Soft Wing Sail

[Joakim]

Ilan
You should take a careful look at the polar you are providing: http://www.omerwingsail.com/performance/

You are clearly confusing TWA/TWS with AWA/AWS. Certainly you are not sailing into less than 20 degrees TWA with good speed. Also you are not going to be faster than standard Elan 37 with spinnaker sailing downwind.

According to the current polar you are sailing with BSP=TWS directly downwind, thus AWS=0.

The standard Elan 37 curves are TWS/TWA and also they seem very slow upwind. I would expect 4.6 kn at 45 TWA, 6 kn TWS, but your polar suggest 4 kn, which I can easily do with my 28 footer, which is very clearly slower than Elan 37.

Joakim

[Ilan Gonen]

Thanks Yoakim for drawing my attention.
You are right that there is a problem with downwind data. I'll check it.

Right now I can think of the fact that I use two different wind vanes, one on top of the mast and the second one at the bow, as the source of the problem.
The wind vane at mast top measures the apparent wind speed and Angle of Attack only (because the mast rotates, you can't measure wind angles). True wind is calculated according to the bow wind vane readings.
When sailing down wind, air flow over the bow wind vain is disturbed by the wing and also, the wind velocity up there is 20% (average) bigger than the velocity at the bow.

Please look again at the polar. We do not sail less than 20 degrees true wind. Also, please have a look at the attached photos where you can see the forward wind vane location, the wind apparent angle on it and all other instruments readings. Very nice performance and I don't think there is any problem in up wind readings.

The standard Elan 37 curves where taken from Elan designer Rob Humphrys.

I hope that in the coming summer, I'll be able to race the standard Elan 37. I'll update the web site once I have the results.

Ilan