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foot propelled jet ski?
Cool project. I like the weird and impractical ideas just to see if it
can be done and to try and learn. 90% of building enjoyment is trying things out. If I just wanted a boat I'd go buy one. Having said that; I'd go with one pump and some sort of traditional rudder thing. If all else fails try the manaquin. Good luck. On Wed, 19 Oct 2005 20:02:03 -0400, "dbraun" wrote: The design criteria that you describe has already been addressed in a commercial product: http://www.hobiecat.com/kayaking/index.html These kayaks have been available for over 10 years I believe. They are functional and reliable. They have rudders, but a paddle is still used for tight maneuvering. |
foot propelled jet ski?
Yeah, but the efficient process is the one most nearly reversible. Minimize
turbulence and velocity change. Roger http://home.earthlink.net/~derbyrm "Brian Whatcott" wrote in message ... Hmmm... thrust - drag = mass X acceleration Brian Whatcott On Wed, 19 Oct 2005 07:04:02 +1000, "barry lawson" wrote: Willliam, Consider the basic principle that thrust = mass x velocity, but power consumption is proportional to !/2MV2. This means that while a small jet at twice the speed has the same thrust as the larger jet at twice the area, the power consumption is four times greater! Big Slow Pumps! For anyway near the same effectiveness the jet area needs to be around the blade area of an oar. Regards barry lawson "William R. Watt" wrote in message ... My main concern is the amount of propulsion that could be provided by foot operated water pumps. I imagine a slow pump action, using, say 3" plastic drain pipe for the pump body. I'll guess have to get out the college physics text and try some calcultations. Anything I should take into consideration? |
foot propelled jet ski?
Toller wrote:
Somebody makes foot powered kayak. Looks dumb to me, but they claim it is efficient. Hobie makes a foot powered boat, but I wouldn't call it a kayak. |
foot propelled jet ski?
Thanks for all the suggestions. You can get more power from the lower body (the muscles are larger) but for the *same* amount of power the upper body puts more strain on the heart. That's what I read while researching heart disease. I have worked before with hull resistance figures for canoes and kayaks. You can get a pretty good estimate of the horpower required to move a hull at a certain speed. Non-athlete paddlers can sustain about 1/20 of a horsepower. It's also easy to calculate the amount of water pumped from the size of the cylinder and the rate of pumping. It's possible to convert the amount of foot pressure on the pump into the speed of the water leaving the pump. I should find out about the efficiency of water pump propulsion. In one book I was lookign at last night it says the shape of the outlet nozzel is important. I once estimated the energy comsumption efficiency of paddling a canoe at about 13% (it's on my website under "Boats"). I agree with one poster that innovation is the fun part about designing and bulding boats. But I'm not crazy about the building part, time-consuming messy physical work costing money, so I try to do as many calculations as possible before starting to build, even though trying to figure out the formulae sometimes drives me crazy. :) -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-FreeNet email must have "notspam" in subject or it's returned |
foot propelled jet ski?
Foot operated pumps for propulsion don't look practical. They would be too inefficient and they would only move the boat forward. The device on the Hobie kayaks is amazing. With all the propulsion under the hull there is no waste in surface turbulence. However it is disappointing that it's only 10% more energy efficient than arm propulsion. I thought it would be less of a strain on the heart. I can imagine two improvements but don't know if they would be feasible. First, as the desinger points out, reciprocating leg action is better than circular leg action, but it would be even better if the action were low instead of high. Perhaps the cranks could bent over or inverted. Second, the fins only move the boat forward. If the fins could rotate they could be aimed in any direction like an outboard motor to steer the boat, and to propel it backwards. -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-FreeNet email must have "notspam" in subject or it's returned |
foot propelled jet ski?
I really would like to see this rig!
"Bowgus" wrote in message ... Too easy ... just need to convert the peddling motion to "flipper power" at the back of the boat. Maybe pick up a mannequin, lop off the top half (don't throw it away just yet), mount the lower half through the stern (aka sterndrive), and set up some peddles and chain drive to a wheel at the back with pins each side to which the mannequin legs attach, As the wheel turns, the legs that pivot midpoint between the wheel and the flippered feet, start flipping. For extra speed (remember I said don't throw away the upper part), attach the upper part of the mannequin to the hull such that the arms are in the water. Another chain from the peddles to those arms such that they do a crawling motion, et voila ... yer laughing ... you and everbody else :-) "William R. Watt" wrote in message ... Any opinions on the feasibility of foot-operated water jet propulson for a small boat like a canoe or kayak? I was thinking of mounting twin water pumps on the (out)sides of the hull to suck water in the front of the pumps and squirt it out the back through a smaller diameter pipe to make a jet stream. The water pumps would be foot operated through levers and a pivot. Got the idea from reading a book on ancient Roman engineering. Could the legs and water jets produce enough propulsion to move the boat at, say, walking speed? I think a separate pump on each side, powered independently by the two legs, would allow the operator to steer the boat by pumping one harder than the other to turn. -- -------------------------------------------------------------------------- ---- William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-FreeNet email must have "notspam" in subject or it's returned |
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