Re: Re: Indoor Props - Pitch versus Ceiling Height
Tom:
It was good to see you at Glastonbury this past Sunday. Your LPP was flying quite nicely and, so far as I could tell, deftly avoided getting hung up despite some adventuresome flight paths due, in no small part, to pretty bad drift.
Your information about your current prop of choice and rubber selection was very informative and reflects a testing regime that I had not been able to emulate with the brand new prop I was using on Sunday. I am persuaded that the high pitch prop was very effective and efficient and, except for being a little too stiff and not flaring as much under high torque as necessary, I think it will become very useful. However, in the limited time available on Sunday I simply could not do the kind of testing necessary to get the right combination of rubber size and length/launch torque worked out. Four times hung up in the beams and backboards was very frustrating, especially when the prop spar got broken retrieving the plane from its fourth perch above the floor.
In the long run it was probably good that the prop spar broke in the process of retrieving the plane from its fourth berth in the structure because the blades have already been affixed to a new spar fashioned to permit more flaring. If only there were to be another flying session at Glastonbury so I could get it sorted out. Whenever the opportunity to do that next presents itself I will certainly incorporate your data into my testing regime.
Thanks, again, for your comments.
Peter Hess
Canton, CT
----- Original Message -----
From: Tom Vaccaro
To: Indoor_Construction_at_yahoogroups.com
Sent: Monday, April 16, 2007 9:53 PM
Subject: [Indoor_Construction] Re: Indoor Props - Pitch versus Ceiling Height
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
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Received on Tue Apr 17 2007 - 08:46:23 CEST
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