Just for the fun, I am trying to calculate what is the total wind force ( lbs/sqft) produced on a sail of a given size, given the wind speed in knts. The ultimate end of this exercise is to determine ( approximately) how much of my total weight ( 85 kg) can be pulled up by the wind on the sail during a beach start or a waterstart.
According to a chart at forum.woodenboat.com/showthread.php?69064-Wind-pressure-on-sails , a 15 mph wind would produce 1lb/sqft pressure on the sail, i.e 40 kg on a an 8.0 m2 sail . If I weigh 85 kg, this means that about half of my weight can be pulled up by a 15mph ( 12 knts) wind when beach or water starting.
By the same chart, a 23 mph ( 20 knts )wind will exert a 2lbs/sqft force on the same sail , i.e. an 80 kg pull on the sailor.
If he or she weighs 80 kg, this means that the wind will have done all the work.
I'll test this on the water in a few months. In the meantime, I'd like to have comments.

Thanks

Ittiandro