After seeing carlosgp5's post, I looked a little deeper. It seems that all the "white cap" formation information on the web is based on the Beaufort scale and they all say that at Force 3 (7-10 knots), white caps begin to form. I don't know if it is at the bottom or top end of the range, but if there is a specific wind speed in knots where caps begin to form, it would be good to know. I have always used the 10 knot rule, but if caps form in less than 10 knots, it would be interesting to know the exact wind speed.
Formula 160; iSonic 111; HiFly Move 105; Tiga 263; '85 Mistral Superlight.
Maui Sails TR 11.0; 9.2; 8.4; 7.6; 6.6; Maui Sails Switch 6.0; 5.2; Maui Sails Global 4.5; 4.0.