flap tracking problem on SS

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flap tracking problem on SS

Postby Jim Bair » Sun Jun 22, 2014 6:23 am

I'm installing the flaps on my SS and they aren't tracking exactly right. They seem to roll smoothly but on each flap, one roller hits the forward end of the slot about 3/8" before the other. It's as if something is off in the build, but so far i cannot figure out what it is. The wings were built at the factory and haven't been damaged. I measured the track connect points and they seem to be installed at the same points. The flaps come all predrilled so they are hard to screw up with some sort of twist. About all the builder has to control is keeping them square and we have checked that and they are within about 1/64" when checking corner to corner. We are running out of ideas of what might be off. I have called the factory and talked to Jac and he says they should roll smoothly and hit the forward stop of the track simultaneously. Has anyone else run into this? Any ideas? --Jim Bair
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Re: flap tracking problem on SS

Postby SuperFly » Sun Jun 22, 2014 8:52 am

Jim,

I had the same problem with mine, and talked to several people, including the factory. I can give you a hand, call me, as it is too much to type.
Best,
Ben Schneider
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http://www.stolairplane.com
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Re: flap tracking problem on SS

Postby jak » Sun Jun 22, 2014 9:44 am

Hey guys let me know what the fix is so when I get asked again I know what to say. Jak
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Re: flap tracking problem on SS

Postby Jim Bair » Thu Jun 26, 2014 9:54 am

After looking it over very carefully and with the knowledge that Jak was sending me a new flap bracket with no holes drilled in it, I laid the bracket on a sheet of paper and traced it, then rotated it around the lower hole so the trailing end raised 3/8", which was the amount needed to bring the flap up even with the other end. This made the upper hole off by about 1/2 hole, and the middle hole off by about 1/4 hole. I traced a new outline and transferred the difference in shape to the bracket and filed off a crescent shape where it meets the tube that was about 1/8" thick at the top and tapered to nothing off at the bottom. This is a vast improvement over the original flap track. The error appears to be the outboard flap attach bracket that is riveted and epoxied to the wing spar was put in position maybe 1/16" too low which transmits to a much greater distance at the end of the flap track. I'm glad I had the wing built at the factory because the odds of the error being even larger had I built it are pretty high. It's a difficult thing to measure and quite a critical little part and not exactly convenient to adjust as the part is welded, riveted, and epoxied. It took awhile, but at least the error has been figured out so I can move forward.

Now I have discovered as another guy did, that I have an aileron bracket that a bolt won't go through. I appreciate tight tolerances, but if there is any weld error AT ALL, the bolt won't go through. The factory didn't check and neither did I before skinning, so now I have to try to fix it with the skin on. Fortunately I can get a small file crossways in there so I think I'll be able to file the hole to get a bolt through.

I would suggest to everyone to test every piece possible before you just put it on assuming it will work. I should have known the factory doesn't test the pieces for this sort of thing starting with the rudder pedals which was basically the first piece I installed and there was a weld burn through and they wouldn't slide into the proper position as a result. There are other pieces like that and I have caught most of them prior to making life miserable, but the flap and aileron brackets were pre-installed on the wing so I didn't think to run a bolt through all of them. --Jim Bair
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Re: flap tracking problem on SS

Postby mac » Thu Jun 26, 2014 10:53 am

Jim...and others:

I wasn't sure exactly what your problem was previously, so I refrained from commenting. Now that you have new flap track brackets, without holes.............clearly you have the same problem two of us have had on the West Coast. This was brought to the factory's attention some time ago and it appears the problem was slippage of the fixture that holds the spar in position when the flap track "attached bracket" is riveted/epoxied in-place. For two of us, this was only a problem with the right wing. The flaps would simply not retract to the proper "up" position.....................i.e. large gap between the trailing edge of the wing and the flap itself, when compared to the left wing/flap arrangement.

Bottom line...........the spar rotated slightly in the fixture before the attach bracket was secured.

The fix was essentially what you are doing.............that being to adjust the three holes in the flap bracket to compensate for the rotation of the spar.

That said, I did it a little differently. Using the old flap track bracket as a template and knowing how much I wanted the trailing edge of the new flap track bracket to raise up, I positioned both the un-drilled track bracket and the old drilled track bracket adjacent each other, place then against the riveted attach bracket on the spar (just to the side of the actual attach point)...............and eventually clamped the two track brackets together and moved the clamped assembly to my drill press. The old holes became the drilling template for the un-drilled track bracket. Little confusing, I admit, but if you stare at it long enough, it will make sense!!

Last bottom line...........I would highly recommend that everything gets rigged and tested BEFORE anything gets covered. Apparently, this spar movement was an "early-on" problem with the factory and has been corrected, but regardless, to assume every bellcrank, bracket assembly, bolt head clearance, etc. etc., is good from the get-go, is a big stretch, IMHO. Best to fix this stuff before covering, when clearance and working room is much improved, if possible.
Mark M.
N49SS under construction
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Re: flap tracking problem on SS

Postby Jim Bair » Thu Jun 26, 2014 4:23 pm

Thanks, Mark. Good advice. I am doing essentially the exact same thing you did, I think, in that I reworked the old flap track with files to get it to the corect shape and holes in the right spot, and will use it as a drill guide when the new track arrives. You describe the picture very well. To get these perfect on a round spar would be very difficult as the lever arm of the flap track is quite long and a very small error at the bracket/spar joint leads to larger errors out where the flap and wing joint is visible. It doesn't need to be perfect, it just needs to be acceptable, and mine now is, at least to me. BTW, by coincidence mine was the right wing as well, outer hinge point. Left wing and all ailerons seem OK. I also had to bend a couple the arms on the flap pulleys slightly that hook to the pushrods to clear the tube in the bottom of the wing the skin attaches to. --Jim
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