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#1
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foot propelled jet ski?
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? |
#2
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foot propelled jet ski?
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 |
#3
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foot propelled jet ski?
William R. Watt wrote:
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. That's what paddles are for. Simple, elegant, effective engineering. I don't understand why people are constantly trying to "update" the basic design of these elegant craft with "Rube Goldberg" mechanical mechanisms. A large part of the beauty of these boats lies in their simplicity and the connection that the paddler has with the water. To eliminate that is to change the very nature of the boat. While your idea could certainly propel the boat, there are at least two problems with it. First, the operator would still need to carry a paddle, as it's necessary for turning and in the case of a kayak, for bracing and rolling. Second, your system would not work for anything but the gentlest of turns except perhaps on a really short boat. There simply wouldn't be enough of a lever arm to cause the boat to turn abruptly. |
#4
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foot propelled jet ski?
That's what paddles are for. Simple, elegant, effective engineering. I don't understand why people are constantly trying to "update" the basic design of these elegant craft with "Rube Goldberg" mechanical mechanisms. A large part of the beauty of these boats lies in their simplicity and the connection that the paddler has with the water. To eliminate that is to change the very nature of the boat. Mostly for hands free operation for taking snapshots or videos. But alas, also because upper body muscles put a greater strain on the heart for the wame amount of power than the lower body. It has something to do with the upper body muscles being smaller and closer to the heart. After a heart attack they encourage you to walk and discourage lifting. While your idea could certainly propel the boat, there are at least two problems with it. First, the operator would still need to carry a paddle, as it's necessary for turning and in the case of a kayak, for bracing and rolling. Second, your system would not work for anything but the gentlest of turns except perhaps on a really short boat. There simply wouldn't be enough of a lever arm to cause the boat to turn abruptly. I can turn the boats fine with a small sail and no rudder or paddle, adjusting sail postition and shifting weigth to adjust boat trim, but there is the daggerboard to pivot on. 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? An earlier idea was separately operated foot paddles, like paddle wheels but without the wheel protruding below the hull, so the paddles would be raised out of the water at some point in their rotation, allowing the boat to drift into shallow water. Also the paddles could be rotated independently in either direction making turning easier, as is done with oars. But the linkages, etc. I can imagine would be heavy and awkward. The foot operated pumps I can imagine would be simpler. -- ------------------------------------------------------------------------------ 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 |
#5
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foot propelled jet ski?
Have you considered the idea of using foot-operated paddlewheels
instead? It would seem to me that they would give you better propulsion for the same amount of effort. Also, I would think that they would actually be easier to build and maintain. You could have 2 wheels (1 each side) and have them set up to mount on top of the gunwales. They'd be nice and quiet too, for those nature pix that you might want to capture with your camera. Hope this helps, Paul |
#6
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foot propelled jet ski?
William R. Watt wrote:
Mostly for hands free operation for taking snapshots or videos. That makes sense. But alas, also because upper body muscles put a greater strain on the heart for the wame amount of power than the lower body. It has something to do with the upper body muscles being smaller and closer to the heart. I'm afraid you're baseing your design on a false premise. The small muscle groups of the upper body are not capable of driving the heart to as high a rate as the large lower body muscles. I'm also an avid cyclist and can tell you from experience that paddling is far easier on the cardiovascular system than cycling is. With the exception of high intensity paddling while surfing or playing in rocks, I never even get winded while paddling. By comparison, I can drive my heartrate into the high 180's on a bike. It's not even remotely possible to generate the same amount of power with the upper body muscles as with the lower body muscles, which is why they cannot drive the heart rate as high. It's also why kayak racers use boats that allow them to rotate at the hips using the legs to help drive the boat. After a heart attack they encourage you to walk and discourage lifting. That's because straining to lift something increases blood pressure, especially if you bend over to do it. |
#7
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foot propelled jet ski?
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 |
#8
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foot propelled jet ski?
Somebody makes foot powered kayak. Looks dumb to me, but they claim it is
efficient. |
#9
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foot propelled jet ski?
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. |
#10
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foot propelled jet ski?
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? |
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