In regards to the stay sail during extreme storm conditions.
in wind of 50+ knots (on deck) and 25+ foot (above the spreaders) breaking waves, we found the stay sail as the only good choice for sail, running off at 150-160 ish. it worked well for the following reasons.
It was very small (and you can sheet it in some if you have a winch and good timing this is with 3 to 1 on boom but with just a sheet ? as the wind can load a line until you can not move it, without relieving some load = direction change)
it was forward which allowed course holding with a little less effort. (wind vane mostly could keep course+/-) we only had to hand steer above 55 and when it was breaking allot.
it was flattened with the stay sail boom, which kept the sail under control, even with great wind speed changes; trough (10-20Kt) to crest (50 to 65+kt) wind changes. ( the sail movement was improved when we added a preventer to the stay sail boom)
it is triangulated with the running back stays at the top = good for mast loading
it seam to provide some lift to the bow (kept the platform mostly out of the water) we only had boarding waves from the breakers or when a odd wave hit from abeam. (never pooped)
it maintained 2 to 8kt speeds which allowed good steerage
above this, water speed, we would have needed some wraps trailing, as above 8kt hull speed steering can become an issue.
NOTE; this was with unlimited sea room = no shore for 400+ miles. Also the wave trains from the wind were moving at 10 to 15kt +/-
If you were off a lee shore this may not be your best choice on its own.
Just another data point,
a side note; during this type of storm your distance traveled through the water can be 2x of distance over ground (all the up and down adds many many miles to the trip)
Best option though is to avoid this type weather if you can.
Norm
