| Jim,
The need for a pump would be determined by the placement of the
fuel tank. Where your building a stock plane to be used for towing as
opposed to wild aerobatics, go with the instructions.
If the plans call for the tank to be right behind the firewall and
you can get the center of the tank "about" even with the carb, no pump
should be necessary. If the tank is back under the wing, or if you
choose to put the tank back there, a pump will be necessary.
In my poinion, pumps just complicate things and if you can avoid
it, do so. If your considering changing the tank placement, you'll also
need to consider where your going to mount the pump. You'll have to
make sure its accessible for adjustments etc. You can do a certain
amount of "setup" on a test stand, but if you need any fine tuning,
you'll need to be able to get to the pump.
If the main purpose of this plane is to tow gliders, a changing CG
due to fuel usage shouldn't even come into play. You won't burn enough
fuel during a tow to make any difference. So, basically unless your
planning on doing some precision aerobatics with your tow plane, KISS.
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| Jim,
I agree with Steve 100%. You should not need a pump - and I would
not worry one bit about changing CG with fuel load. This ain't a
pattern ship. You will get trim changes with throttle changes, you
will get roll with rudder and other things that sport planes do that
would be undesirable for a pattern ship. Keep your setup simple and it
will be more reliable. All pattern ships use pumped engines for two
reasons: To allow the tank to be on the CG so you do not get a trim
change as the fuel burns. To keep the engine from changing mixture on
long verticals.
Charlie
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| I would prefer not to use a pump, if for no other reason than the
cost savings.
It was presented to me that a pump would increase, not decrease the
reliability of the engine by providing a constant fuel flow.
Thanks for the information.
Regards,
Jim
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| RE: -1
I will start without a pump and see how it works. I can always
add it later. This airplane has a fiberglass fuselage with no
bulkheads so ease of access is not an issue.
The Klein pump apparently requires drilling a hole in the crankcase
which I do not want to do if I do not have to.
Also I may not need to use a 24 oz. tank, although this was what was
recommended. I will wait to see what the fuel consumption is on
the engine I finally choose. A smaller tank should present less of
a CG issue.
Good luck at the Glen, N.Y. meet! Try to say hi to my clubmate
Todd Sheehan who will be flying a R/C city Punch in advanced.
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