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). Since we know the time (108.74 seconds) for the winner over 500 meters. and distance we should easily get that converted to the speed in knots. I get about 9 knots as their speed. About what a top single Olympic kayak paddler can do. The hard part working it out that way will be to figure the drag. Does anyone know the waterline length and width of a dragon boat? Knowing the wetted surface and draft as well would be even better but I could probably make a pretty good estimate of the wetted surface from the waterline length and width. Using 40 feet as the waterline length, 4 feet as the waterline width, 5000 pounds as the displacement, .8 as the prismatic coefficient and then stretching the limits of my drag spreadsheet in doing so, I'm going to estimate there is 120 to 150 pounds of drag at 9 knots on a dragon boat. 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. Sorry to be so long getting this done. I've been working double time to try to catch a kayak thief. Matt Broze www.marinerkayaks.com *************************************************************************** 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/ ***************************************************************************
My only advice on catching a kayak thief would be to watch for meth addicts carrying a kayak under their arm. Or watch for meth addicts advertising kayaks on ebay or craigslist. I guess my horsepower question could be expressed as: how big an outboard motor would you need to push that dragonboat at the same speed if the paddlers all decided to go on cigarette break simultaneously, and we compensate for the weight of the outboard by tossing one comparable paddler overboard? Brad Crain Quoting 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. > > Sorry to be so long getting this done. I've been working double time to try > to catch a kayak thief. > > Matt Broze > www.marinerkayaks.com *************************************************************************** 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/ ***************************************************************************
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/ ***************************************************************************
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/ ***************************************************************************
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