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Old 03-08-2013
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Re: Full or fin keel?

According to the US Sailing calculator http://www.sailingcourse.com/keelboat/design_winds.htm my AVS is 193.64

http://www.sailtrain.co.uk/stability..._stability.htm and http://www.radford-yacht.com/stablty1.html both explain the AVS
According to the RADFORD "Safety of Small Commercial Sailing Vessels Code of practice"(see table below and/or link), the 110 degree AVS that someone stated was typical of fin keels would not even be safe in Catagory 2 (up to 60 miles from a safe haven)


Historically the older style boats had a much higher AVS even though thier narrower beam. Typical sailboats produced from the early 70's on have LPS's (limit of positive stability = AVS) in the 100-120 degree range. "Designs typical of the 30's and 40's (e.g. many Alden designs) have LPS in the 160 degree range. from "http://dan.pfeiffer.net/boat/ratios.htm

The actual formula is: AVS = 110 + ( 400 / (SV-10) )
SV is the screening value and is calculated by:
SV = B2 / (R x T x V1/3)
Expanding SV in the first equation gives:
AVS = 110 + ( 400 / (B2 / (R x T x V1/3))-10) )

B = beam of the hull (no rub rail) in meters
R = ballast ratio
T = hull draft at B/8 from centerline in meters
V = displacement volume in cubed meters

It's not so much as a wide boat being more stable right side up, but upside down....I wide boat is not going to want to right as quickly as a narrow boat.

Last edited by wolfenzee; 03-08-2013 at 02:34 PM.
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