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Balancing elevators after paint?

Pmerems

Pmerems

Well Known Member
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Gents,

How many of you have balanced your elevators after paint?

Mine were balanced (with the pushrod disconnected) prior to paint. After paint I had to add a considerable amount of weight to balance them again. Fortunately I installed a nutplate in the forward tooling hole in the end rib (during elevator construction) which allowed me to attach the additional weight securely.
 
When we had our 10 painted, I asked this question at Vans tech help.

The reply was that if originally balanced to plans, it would be OK. The plans balance figures take into account future paint.

This was for the 10, YMMV
 
I did, during construction, I did not remove any led, after paint, I drilled some holes in the led to balance it out.
 
I left all the lead in prior to paint, but I still had to add lead after paint. I balanced each elevator separately.
 
It is standard and fundamental practice in the certified world to rebalance flight controls after repair, alteration or paint. E-AB airplanes should be no different because the physics involved don?t care what the airworthiness certificate says. Flutter is flutter.
 
Would someone help me understand the specific correlation of static balance of a control surface with flutter - a condition of dynamic instability. And I'm an engineer, so please speak to the correlation. I understand the impact of mass, stiffness, excitation forces, etc. on the phenomena.
 
Last edited:
Low Pass said:
Would someone help me understand the specific correlation of static balance of a control surface with flutter - a condition of dynamic instability. And I'm an engineer, so please speak to the correlation. I understand the impact of mass, stiffness, excitation forces, etc. on the phenomena.
Click to expand...

Picture the horizontal stab + elevator from the side. Imagine an external force suddenly lifts the tail of the aircraft upwards. If the center of gravity of the elevators is forward of the hinge line, the elevators will move in a direction opposite to the force applied - in this case, the trailing edge of the elevators will move up. With the C of G to the rear of the hinge line, the trailing edge of the elevators would move down.

Notice how one configuration would tend to dampen such disturbances, while the other would tend to excite it.

Greatly (over) simplified explanation that does not account for resonance etc. but that's the basic idea. Of course, stiffness etc. also plays a huge part but we trust the basic design accommodates those concerns provided it is built correctly and balanced.
 
I have been flying my -6A for several years now without paint. I am currently in the process of painting the aircraft and find that the right elevator, after paint, needs some additional weight added to the front horn to achieve balance.

How are you folks securing the added weight to ensure it does not break free and possibly jam the elevator against the horizontal stab? I could just epoxy some lead shot in the required area, but my thinking is that it could break free.

The left elevator, with the manual trim tab, did not need any added weight. I needed to remove some weight.
 
BALANCED EACH

I am with Dan on this and also balanced each after paint.

I made them nose heavy before paint in anticipation, but had to add some weight after anyway. I chose to buy some tungsten cylinders about 1/4 diameter, drilled holes in the bottom surface, scratched them to give flox a place to grab and floxed them in.

If doing another I would make allowance for and build a replaceable weight.
 
I left mine trailing edge light in the hopes of paint will balance it out but with the Base/clear coat type paint, I had to add 5.5 oz. of weight to balance it. Each were of course balanced separately.
 
The best way is to plan ahead and install a nut plate in the tooling hole. I did not plan this way so ended up mixing some buckshot with epoxy resin (West system) and pouring it thru the tooling hole. I made a couple of test run prior and it adhered very strongly.
 
Mehrdad,

I was actually trying to determine if you are getting the elevator to ballance nose heavy, tail heavy or in trail after painting. I did the foam blocking and epoxying on the sides so I know the elevators are going to naturally be tail heavy to begin with. I have installed two nut plates on the elevator horn to add lead if needed

Thanks, Mark
 
Balanced should be just that, neutral balance. The surface will stay level, or where it was put when you remove any support.
 
Balanced

Learning from someone else, I balanced each with the counter weight down approximately 3/8." After painting each half, individually, was close to perfect in trail.

I had no provisions for adding or removing weight. Probably not a bad idea. If you are past that point in construction, the above method worked great.
 
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