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DIY: Board mount angle

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kjorn
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DIY: Board mount angle

Postby kjorn » Mon Aug 24, 2015 10:20 pm

My board is a twin tip, both ends have some rocker. I'm putting two longboard fin boxes into it to attach the hydrofoil to.

Should these be inserted flush with the bottom of the board, and follow the rocker? Or should I angle them so they are horizontal?

I'm worried that following the rocker line will mean the foils will have a negative AoA when the board is flat on the water. The board is 115cm long. The rocker at each end is 3.5 cm

Thanks :thumb:

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Re: DIY: Board mount angle

Postby kjorn » Mon Aug 24, 2015 10:32 pm

Ive attached some pics.
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20150824_222348.jpg
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Re: DIY: Board mount angle

Postby Hawaiis » Mon Aug 24, 2015 11:34 pm

If it was me, I would just follow the contour, so you get more lip on the front for waves.

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Re: DIY: Board mount angle

Postby kjorn » Tue Aug 25, 2015 9:24 pm

Thanks, that's what I'll do. The thread on wake skates showed a similar set up, the foil mounted a little in from the rear edge.

:thumb: :thumb:

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Re: DIY: Board mount angle

Postby Soren Gabriel » Wed Aug 26, 2015 5:34 pm

Be aware that the AOA of the foil will be negative when you are sailing if your mount follows the contour of the board (if you mount it behind the center of the board). That means that it takes a lot of weight on the back-foot to get up foiling and that the foil will pull down (and stop you and eventually break the board) when you go from foiling to sailing on the water.

I am talking out of experience :oops:

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Re: DIY: Board mount angle

Postby Hawaiis » Wed Aug 26, 2015 10:38 pm

Most foils have positive lift, the mounting point is about where you want to place your rear foot.
In the beginning you will be more worried about the foil popping up too early.

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Re: DIY: Board mount angle

Postby kjorn » Thu Aug 27, 2015 11:58 pm

Soren Gabriel wrote:Be aware that the AOA of the foil will be negative when you are sailing if your mount follows the contour of the board
This was my exact worry. I don't want the foil to be point towards the bottom of the ocean when the board is planing on the water.

I'm going to try to get the fin boxes as close to horizontal as I can. I cut the holes for the fin boxes today directly under my back foot, they are long enough that they go back towards the tail quite a bit so there is some room for adjustments.

Thanks for the help guys, I really appreciate it!! :thumb: :thumb:


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