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Re: Peter R Payne and proper boats.

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  • Richard Mundy
    Hi Jean-Yves, Yet another thing to think about. I had thought about momentum of the water column, but not its inertia. Dick ... and ... progress ...
    Message 1 of 29 , Jan 23, 2009
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      Hi Jean-Yves,

      Yet another thing to think about. I had thought about momentum of the
      water column, but not its inertia.

      Dick



      --- In pop-pop-steamboats@yahoogroups.com, "Jean-Yves Renaud"
      <boite.de.j-y@...> wrote:
      >
      > Dick, your biscuit tin/blow lamp boat moved back and forth (more or
      > less as every pop-pop boat) not because of the suction, but because
      > of the inertia of the water contained inside the pipes.
      > It very easy to demonstrate that the suction is not the cause. On a
      > classic pop-pop boat with two pipes, just bend one on port and the
      > other one on starboard. Thus, there will be no more thrust (port
      and
      > starboard being equal and opposite). The boat will no longer
      progress
      > forward, but it will go on vibrating back and forth as before.
      > If you have a single pipe engine, just bend the outlet vertically
      > downward and the result will be the same.
      > Jean-Yves
      >
      >
      >
      > --- In pop-pop-steamboats@yahoogroups.com, "Richard Mundy"
      > <coracles18@> wrote:
      > >
      > > Hi Jean-Yves,
      > > you keep knocking down my skittles:-).
      > > Seriously, I value your input hugely. Apart from a few
      experiments
      > > perhaps 10 years ago, I am coming at this subject from a 'what
      if'
      > > angle. I remember my biscuit tin/blow lamp boat moved forwards
      then
      > a
      > > little back per cycle. So there is a slight reverse pull on the
      > > intake. I suspect tho that that the valves unless very carefully
      > > designed would further reduce efficiency and as you suggest make
      > the
      > > forward facing inlet pointless.
      > >
      > > On the subject of nozzles, I have no experience, I just wondered
      if
      > > it had been tried.
      > >
      > > Conventional boilers work at high pressure so the steam can hold
      > more
      > > energy. In a pop pop the boiler is, via the water, open to the
      > > atmosphere. effectively like a kettle, and the steam produced is
      > very
      > > rapidly condensed by contact with the water and the unlagged exit
      > > tube. All this accounts for at least some of the inefficiency of
      > the
      > > pop pop, hence throttling the output to up the pressure and speed
      > up
      > > the output flow. But will it still work? If it actually reduces
      > > efficiency, why?
      > >
      > > Dick
      > >
      > >
      > > --- In pop-pop-steamboats@yahoogroups.com, "Jean-Yves Renaud"
      > > <boite.de.j-y@> wrote:
      > > >
      > > > Hi Dick,
      > > > I would like to comment 2 topics of your last post: facing
      intake
      > > and
      > > > nozzle.
      > > > 1°) Facing intake.
      > > > Everybody thinks at the beginning that using a facing intake
      (and
      > > > valves) could improve the performance of pop-pop propulsion.
      Even
      > > > Peter Payne thought that. But facing intake is useless, or more
      > > > exactly so inefficient that it becomes useless.
      > > > • By math demo it can be proven that the effect of such a
      > > > modification is negligible.
      > > > • For those who dislike math, there is an easy way to check
      > > > that sucking is far less efficient than blowing. Try to blow a
      > > candle
      > > > by sucking air!
      > > > • In addition, to prove this inefficiency, 2 years ago I built
      > > > a small boat with an electric pump to show that sucking water
      on
      > > the
      > > > bow has a negligible impact; though a jet backward propels. The
      > > > pulling force (when sucking) was roughly 20 millions times
      weaker
      > > > than the pushing one.
      > > > 2°) Nozzle.
      > > > The thrust of a waterjet evolving with the square of the
      velocity
      > > of
      > > > the water that is expelled it seems evident that a nozzle could
      > > > improve the performance. However, on a pop-pop engine a nozzle
      > acts
      > > > also on the frequency, stroke volume…and this is detrimental.
      We
      > > > don't know enough to give precise figures, but it seems that
      the
      > > best
      > > > nozzle has a diameter reduced by only 5 to 10%. On this forum
      > Daryl
      > > > is very likely the one who has got the best practical knowledge
      > on
      > > > this topic. Most of his engines are provided with nozzles and
      his
      > > > engines are among the best ones if not the best.
      > > > Jean-Yves
      > > >
      > > >
      > > > --- In pop-pop-steamboats@yahoogroups.com, "Richard Mundy"
      > > > <coracles18@> wrote:
      > > > >
      > > > > Hi David,
      > > > > I think the condensing is done in the tube, which creates
      > another
      > > > > problem. Condensing steam in a tiny tube is a lot quicker
      than
      > > > doing
      > > > > it in a big tube.
      > > > > An interesting aspect of Paynes original patent is using the
      > > > momentum
      > > > > of the returning water to compress the remaining steam in the
      > > > boiler.
      > > > > This should raise the boiling point so the steam has more
      kick
      > to
      > > > it.
      > > > > If this effect is significant I have no idea.
      > > > > More important I suspect is to have a forward facing intake
      and
      > > > > valves.
      > > > > Also, what about an output nozzle? you can significantly
      > increase
      > > > the
      > > > > velocity of water coming out of a hosepipe by sticking your
      > > finger
      > > > > over the end.
      > > > > This would also increase the pressure in the boiler and give
      > the
      > > > > whole thing more go?
      > > > >
      > > > > Dick
      > > > >
      > > > >
      > > > >
      > > > > --- In pop-pop-steamboats@yahoogroups.com, "David Halfpenny"
      > > > > <dh1@> wrote:
      > > > > >
      > > > > >
      > > > > >
      > > > > > --------------------------------------------------
      > > > > > From: "Richard Mundy" <coracles18@>
      > > > > > Sent: Tuesday, January 20, 2009 7:44 PM
      > > > > >
      > > > > > > As the engines grow bigger there is a need to create a
      lot
      > of
      > > > > steam a
      > > > > > > lot faster.
      > > > > >
      > > > > > AND then condense a tube-full of it in a similar time, in
      the
      > > > very
      > > > > boiler
      > > > > > you have just heated it in!
      > > > > >
      > > > > > That is exactly the snag that Newcomen had - though with
      much
      > > > less
      > > > > thermal
      > > > > > capacity to heat and cool each pulse.
      > > > > >
      > > > > > David 1/2d
      > > > > >
      > > > >
      > > >
      > >
      >
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