RV-3 rudder/tail wag

We have been working on a RV-3 which was originally built from plans. We have noticed that when we are flying at speeds of 140 or higher there is a left and right oscillation in the tail of the airplane. The magnitude of the oscillations appears to grow as the speed is increased. Or, as the time the feet is off the pedals at the higher speeds. We have checked the vertical stabilizer attachment, the rudder attachment, and tried tightening the rudder cables. Has anyone else experienced this behavior? Any ideas of other things we can check??
Thanks,
Steve Will
Pennsylvania

Is it possible the rudder skin isn't flat at the rear near the trailing edge bend?

If the rear portion of the rudder skin bends down to the trailing edge radius at the end of the skin stiffeners, it could cause what you are describing.

Regards,
Jim Ayers
RV-3 sn 50 N47RV

Make sure the rudder skin is not "oil canning" as this will cause an oscilation.

Ed

Check your trailing edge

Same comment... you rudder's trailing edge is likely not fully bent. When building any control surfaces the trailing edge should be bent so that when the spar is inserted it the skin lays flat on it with no gap.

You can partially correct this with a wide seamer with some duct tape on the jaws. GENTLY squeeze the trailing edge by working your way up and down the trailing edge with the seamers progressively tighter. If you have good sized blobs of RTV in the trailing edge per the plans this may not work. This same technique can be used when squeezing ailerons for a heavy wing condition (after you've checked the aileron mount height).

RV-3 rudder/tail wag resolved

We have tried all of the suggestions from the forum and from Vans. The last thing that we had tried was to tighten the trailing edge radius of the rudder. We flew last night at 170 with our feet off the rudders. Thanks to all who helped with their suggestions.