This may be a stupid question.

[irwinsailor]

Last friday night we went for a sail in 21 knot winds on lake Michigan. It was the fastest sail I have ever had. My question is : is 8.9 knots per hour in 21 knot winds in a 64000lb boat fast?

[29cascadefixer]

My understanding ( such as it is ) is that the theroetical( sp ?)top speed of a displacement type hull is the square root of the waterline length. In your case I'm estimating around 7.5 - 8 miles per hour. Your speed was close to 9 knots which translates into about 11 miles per hour. Good on you ,Sir. I would say you had that Lady planing. Whooe.....

[GordMay]

Hull Speed (Kts) = 1.34 x Square Root of Waterline Length (Ft).
If LWL = 55' Then Hull Speed = 9.9 Kts.
See:
http://sailingusa.info/cal__hull_speed.htm
And a great boat design informational at:
http://www.tedbrewer.com/yachtdesign.html
Ted Brewer Yacht Design

Regards,
Gord

[irwinsailor]

So that old girl can move! I knew that hull speed was 9.9 knots for our boat, I just did not think I could come that close to it so soon.