Chuck, thanks again for sharing all this info!
We must be doing something wrong, because to prevent stalling at the suggested CG, we had to lower the wing's leading edge until I couldn't be sure the wing and stabilizer were at different angles. It went from stalling in the glide to just descending in a straight line without pulling up, with just a tiny adjustment. So, we raised the wing's leading edge a bit, and moved the CG forward. Then it glided without stalling and with pitch stability.
Is it fair to test glide these models? Seems they probably won't have the prop stopped at any time in a powered flight. A stopped prop can't have the same drag as one at low power near the end of a flight.
Even after it glided OK, we had trouble with stalling under (partial) power until we added a little bit of left rudder to tighten the turn. This was in addition to having some stabilizer tilt already. I ran out of ideas. The thrust line isn't adjustable. The propeller bearing presses into a plastic mount glued into the front of the fuselage stick. If it was adjustable, I'd have tried removing the right thrust and adding a little down.
We know that flying with a partially wound full motor isn't as good for adjustments as shorter motors wound fully to have the proper torque at the beginning of the flight, But, it was the only choice we seemed to have, if we didn't want to end the testing. Jack had only one short motor. I wondered if he'd make another one there, but he didn't do so.
Jack is using a 15:1 winder, backing off five turns of the crank, 75 turns in the rubber, regardless of how many turns he flies with. So, he may be over winding and unwinding too much with shorter motors. A motor one fourth as long probably should be over wound and backed off one fourth as much..
He's using 0.056 rubber, because the 0.052 also supplied wouldn't make it climb on his previous outings. I'm not sure it that's width in inches or grams per inch, or even some other unit. But, if it is the same units, then his plane needs a lot more power to fly than your plane! But, Jack did say his model seemed to climb more steeply early on than those he'd seen on the internet, so maybe the rubber is too thick. His motor is at about 1,950 turns when wound fully. Your must be about 2,600 turns.
We aren't using a torque meter. I haven't asked if Jack has one. I'm pretty sure he'd be using it if he did.
Don Weigt
Received on Mon Jan 23 2017 - 23:00:38 CET
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