You have probably already thought of this but what about inlaying some strips of ply to mount the uprights of the foil to ? It would be fairly simple and help spread the load.
You have probably already thought of this but what about inlaying some strips of ply to mount the uprights of the foil to ? It would be fairly simple and help spread the load.
Thanks, i Didn’t think of doing that but I now see it would need those ply inserts on the bottom and top to secure the thru bolts. See pic A…
I’m also thinking that the whole length of the board would need to be really strong because when you drop into a wave and bottom turn the force/ weight of your body pressed down thru your feet is going to snap the board on either side of the ply inserts. Pic B…
Got any suggestions ?
Check this guy foiling without foot straps…
Food for thought…not an actual solution
Spreading the load using something like this:
I’d avoid drilling holes through it through, that’ll just introduce weak points into such stringer…
Some kiteboards use thing plywood inserts on the deck under the footpads.
Based on your sketch, you’d likely want the plywood to extend forward and aft well past the foil mounting point to spread the load over a wider area. Also, the longer you can make the mounting base of the foil the better off you’ll be as far as point loads.
That video shows what you’re talking about with a high flying height being inherently unstable.
I still think the single foil approach is making it much harder, especially after seeing your aluminium version with dual legs actually work.
The balance aspect is like the difference between riding a unicycle and riding a bicycle, I think you’re on to something with the dual foil approach, one for flying and one for control.
Have you tried riding any of your foils behind a boat? Seems like that would give you a really good feel for their characteristics in a more controlled environment.
Just throwing in my .02. You’ve got my mind spinning with ideas though, wish I had the time to play around with some of them.
An interesting link on foilboards:
http://www.foilzone.com/phpbb3/viewtopic.php?f=1&t=15782
Edit: throwing some links in here for future reference, got on a Google tangent on foils today at lunch 
http://www.boatdesign.net/forums/hydrodynamics-aerodynamics/hydrofoil-boat-design-45986.html
http://www.foils.org/upright.htm
http://www.wfoilsail.com/unique-wfoil-concept
https://www.google.com/search?q=hydrofoil+boat&hl=en&tbm=isch
to the lab control."i think that’s the way forward after I _zpsd93bdfde.jpg[/IMG]and use something like this for control on top…[IMG]http://i153.photobucket.com/albums/ surf.
Spoke to I don’t think I ever really felt a wave until I flew over the surface of the water and was able to sense its interior; for, with a surfboard, one is limited to experiencing the phenomena of its surface—of the boundary between air and water—and cannot truly feel its inner breath, its pulse, its life, as one does with a hydrofoil.http:// cans.
Thin kiteboard/windsurf type wood or high-density foam inlays will be inadequate for the leverage of a foil on a strut, even if the strut is short.
A foot only has the effective leverage of 1-2" on a footstrap insert, while the strut concentrates the force of the whole foil (at least equal to 2 feet) and applies it with much more leverage -probably up to 12" even for a “short” strut. The width of the foil, as well as the strut length, adds to the leverage …
If i wanted to to approximate the current commercial foilboards, I’d make a solid wood block the thickness of the board, and pot inserts into it to fit the flange on top of the strut. I would cut all the way through the board and replace it with the wood block epoxy-ing the wood in place bridging the full thickness of the board. Then fair into surface and reglass with patches of incremental size extending out from the insert block. How much glass? I would guess 24-30oz right over the inserts on the bottom tapering to 6 at the outside of the biggest patch. Or maybe you’de feel safer with another layer… The deck and bottom would each need a similar treatment.
Over this I’d lay a 3-4 inch wide 6 oz glass tape down the stringer on the deck, almost the length of a normal deck patch. On the bottom, I would do a similar tape but make it shorter maybe 6" behind to 12" in front of the inserts. The top tape would help against buckling. If the board was lightly glassed to start, I would even add a deck patch on top. The bottom tape would add strength and stiffness augmenting the I-beam effect of the stringer near the inserts, but allow some flex forward. maybe.
A pain, but perhaps emulating success would see you through.
If you don’t want to bother, grab a beater board or half an LB or what suits your fancy and throw on deck and bottom patches, handle it like a giant glass-on keel, 3/4-1" radius epoxy high-density fillets at base, plenty of glass tabbing layers over, like 60oz +.
Destroy/discard board when done.
Although come to think of it, a sharp japanese pull saw could be used to handily liberate the board from the foil assembly. I’ve cut through 2-3 inches of wood under 50+ ounces of glass and carbon with them, like butter. Just don’t ask the same saw blade to do that job too many times. Use a brand new cheap one. That is probably what I’d do, I think.
Just saw your last post, brokite does a great job in my humble opinion as a kiter and kiteboard builder.
I would make a foil, kind of like they make their kiteboards.
Not sure a surfboard, even for foiling, needs nearly that weight of carbon in the skin overall though!
But if you make a special board, thin and with lots of carbon, it will be cool no matter what…
Considering that Laird appears to be using a standard kiteboard, I think following Brokites technique is a good idea, its great that he’s done a step by step showing how they build their kiteboards.
The only additions I would do is to use 2 or 3 core layers to build up the strength because paddle in boards are a lot longer and wider than a kiteboard. The extra layers will add some bouyancy too.
Stars are feet, red line is the strut.
maybe do 3 cores of increasing thickness so you can build the strength over most of the boards length but thin it out near the nose. Even taper the cores so the look of the board is smoother from the side. It doesn’t need rails so they can be square or slightly beveled.
I think I could put several slits and then slide carbon in rather than slicing it up into 5 pieces like he did. He says that wrapping the slices in carbon makes “stringers”.
I’m not sure how much carbon and strength is actually needed, but if you’ve dropped into a hollow 8 footer and you’re airborne/ foilborne, then how much force will you put on the board during a deep bottom turn ? Maybe 3 times your actual weight ? I can feel the increase in G’s even when I’m prone foiling.
I think the area from the tail up to the start of the nose rocker is going to need REAL strengthening to handle that sort of downward pressure.
The tow in guys are cruising on the bigger waves but theyre not laying the board over or putting in hard bottom turns that you get with paddle in foiling.
Pablo foiling…
I believe you would have to be going very fast to get 3 G in a tight/hard cutback or bottom turn.
Did some calculating a while back for equivalent weight while making tight cutbacks on my street carvers. Can’t remember the exact velocity I used for a tight, hard 180 cutback. But it was in the 20 mph range. My physics is a bit rusty, but I came up with somewhere around 1.25 times my weight being exerted on the deck.
The main issue is the point pressure, since the struts are focusing your weight at specific points. But the surface area of your feet isn’t all that large either. I believe your biggest concern would be the minimum compressive strength of your board’s surfaces (lb/in^2 or Kg/cm^2).
Centripetal acceleration:
a = v^2 / r
Gravitational acceleration:
32 ft/sec per second
Still looking from here… Love to see the beach shots some day… Very cool stuff.
TayAt times like this I wisbecause week or to the shack, out…
Here’s the t ?
Will the in which case 2 sego. (as suggested by posting.
Didn’t want to comment on G Force without doing some calculating. I might have been a good bit off, depending on the radius of your turn.
Did some quick calculations. Earth’s gravitational acceleration is 32 ft/second per second. Times 3 = 96. So if my calculations are correct, a turn with a fixed radius of 10 feet at 21 mph will produce a centripetal acceleration of 96 feet/second per second.
Thanks for crunching the num. gives it murky.com/albums/s225/SURFFOILS/2013/d04398ffbddd7f2a1b2df8d34d2e25dd_zps79bd79bd.jpg[/IMG]
As every you soon with the video…
good stuff
what size is that surfboard you're making , Brett ?
cheers
ben
p.s. - have you found any other videographer to do the beach footage , yet ??
Ben, the eps board is 5’8" and no I haven’t found a surf guy to shoot the video. Hop on a plane and come over !
![murky.com/albums/s225/SURFFOILS/2013/d04398ffbddd7f2a1b2df8d34d2e25dd_zps79bd79bd.jpg[/IMG]](http://murky.com/albums/s225/SURFFOILS/2013/d04398ffbddd7f2a1b2df8d34d2e25dd_zps79bd79bd.jpg%5B/IMG%5D){kind=link}
this is an amazing shot!
Hi Surffoils.
Thank you for the very interesting thread. I’ve only recently returned to Swaylocks after a few years away from the coast, and am enjoying the developments in your journey. The thing that I love about it is that I find myself slack-jawed and gazing into the distance as I imagine scenarios and possibilities.
One question: is the strut flex beneficial or desirable? If not, is there any reason that you couldn’t have two struts mounted to perimeter stringers or fishplates that connect to the outer flanges of the foil? This might create a bit more drag, but could add considerable rigidity to the assembly.
Apologies if I am suggesting something that has been tried already, I haven’t gone into every link on every post.
Cheers,
Craig