SailNet Community - View Single Post - Full or fin keel?
View Single Post
post #644 of Old 03-08-2013
Senior Member
wolfenzee's Avatar
Join Date: Jul 2008
Location: S/V Waltzing Matilda, Port Ludlow, WA (NW Puget Sound)
Posts: 497
Thanks: 2
Thanked 2 Times in 1 Post
Rep Power: 9
Re: Full or fin keel?

According to the US Sailing calculator my AVS is 193.64 and 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 "

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 01:34 PM.
wolfenzee is offline  
Quote Share with Facebook
For the best viewing experience please update your browser to Google Chrome