I am trimming a new plane and have something that is puzzling me. First let me say the plane is an "older" ARF of a 35% edge from a "not too popular" supplier and may not be built as strait as one would like. I am going to check all my incidences and surface throws again and I have read the recent articles in MA detailing Peter Goldsmiths methods as well as others, but here is my problem.

When pulling vertical lines the right engine thrust seems very close...only a little right rudder after climbing for several seconds but on downlines the plane yaws quite a bit to the right. It is VERY noticeable and is actually very difficult to straighten out using only rudder unless some power is applied?? Also When doing outside loops there is a Very Bad yaw to the left....VERY BAD..... Inside loops seem pretty decent. I am thinking that maybe I have some unever down throw on the elevator servos. They are hitec digitals that I purchased used on RCU....maybe programmed differently??

I obviously have some work to do but thought I would ask for some comments/ suggestions here as I get started.

Thanks,
Steve

I would reduce the right thrust and mix rudder to throttle to overcome the bad tendencies.

It seems to me that you have LEFT thrust and lots of RIGHT rudder trim is applied to compensate. That is why the plane wants to go right on downlines (low throttle setting which cannot comensate for lots of right trim).

Sooooooooo, I would strongly suggest that you check the thrust angle on the plane. Rule of thumb, it should be around 2 degrees to the RIGHT...

At least to me, it does not look like un-matched elevator servos.

I am pretty sure I have 1 to 2 degrees of right engine thrust but as I said i am going to double check everything. I am not sure where my rudder trim ended up last night after test flying but will check.... Thanks for the input so far....

Steve

This may be an odd reply but what type of propellor are you using. Is it constuction of wood or composite? The rotational weight of the propellor acts as a groscope. The airframe is attached to this gyroscope and its natural reaction is to reacts in the opposite reaction. This is the reason why engine offset is set into the firewall. Switching to a lighter propellor will decrease the rotational mass and lessen the adverse reaction.

There's the problem--chuck them Hitecs in the trashcan and buy a decent JR or Futaba.

Just kidding.[:-]

Sounds to me like an engine thrust problem. The reason it yaws left on outside loops is because of the thrust problem. You will still need right rudder to correct torque on the big vertical upline going outside.

I'd definetly check elevator throw. Both up and down deflections. It's critical and can make a huge difference.

With any overpowered airframe--you should expect to need right rudder input on big vertical uplines. No plane is going to fly straight up on a big vertical line. If it does--then your going to have to dial in left rudder trim to make it fly straight when on the flat-horizontal lines.

It's a thrust problem.

Does the plane string out? Is the tail of the fuse. lined up with the firewall? Could be the plane isn't built straight. While the wings and stabs may be liined up to each other--it all may be tweaked off from straight with the fuse. Just a thought.

Let us know how you come out.