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Help! Flab bracket screwup

R

RScott

Well Known Member
Help! Flap bracket screwup

I got carried away match drilling the flap brackets (925A) to the ribs and drilled the center bracket to the rib using the prepunched holes in the rib for alignment. I did this before riveting the outer brackets and using a string to insure alignment, as instructed. Oops! Finally following the instructions, I checked the alignment after riveting the outer brackets and found the center bracket (clecoed in place) is about .040-.050" low (the string is high in the hole with the wing upsidedown on the table), but OK fore & aft.

Options: Discussed the first 3 options with Van's & thought of the 4th after we hung up.

1. Go with it as is. Would force a slight curve in the flap and put a little strain on the flap motor and brackets.
2. Make a new bracket. Van's does not have any 925A's without holes prepunched.
3. Drill out and replace the rib. We all know the problems with drilling out rivets and there are about 35 or so rivets to drill.
4. Drill out holes in the bracket to take a 5/32" rivet, use the slop to properly align the bracket, clamp it in place, then redrill the rib to 5/32" thru the bracket to insure alignment. May not get enough slop to make it align exactly. Need appropriate 5/32" rivets and an angled 5/32" rivet set which I may be able to borrow.

I doubt that all of my screwups are original. Any of you have a similar problem? How did you fix it? Does it really work OK with this amount of misalignment? So, what would you guys do?

Thanks.

Richard Scott
 
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option 5

5. Leave as is and decide after installing flaps if further action is needed. (You will need to build flaps before closing the wing)

My flap brackets were not in perfect alignment either -I left it be. Flaps are now installed and there is no drag and will be no strain on the flap motor.
 
Richard,

My responses to the options you listed:

1. I don't think I could ever get comfortable with that much misalignment.
2. This is the way I'd go. Not difficult to fab a bracket.
3. A lot of work, and a lot of potential for bad holes ( depending on your drill-
out skills).
4. I don't think you'd get nearly enough movement, consistent with good hole
clean-up to an oversize. Unless you went really big (3/16" or 1/4"; not
good).
 
tsneidin said:
5. Leave as is and decide after installing flaps if further action is needed. (You will need to build flaps before closing the wing)

My flap brackets were not in perfect alignment either -I left it be. Flaps are now installed and there is no drag and will be no strain on the flap motor.
Click to expand...
I agree. We're talking four or five one-hundreths here! Just check flap travel before you rivet the bottom wing skin on. Good luck.
 
Thanks for the input. I think I'll follow Tsneidin's & Steve Moore's suggestion to see how it works out before I do anything. I'll build the flap, cleco the skin and gap seal in place & try it out. won't be a rigid as if it were riveted in place, but should be close.

I did take a rubber mallet to the bracket, which was clecoed in every hole and gave it a few good taps. Took the misalignment down to about .030, although that may have just been moving it on the clecoes.

Van's says the pivot hole (the one that takes the bushing) will have to be reamed to final size, which adds a complication to the choice of making a new bracket since I don't have an appropriate reamer. I sure don't want to replace the rib. So if the misalignment does cause binding, I think I'll go with the oversize rivets first. ACS sells a 5/32" offset rivet set for about $9 and I already have a straight one. If that doesn't work out, then I'll be into replacing the rib and can use a new bracket & do it right.
 
Don't replace the rib. You may cause more trouble taking out all the rivets. If you have to move the bracket move it. Before you re-rivet it make a doubler. This doubler should nest inside of the flange of the rib and the rib web. Rivet the doubler to the web and the rivets for the bracket will hold the flange area.
See AC-43 for instructions on doublers.

Cheers
Norman
 
I would correct it...

Making a new bracket (very easy if you have some 1/8 " thick 2024 T3 material, have access to a band saw and 1 " wide belt sander) would be the best choice. Using the doubler approach would be acceptable also, but I would recommend you avoid driving 5/32 rivets in this confined area because it depending on your skills it could be asking for more problems.

Here is my reason for correcting it...

You may get all the bolts in, and it may not have enough drag to load the motor but is still bad for longevity.

If you have to flex the flap to install the bolts, the flap is being flexed/tweaked every time the flaps travel up and down. This has the potential for causing skin cracks at rivet holes, etc., though it may take a few years to occur. If you end up building a flap with a slight bow in it in the opposite direction, you will then have a problem that is amplified even more.

I firmly believe this is just one of many reasons why some builders have cracking problems with control surface skins and others don't. I can not say for certain that it will cause problems in your case but since it is easy to correct now. Why take the chance?
 
Don't know how to do this myself, but ....

I have heard of others welding metal into the hole and then redrilling to change the location. Don't know if this would be more work then building a new bracket.

Kent
 
kentb said:
I have heard of others welding metal into the hole and then redrilling to change the location. Don't know if this would be more work then building a new bracket.

Kent
Click to expand...

I presume the bracket would be 2024 aluminium. My understanding is that 2024 cannot be successfully welded without a high probability of producing cracks in the surrounding material??
Fin 9A
 
The brackets are powder coated steal. About 1/8 inch thick. Sort of a trangle with a 3/4 inch flange bent into the bottom.

Kent
 
Kent,

You are probablly thinking of a different part. The part in question is the W925A and it is listed as 0.125 2024T3 Al.

FWIW, I bought the material from Van's today & am going to just make a new bracket, per Scott McDaniel's suggestion.

What had me hesitating to make a new one was 1, I don't have a 3/8" reamer and I have never reamed anything except for using reamers to match drill and didn't want to screw up the pivot hole & have to start over again, and 2. I didn't want to screw up the holes in the rib by match drilling thru them to drill out the new bracket. Got everything figured out now and a reamer, if I have to buy one rather than borrow one is about $20. So, it's back to work!

Thanks to all you guys who commented / suggested solutions.
 
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