Bill Roberts gave me this info awhile back and I am curious about what you might think.



I want to try to tie in exact crew weight with Portsmouth. I will use my boat for demonstration.



Overturning moment divided by restoring moment does this I think. Overturning moment is related to sail area times 40% of mast height. Restoring moment is related to TOTAL sailing weight times 1/2 of the boat width. So here goes:



ARC22



O.T Moment = 360[sail area] x 40% x 38.5 [Mast Height]= 5544

Rest. Mom. = [467 boat wt + 400 crew wt] 867lbs x 6' = 5202

OT Mom/Rest Mom = 1.065



Next multiply ARC22 Portsmouth Rating [58.5] times the OTmom/RestMom 1.065 you get 62.34.



This factor/rating takes into many factors: exact crew weight, boat specs as a base factor for both sides of the equation, and demonstrated boat performance from MHC.



fair winds



thom

Thom,



This is a commonly used approximation. Sails generate lift, and it is not a direct relationship to surface area. Different aspect and curvature ratios, in combination with the mast characteristics will give significantly different heeling moments for your equation...oh bother





Sail Fast





Matt