I don't know how to mathematize this problem, but based on a childhood spent in Florida, a 3 hp Evinrude pushing a 14 foot flat-bottomed rowboat with just me (age 16) in it would top out at about 3-4 mph. Therefore it was prudent to plan trips with the tidal current as much as possible. Brad Crain Quoting Dave Kruger <kdruger_at_pacifier.com>: > Matt Broze <marinerkayaks_at_msn.com>: > > Bradford asked: > >>> 1. How many horsepower does one dragonboat generate? 2. Do paddlers >>> develop asymmetrical/lopsided bodies?<<<<<< > >> Is it a trick question? The dragonboat doesn't generate any horsepower >> at all. It just generates drag when horsepower moves it. >> >> To answer the question you likely meant based on what I think is >> the horsepower that a very strong paddler could generate. The 20 >> paddlers times about 1/5 of a horsepower generated by each paddler >> would generate >> about 4 horsepower total. Horsepower = drag in pounds x speed in knots >> x 0.003069 (I think). >> >> I get about 9 knots as their speed. About what a top single Olympic >> kayak paddler can do. If HP=speed in knots times drag in pounds >> times .003069 then that gives between 3.3 to 4.1 horsepower needed >> to move the >> boat that fast. > > Matt, I can not evaluate your method, but if 20 paddlers at about 200 > lbs each plus boat comes in at about 5000 lbs, my gut feeling, based on > some time in small power boats says 4 hp ain't enough, even considering > this is at the shaft, not the "rated" hp of the engine. A 10 horse > outboard will push a _lightly_ loaded jon boat with two passengers (all > up weight about 600-650 lbs) up to about 20 knots. Figuring five hp at > the shaft, and figuring the drag goes as the square of the speed, that > means you'd need only maybe 1.25 hp at the shaft to hit 10 knots in the > jon boat. If the 10 hp motor actually delivers 10 hp at the shaft, > then you'd need 2.5 hp to hit 10 knots with the jon boat. > > In any case, I can't see how 4 hp would be able to generate 10 knots on > a boat + passengers displacing some 5000 lbs, although the dragon boats > are no doubt fully in displacement mode, are a lot longer than a jon > boat (which would be planing at 10-11 knots), and a low-speed > propulsion system (e.g., paddle) is a lot more efficient than a high > speed screw (e.g., outboard three-bladed propeller running at high > revs). > > -- > Dave Kruger > Astoria, OR *************************************************************************** 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 Sun Sep 30 2007 - 19:48:01 PDT
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