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imperfections

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darippah
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imperfections

Postby darippah » Tue Mar 04, 2014 6:16 am

hi guys

I just completed my first hydrofoil, and as expected, the board is not perfect even to the untrained eye. I'm hoping the images attached give good detail on the issues I am trying to describe.

Everything seems to be "off" by a 1/4 inch or so and i'm wondering what to expect as a result. I'm kind of just looking for something that works okay as my first experiment - especially since I have never ridden a foil board before

another issue that concerns me is my front foil fin seems to have much more flex than expected- this is a combination of the ultra high aspect of the fin and mounting by 3 screws only instead of using fiberglass or other such strong bonds and since the surfaces aren't perfectly prepared for each other

I probably won't get to ride the foil for a bit and I'm wondering if it would be wise to spend the time on trying to perfect the joints and replacing the front fin with something of lower aspect ratio in order to avoid flex

thanks in advance for the replies, and a special thanks to hawaiis and all that have shared ideas and inspiration for DIY hydrofoil builders
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ChristoffM
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Re: imperfections

Postby ChristoffM » Tue Mar 04, 2014 7:15 am

Based on some of the home made foils that I have been able to ride I do not think that the few imperfections will make it impossible to ride. BUT, what I find much more important than the alignments and finishing is the strength and stiffness. The foil must be very solid. I find it possible to ride a foil that is even worse misaligned but solid to be much easier than a perfectly aligned foil that flex when you ride. I would suggest spending time making everything stiff (even if you thicken it up with lots of glass) and making the joints really solid.

Then once you have tested it, you could spend timeon making hte finishing beautiful.

Remember to leave a way of changing the rear wing angle. It is quite important to tune the rear wing angle to get a foil to be nice and stable and with low drag. A badly tuned rear wing can add more drag than a lot of surface imperfaction and distortions.

In very flat water and light wind you can get away with a sligtly less solid foil, but at best you will get sudden stalls where the foil throws you off, and at worst the foil could break while you ride (which has happended to me twice!)

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Hawaiis
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Re: imperfections

Postby Hawaiis » Tue Mar 04, 2014 7:47 pm

ChristoffM wrote:Based on some of the home made foils that I have been able to ride I do not think that the few imperfections will make it impossible to ride. BUT, what I find much more important than the alignments and finishing is the strength and stiffness. The foil must be very solid. I find it possible to ride a foil that is even worse misaligned but solid to be much easier than a perfectly aligned foil that flex when you ride. I would suggest spending time making everything stiff (even if you thicken it up with lots of glass) and making the joints really solid.

Then once you have tested it, you could spend timeon making hte finishing beautiful.

Remember to leave a way of changing the rear wing angle. It is quite important to tune the rear wing angle to get a foil to be nice and stable and with low drag. A badly tuned rear wing can add more drag than a lot of surface imperfaction and distortions.

In very flat water and light wind you can get away with a sligtly less solid foil, but at best you will get sudden stalls where the foil throws you off, and at worst the foil could break while you ride (which has happended to me twice!)

Exactly, I found bamboo wood have resonance that will create huge vibration if too high aspect ratio even reinforcement with glass doesn't help. The low aspect ratio wings seem to work better. For high AR wing like yours, maybe a hardwood, carbon, aluminum or Titanium will work better.

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darippah
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Re: imperfections

Postby darippah » Thu Mar 06, 2014 2:51 am

thanks for the great info. I'll throw on a few more layers of glass and see if that helps. will also make a new front fin with lower aspect ratio out of some leftover scraps of birch plywood with an epoxy coating


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