Hydrofoil Board Build Jan Feb 2020

[tweegster]

Was off the water for a bit with a busted rib, so my very understanding wife let me take on a little project to pick away at after the kids go to bed.

Figure I would post some pics and share my experience. I have done a few moderate board repairs, and a few other small composite jobs, but this was my first board. Lot’s of good info / tips available online, notably Swaylocks.

My current hydrofoil board was a 5.0 converted surfboard. Good for learning, but heavish. limited rocker and more size and volume than what is required. The mast track is too far forward for a surf foil, so despite drilling my plate to get the mast another inch back, I still learned and ride it strapless.

For reference:

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[tweegster]

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New board design was for a larger pocket hydrofoil, due to not wanting to give up light wind performance. I reviewed and blended designs from Ketos, groove, slingshot and Moses.

Dimensions 46”L 18.5”W 1.75” thick (due to track mounts).

For core I used 2” HD EPS roughly 1.8lb foam. I found PU foam fake steel I beams that Rona was blowing out for 10 bucks a piece. These were super dense foam, easily could stand on them. Thus made a good stringer, that blended into foil track mount block as one piece.... perfect! What are the chances!

Someone also installed a bandsaw in the workshop, this was invaluable without a Hotwire setup.

Cut out the rocker into the HD stringer, then made a rocker table to match and gorilla glued the eps to the stringer. I got about a 50% spring back in rocker, 2 in eps does not like to hold a bend. That was okay tho...

[tweegster]

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Final shaped the blank, and bonded in the chinook foil tracks. Lesson learned: use a router, cutting the slots by hand was kind of rough and used more resin/microballons and results in more weight.

Sealed the blank with skim of epoxy mixed with micro balloons. Once this set up partially added the 9oz carbon fibre warp cloth (twice the strands lengthwise) and 5.6oz carbon twill weave to bottom. I had screwed a screw from below the rocker table into the HD stringer, this held my 4” of rocker perfectly. After the carbon bottom was on, she was stiff and held shape.

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I had help from Sean for laminating and two sets of hands really helps to lay carbon straight and get it all down and trimmed using fast epoxy. He even brought his own beer which kept costs in check.

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[tweegster]

Top side done the next night. 9oz patch over foil mount upper surface.

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9oz warp on standing deck.
9 oz warp over whole thing. Then 5.6 oz twill wrapping the rails in a free lap.

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Too bad I can’t just ride it like this. Was very happy at this point.

Need to paint white to stop it from overheating and delaminating. Could also add a goretex vent, but that adds complexity and another piece to fail.

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[tweegster]

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Hot coat of epoxy/micro balloon/ white pigment.

If I was to do it again, I would do a regular epoxy hotcoat, then the design in lightweight filler. This would let me be a little more sloppy sanding and get the hot coat on right away.

The way I did it is slightly lighter but a pain and had to let the previous layer setup more so less chemical bond.

Sanded white to brushed look. Next I regular hot coat to fill the bare carbon.

Sanded again, then add orange visibility details with acrylic paint.

Why an eye? Check out surf eyes, I guess the white pyjamas tends to mistake you for a seal. So making it clear you are human and looking at him might stop an attack as great whites don’t actually eat humans normally and want a surprise attack. I figure the same logic applies to Great whites attacks on Sauron.

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[tweegster]

Was going to leave it at 400 sanded finish as this is the lowest drag, but it does absorb stains and I still had some pinhole/imperfections.

Ended up using minwax Matt finish, this was fast and very happy with the finish. Make the carbon and colour pop.

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3m deck pad, did not end up putting insets for straps, can do later if req.

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All done, bolt it up and back on the water in a seat harness 15 Feb.

[tweegster]

First ride review:

Weight - 3.5kg (on par with fibreglass production board).

Board w/NP surf foil sits on its side and drifts downwind at a 45. Perfect, easy to catch and spot. Put feet on and go.

Much much smoother transition to and from foiling.

The stiffness in the board makes foil more controllable and much less twitchy, amazing difference.

Better lean over, less width in nose (last minute adjustment) makes side touches happen behind your front foot. No twisting moment (my old board did this and made it hard to recover, wanted to dive deeper into wave).

Due to the lack of stiction on take off and square rail, I don’t think I gave up any bottom end.

Touch down foot switches are smoother, but you do notice the less planing surface, so some loss there.

Fits in the car trunk!

Fun three week project!

Cost about $350 and 20 or so hours. Not going to make a living at it.

[Michael]

Nice work!!