The fastest sailboat speed is about 68 knots, and I think the wind speed was about 25-30 knots at the time of that run. This is coming from an article in the latest mechanical engineering magazine highlighting the Sailrocket II. That has a pretty radical design though.
If I remember my basic sailing theory, a broad reach (90 degrees to the wind) provides the fastest speed, at least in a conventional sailboat without a spinnaker. The airfoil shape of the sail can magnify the effect of the wind beyond what the raw surface area of the sail and the wind speed alone can do. I don't know however if spinnaker equipped sailboats travel faster downwind or on a reach.
Last edited by subzali; 08-16-2013 at 08:44 AM.