At 11:37 AM -0800 1/9/02, John Blackburn wrote: > >The COG and COF are the same the same for longitudinal and transverse >axes, (not vertical though) otherwise the boat will trim/list until they >are, however the boat turns about the point where the volume of water >forward and aft of the COF are equal. The effort (force x lever arm) >required to rotate the hull is the same, no matter which end or anywhere >along the hull it is applied. Also the COG/COF changes during the sweep >as your body moves forward and back. Don't we have a terminology problem here? It seems like we are using COF (center of flotation) as the equivalent of COB (center of buoyancy). The COG (C. O. Gravity) and the COB will always be vertically aligned, but COF is the geometric center of the waterplane. I.e. if you made a paper cutout of the shape of the waterline, COF would be it's geometric center. COB is the geometric center of the submerged volume, not just the waterplane. COF is a center of area, where COB is a center of volume. As an extreme example to show the difference, imagine a bottle held underwater at a 45 degree angle so that just the neck is above water. The COF will be the center of the small ellipse at the surface, where the COB will be somewhere in the middle of the bottle several inches away from the COF. In a kayak the COF and COB tend to be close but they usually are not in the same place. COF is the location of the axis about which trim will change if you shift weight fore and aft. It does not move (much) when you change the trim where COB and COG do change substantially. Not trying to pick nits, just want to make sure we are all on the same page. -- Nick Schade Guillemot Kayaks 824 Thompson St Glastonbury, CT 06033 (860) 659-8847 *************************************************************************** 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 Jan 10 2002 - 06:59:23 PST
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