Forums > Windsurfing Foiling

Hot rear wing

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Created by Ant-man > 9 months ago, 12 Dec 2019
Ant-man
NSW, 177 posts
12 Dec 2019 5:52AM
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Not sure if this is a real phenomenon but after a short but fun light wind foil session yesterday as I was exiting the water and placed my hand on the rear wing. To my surprise it felt warm/hot to the touch.

Anyone else felt this?

When considering the pressure differentials that are acting on the foils and the relatively small surface areas it sort of makes sense and could be possible but I'm not sure if it could be something else.

Water temp about 21 degrees C.
Naish foil (Carbon rear)
Board speed around 15knots
Fun flowy session (lots of turns and changes in elevation)
Intermediate foiler.

Happy to hear it's all in my head.

powersloshin
NSW, 1654 posts
12 Dec 2019 6:29AM
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you should consider that the LT fin never gets hot and is much more user friendly, there are at least 500 LT happy users.......

WhiteofHeart
762 posts
12 Dec 2019 3:46AM
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Never experienced that, but 21 degrees C is about 5 degrees warmer than the hottest water i've ever surfed in..

That being said, I've read that for speedsurfers there is a serious problem where fins start boiling the water around them at a certain speed, therefore preventing boards to reach speeds much higher than 100km/h, or needing a much less lifty fin.

Th?t being said.... a stab does almost nothing. Like, literally almost nothing. You can ride a windfoil without stab (yes, personal experience, fun experiment too), and if you're riding stable (straight), more powerful foils (like the Starboard 125++ or similar) will have their stab at a near 0 degree angle generating near 0 preassure differential.

Subsonic
WA, 2963 posts
12 Dec 2019 5:12AM
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It could be cavitation. You'll know if it is when the trailing edge of your hot rear wing starts to disintegrate.

lakeeffect
107 posts
12 Dec 2019 6:23AM
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I've studying cavitation in main engine fuel pumps for gas turbines. The literature says that an imploding bubble generates 5000 degrees Kevin locally . But its so small a volume that you can't see it at the discharge temperature of the pump. It gives me pause that you can feel it in the foil. Shoot it with a cheap infa-red temperature sensor and see it its above the water temperature. Its possible!

segler
WA, 1597 posts
13 Dec 2019 12:19AM
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You have to try to measure while actually foiling in real time.

About all you could do is mount a thermocouple onto the stab, run the wires up to a reader on the board or boom, and try to read the temperature while actually foiling. Oh yeah, somehow insulate the thermocouple from water temperature so that it reads ONLY stab temperature.

Even a hot stab will equilibrate to water temperature very quickly. The heat capacity and heat transfer rate of water is so massive that a thin stabilizer will be brought to water temperature almost instantly. This is the whole idea behind water quench in metallurgy.



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"Hot rear wing" started by Ant-man