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Old 06-20-2012, 04:59 PM
Captain Cowboy Captain Cowboy is offline
Join Date: Sep 2009
Location: State College, Penna
Posts: 46
Default Aircraft Rigging Problems

Now flying our 12 and have a 5 degree/sec roll to the left if release stick pressure with rudder trim tab installed and used for centering the ball and with the ball centered in level flight with 5000 rpm from the rotax at about 95k. Looked at Vans info for acceptance testing and don't want to crush the trailing edge until I have exhausted all possible other options. No wheel pants installed yet. Slight difference in alignment at the trailing edge of flaperons with stick centered, about 1/8 inch difference. Aircraft close to 1050 lbs with 10 gals of fuel and pilot in left seat. When we weighed the aircraft, right scale about 13 lbs heavier than left side. No drastic warp of flaperons, no unusual misalignment of vert stab or rudder, LOOKING for ANY SUGGESTIONS FOR HELP to trim this great machine up. Thanks in advance..!!!!!!!

Doug Robison
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Old 06-20-2012, 05:44 PM
HDDAHL HDDAHL is offline
Join Date: Feb 2007
Location: hilton head sc
Posts: 97
Default Rigging

Don't think rudder trim tab is involved, certainly not to the degree you describe. It will help coordinnated filght, keep the ball centered, etc. Your options are two, imho.

1. Squeeze the light wing

2. Add a trim tab to one flaperon.

3. Add an adjustable mechanical spring loaded flaperon trim mechanism.

I would go with the squeeze route first. Don't see the downside. It worked for me years ago with a six I built. I'm not sure how trim tabs work with flaperons, though the mechanics seem the same as with ailerons.v

Doug Dahl
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Old 06-20-2012, 06:15 PM
rvbuilder2002's Avatar
rvbuilder2002 rvbuilder2002 is offline
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,705

If the roll trim is off that much, it is highly likely that your flaperons are not the proper shape. This can actually effect flying /handling quality's.

To do a quick check, lay a straight edge on the flaperon cord wise (so that it parallels normal airflow) Check that the aft skin is flat between the lap joint of the leading edge skin and the radius at the trailing edge.
If you find they are not (rather likely), squeezing the T.E. until they are would likely totally solve your trim problem, or at least get it very close to were just a small amount of tweeking will make it near perfect. It will also make your RV-12's roll response act the way it is intended to.
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Old 06-21-2012, 06:01 AM
BigJohn BigJohn is offline
Join Date: Nov 2008
Location: Gloversville, NY
Posts: 1,588

Just to add to what Scott said..............

Once you get the flaperon surfaces flat, and need to "tweak" the flaperons for roll trim, do so with VERY small adjustments. It is easy to overdo it. Ask me how I know It will most likely take several test hops with very small squeezes each time.

Another suggestion. Pad your seaming pliers with foam (sticky back weather stripping works good) and use them for the gentle squeezing. The 3" surface will help you not to kink any spots in the metal.

John Peck, CFII, A&P, EAA Tech Counselor, Flight Advisor.
Master Pilot Award, UFO Member.
RV-12 N37JP 120176, built 2011, sold 2020.
One Week Wonder Build Team, OSH 2018.
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