I have a Goldberg Cub that is completed and ready to fly. I did not build this particular plane but it appears to have been built well and completely stock.

My question concerns the elevator pushrod. It is square balsa with your normal wire ends attached at each end. The rear wire pushrod is shaped to exit the fuse and hook up to the elevator control horn...ok so far?

OK, now if I push gently down on the elevator the entire pushrod moves sideways (to the inside of the fuse that is) before it starts to move the servo allowing for a fair amount of down travel on the elevator which I am thinking could lead to flutter. Is there a way to elliminate this sideways travel of the pushrod? Somehow, I need to be able to stop the metal part of the pushrod where it exits the fuse from moving inwards before it moves forwards.

Any suggestions?

Cheers

Mike

Mike:

That's a crash that hasn't happened yet.

What you need to do is make the wire part as straight as you can, if you have to change the location of the exit do so. If it still flexes replace it with a stronger wire, or replace the entire pushrod. Avoid bends in the wire part of push rods as much as you can. The straighter the better.

If you can push the elevator down without moving the servo aerodynamic forces can push it down too. Might be that last bit of elevator deflection you need to pull out of a dive.

Bill.

I used that same setup in my Goldberg Cub. I don't have a flutter problem, however, if I go into a dive, it take a while to pull out. There are fiberglass pushrods available. Perhaps that is a better choice.

I take it that this is the stock 2-56 wire. I flew mine that way for over two years with out a problem. I had a bad landing and replaced all of the radio gear so I up graded to 4-40 rod and did not have the flex in the wire after that.

Dru.

I've had about 6 CGM Cubs in my family over the years. Every one had the stock push rod assembly, and none ever experienced a problem.

This should have no effect whatsoever on Flutter, but like w0mbat said, it could make pulling out of a powered dive tough. But then, if you're pulling out of a powered dive, you shouldn't be doing it in a Cub anyway.

Bottom line, I would say fly it first before you do any surgery.