Down Thrust or C of G

Two identical MXS, same equipment, etc, etc.

I can't seem to make up my mind which could be the issue. MXS No.1 flown by Dave B at weekend was trimmed out but appears to climb when throttling up to full from half. Looking at elevator trims hardly any adjustment required there for level flight. It's identical twin, MXS No.2 flew okay!

I think that there is not enough down thrust looking at the model held level. So, I have added some using some 0.5 mm washers. Down thrust is noticeable now. Strangely No2 motor mount is as per factory and flies okay. They both use identical batteries in exactly the same position.

So, is down thrust going to help or move CG by adding some ballast in the nose? Avoid latter if possible.

Or is it just me and Dave? :lol:

Phil, I trimmed the first one to fly straight and level at half power so that you could have a fly with it.

Is the elevator servo ok? Is the elevator stab at the correct angle? Other than, must be downthriust prob or motor mount flexing?

Sounds like down thrust to me Phil, if you trim to fly level at part power and it then climbs with full power with a symetrical section. Nothing to do with cg.

First flights with my Ripmax Mustang showed the same problem, climbing steeply
on full throttle.It took a couple of goes at increasing the down thrust to sort it.
I settled for straight & level flight at about half power with a shallow climb at full power.
Since the model was new out of the box & assembled carefully & checked correct incidences
together with c.g , problem was somewhat of a surprise.
It was suggested the problem be solved by mixing some down elevator to throttle but I preferred
adding downthrust.
Colin.A.