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Whistle While You Foil--or not?

 
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eric

Since 13 Jan 2006
1658 Posts

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PostWed Dec 02, 20 5:23 pm    Whistle While You Foil--or not? Reply with quote

My first front wing whistler. It's bad, like "Is it Safe?" from Marathon Man bad, like nails on the chalkboard bad. Put a new from wing on--only change--and it's train whistle on.

To date, I tried a subtle "Donaldson Curve" but it had no effect. Anyone dealt with this successfully? Anyone gone from REALLY LOUD on ALL points of sail at pretty much every speed to silence?

Thanks,
Eric

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Freeride Kiting

Since 08 Jul 2011
668 Posts
Alaska / PNW / Baja
Instructor



PostThu Dec 03, 20 11:07 am     Reply with quote

We have a number of Foils surf and classic series from Lift that sang to us. Specific to Lift, but applicable to almost carbon setups that sing. Nick put out a simple video.

https://www.youtube.com/watch?v=lYRKr04fqbI

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eric

Since 13 Jan 2006
1658 Posts

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PostThu Dec 03, 20 3:10 pm     Reply with quote

^^^

Perfect, much obliged

Eric

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Nak

Since 19 May 2005
3908 Posts
Camas
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PostFri Dec 04, 20 9:29 am     Reply with quote

That's a good video, but it's better if you know what you're shooting for. Look at this figure, it's a table of the results of several studies into the subject. In the video, Nick is going for the bottom shape in column two, a very quiet leading edge. However, angle is critical and must be 30 degrees. Go up about six shapes in that column to see what happens if you end up with a 45 degree angle. BTW, that's total angle of the edge, not sanding angle. to get 30 degrees, you'll have to sand at a 15 degree angle top and bottom. Sand at 22 degrees and you'll still be whistling.

Of course this tailing edge is exceptionally sharp and dangerous. You can blunt it by sanding a 90 degree blunt edge no more then 1.5mm wide. You have to use a very rigid sanding block and get it right at perpendicular to the wing. If you go thicker than 1.5mm you'll get whistling.

I personally sand to get the trailing edge shape in column one, second from the bottom. I put a 1mm blunt edge on it as well. This is just as quiet as the videos trailing edge, and far safer. It's also a lot more forgiving of sanding angle. Any angle between 60 degrees and 90 degrees works. The only difficult part is getting the radius, and thta's not so bad. I just sand without a block to get the radius and check my work with 18x magnifying glasses.


   31-Table1.1-1.png 

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