Join Date: Jul 2008
Location: S/V Waltzing Matilda, Port Ludlow, WA (NW Puget Sound)
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Re: Full or fin keel?
Do not remember which number, be it capsize or comfort ratio, but was not one of them "hood" a naval architect that came up with that ratio. Later said it was good, but at the end of the day with some of the newer designs not as useful as with past designs. Not saying that that ratio should be thrown out per say, as it favors longer/skinnier designs vs some of the fatter hulled designs of today. Rather apparent that hull design will potentially make or break a design depending upon useage as to if it will or will not work for the end user. Not just fin vs full vs bilge vs CB or some combo there of!
The more I type, I believe it is the motion comfort ratio number. Even short will come out on the lower side of things than width. As a 30'L 10' wide boat will come out with a worst number than a 60' x 20', even tho the length.width ratio is equal. I am also recalling disp being part, maybe that needs to be equally doubled to get the same ratio, where is going up double in length, usually (typically) quadruples or equal the disp of the boat. That would be an interesting plug in numbers to see what or if one can get different equal length and beam to equal....
It was Ted Brewer that thought up the "comfort ratio" Ted Brewer Yacht Design
this link actually explains what the numbers mean.
"COMFORT RATIO (CR): This is a ratio that I dreamed up, tongue-in-cheek, as a measure of motion comfort but it has been widely accepted and, indeed, does provide a reasonable comparison between yachts of similar type. It is based on the fact that the faster the motion the more upsetting it is to the average person....." Not all of the ratios in those calculators are actually valid....this one actually is.
A friend of mine with a nice wide Catalina figured because my boat was much narower and shallower it would be rougher....in actual comparison and calculator agreed with each other and proved him wrong (according to the calculator is is 46.7 vs 23.9).
Last edited by wolfenzee; 01-09-2013 at 02:05 PM.