Trim problem

[Bob Reynolds]

My son took a GWS Lite Stik wing (big wing , 300 power, al tube body) and built up a twin around the wing. Flat center section with dihederaled tips. Center body caries a stearable nose gear, batery, esc, and radio. Booms at the dihederal break cary the motors (slow stick small geared motors), the main gear, the rudders, and horizontal tail. Controls are rudders and elevator. He has the wing set up with the same amount of incidence as on the Stik.

Under power the plane wants to fly nose high and is very controlable. But it looks as if it needs to get the tail up and fly level. From up high he cut power and it glided prety much as a light rock, some what level and carrying a touch of up. When power was applied again it went back to the nose high attitude.

What does this plane need?

[BMatthews]

We'd need more info or pictures.

If he used more than one wing to produce a hybrid so that the wing area was increased but didn't make the horizontal tail larger then he would produce problems with having a tail that is too small for the wing.

From there all sorts of things come under scrutiny. Thrust angles, CG locaton, large bulks that produce odd drag directions and likely many other things.

[JetPlaneFlyer]

On the face of it I'd say that downthrust is required to stop the nose pitching up under power. A too far forward CG could also be part of the problem.

A photo of the model and knowing where it ballances as a % of wing chord would narrow down the options.

Steve

[Neil Walker]

It could simply just be too heavy and that's the angle of attack it ends up needing to be trimmed at to produce enough lift for the airspeed it's flying. Look at how much heavier it is that the stock kit with all that extra stuff on board.

[peterangus]

Bob

Any aeroplane will perform as you describe, if its max level speed is limited to [say] 1.2 x stall speed.

More power, to put the speed up to [say] 2.5 x stall speed will transform its flying manners.

[Texas Buzzard]

On the face of it I'd say that downthrust is required to stop the nose pitching up under power. A too far forward CG could also be part of the problem.

A photo of the model and knowing where it ballances as a % of wing chord would narrow down the options.

Steve

I agree with Jet Plane Flier.
This sounds like the CG is too forward and the wing has a bit too much pos. incedence. This makes for a stable plane but would be sensitive to power aplication - nose up like a free flight. Try a slight amount of downthrust. Shim the rear of the wing up with matchbook cover ( two thicknesses ).Move CG back about 1/2" to start.
Shim motor mount for slight downthrust - maybe 1/16th" ply.

Have sufficient elevator throw and go from there. Good flying to you.