New Wing Sail

[bjn]

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/imarusic/proceedings/13/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.

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.

 

[bjn]

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.

 

[bjn]

Latest news from VPLP is to put 400 square meters of this wingsail on a 47m by 16m luxurious catamaran yacht.

 

[bjn]

Oops, forgot to post link:
VPLP Design reveals wingsail yacht concept Evidence https://www.boatinternational.com/yachts/news/vplp-design-reveals-wingsail-yacht-concept-evidence--35453

What to you think about this soft reefable wingsail?

It's missing the flap used in the C-class for example.

Also, about the earlier discussion of 2 times more power in the sail, according to this video, the factor is about 1.3 (30% higher lift coefficient)