From: "Matt Broze" <mkayaks_at_oz.net> > However, contrary to his hypothesis, the hull does not pivot > around the COF unless the hull is both completely symmetrical > and the COF is also not moving. > > A hull pivots around its Center of Lateral Resistance. Strictly speaking, the hull can be seen as pivoting around any point. Rotation is rotation and the rotation is the same regardless of inertial reference frame chosen. Naval architects normally choose to use the center of gravity for convenience. If you play with physics problems, you'll quickly discover that choosing a good point of reference (or origin) can make a solution easier. For hulls, choosing the center of gravity can make a lot of problems simpler, hence the preference. Aerospace engineers are split on the issue. Some use a reference point in front of and below the aircraft, some use the center of gravity while others use the wing quarter-chord. In every case, the choice reduces the complexity for the task at hand and reduces the likelyhood of error. Yours truly, in his aircraft engineering days had to convert all these data to a common reference point to determine aircraft loads (and thus stresses etc.) This lead to many arguments among the various groups (until we agreed I was doing it right :-). Matt's example of the saucer is an interesting one, as he makes a good case for focusing attention on the center of lateral resistance. However, if you shift your focus, you can get the same results for any center of rotation. Over two-thousand years ago, Aristarchus of Samos pointed out that an earth-centered universe with the planets revolving around the sun and the sun and moon revolving around the earth explained the retrograde motion of the planets as seen from earth. When Galileo was on trial for espousing the sun-centered view of the universe, Tycho Brahe presented Aristarchus' model as an alternative that didn't match Galileo's but solved the same problem, thus making Galileo look bad. What is remarkable is that with so many of the era's prominent scientists looking on, no one seemed to notice that the two models were identical, but taken from a different reference point. Rotation was confusing then as it is now. So how you see things depends on how you look. But the answer should be the same. Mike *************************************************************************** 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 Jan 09 2002 - 22:57:45 PST
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