h a l f b a k e r yAssume a hemispherical cow.
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//Silent// ? I don't think so. The putt-putt boat toy is fairly quiet, but scaled up it might sound more like
!!PUTT--------PUTT!! |
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I could see trying to build this if I were stranded on a desert Island, though. |
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Part of the reason that the miniature pop-pop boat works is the scale. |
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The principal relies on the water creating a fluid piston in the tube which is propelled backward when some of it boils. This works OK in small tubes, but becomes less effective when the steam /water boundry becomes turbulent and condensation occurs before much momentum has been imparted to the water. A search for the largest pop pop boat only shows models about a foot long. |
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I'm sorry to disappoint you, but a lot of *driftwood* doesn't burn well, as it has been soaking in water for so long. (from personal experience of lighting beach fires) OR are you carrying a cord of firewood in a tiny boat? |
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it's true that wood fired propulsion is going to require frequent stops on shore for re-fueling. (Not something you can do at sea [csea] so a sail and a compass would be a more effective use of your time.) |
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As of this writing, if you could make a ship engine that could run on watered-down crude oil, I know of an apparently inexhaustible refueling spot. |
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//wood fired propulsion// Well, one good thing about it is:
you can cannibalize the structure of the boat to feed the
engines. If I recall correctly, this was actually done by one of
the first transatlantic steamships. (Quick Wikipedia check
shows it was the Sirius, racing the Great Western
<link>) |
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//This works OK in small tubes, but becomes less effective when the steam /water boundry becomes turbulent and condensation occurs before much momentum has been imparted to the water.// |
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Might a larger boat use a bundle of small tubes rather than singular large tubes? |
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Small tubes impart too much friction and may cause
pipe
cavitation and bursting due to low pressures (due to the
energy loss by friction). I know this sounds crazy, but
it's
true. Pipes will literally implode/explode (air bubbles
spontaneously
formed inside due to low pressures implode almost
immediately and this
energy release makes the pipe explode) if there isn't
enough pressure,
and
friction is the number one contributer to the depletion
of
pressure. You need
large pipes for larger ships. It's called scalable design,
or
some such. And larger pipes equates to turbulence
which brings its whole separate bag of problems...
Ahh... engineering: full of finicky optimizations. |
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I also believe that the resulting ships will be pretty
freakin' loud. |
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How about many small tubes?
No scalable design problems that way. |
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How about 'yes, there will be problems'. For a given flow-
rate you will only be increasing the
frictional forces with more pipes, decreasing the flow-
rate; and the flow-rate is
what determines the power output; and the minimization
of friction is what increases your power output. I may be
wrong, but
I'm against this one. People underestimate the amount of
friction in pipes and how it changes with diameter. |
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