Calculating Cruising Speed

Hi Steve. With a 36 foot waterline, wouldn’t the boat (at least theoretically) have a hull design speed of about 8 knots? [sqrt 36 = 6 x 1.34 = 8.02] Do you find that such boats won’t sail at the design speed? Sidney

Hi Sidney: Theoretically, your CSY 44 will go eight knots–but not very often. The issue is what speed can you average, and my guess is that a CSY would average a speed length ratio of one to 1.05 times the square root of the water line length. There are many factors in involved, including displacement length ratio, beam, prismatic coefficients, fin design, and rig. For the CSY most of these ratios are not oriented towards performance. This is covered in much greater detail in our Offshore Cruising Encyclopedia. Regards–Steve

Posted by Steve Dashew  (November 30, 1999)

Comments are closed.