Re: low ceiling- long duration...

From: <dgbj_at_aol.com>
Date: Thu, 16 Nov 2006 06:36:28 EST

Caner,
 
The most popular method seems to be to make the propeller blades flare to a
higher pitch, to reduce the rate of climb and reduce the revolution rate of
the motor, lengthening its run time. The flared prop is more inefficient, so
much of the energy in the higher torque end of the curve gets wasted,
compared to what you could do in a higher ceiling. You make the prop flare by
putting the pressure center of the blade chords ahead of the torsional axis. For
example, put half or more of the chord ahead of the spar. Look at a bird
flight feather. Note that the quill runs along about a quarter of the chord.
This feather is aerodynamically balanced along its torsional axis. On the non
flight feathers, the quill runs down the center.
 
Another method is to make your flight below the spike in the rubber torque
curve. Just don't wind the motor all the way. This wastes the high energy
available at the high torque end of the curve, while carrying the full weight
of the rubber, but it keeps the plane from climbing rapidly to the ceiling.
You can try a longer, thinner motor that will give less torque and more
turns, but you don't want to run out of torque and land while there are still a
lot of turns left.
 
Something that I have seen done unintentionally is to have the plane bank
severely on high torque, so it flies around without gaining altitude until the
torque comes down, then the plane levels and begins to climb. I have seen
planes released above the head, fly down almost to the floor or even bounce
along the floor, before beginning their climb. Usually I recommend launching
close to the floor to utilize the full height of the room, but in this case I
would recommend launching as high as you can reach. The way to do this is to
reduce some of the things that are done to correct torque roll; offsetting
the wing to the left, left tip washin, right thrust. You want the plane to
roll left and sideslip, something that is usually avoided.
 
Gary


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Received on Thu Nov 16 2006 - 03:39:22 CET