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Old 04-18-2017, 01:18 PM
bjn bjn is offline
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Location: Stockholm
Originally Posted by Ilan Voyager View Post
The aspect ratio is not the most important. The thing resides in the slot and the 2 rather thick profiles. Do not forget the camber or fullness impossible to get on a soft sail without stalling...the two parts of the wing and the slot have to be treated as one very cambered and rather thick wing with ventilation of the extrados of the flap.
This is probably true. The wing can create more lift. But because of tip losses in limited span, the difference is smaller than in infinite span. So I think it's impossible to get a ratio of 2.

This report shows a lift coefficient of 1.6 for a windsurf sail. So that would need a lift coefficient of 3.2 to double the lift. Which I think is near impossible in infinite span. And very much impossible with the aspect ratio of a windsurf sail. I think a wing will not be able to have a lift coefficient of more than 2 with the aspect ratio of a windsurf sail.

I'm wondering what will happen to these soft wings in really strong winds? They might deform. I hope they have tested that.

Originally Posted by Skyak View Post
Take downwind -That VPLP wing will be inferior to the conventional sail because it is split down the middle. Not 2X better -actually inferior.
I think this is wrong. A wing will never be sailed dead downwind. It will be sailed at an angle to the true wind to get the apparent wind at 90 or more forwards.
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Old 04-19-2017, 04:36 AM
bjn bjn is offline
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Originally Posted by Konstanty View Post
Don't worry about drag induced in the ends of sail. There is end plate of the wingsail.
The endplates will act to increase the effective span/aspect ratio. Effective span will more or less increase like if the span was increased by the length of the endplates (within limits, of course). The endplates in question are very small, and will barely change the effective span at all. So will not stop the induced drag=)

It's not possible to stop the induced drag. You can only decrease it a bit with the endplates, or by increasing the span/aspect ratio.
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