Aileron balancing

[scrouch]

I'm at the aileron control installation stage on my LEZ and have a balancing issue.

On side balances fine- when filled and painted it will be in the proper range per plans. The other side, however, hangs tail down well out of range. I tried adding the max .3 lbs at the rod side, but due to the short moment arm to the hinge balance point, had little effect.

I then ground off most of the glass (about 75%- both sides) almost to the foam. Even in this condition the aileron is only just w/in the range. It will never pass w/ a layer of glass, filler and paint. What to do?

Has any body gone thru this & how did you solve the problem?

[Wayne Hicks]

Personally, I would have done this:

 

1. Cut off the balancing rods

2. Rebuild the balancing arm by adding blue foam to make up the correct distance for the balancing arm.

3. Reinstall the balancing rods and reglass the rods to the ailerons.

4. Remove a sliver of bottom skin along the wing's spar cap area, enough for the aileron to swing freely by the required distance.

 

You're in trouble if you've sanded into the second layer of glass by 75%. We are only alowed to sand partially into the top layer only. I would reglass the ailerons with the fixes mentioned above. I wouldn't use them they way they are now.

 

But that's the great thing with fiberglass. All can be repaired.

[Wayne Hicks]

Re-reading a bit more carefully, if you've sanded 75% -- does that mean 75% of the combined thickness of both UNI plies? As in 100% of the top uni skin is gone and 50% of the bottom ply is gone?

 

The math doesn't matter. If you've sanded into the underlying bottom ply at all, then you've sanded too far. Sorry.

 

If more than 50% of the bottom skin is still there, then you might get away with glassing the top ply back on, orienting that new layup in the opposite direction on the 30-degree bias. If less than 50% of the bottom skin remains, (and if it were me), I'd consider CAREFULLY sanding the cores all the way down to the micro and reglassing the two plies of UNI.

 

...Wayne

[scrouch]

Wayne, your comments are appreciated. The reason I sanded most of the glass and filler off is that the control surface was not going to balance the way it was- as built by others. I figured that the only way was to remove the offending (too heavy) build-up and re-glass carefully. But, you have pointed out something I have not checked. The balancing rod may not be the appropriate distance from the hinge point. Just a little would make a big difference. I'll check that out.

I never intended to sand it down and then used it in that condition.

What I'll do now, thanks to your input, is check the rod location, sand down to the foam, and then reglass as per plans.

Thanks for your help. Your comments have been extremely useful now & in the past in preparing my project correctly.

[Jerry Schneider]

The balancing rod may not be the appropriate distance from the hinge point. Just a little would make a big difference. I'll check that out.

I had the same problem. Another place to measure the proper placement of the balance rod is to measure from the leading edge of the rod to the trailing edge of the aileron. Mine was off significantly and re-locating it solved all of my balancing problems.

[scrouch]

Jerry, I did a quick ck and found the out of balance aileron's rod is about 1/4 to 3/8 inch closer to the hinge centerline than the one that is nearly balanced correctly. You guys may have id'd my problem. I'm going to ck all the dimensions per plans & then redo to correct. Thanks for making a head scratcher more understandable.

[ibmagman]

I just rebuilt my tail heavy ailerons. here is the tale of my adventure:

I removed the ailerons and weighed them at 5.5 lbs. I have not yet been able to find the max acceptable weight for ailerons from any source including an inquiry to "da man". The first thing I did was to add lead tire weights stacked on top of the bass balance rod. I had them stacked 4 high the entire length of the aileron! At this point, the ailerons balanced to "top surface level". I needed 5 lbs of lead. What now? So I sanded the crap out of the ailerons until I was 1/2 way through the first layer of glass as described in the CP's as the standard RAF method to balance control surfaces. Well, I was able to shave the weight down to only needing 2 lbs of lead required and bringing my max weight up to 7.5 lbs prior to final finish. This was not going to cut it. It was time for aileron surgery. Get a totally flat surface. I used a new 36" door from Home Depot on top another table. Lay your aileron down with flat bottom down and stake some small finish nails down along the trailing and leading edge and a few on one end. This marks the profile of the aileron. Put both ailerons side by side and do both together. Remove the aileron and cut off the old 3/8 dia mass balance rod. Put the aileron back in the profile tool after cutting off the 3/8 rod. Add a new carbon steel 7/16 dia mass balance rod and bump the rod to the FWD nail stops and flox in place. After cure, sand the new floxed in place leading edge nice and round and add 1 ply bid. You have not changed the length of the aileron and no additional work will be required to the wing trailing edge. Additionally, you have not changed the effective length of the effective snatch angle (relative to the hinge line) of the lower aileron leading edge. Be sure to use peel ply for final finish blending purposes and be positive that the bottom of the aileron is dead flat and NOT bowed! Next, use the Cory bird finish technique and add 3 coats of pure structural epoxy. Sand this down untill the aileron is flat. Sand progressively starting with 36 grit knocking down the high epoxy spots and finishing with 320 grit. Do not cut through all the way to the old finish or you will get some nagging pin holes to finish. Prime lightly and paint. Mine are not that pretty up close but they balance perfectly and the total weight is 5.2lbs per aileron with paint. A side note: There are several Canards flying with 7/16 dia mass balance weights. I know of one Long-EZ that is painted silver and has an 0-360.

 

Fly safe

 

Steve Morse

magman

[Stinky]

Steve;

 

Thanks for the write up.

 

Do you have pictures or a URL to where pictures might be posted? I have a similar situation and have decided to switch to the 7/16 inch rod. Before cutting I'd like to know if I should cut just enough to knock the 3/8" rod out of place. Or should I cut back into the foam and then micro foam back into place after I position the 7/16" rod?

 

Carl

[Steve Innova]

I suspect some of the problem is variability in foam density.