That flap doesn't really do anything. It only benefit is that it smooths out turbulence around the bottom part of the mast. I do not consider that flap area to be of any use with respect to produced sailpower.
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<br>In light air the wind has a very strong gradient along the mast and hardly blows near the mastfoot. So any area there is usely, you want it up high in the mast.
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<br>In heavy air you'll fly a hull and a large part of the flap is in the turbulence of the raised hull and in these conditions the amount of sailarea is of secondary importance. The shape and depower controlls are far more important.
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<br>These are the reasons why I say, forget about that larger main and dispensate all boats before 1 jan 2002 and use the iF20 setup for the US.
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<br>Barry, you have an e-mail from me in your box about 2nd hand mains.
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<br>Wouter<br><br>