This is fun :) I'm learning all sorts of things!

Modern sailcloth seems to come in at about 20oz per square yard but I'm going to double that weight to allow for much coarser fabric and the fact that linen absorbs water very readily. 45sq/yds a sail = 110lbs. 15 sails = 1650lbs. Not sure how much raw flax you would need for that (50% wastage?) and did they process it on site or did each family make a sail and bring it along? I wonder where they stored the sails during most of the year when they were not needed? Perhaps they were re-cycled into much needed winter clothing.

According to this site.. http://www.noahs-ark-anchors.com/content/wind.htm
..at Beaufort Scale 2 = 7.5mph, wind pressure is 0.14lbs/sqft. This gives a pressure on the most "open" sail of 56lbs. The other sails as they rotate would of course generate less and less power as they presented a more and more acute angle to the wind and also came into the "shadow" of the following sail.
Sail aerodynamics are extremely complex and I lost the will to live when I came across complicated formulae using Newtons and Pascals :(

This calculation gives the average wind speed for Stonehenge.. http://www.bwea.com/noabl/
grid ref is SU1242.
4.8M/Sec = 10 mph.
Jim.