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Kayak and Canoe Design Bulletin Board
Suction and such...
Posted By: Pete W. P.
Date: Friday, 17 September 1999, at 11:42 a.m.
Hi folks,
Thought Id bring up a couple of things beneficial to an improved coefficient but never seen on a kayak. Im being layman all the way here so if I dance around the bush my apologies...
On larger ships , like oil tankers and the like they have this unusual protrusion right where the hull meets the water at the farthest tip of the bow. Looks like a ship giving birth to a submarine. I beleieve they have them on the stern too. I can pretty well guess what the advantages of it are, an extension of "boat-tailing" the hull of the ship. Aside from the uncertain probablilty that such a protrusion might be broken off a kayak on beach landings and such, wouldnt such a hull exstension actually work out beneficially for a sea kayak?
I recall a late ballistics guru [assasinated by Israeli agents] Gerald Bull who specialized in extended range artillery. One of his chief triumphs in design was his ability to fill the suction behind the fired artillery shell. As we all know, any object moving thru a medium creates pressure as it moves acroos its forward surfaces. Conversely there is a suction in the "wake" of the projectile that literally retards its forward motion. Bulls genius got around that problem by having pressurized gas "fill the vaccum" behind the speeding projectile. The result of this drag being canceled out allowed the artillery shell to go significantly farther. The grabby fingers of drag had to a great degree been neutralized.
I cant see how pressurized gas, or water would be practical on any light craft, but Bulls achievement does underscore the powerful effects that a wake of turbulence can produce in so far as a genuine suction. Perhaps this is to some degree the reason for the purpose for having a "submarine growing off the stern" of a huge ship. The bow effects are fairly obvious I'd imagine.
Pete
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