Repairs for oversize holes? Other ideas?

[avspecguy]

Hello everyone,

I have been a member for some time but this is my first post so wish me luck! I believe we are so fortunate to have this website available to us. What a wealth of information about our little birds.

During the last annual of my aircraft I decided to undertake a recover project to include the wings, ailerons, flaps, and horizontal tail surfaces. Although the fabric itself was in excellent condition, the silver coats and top coats had become extremely brittle and apparently not stuck to the fabric very well. If you pushed on it hard enough with a finger the paint would crack and you could break off chips of paint that left the bare fabric exposed. To complicate things, someone had used enamel paint, applied with a roller to the top of the wings to make it look nice while it was for sale. I did look pretty good until you looked close. The bottom of the wings looked like they were done yesterday although the cover was put on about 35 years ago. The fuselage was recovered about 25 years ago when it was converted to a tail wheel and it still looks good.

Removing the covering certainly makes it apparent that the airplane is approaching it's 65th birthday alright. We have found several items of interest and I will be posting pictures as I go so I can seek advice from all of the experts out there. I am fortunate to have an IA who is very knowledgeable about aircraft like ours, but many heads are always better than just a couple.

The first item I'm posting pictures of is the attach points of the horizontal stabilizer. As many of you already know they are joined by sections of tubing that pass through the fuselage and there are bolts that hold it all together. The clever people who put it together the last time had trouble getting the bolts through the holes so they just drilled new ones! That makes for some pretty funny looking holes. Most of the holes could be drilled out for an oversize bolt, which would work but we'd rather not do that. We were thinking also that we could weld the correct size washers to the top an bottom of the stabilizer tubes to make the new holes of the correct size. Also, we talked about trying to weld the holes shut completely then re-drilling them. In any case we will have to replace the tubes that go through the fuselage since they are in the same condition. Does anyone know if those are just from stock 4130 tubing? Here are the pictures:



I'd love to hear from you if you have input on the best way to proceed.

Thanks for reading! (and helping if you can)

 

[Stephen]

Replacing the tube is a good idea. Univair sells new tube liners for about $100. As far a fixing the leading edge of the horizontal stabilizer goes. If you can't use the existing holes, I would weld them closed, file out the tube so the liner slides in easily, then redrill. But, don't redrill untill everything is done and aligned.

 

[Steve Pierce]

The liner tubes normally need replacing at recover due to rust. The holes were hand drilled and no two are the same. I did not see any pictures so from your post I take it you have multiple holes. I would weld up one set of holes and back drill the holes in the liner tube at final assembly or dry fit and dry prior to cover but be sure and mark the tubes top, bottom, left and right since they will only fit one way. It is hard to drill where a hole has been welded up. One thing I have learned, prior to drilling I take a flat file and clean the paint, glue and fabric from the ends of the stabs where they meet the fuselage. This will allow a tight fit at assembly. If this is not done you get slop between the stabilizer and the fuselage when the paint, glue and fabric weat from the up and down action of the trim. I have fixed the gap on airplanes in the field by putting the appropriate size safety wire in the gap.

 

[Jim]

Hi,

A welding professional friend of mine once showed me a technique they often use. A block of carbon on the back side of a weld site will allow you to weld, gas or electricly, and not make gobs of crap back there. Carbon files real easily so making a rod that slips into tubing will allow you to make the repair without needing interior dressing. I have several carbon hunks that once upon a time were brushes from a rather large electric motor.

 

[Wag-builder]

If you back up the weld with copper you will get a smooth surface. Find a piece of copper pipe/ tubing and slide it inside the stab and weld the holes, I think you will be happy with the results.

Steve

 

[avspecguy]

Thanks to everyone for your replies! It sounds like welding the holes in the stabilizer shut & redrilling is the consensus. I'll get new liners as suggested and drill them to match.

thanks for the welding tips. I have heard of using copper before but not carbon.

I'll post some pictures when I get the repairs made.

Thanks again.

 

[avspecguy]

Well, I've run into the next issue that I could use some advice on. It appears that someone who recovered this aircraft in the past did some PM on the steel fittings that are installed in the aileron and flaps for the hinges. They are prone to corrosion due to the lack of paint/primer between the steel and aluminum parts. All except one appear to be in satisfactory condition. The one that needs attention is the only one that looks like it's never been messed with. I'll try to post some pictures tomorrow but the steel fitting caused the aluminum spar (outboard aileron hinge) to corrode almost completely through. When we first looked at it we though we might be able to install a doubler onto the back of the spar but now that it's drilled apart it is definitely more serious. Now we are thinking about splicing in a new section of spar and/or ordering a new spar from Univair. I don't see it listed on their website as a separate item from the aileron though. We might be able to fabricate one but we would have to find a longer brake than what we have available.

Has anyone out there had to make a similar repair? Ideas and advice are always welcome! Thanks.

 

[JPerkins]

Just replaced the spars in both flaps and ailerons on mine, posted under the Stewart wingtip wing overhaul thread. Peruse through that and see how I did it as well as a link that Steve Pierce posted on a javron build of a guy building the ailerons. I ordered spar blanks from Dakota cub. They shipped me spar blanks for super cub aileron and flaps even though I remember the guy reap eating PA-22 back to me.
If you call Univair you can order them that way.

Sent from my SM-G930V using ShortWingPipers.Org mobile app

 

[avspecguy]

Jason,
Thanks so much for the information. I'll look at those threads right away.

 

[avspecguy]

Hello everyone,

It's been a while since I've posted here and a lot has happened since then. Life has kept me very busy for the past year, but I have made a lot of progress on my recover project. I'll try to post more about the project in the coming days and weeks.

Regarding the welding repairs for the horizontal stabilizers (pictured in an earlier post), I had intended to make those welding repairs myself but finally relented and took them to a pro here on my home airport. He got them done quickly and did a great job. Interestingly, he used and aluminum plug inside the tubes while he did the welding. I was a bit surprised so I asked about that and he said he does it all the time and that the aluminum heat sinks so fast that it works great. I don't have any pictures to post, but I re-drilled the holes with new liners, and I'm happy to report that those surfaces have been covered and painted. The are all wrapped up awaiting re-installation soon.

 

[avspecguy]

As I said in one of my earlier posts, one of the aileron spars was showing signs of trouble at one of the hinge points where the steel fitting is riveted. The picture below shows the view of the trouble spot as seen from the trailing edge. The picture was taken AFTER I removed the steel fitting from the other side, so the crack was not there. You could see the dull grey area that there might be some corrosion there.



Here is a pictured of the other side of the same location with the fitting removed...


Yikes! ... and here's some photos of the steel hinge fitting, one taken with different lighting. What's that? Powdered aluminum?


Okay, if one is THAT bad, the rest of them are probably not very good, so I drilled some more of them apart and here's what I found...
Well, by now you are getting the idea.

So, I started drilling all of the ailerons and flaps apart one at a time, and wound up with a pile of parts to reassemble each time.
I was able to sand blast most of the steel fittings and reuse them, but some of them had to be replaced due to previous attempts at repairs with oversize holes that I didn't want. For the most part, they tried to get the fittings out and succeeded in some cases. You could still see where they scraped a little bit with a screwdriver or something then just bashed some new (oversize) rivets in place... All cleverly disguised with a brush coat of zinc chromate over the outside. Even when they were successful at removing the fitting there was no primer or chromate or anything between the steel and aluminum parts except the remaining corrosion.

So with new spars from Univair, an assortment of new bulkheads for the leading edge skins, a few new ribs, a few new steel fittings and a bunch of other little pieces of sheet metal and a bunch of rivets (AN456) I started putting things back together. I was trying to figure out how to match drill the new spars so I asked my IA for his advice. He suggested using match drilling strips of plexiglass cut to the width of the spar which worked beautifully!
I hope you can see this. I tried to put in a couple more pictures but I hit the limit for this post.

I'll try to put another post up tomorrow with some more info on the flap and aileron assembly process.

 

[avspecguy]

Hey everyone, it's been a while again, but here are some more photos/info on my project.

As I was saying in my last post, I used plexiglass to match drill the new spars and it worked beautifully.

After application of some epoxy primer I was ready to begin reassembly.

Next, I needed to install the bulkheads in the new leading edge blanks that I ordered from Univair (originals were all dented up). Here's the problem with those blanks... They were fabricated from .032-T3 aluminum and the originals were .025-O. That might have been okay but they weren't shaped very well at all so the didn't really fit the bulkheads (nose ribs) satisfactorily. I used the leading edge blanks that I ordered on the ailerons, but it was after I spent a whole day trying to re-radius them to fit. Needless to say that was a major pain! Fortunately they were slightly oversize so I was able to install the bulkheads, then trim the trailing edges after they had been clecoed the spar and marked for trimming.

I needed more leading edge blanks for the flaps too after I had used the Univair blanks, however, I decided to try making my own out of .020-O like the originals. For some people that would be easy but for a beginner like me it was a head scratcher. What I came up with was to cut a channel into a 2X4 and then use a dowel that I taped to the edge of a piece of plywood to press the aluminum into the channel. I used a piece of 5/8" dowel pressed into a 3/4 inch channel and the radius was perfect. It was much better and much easier to work with than the Univair parts.

You can see from the pictures how it worked. I used the pictured clamps to push the aluminum into the channel. Pretty sweet!

Now that all the pieces are ready for final assembly, I needed a fixture of some kind to hold it all with the proper twist (per Piper drawings from SWPC). More to come on that. I'll post again soon.

 

[Steve Pierce]

Hmm, I looked at the drawing and then went and measured the leading edges I have and both the drawing and my stock ar .016". How did you get the roll in the top of the skin?
Here are some pictures of my jigs. https://www.shortwingpipers.org/forum/showthread.php?6955-aileron-flap-jig&styleid=5

 

[avspecguy]

Hi Steve,
Every time I get on this site I wind up surging around and looking at all kinks of stuff and run out of time to post a reply. So much useful information!!! I've been meaning to reply to your post for some time now so here goes.

In that last post I wrote that the leading edge skins were .025 in one paragraph and .020 in another. I meant to say .020 in both cases. Anyway when I get back to my hangar in a week or so I'll double check the thickness of the originals which I still have. I used a thickness gauge to check them so I could have been mistaken. I'll check with a micrometer or caliper next time. Anyway, I used .020 for the replacements...

I'm trying to remember how I put the roll in the top of those skins for sure, but i think I just formed them (gently) over the edge of my workbench by hand. It was pretty easy since they were soft aluminum as I recall.

I saw some pictures of your jigs and also looked at what Jason Perkins did. I started out trying to do it Jason's way and gave up of it later, I think because it wasn't going to work after I installed the hinge fittings. I was seriously considering welding up my own fixture like yours but started brainstorming for something I could do quicker. After noodling around on it for a few days I came up with something I though would work. By the way, I had not seen the post about the Javron wing build. Had I have seen that I probably would have done it that way, with the plywood and shims,

I did the initial assembly of the ailerons and flaps just by riveting all the steel fittings and ribs in place. Then I clamped everything down to a couple of 2X4s to get to assembled -minus the leading edges.



For the final assembly here's what I came up with. I have this workbench that a Sherman Tank couldn't hurt and it's about the same length as one of our ailerons. I bought a few pieces of steel angle. I cut some pieces a couple of feel long or so and clamped them to the ends of the workbench in the vertical and made sure they were perfectly upright (in the same plane) with the aid of some fishing line and a level. Then I bolted a couple of pieces horizontally in the correct position so that I could clamp the aileron or flap to it with some pieces of rubber tubing slit lengthwise for cushions. So that I could get the correct twist, I simply put washers in one end or the other I turned out the the same spacer work for both the aileron and flap on the same side. I had to get creative on the clamps. I used tape, clamps zip ties, you name it, but it worked.



I see now in looking at these pictures again, I just used some small pieces of angle at the bottom (near the spar area), but I had to use a bar across the bottom for the flaps.

Gotta run for now.
Pat

 

[Mushroom]

Hi Folks,
I find myself in the same situation as avspecguy in the beginning of this thread. I have oversize and snowman looking holes in my horizontal stabs that I need to address. Steve stating they are drilled at assembly and are a match set explains why sometime in the past they ended up it his way. A couple questions though for which I’m looking for some advice. I do plan on welding my the holes up horizontals. My question is do the bolts have to be in the vertical plane or can drill the new holes slightly off vertical to avoid drilling through the weld? Also I need to replace the short tube that passes through the fuselage, but the longer tube (and some how I’ve acquired 2 of them) seems to be in good shape. Would it be ok to rotate the tube 90 degrees and redrill new holes through it at assembly? If there’s a strength or fatigue issue I can just spend the 100 dollars and buy a new one.

Thank you,

Pat

 

[dgapilot]

Welding up the holes in the stabilizer will be OK, biggest issue will be cleaning out the ID for the cross tube to slide in. I don’t think drilling a few degrees off vertical will be a problem. I wouldn’t drill a second set of holes in the cross tube. I think it would remove too much material as it is only .049 tubing. Do not weld those holes as the tube is chrome plated, and you would be introducing chrome into the weld puddle, making that portion of the tube very brittle.

Go spend some money with Univair on some new tubes! $66.66 for the rear one, and $104.25 for the front one.


Sent from my iPad using Tapatalk

 

[Steve Pierce]

You could drill the new holes inboard of the figure eight you have now. If you do not drill vertical you will be pushing the fabric down ever so slightly either on the top or the bottom. It is not recommended to add another set of holes 90 degrees in the liner tubes. Charlie Center, Cross Wind STOL tells a story about one that broke that was drilled that way.

 

[Mushroom]

Thanks for the input gentlemen. I will order new tubes and after the horizontals are welded, drill them vertical slightly inboard. I see the print gives a range of 1/2 to 1 inch for that hole location from the end of the tube.

 

[bluejeepdad]

I just found this, and it didn't seem like a good thing:



A couple of minutes spent searching and I found the answer here.

I wouldn’t drill a second set of holes in the cross tube. I think it would remove too much material as it is only .049 tubing.

It is not recommended to add another set of holes 90 degrees in the liner tubes. Charlie Center, Cross Wind STOL tells a story about one that broke that was drilled that way.

Thanks so much David, Steve, and everyone who contributes to this community!

Tim

 

[Jeff Pralle]

The liner tubes normally need replacing at recover due to rust. The holes were hand drilled and no two are the same. I did not see any pictures so from your post I take it you have multiple holes. I would weld up one set of holes and back drill the holes in the liner tube at final assembly or dry fit and dry prior to cover but be sure and mark the tubes top, bottom, left and right since they will only fit one way. It is hard to drill where a hole has been welded up. One thing I have learned, prior to drilling I take a flat file and clean the paint, glue and fabric from the ends of the stabs where they meet the fuselage. This will allow a tight fit at assembly. If this is not done you get slop between the stabilizer and the fuselage when the paint, glue and fabric weat from the up and down action of the trim. I have fixed the gap on airplanes in the field by putting the appropriate size safety wire in the gap.

FYI I have seen the safety wire “repair” many times and seen it wear a groove in the liner. Not something I want happening on a critical flight control attachment.

I replace the liners if the holes are wallowed out, miss drilled, rusty, have more than one set of holes in them. At roughly $100 each the liners are inexpensive considering what happens if one were to fail.

Steve you are absolutely correct removing the paint and especially heavy powder coat is a must. If I am installing the stabs alone I use a ratchet strap hooked around the end of each stab and gently pull both stabs together after I drill and bolt the first side. Assuring a close fit. These liners are not raw tubing. They are plated and polished so a weld repair increases corrosion potential making replacement difficult in the future. I also coat the liner with good synthetic grease or, especially the aft liner, anti-seize.

 

[Steve Pierce]

I have not seen the groove. Usually can't get the safety wire that tight but could use brass safety wire as well.

 

[bluejeepdad]

FYI I have seen the safety wire “repair” many times and seen it wear a groove in the liner. Not something I want happening on a critical flight control attachment. ... Steve you are absolutely correct removing the paint and especially heavy powder coat is a must. If I am installing the stabs alone I use a ratchet strap hooked around the end of each stab and gently pull both stabs together after I drill and bolt the first side. Assuring a close fit. ...

I'm not sure I'm following this, are we talking about sliding the stabilizers on fully so that the inner ends are in contact with the outer ends of the fuselage tube (rear) and the yoke tube (front)?

 

[Jeff Pralle]

Yes. The stabilizer “link” The part that is mounted in the fuselage has the liner tube going through the center. Then the stabilizers are installed on the liner tube and bolted to the liner tube. It is necessary to make sure the stabilizers are pulled in tight to the stabilizer link upon install before everything is drilled and bolted. Leaving any play between the stabilizers and the link is a large contributing factor to airplanes that shake when they are put into a slip or at very high pitch angles with high power settings especially with long props. It is easy enough to verify by mounting a camera looking at the tail in flight. A very simple install procedure that is often overlooked.

 

[bluejeepdad]

Thank you, Jeff. That was exactly the information I was missing.

 

[Adam Hile]

What did you come up with for skin thickness on the aileron leading edges, do you remember? Did you use 3003H14 or 2024-0? Not finding much available of either at this point. May just order new LEs from Dakota. Also, what rivets did you end up using for reassembly, AN455A or MS20470A rivets? I don't see much of a difference either way. May go with MS20470A instead of AN455A because we have those in stock at work.
Thanks
Adam