Peter, Stability curves account for gravity. They assume a given center of gravity of the boat and contents. The stability curve is a graph proportional to the horizontal distance between the CG of the boat and contents and the Center of Buoyancy (CB) of the boat itself. i.e. the graph is a righting moment for a given gravity condition. A paddler with a higher CG will change the curve. The change in the curve can be fairly easily determined without re-testing the boat by subtracting the difference between the old CG height and the new CG height and multiplying by the sine of the angle of heel. http://www.guillemot-kayaks.com/VCG.gif shows a family of curves for different CG heights. A paddler with a higher CG will feel equally less stable in all boats. A paddler with a lower CG will feel more stable. Notice that the shape of the curve doesn't really change in character, it just moves up and down. And it moves in a predictable way [GZ = AZ - AG sin(angle)]. It will move in the same manner for all boats. A paddler with a "non-standard" CG should be able account for the difference. Two boats with the same stability curve will respond the just like each other for all paddlers regardless of the paddler's individual body type. If someone wanted to, they could make a little correction graph for their body which would work for all boats tested at a given CG. It shouldn't be necessary. Just because the curve changes does not mean that the characteristics of the stability curve are irrelevant to anyone who does not match the assumptions of the curve. It just means that each paddler needs to learn for themselves how the curve relates to how they perceive the boat's performance. If we were able to come up with a measure of secondary stability it would be relevant to all paddlers. While the high CG guy might not find a boat with high secondary stability as stable as someone with a low CG would find it, he would find that two boats with the same secondary feel the same. The goal of finding a measure is not to compare people, but to compare boats. As long as the comparison works consistently between boats, it should be considered a good one. The stability curve and its characteristics such as the slopes and areas have this property. While the slope and area do change with different CGs, they change in consistent, predictable ways. Nick -- Nick Schade Guillemot Kayaks 824 Thompson St, Suite I Glastonbury, CT 06033 (860) 659-8847 Schade_at_guillemot-kayaks.com http://www.guillemot-kayaks.com/ >>>>"It's not just Art, It's a Craft!"<<<< *************************************************************************** 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 Wed Nov 22 2000 - 15:39:09 PST
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