Midwest Magician problem

I built a 48" Magician from the Midwest plans. It flys just fine while flying straight and level. The problem occurs only when doing loops, however inverted loops are fine. The best way I can decribe this is, when doing a loop, the plane acts as if you are moving the control handle up and down very quickly as the plane makes the loop. My original thought was a warped wing (looks fine), or too much movement on the elevators (limited their travel)or maybe not properly balanced (the C.G. is according to the plans), but none of these appear to be a problem. I even tried slowing the plane down to the point of barely being able to make a loop. It still does it.

I'm thinking now that the elevator is getting turbulent air from the wing. The elevator/stab is higher than the wing on these planes. Maybe it's getting caught in the "wash" from the wing. That would explain why it seems fine in inverted loops. The problem with this theory is the fact that this is a proven design... So why doesn't mine work? Any ideas??? I'm at a loss.

Sounds like maybe your push rod to elevator is flexing. Do you have a fair lead on the pushrod? If this is the case, the reason it doesn't do it on outsides is because the pushrod is pulling instead of pushing. You did not say if it has flaps or not, but it should not make to much differance except that the pushrod is longer and would probably make it worse.

Flexing elevator is my best guess...pushrod, nylon horn or one side of the control surface.

LAST EDITED ON May-07-06 AT 05:28 PM (CST)
 
When you say "limited the controls" did you just put stops on how far the elevator travels? Or did you narrow your handle spacing to reduce the sensitivity?

Also, how heavy is the model? If the weight is excessive it could be stalling in the maneuver and that is giving you the bucking sensation.

LAST EDITED ON May-08-06 AT 11:16 AM (CST)
 
Hi Jim,

Makes sense, so I checked it out. There is a guide for the pushrod, and the rod is plenty beefy. Also, the control horn is metal, and quite rugged. No flex there.

Bill,

There is a piece of metal rod that links the two halves of the elevator together. Could that be "springing" in flight?

Larry,

I limited the controls by changing the position of the rod on the control horn. It now has what I would consider too little movement, however it still has the problem. I do not know the weight of the model. I'll check it and post here...

I do appreciate your time... Thanks!

QR1,
You are saying the plane briefly wants to roll with hard up elevator and then straightens out, right? Have you disconnected the pushrod from the elevator to see if anything is binding? If the joiner wire flexed it seems both inside and outside loops would suffer the same. If the elevator is binding on the up side and not the downside I could understand why the difference.

Bill

LAST EDITED ON May-08-06 AT 06:23 PM (CST)
 
Tail Heavy!
In thrust!
Needs lifting Stab!
Lead-outs back about 1/8"
Less line length!
Carved the wrong side of the fuse! The outside to the circle has to have the curve or banana shape.
Line size…….015-OR .018
Need to add 1.5 " to the fuse.....