Re: Indoor Props - Pitch versus Ceiling Height

From: Tom Vaccaro <tomv36_at_cox.net>
Date: Mon, 16 Apr 2007 21:53:55 -0400

Peter,
I've only been flying indoor models for a couple of years now, all my
flying has been at Glastonbury and I've only built and flown three
LPP's. My current model is a Frankenstein made up of parts from the
three of them. In my inexpert opinion, the model doesn't matter too
much, it's the prop that's most important.
John Kagan and I have been friends since we flew F3B models together
years ago. I met Max Zaluska at a contest three years ago at
Glastonbury and we have become friends. The first time John and Max
came to my house and looked at my props they actually laughed at me.
Not exactly the way to encourage a beginner but i guess they knew I
could take it. They also offered a lot of advice that has resulted in
a prop that works very well at Glastonbury.
It's based on the Jim Celm shape with a flexy basswood spar (john's
input), the spar located right at the trailing edge of the blade and
the blades constructed of .025 C grain laminated at a 45 degree angle
to the spar. It is pitched at 19".
My best time at Glastonbury is 8 min 34 sec and my best official
contest flight has been 8:05.
Here are my observations with respect to matching rubber to prop
(comments are welcome):
When I flew the model with a 10" loop of .085 3/99 tan 2 and launched
with a torque of 1.8 to 2 (units unknown-readings from Wayne Johnson
torque meter) I couldn't keep the model out of the rafters. I reduced
the cut to .075 and started using longer loops, up to 13" and finally
settled on 11.5 to 12". A 12" loop takes 1650 turns, back off 150,
launch torque 2.7. The model climbs with authority and after a couple
of lucky bunps form the curtains near the ceiling settles into a very
slow climb and a long cruise. we observed that on the best flights
the model didn't begin to actually loose altitude until about 5
minutes into the flight. Another observation was that the longer
thinner motor seemed less sensitive to launch torque than the shorter
thicker one. The launch profile didn't seem to change much when
launching at 2.1 to as much as 2.7 which I attribute to prop flare
and a shorter burst from the longer motor. Not sure of the physics at
work here and would appreciate some input.
Tom
Received on Mon Apr 16 2007 - 18:55:24 CEST