After Belgrade, where I struggled with too high prop RPM to gain any
altitude, I have built a new pair of prop blades, with slightly wider
blades, and constructed in the "Kagan style" (boron reinforced balsa
outline without a spar). These seem to improve my RPM, got one decent test
flight yesterday (went into a RC indoor session, where the guys were kind
enough to give me a few flying slots when they were practicing indoor stunt
pattern in the other end of the hall). This half-motor flight was aimed
only about half the ceiling height (10m) as we have our Finnish Champs next
Sunday, and I want to adjust my prop to those conditions.
The initial RPM from 40 to 35 was good. I just wonder if the flat part of
the curve from 2 to 4 minutes is already on the spring, or if the torque
curve of the motor is so flat that all changes disappear in the rounding of
the numbers. Then from 4 to 6 minutes the prop seems to switch over to low
pitch, quite rapidly even though I have tried to make harder springs than I
have had before. I wonder if this rapid change would also indicate excess
friction in the prop hinges? Finally, the bottom pitch of the prop is too
low, the model had been coming down towards the end of the high pitch, then
definitely climbed when the RPM peaked, so I need to adjust the low pitch
higher. That should also increase the duration some....
The flight was on a rather fat motor, 100mm loop that took only 580 turns
(up to max torque of 27 g*cm; it would take more but during the short slots
to fly I did not want to break a motor). I backed off 15 turns to a launch
torque of 20 g*cm, and landed with 40 turns remaining.
-Tapio-
- application/x-ygp-stripped attachment: stored
Received on Sun Nov 25 2012 - 23:17:07 CET