaces (not hinged). Because the canard is continually keeping the slave from pitching too far down, unless the CG is moved forward by you shifting weight to the front of the board. Can the canard stall before the slave/main foil, since it is already at a slightly higher AOA, or are the foils so shallow that the hull of the board contacting the water will prevent this?
Or, are the foils of comparable area, so none of this makes sense?
Also, I see you have concave and convex foils, have you tried dihedral/anhedral? By looking at lift force vectors, it seems that a concave foil would allow for more maneuverability, as the 'spread' of the lift vectors would try to destabilize the foil a little in the yaw axis, while a convex would try to 'track' more. But once engaged in a turn, my guess is that the convex would hold more/generate more turning force/want to stay in the turn longer than the concave. Of course, I am not thinking of the other struts that attach it to the board, just the main foil. Dihedral/anhedrals seem like they would be much easier to analyze than curved surfaces for their effects.
Keep the pics and explanations coming, I appreciate the work you have done, and that you are sharing with us. I don't think I am near a good enough fabricator to try this stuff, but it's nice to know someone has worked these things out, I bet the ride is awesome.
This is a hydrofoil board ( tunnel running as semi 'slave' fin, also nice dialled up with lift )
One of our previous successful hydrofoil designs from the mid 90's were two inline singlefins with flat bulb tipped foils attached to each fin. . . foils 12 inches across and two inches fore and aft, half an inch thick. The front inline single was 25% up the board from the tail, the back one right on the tail. . . . the front single just tall enough to mount the wing 3 inches or so from the bottom.. . the back fin ten inches deep with the wing 5 inches from the bottom. .. . the front wing a degree or so higher in AOA than the back one. .. . they flew by the way.