Hey everyone. Let me explain my situation, then ask the questions.

Giant Scale plane with weird characteristics I can't quite figure out. Stabs are NOT Adjustable. Wings are using dowels so can be adjusted but want to be careful as it will be a bit of work.
Balance point right where it should be. Down trim needed for straight and level flight. Down lines at idle pull to the canopy noticeably but come straight down vertically. Knife edge is good as far as elevator trim goes. Slight amount of roll coupling though. Vertical uplines are straight as best as I can tell both laterally and vertical.

I was thinking of using a very slight amount of either flaps (both ail down) or Spoilers (both ail up) as a test bed to see if wing incidence changes will help with the trim issues. My thinking is that overall incidence will change with this move even though the wing hasn't really been moved.

I can easily use washers on the engine also but can't seem to understand the down elevator and pulling to canopy issue. Maybe I'm just not seeing the problem.

Any suggestions??

Thanx

ed

Ed,

I think the first thing I would do is verifiy the CG to be nuetral or slightly nose heavy. Take off and pull a 45 degree inverted climb at about 1/2 throttle. Let go of the sticks and see what the nose does. If it stays right there your CG is neutral, if the nose starts to point up you are tail heavy and if it starts to drop you are nose heavy. The fater it moves in either direction indicates just how heavy you are in that direction. Try to get it to either completely neutral or very slight nose heavy (espeically nose slightly nose heavy with a full tank)

Onjce you have that if it still takes a bit of down trim in straight and level then I would start off by adding one degree of down thrust.

The confusing this is the pull to the canopy on anything other than a vertical downline. That could indicate a wing incidence problem. I would find a trimming chart, startt at the top of it and work your way down. Figure around 20+ flights to get a plane trimmed correctly

Yes Ed dialing the ailerons like flaperons up and down will act like an incidence change.

But what is the problem with flying the model with a little elevator trim in it? Yes it could become speed sensative but you said it pulls to the canopy on downlines a wing change to the negative to reduce down trim will make this problem worse. I think you are pretty good. Mix a little down elevator at idle or come up with a way to adjust the stab. If its not glued in place there may be a way to shim it. I know the Carden's use those little plastic angles. I shimmed mine.


Allen

Thanx so far guys.

AAM, the reason is I want to compete in IMAC with a plane that flies like a Pattern Plane. Before the laughs come out, yes, I have had an Aeroworks 37% Extra that was dialed in almost identical to my Olympian(at the time) Straight down lines, simply flew straight in every aspect. The stabs are attached with blind nuts that are not accessible (read I''m not willing to dig into the fuse.)

Will try the CG thing first although it balanced prior to flying slightly nose heavy with empty fuel tank. I have been wrong here before:. I can change the incidence on the wing but have to make sure I do it correctly.

The puzzling thing is with an fair amount of down trim, still pulling to the canopy on downlines. That is why I am thinking wing incidence problems. If I add down thrust to the engine, that would nuetralize the elevator, this would only increase the amount of pull to canopy on downlines, if I add Up thrust to the engine it would require more down elevator trim for level flight, which in itself may help the downlines. Simply need about 3 days of decent weather to work on it.

Any other ideas/notions welcome.

Ed

In my experience there is no such thing as a wing incidence problem. The wing flies at the incidence it needs to generate enough lift to support the plane. The only effect that changing wing incidence has, is altering the angle at which the fuselage flies and this is a presentation issue. What changing the wing incidence does is alter the engine thrustline. So the first thing you want to try is trim for straight and level and then chop the power. If it climbs there is too much downthust, if it dives there isn't enough. By all means rectify these issues by changing the wing incidence provided you are happy with the fus. flying angle, otherwise change the downthrust.

Once this issue is correct, if it pulls to the canopy on downlines at idle its a CG problem. Either move it back or if this introduces other problems such as knife edge pitching or directional instability, mix it out.

Malcolm

If the c of g test(45 up,etc as already described) is ok, it sounds as though the only probs remaining are the slight roll coupling and the canopy-pull on downlines?
If the existing downtrim on el doesn't cause a pitch to the wheels in K/E, why worry about it?
My guess would be that a small %age of down el -at-idle-throttle mix would cure it,along with the usual rudder to ail mix for the roll coupling, and,given the lack of easily-achieved incidence adjustment, would be the first things to try.