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Okay, you can tell I'm bored... my brain went there.... so...
Take a standard longboard. Add a rectangle made of metal, about 16-18" wide, and bolt it to the bottom of the board, near the tail, so that you have a "loop" that the water will pass through...
(top of board here, with "loop" hung beneath it.) ___________________ |______._____|
Now, make the bottom of that Loop a foil shape, so it will create lift and plane. (ASIDE: *maybe* even allow it to rotate slightly from front to back, so it can pivot/self-adjust, not sure) ... now when it gets moving, will this not plane out, then the hydrofoil causes lift, then ...?
Or do I need to go get a glass of wine or something?
I once read a thing on-line about a guy trying one out at san-o. Said it worked. I think it might be hard to trim with it, maybe have a keel like extension with wings at the base, kinda like a star fin except on a bigger scale. Would probably need a longer board and bigger wave to get it moving.
Hey Falc Go to www.neilpryde.com...go to bottom left hand index about hydrofoils It's been done, but mostly with shortboards. That foil is being tried currently in both surfing and windsurfing, besides kiting (not successful so far) modes. Seems only problem is that you can't turn as sharply, or quickly, as a normal setup. Smooth ride, great glide, can make flat sections. Too bad, you are not surfing the wave face.
Hell, wouldn't be that hard to make... I think I will give it a shot, find some POS log that nobody cares about and patch it in/on/through.
Shortboard might be better, but ya have to get a hydrofoil up to speed in the first place, and I don't know what that speed might be, but.... since part of the idea is for smaller wave days... I don't know, my mind's just playing with the concept right now. Trim WOULD be an issue.. too much lift aft and the thing's gonna dive the nose (cus it can't possibly support weight out there as ya step forward) so... Hrm.... need to place it as far forward as is likely to stay submerged.... I see alot of trial-and-error drillholes. Could be a blast... or a freaking disaster... but it still beats a day spend in an office, so...
Yeah, Sved, I hear ya... not sweatin' 'em much anymore... while trying to keep my ears open to legit positive critique.
Lee, the info's not there that way anymore on their site... even after I corrected the link.. but thanks!
Hey Falc Sorry. There is a posting about foils in the regular windsurf forum, about 10 down from the top. You can always use TWO foils, like my bud Rich Miller, here in Berkeley, for his windsurf board, to make it easier to ride and auto trim.
1) Stabilizing angle of attack. The normal range of AOA for surfing is too large for a foil - you'd need independent control of this for surfing. Something like a canard, or tilting system controlled by board/water angle. Other suggested a 2 foil system
2) Turns. Airplanes turned like crap before ailerons. Any decent hydrofoil surfboard will need ailerons, or the equivalent. These are little subwings on an airplane. On one side they turn up, and the other side they turn down, and this makes the plane rotate into a turn. This will need to be done based on rider weight or water flow to make a decent passive system.
I'd recommend reading a LOT about these issues in aerospace before trying it on a surfboard. Otherwise, you will merely retrace the failed efforts of the last 30 years.
One key factor to keep in mind (learned the hard way, after buying a sloop designed by an aerospace engineer) is that aerodynamics are decidedly different than hydrodynamics... inherently so, since (1) water can't be compressed and (2) it's exponentially more dense than air. That in mind, the aeleron concept DID come to mind for turning... but just a dab would definately do ya, so I figured I'd see if I could get it to plane out and rise stable first.
Two foils... that could be a solution... Or three, actually.. two smaller ones at the sides, further forward, and the main one centered a bit aft. Hrm.... thinking aloud again, but if those smaller foils could pivot on their axis points...?
for some reason i dont see it turning so well, i just see the board as being a cruiser, a wave thats easy to get into but peels for a long time might be best, just smooth simple glide. could probably get going really fast.
The bottom of the board already is a 'hydro' plane. You just need to adjust your bottom curve to make it glide better. I adapted some advanced hydrofoil technology to my modern shortboard bottom curve and shape over ten years ago. The results were reduced drag, increased drive, and speed and control I had never been able to take advantage of before. A huge leap in my surfing and board design.
Does the word 'reflex foil' mean anything to anyone?
Here's what it is: Just like an AERO wing creates lift by its shape (if you don't get that one, research it elsewhere, please,) a wing shape moving through water also creates lift. BUT, since water is so much more dense than air, it requires an equally exponentially lesser surface area to create sufficient lift. In other words, once the thing moves fast enough to create lift, a 1 foot "wing" could lift you and your board right on up out of the water altogether. Of course, that's not surfing anymore... and I'm just now realizing that it won't keep on moving once the board's out of the water, so the whole idea was probably a bust, but... at least now ya understand how hydrofoils work.
quote:Originally posted by Gee Dub: Thanks Falc, my typo error.
The bottom is the planing area, then combined with rail transitions and thickness distribution it becomes a foil.
Hey Falc I'm not so sure! Seems the guys ride the swell by staying slightly high on the face, and continuely head the board downwards, using gravity, to keep up momentum, thus staying up on the foils. It works once you get up to speed, and the key is never to slow down or ride out onto the flats. Oh, the NP site is working fine, just the last selection on the left,...rush foilboards....he windsurfs, kitesurfs, and paddle surfs his single foils!
Gee Dub, the critical difference between a planing hull and a foil is laminar flow. Any elongated surface flowing across water will create turbulent flow, and this includes all surfboards. Once you have a distance of more than 6 inches in line with water flow, it is a bust.
A principal reason to use a foil is increased speed. The foil should only be a few inches long (in the direction of travel), but must support the rider's weight across the direction of travel. It has laminar flow and a small wetted area, two reasons it is MUCH faster than a planing hull like a conventional surfboard.
Foils are, plain and simple, wings underwater. They work by re-directing water downward. The equal and opposite force (and water displacement) support the surfer and board. The foil has to be angled up from front to back. "Foiling" has a positive impact, but lift is all about angle of attack.
Even if you got one foil right, you are in a precarious position. Subtle fore-aft weight shifts disturb the balance. You don't see many planes with only one wing. Most have a principal wing, and a second set of wings to easily balance the aircraft. These are in front of, and behind, the center of mass, which makes balancing easy.
And this has already been achieved for surfboards, by many inventors. The tough part is steering. No one has developed a good passive system for operating ailerons, or other winged steering, for surfboards, and it is rather non-trivial to try to make one. So what happens when you can go really fast, but only in a straight line?
Did it to a shortboard and a longboard but the heavier the board is on top, the harder it is to balance when the foils lift up. Once the board is lifted up its shape is useless so its better to use a basic design thats light and easy to paddle. I made foils out of aluminium sheet, polycarbonate, soild wood, ply, cloth and resin. Its a simple thing to build and ride, the speed needed to lift a rider is quite low as long as you have enough area to the foil. The longer the struts that lift you the greater the height you get and also more room to surf vertically and even bunny hop things but the higher you go the more balance is needed. Foils dont need to be wide, if youre using a single foil, as long as its 24 inches long you can make it 8 inches wide and it will get up and fly and be steady enough to carve with on your first go.
I tried all the tricky shapes and designs to find the best shape and a rectangular shape with a rounded nose / square tail is good for 95% of waves. If youre riding tubes you need to lose area and go with a pintail.
Foils dont need to be foiled like fins, I started with all that NACA foiling and went to flat sided foils with rounded edges and they work just as well as the NACA ones. Start with a bodyboard so that you get used to riding above the water, its a total trip to start paddling in the water and within 2 seconds youre a foot above the surface and flying in the air. Later standing on a board is easy. More pics or info if you want. firstname.lastname@example.org .
A couple of more things Ive learnt. Theres no need for AOA or angle of attack, just parallel to the bottom of the board is perfect. With the board and foil at 0 degrees ( horizontal) and the water rising up the face of the wave and gravity pulling you down, you dont need any more AOA and the closer you get to the barrel you'll find you need to reduce area as well. I tried AOA on single and double foils and despite the science thats offered, in reality, you dont need or want any AOA. Also if you AOA your foils then you'll have your board and foils set at different angles and that makes for much slower paddling. When youve got a foil underneath you you dont want it to slow your paddling. AT 0 deg AOA you can feel the foil is there when you paddle but its a minor difference. Foil area is controlled by the waves you ride, the best waves are 'rolling' ones where its like a crumbling mountain and not like Pipeline. You see that Laird and the guys dont ride hollow waves on foils. The bigger and longer the area of the rolling wave the better so theres more room to manouver. Once a wave face shortens and starts to hollow out the forces in the wave start to lift the foil many times stronger and its like a bronco ride, to counteract this I point the board ( and foil) down into the bottom of the wave to stop the foil popping out of the surface but its not a solution, just too wild a ride and it gets scary with the foil/board and me jumping out of the wave. Ive tried staying at the bottom half of the wave when it tubes but its hard to find the sweet spot at the bottom of the wave where theres speed and just enough wave power. And dodge the falling lip at the same time.
Ive added to my post above. Heres some more. With the struts I first thought to keep them short and I tried ones that were 5 inches high. They lift quickly but also drop quickly. Then I tried struts that were 18 inches high, Once youve got the speed youre flying, and the extra height from the longer struts mean you can alter your altitude as you ride. The longer struts mean you lift up and over the chop and the first feeling is of smoothness, no chop no chatter, just this 'SSSssshhhhhh' sound at the struts power along.
The height brings a bit more effort as you now have to pilot the foil smoothly at an even height over the water. You have to control it so it doesnt do a 'roller coaster' up and down along the wave. One of the best moments was riding it at Freshwater Beach in Sydney and I caught a wave as a couple of board riders were paddling out... As I took off they were looking so I pulled the nose up a bit, the foils lifted me clear of the water by a foot and I flew past them with my head about 2 feet higher than theirs. They had to look up to see me. They mustve thought 'Holy Jesus, now weve got to deal with this too !' Seeing 2 metal struts slicing towards them at speed mustve given them something to think about too....
Foils... 1 foil is better than two. I started doing 2 foils putting one at the nose and the other at the tail with the belief that I needed a long 'wheelbase' for stability. Wrong. I made about 60+ versions of double foils until I decided to try a bigger single version. Now its simpler to make and ride a single foil everytime. As long as you use anough area, a single foil is easier and more fun to ride and control. A short ( nose to tail dimension) foil is quicker to change lift and a bit too sketchy, so I lenghtened them out to 24 inches and now its like a cruiser and Ive got total control. Common sense would tell you that you need to use a wide ( side to side dimension) foil for stability ?....I got that wrong too ! 8 inches wide is totally stable and maybe its the struts that give it extra balance too. Certainly youre flying above the water and a minor amount of surfers balance is required but its easy to take off, do a proper bottom turn and carve a few S-turns on your first wave. I tend to ride beack breaks and points so I havent tried to make foils for every type of wave. Because foils dont need a breaking wave just an angled face, theres room to experiment with foils and see if they can be used to ride unbroken ocean swell or maybe tap into the energy just behind the crest of a wave.
holy crap surffoils! ur crazy! im intrigued... when you say that about non-breaking waves, it makes me think of attaching one to a board thats just designed to paddle really fast, to get into waves early and get up out of the water asap. maybe just based on a 7'6" lightweight pig platform. thoughts on board selection?
to clarify, you like foils with a 24" chord and 8" wingspan? or 8" chord? and for the foil shape, it sounds like you just sorta round the edges, rather that foiling it out naca style?
you weld this together? and attach it to the board in what fashion?
thanks for all the info
-------------------- The glide shall not be truncated
I think thats where Id head with a lightweight speed paddler but it depends on what waves youre hunting. Maybe a Simmons type of board ..? Short/ lots of bouyancy/ no rocker. The speed you need to lift is low and even on a bodyboard the foils lift before you get 1/2 way down a wave. Remember that the board is just for paddling, once youre in the air the board is just something to hang / stand on and youre balancing on the foils. I went with a bodyboard as the riding platform because its light and easy to build onto, but any board would do.
Yes 24 in chord X 8 in wide. If you look at the pics you'll see I tried it both ways just to see what the difference in control is. Did you look at the pics in the link ? The best single foils were cheap 3 ply that I glassed with 1 layer of 6 on the bottom and 2 on the top just to seal it from the water. The leading edge is rounded back 1/2 in and the trailing edge is tapered maybe for 1 inch. Basic shaping just to remove the edges. In the pics you can see that I connected the board and foils with the aluminium struts and a footplate at either end. The board and strut were held together with thru bolts and the foil was connected to the lower end of the strut with 1/2 in wood screws. Couldnt get simpler than that and never had a problem with that configuration for 3 years. Let me know if youre thinking of making one.