Paddleducks
Old Yahoo Group => Yahoo Messages => Topic started by: dragoncity on June 17, 2005, 09:36:52 PM
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Derek,
In my researches while designing/building P.S. Industry I was directed to an
article in a Aust. Model Engineering Magazine ( not sure what issue) when
the writer had the same problem when fitting out a full sized side paddlewheeler
of a new design.
They came up with a system that appears to be quite a useful starting point,
which in I call the "rule of thirds" :
1) choose a wheel diameter.
2) the paddle width should be at least 1/3 of the diameter
3) the paddle height should be 1/3 of the paddle width.
eg : 155 mm diameter, gives 51.6mm wide x 17.2mm high
I checked this simple rule of thumb against what information I have
about P.S Industry (full size) and found my paddles are a little
larger than this, but not by much.
eg : 155 mm x 68mm x 20mm
and I think that either size would be OK.
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Interestingly , I spoke to a paddle engineer ( in Echuca ) and he said
that "in general" the number of floats should be arranged so that
as ONE paddle enters the water (#1),
ONE paddle will be vertical in the water (#2),
and ONE will be leaving the water (#3).
-- the rule of thirds again !!
Of course on articulated ( feathering) types the rule is probably quite different.
And this will all "fail" when you are running empty verses full loaded !,
On my Industry I'd end up with 5 floats working the water (1 entering , 3 in , 1 leaving) IF I was loaded to the gunwals,
as these boats often did, while lightly loaded you might only get one float doing the work. I might try
it one day, in the summer in case I have to swim to save a sinking ship.
However there are always exceptions to the "rule", in fact the
P.S Alexander Arbuthnot's floats are so large that only ONE paddle
is in the water at a time, approx 4' x 18", so the engineer said, and this was also
a function of the paddlewheel speed
to avoid cavitation, ie: too many floats spoil the thrust !
Unfortunately, I did not bother to count the actual floats while I
was there, will do so next trip.
Hope this is of some use.
Your question does bring up the subject of just where does one find out REAL
information about appropriate dimensions, weights, speeds, etc, on model paddle boats ??
Its fairly 'easy' to get some info on full sized ones. For myself, being an
experienced racing yacht modeller, I'm used to working from NO info, and figuring it out, but it pretty hard for new
comers to the 'trade'.
Cheers,
And thanks for your kind words in the newsgroup.
Brett S Hallett