Originally Posted by Ilan Voyager
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. http://people.eng.unimelb.edu.au/ima.../Alexander.pdf
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
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.