Jax,

I hope this doesn't surprise you to much but look again at any sail
working. You will see that both sides are curved

Ole Thom

No kidding, Thom?? Gee, you mean all those sailing that say a sail works
"because it is curved on one side" are wrong? But, but, but, it is printed on
paper and if it were wrong they wouldn't print it, would them.