Peter wrote: (SNIP) Nick already responded regarding CG etc. so I won't repeat him here. Peter's following comment is good. > > But as far as secondary stability goes, without a lot of testing, I would > guess that the farther you can heel a kayak and still feel stable, the > higher the secondary stability. This might show up on a chart where the > further to the right (high heel angle) that a curve of overturning or > gravity forces crosses below a curve of the righting forces. Something you > can not see on the stability curve of righting forces by itself. > The U.S. Navy plots heeling moments against righting arm curves for wind forces and for centrifugal forces (high speed turns) and free surface effects (damaged hull stability). They require that, where the heeling moment curve an crosses the righting moment curve not exceed 60% of the maximum and that the area between the righting arm curve and heeling arm curve exceeds 140% of the area to the left of the intersection point through a 25 degree roll. They call this area (above the heeling arm curve) the residual righting energy or dynamic stability. It includes all the energy even beyond the maximum. For high speed turning energy above the heeling arm must no be less than 40% of the total energy in the static stability curve. The heeling moment due to wind, the heeling moment in a turn lend themselves to simple calculation. I can visualize how one might also calculate the heeling moment from a breaking wave by applying an arbitrary transverse water velocity to the righting arm. This would probably support the argument for lower initial stability but may prove confusing to some. Have to think about that. Cheers, John Winters http://home.ican.net/~735769/ *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************Received on Thu Nov 23 2000 - 07:54:12 PST
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