3/02 has more energy packed at upper end of torque curve than SS. This would explain different results at same launch torque. They are seeing more stress on the model immediately after launch. If it is not the motor stick bowing then look at wings flexing (inside of circle leading edges at the end of wing). Many of bipe planes this year will tuck under as described from faster speeds at launch (weak spar wood), although it can be induced from other causes. The 3/02 may be causing an extended time of stress from faster speeds leading to decline in altitude.
A fast way to tell if wing is flexing is to place a 1/16 post between the wings at end of wing leading edge, to stop the tucking under.
Note that this problem will increase moving from a 2/3 rds motor to full SS and even worse when 3/02 is used.
MS
----- Original Message -----
From: Dave Drummer<mailto:beammeup_at_fast.net>
To: Indoor_Construction_at_yahoogroups.com<mailto:Indoor_Construction_at_yahoogroups.com>
Sent: Friday, April 14, 2006 11:04 AM
Subject: [Indoor_Construction] SO plane possessed?
Wednesday my students were doing some flying to ready their planes
for the upcoming PA SO competition. They were flying 2/3 length
loops, since our ceiling is at 19 ft., and the state site is about 28
ft. Our best monoplane was flying pretty consistently at about 2:00,
no touch, with Tan SS rubber. They put this plane aside and worked
on trimming the second plane, a (new) biplane.
After trimming the biplane, they went back to the monoplane and
switched to some Tan II (03/02, purchased our first year of SO
competition, saved for state competitions). Initially, they tried a
loop cut to the same size as the SS rubber, and launched at the same
torque, 0.35 in-oz. according to our homemade torque meter. Upon
launch, the plane headed down for the floor. Checked the wing and
stab incidence, they had not changed from the initial flights.
Checked for motorstick bend with a straightedge - we didn't see a
problem.
They were finally able to get it to fly by launching from about 3
feet off of the floor - the plane lost altitude for the first few
circles, then started to climb back to to the ceiling. This technique
eventually resulted in flights in the 2:05 - 2:15 range. Thursday,
they flew the same plane with the Tan II, same launch torque as the
day before, and it climbed normally without the initial loss of
altitude! We are really baffled about this. Any ideas as to what
could be causing this strange behavior?
Dave Drummer
Kutztown Sr. High School
www.LehighWheelmen.org<
http://www.lehighwheelmen.org/>
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Received on Fri Apr 14 2006 - 12:51:49 CEST