I ask this question because my Continental has/had a slight hunt to it and nothing I did seemed to affect the problem.  While looking carefully at the plane I realized I had very long struts and very wide wheels.  It occurred to me that the landing gear could generate a pitch down force from drag and leverage.  So I cut the gear struts by 1 1/8" and replaced the 1" wide wheels with 1/4" wheels and also removed .6 ounces from ahead of the CG.  In still air the plane now tracts very well in gusty air there is still some bobble but I wonder how much of that is in the 1960's airfoil design.  When the motor quits the plane remains level and settles to the ground with no noticeable handle input, so I think the CG is correct.  All the surfaces are at 0 degrees and so is the motor.  Has anybody else ever experienced this kind of symptom?
Andy

Well Andy it seems you have answered your own question!  You have certainly removed weight and "windage", and you have achieved a perceptable change.  As I recall the original Continentals were "low riders" with long & SKINNY wheelpants.  Did you keep the wheel pants or fairings on the new gear?

I have heard of what Doc described happening on Pylon Racers.  While our speed & forces are much lower, its still plausible that there is cause/effect for the change you described.

So is that the "silver bullet" you have been looking for?

Andy
It affects 100% scale planes pretty dramatically. It will also affect our models. If you go to retracts, be ready for another est of changes.

bob branch

The original Continental design called for wheel pants and strut covers, but because I need longer struts for prop clearance and in an attempt to save some weight I left the wheel pants and strut covers off.  I just never considered wheels could be the cause of trim problems.
Andy

Do you think the vertical cg might have also entered into the formula a bit?  You did change it when you made your switch.

On real planes that go over 100 MPH, retracts as needed to achieve acceptable performance.  On slower airplanes, the gears are usually fixed to save cost and dedicate more weight capacity to payload.  In some Cessna products, fixed gears are actually FAVORED for mountain flying.

Stunt planes want to fly at 50-55 MPH.  Landing gear drag and other parasite drag is beneficial in that it allows more power to be added without increasing speed.  This is one reason Al Rabe's bulky models were able to defeat most of the streamliners.

The drag of undercarriage is an even trade vs the offest rudder.  Also, a common design factor is the entire fuselage offset upward vis-a-vis the center of the wing.  Prago!  It's in there.