Interesting test session!!! Tested a 1990 Gaastra speedfoil Pro 4.4 (£0.99 on ebay) against a modern 7.0! I was curious as to what difference 24 years of development could do....with suprising results. The first thing I found was how little downhaul the sail would take...it was designed around an alloy mast! Just takes the creases out the luff; The 7.0 has a power zone and a flatter area above with a loose leech..the speedfoil is 4.4m of power!..like a wing sail.
On the water obviously the speedfoil was a lot smaller and was only ok in the gusts and the 7.0 was good all the time. No suprises
Top speed on the 7.0 was 35.5 knots...top speed on the 4.4 was 32.5 knots...thats about 8%
I'm not saying the 1990 sail was fast but I think it went suprisingly well and shows how important boards and fins are how much they have changed.
Maybe it could have been faster on a 5.0 or 5.7 speedfoil as I was far from powerwed...Makes you think what a modern effort super efficient wing style sail could do...look at sail rocket!
Could more power and tighter leech come round again for speed now all the other components of the setup improved so much in 24 years?