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Henner Trabandt
05-16-2008, 09:20 AM
Hi guys,
yesterday I had a Problem. May be you can help me:
We got two Bristol Scout biplanes. The yellow one is mine, scale 1/8th weight 1300 gramms and flying like a trainer. Power supplied by three lipo-cells of 2000 mAh, engine by Hype and propellar 9X4".
The green one is built by my son-in law. It is the same plane built from the same plan. He built it a bit heavier, 1450 gramms, a bigger lipo-cell of 3200 mAh prop 10x4, 30 Amps at full-power. So it has got power enough.
I tried to take off. Running easily straight ahead. But immediately after take off it turned on its back and crashed into the grass. None of my biplanes (I got 5 of them in different sizes) did ever show this. What went wrong?

Henner

pd1
05-16-2008, 02:12 PM
Henner, Sorry about the crash.
With so little information I can only speculate.

From your description it sounds like the plane stalled and rolled over.

Was the GC in the same place on both planes?
Did his have any warps?
Was the incidence of the wings checked?
How about elevator throw, was his greater than yours?
Or was it possible the plane just lifted off a little early and stalled before it had sufficient flight speed?

I've done that on a couple of planes, then over thought the cause.
Some planes don't take too kindly to a lot of elevator for take off.

Hope you find the cause.

Paul

Henner Trabandt
05-16-2008, 08:41 PM
Thank you Paul for your answer. I think the elevator was one of the problems, weīll have to reduce the throw. GC and incidence were ok. It isnīt very much damaged, I think we can fly again this weekend.

Thanks, Henner

Gnascher
05-16-2008, 09:48 PM
Perhaps the landing gear are on the wrong side of the plane. :p

I think Paul's probably covered the bases here, hope you have better luck this weekend!

FlyingMonkey
05-17-2008, 02:14 AM
Might also want to adjust the dual rates and expo on his radio.

I noticed in the photograph (I assume it's from just before the incident?) that the elevator on the green plane is up slightly.

You might want to make the plane just a tad nose heavy before the next flight too. With the added thrust, potentially higher throws, and the fact these planes are inherently unstable, it wouldn't surprise me that one would loop like that on take off, especially if full throttle and full up elevator was applied to "compensate for the heavier plane".

Biplane Murphy
05-17-2008, 04:16 AM
Could also be a thrust angle problem...

Bub Steve
05-17-2008, 04:32 AM
Henner::petty planes there my bub, If she rolled off striate without any need to give some right rudder on take-off, she may have to much angle on the mount, your bub,steve

Biplane Murphy
05-17-2008, 04:34 AM
Henner::petty planes there my bub, If she rolled off striate without any need to give some right rudder on take-off, she may have to much angle on the mount, your bub,steve

Yep....I had a pitts kit that had too much right thrust.....It flipped over everytime on takeoff, until I remedied the thrust angle...

Henner Trabandt
05-17-2008, 08:52 PM
Thank you guys,
this may help me very much. "Thurst angle", this was the word I was looking for... We had only 2 dergees to the rigth and 3 deg down. We shall add 1 deg right and the same down. And of course the elevator throw will be reduced and the GC a little bit foreward. It MUST fly! Weather forecast isnīt very fine, rain all the Sunday, but we will see,
Thanks Henner

Henner Trabandt
05-23-2008, 05:48 PM
She is flying!

So, what did we change? we enlaged the thurst angles, reduced the elevator throw and set the G/C a very little bit foreward. Flew nicely, like my own one. Take-off easy, was not possible to stall. Can be flown at very low speed.
Thanks for your advice.
Henner

pd1
05-23-2008, 05:52 PM
Flight shots look great.
Glad to hear it's flying well.

paul

Biplane Murphy
05-23-2008, 06:50 PM
Cool...Glad to see her in the air....:)

Bub Steve
05-23-2008, 09:40 PM
She is flying!

So, what did we change? we enlaged the thurst angles, reduced the elevator throw and set the G/C a very little bit foreward. Flew nicely, like my own one. Take-off easy, was not possible to stall. Can be flown at very low speed.
Thanks for your advice.
Henner
Looks GREAT!! your bub, steve