Nick wrote; > Well that seems to leave an awful lot up to unreliable human judgement. > Next you'll be saying people should just paddle a boat to determine how > efficient it is. :) Well, here I go trying to be conciliatory and I get rapped on the knuckles. No pleasing you guys :-) >I won't try to convince you of the entertainment value > of being able to roll. It must entertain people. No need to convince me. I have watched them roll after roll after roll and always seeming to have fun. Hey, some people like S&M too. Who can judge what constitutes fun? Not me but maybe someone else can. I hope no one thinks that I don't have fun paddling just because I don't roll at every opportunity. (Maybe I should ask Prof Inverbon how he feels about it. > some value to being able to get an idea about rolling performance from > looking at the stability curve. For one it is less open to different > interpretations than descriptive characterizations of sheer shape. No question about it, I agree that quantitative beats subjective hands down. But, I did not suggest descriptive interpretations of sheer shape. If one wants to apply quantitative measures to stability why not go all the way and calculate the roll damping characteristics of the upside down boat? Why just partial science? > I agree that the shape of the sheer is effecting the easy of rolling, but > how do you describe a sheer shape such that it will consistently > characterize what is pertinent to ease of rolling. My hypothesis is that > the slope of the stability curve supplies the information required in one > easy-to-interpret format. Does it provide the dynamic information. Keep in mind that the stability curve provide "static" stability. Rolling has a large dynamic component. Consider this, suppose a boat had stabilizing fins. They would not show up as a significant aspect on the static stability curve but would show up as a significant roll damping device. I will dig into my bag of books and see if I can find information on roll damping. > The rise of the bow may also effect rollability, but some bows have a lot > of volume while others don't. Again, you have the trouble of interpreting > the data accurately. Maybe not if you look at rolling phenomenon as the combination of righting moment and roll dampening. The bow could provide reduced static stability but increased roll damping. Neat Ehhh? > Wide flat boats with high inverted stability will be hard to roll. The > slope of the curve will reflect this because the slope will increase to > account for the large change from inverted to upright. But two boats with > roughly equivalent inverted stability could have quite different rolling > characteristics (due to different sheer shapes or other factors) and I > suspect the slope of the curve would reflect the differences. No question the stability curve reflects the static condition but how does it reflect the roll damping aspect? Can you establish the degree to which each contributes? Suppose we looked at the upright condition and then related that to the upside down condition. What similarities exist? Cheers, John Winters Redwing Designs Web site address http://home.ican.net/~735769 *************************************************************************** PaddleWise Paddling Mailing List - All postings copyright the author and not to be reproduced outside PaddleWise without author's permission Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************Received on Fri Jun 30 2000 - 18:57:09 PDT
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