Robert wrote: > > I imagine this angle is related to viscosity or how much molecules of a > particular substance are attracted to each other (I can't remember the > word for this, cohesion?). If I were paddling in mercurey would the > angle be more obtuse and in gasoline more acute? > I searched and could find nothing about the effect of viscosity. Perhaps because when Lord Kelvin proposed the theory of wave patterns he did not think about bodies moving through anything but water. I don't know that for sure since I have not read his paper but, like Matt, I could not find anything that says otherwise.. Anyway I did find some interesting stuff. For example the angle 19 degrees 28 minutes (half angle not full angle. For some reason naval architecture books seem to prefer half angle over full angle) does not seem absolute. For example, Commander Hovgaard presented a paper to the Society of Naval Architects in 1909 reporting that observations of full size ships showed angles between 16 degrees and 19 degrees. On one Danish torpedo boat he observed an angle of 11 degrees. His observations in the US Navy test tank revealed even smaller values particularly at high speeds. (non-planing craft but no reference to what "high" meant. Admiral Taylor attributes the difference to the forces being distributed over the entire boat rather than a single pressure point. Nevertheless he also says that the Kelvin wave patterns agree "reasonably well" with practical results. Gilmer (professor at the U.S. Naval Naval Academy) writes that the 19 degree 28 minute angle applies to a thin body or pressure point moving in a straight line through the water. So the hull shape seems to affect the angle. This ideal condition does not seem to take into consideration the stern wave that boats develop. Apparently Kelvin's paper contains mountains of complex mathematics to arrive at his conclusions. That discourages me from trying to obtain the paper and report on its contents. :-) Sorry to bore everyone but I found it interesting. %0 Cheers, John Winters Web site address http://home.ican.net/~735769 *************************************************************************** PaddleWise Paddling Mailing List - All postings copyright the author and not to be reproduced/forwarded outside PaddleWise without author's permission Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
This archive was generated by hypermail 2.4.0 : Thu Aug 21 2025 - 16:33:18 PDT