N83002 Fuselage Repair

bsafran · Post by **bsafran** » Tue Jan 03, 2012 17:41

The tube that supports the door hinges (tube 68 / 70) needs replaced. Whenever you cut out one tube to make room for its replacement, you have to be careful not to make more work for yourself. If you get too aggressive (or careless) it is easy to nick or damage a nearby tube while you are grinding away at another. The first picture shows the section of the fuselage we are replacing. The second picture shows what is left of the top of the tube when you take a hacksaw to it. The third pictures shows what is left after grinding away and removing the tubing and most of the weld material. Don't try to save yourself some work by grinding the weld right down to the tube. Get it close and then sand or file the last bit. There is enough work to be done to this plane with the existing damage without adding to the job by grinding too deep or gouging an adjacent member.

bsafran · Post by **bsafran** » Tue Jan 03, 2012 18:07

Removing the remainder of this tube can be vexing! You have to grind out the tube from the inside out where it blends with the square tube forming the bottom of the door frame and the other one going on a 45 degree angle down to the gear area. The hardest part is grinding out the bottom of the tube where it straddles the strut fitting.

bsafran · Post by **bsafran** » Tue Jan 03, 2012 18:17

Proper lighting really helps when you are trying to evaluate all the damage that has occurred. By this, I don't mean bright overhead lights, but lighting that is almost parallel to the tubing. Any bulging of the tubing can be seen better when it can cast a shadow down the tube. This picture hardly shows the bulging of the two tubes that need repaired because the flash is direct in line with the view. I might have missed these out of tolerance parts if the shop lighting didn't highlight them.

kyleb · Post by **kyleb** » Tue Jan 03, 2012 21:03

bsafran wrote: You have to grind out the tube from the inside out where it blends with the square tube forming the bottom of the door frame and the other one going on a 45 degree angle down to the gear area. The hardest part is grinding out the bottom of the tube where it straddles the gear fitting.

Brian,

I'm probably dense, but could you re-explain this statement for me? I don't understand the part about "grinding out the bottom of the tube where it straddles the gear fitting". Does the tube split around the gear fitting so you have to grind it on several sides?

Thanks,

Kyle

bsafran · Post by **bsafran** » Thu Jan 05, 2012 08:25

There have been numerous repairs to this fuselage in the past, each one probably done by different mechanics at different times. Each tubing splice has the chance of locking in a slightly incorrect alignment. This is not bad, certainly not illegal, but it does make it hard to settle the fuselage into the jig if everything isn't lined up right. This fuselage was racked to the side just enough to interfere with the fixture. The first picture shows a repair on the left side between the gear fittings. We want to replace this splice anyway to help the owner when it comes time to put the fabric on. The second pictures shows where we started cutting out the tube. This space let the fuselage relax back to where it should be and the frame finally aligned with the jig and settled right in.

bsafran · Post by **bsafran** » Sat Jan 07, 2012 18:33

The tube that holds the door hinges has been cut out and only where it contacted other tubing remains. If you look at the Aeronca drawing, this tube has two part numbers, # 68 and #70, but it is actually one tube. The first picture shows where it passes between the bottom of the door frame and another tube that angles down to the bottom of the fuselage. The tubing in that area has to be removed without damaging the remaining tubes. It must be ground from the inside of the tube out to the contact area of the joining tubes. The second picture shows the owner of this plane helping out with the die grinder eliminating the bad tube from the inside. (Doesn't he look nervous because he knows if he screws up we will have to fix it!) The last picture shows how the tube is giving way to the grinding. Once all the #68/70 tube is removed from this area, we only have to smooth off the exterior weld.

bsafran · Post by **bsafran** » Sat Jan 07, 2012 18:55

A tough part of replacing the door hinge tube (#68/70) is where it contacts the bottom of the fuselage. It just doesn't mate to the bottom tube, it must also straddle the forward strut attach fitting. The first picture show what was left of the tube when we cut it off down at the bottom. Now you have to carefully grind away what remains of the tube to make way for its replacement. When you do this, please, please, PLEASE take every precaution to not damage the surrounding tubes or the strut fitting. This is a very congested and complicated area of the fuselage - one of the more difficult places to fix. The next two pictures show where most of the tubing has been removed and VERY careful removal of the weld material is still to be done.

bsafran · Post by **bsafran** » Sat Jan 07, 2012 19:15

There have been many repairs to this fuselage that have unfortunately pulled it out of alignment. One of the places that this can't be tolerated is in the engine mount area. The thrust line of the engine must point straight in line with the tail. If the four points on the fuselage where the engine mount bolts on are not properly inline, the thrust vector will pull the plane off to one side or the other. We know that this line is not right on this plane, but how do you fix it? By assembling the front part of Bill Pancake's jig around the engine mount area, you can start to see where this tube goes this way while that tube goes that way. Then you can see which tube to cut, repair or replace to bring the front end back where it needs to be. These pictures show the build up assembly of the front portion of the jig to help us visualize the damage to the fuselage and the best course for correction. The airplane owner is even helping form the jig around his frame and seeing just what needs to be done to fix his airplane. His name is Don (Donnie) Gunkelman and now he is an celebrity because his face is on the internet!

bsafran · Post by **bsafran** » Thu Jan 12, 2012 22:45

The bottom of the tube that holds the door hinges (#68 and #70) dives down into a hard to work on section of the fuselage. Be very careful when you grind away the tube and the weld material. The first picture shows the existing end of the tube. The second picture shows the ground away portion. I can't tell you how nerve racking it is to take a grinder to this area. If you grind too far or nick a nearby tube or fitting, you just bought yourself an expensive headache. The removal of the material is not done yet. It's just as close as I dare go with a cutting wheel and a dremmel tool. The remainder of the weld material will have to dressed out with a sander and file.

bsafran · Post by **bsafran** » Thu Jan 12, 2012 22:55

The step on this plane was of the wrong material and out of alignment with the blueprint and Bill Pancake's jig. It has to be replaced with correct streamlined tubing and positioned properly.

james gevay · Post by **james gevay** » Fri Jan 13, 2012 10:44

What your finding is probable very typical for any 60 year old plane.
Please keep the posts and pictures coming, they're very interesting.

Paul Agaliotis · Post by **Paul Agaliotis** » Fri Jan 13, 2012 16:10

Those steps take quite a beating. Most people people get a big angle on them like their getting astride a horse. I've installed added tubes inside and rosette them in place for some added support, ACA added a little gusset. I use their step for repairs, not the cheapest but saves some time.
Nice photos you have posted Brian. It lets everybody see the time involved in repairing a fuselage.
Paul

bsafran · Post by **bsafran** » Fri Jan 13, 2012 18:00

Actually, the whole intent of this thread is not to intimidate a Champ rebuilder about the time he will spend fixing a fuselage, recovering a wing or rebuilding an engine. It is only meant to show that when you look at the big project by only focusing on one little task at a time, an award winning Aeronca might be in your future. Anyone, I mean anyone, can carefully cut out a tube. Anyone, and I mean anyone, can fabricate a tube to replace one they eliminated. You only need a skilled welder to finish the job and an inspector to make it legal. I hope that everyone who looks at each picture in this fuselage repair thread can say to himself "I can do that!".

bsafran · Post by **bsafran** » Wed Jan 18, 2012 01:56

Tubes 46L and 46R connect to the bottom engine mount points and join with tube 47 where the front control stick assembly bolts on. This plane has taken a jolt which has pushed both 46 tubes back and buckled them at the joint with tube 47 (why do they call it a tube when it is actually square?). The damage where these tubes compressed isn't easy to see when you have regular overhead light. However, when you shine a flashlight down the tubes, the bulging jumps out at you. The ends of these tubes will have to be cut out and new sections spliced in.

bsafran · Post by **bsafran** » Wed Jan 18, 2012 02:10

The compressed areas of tube 46L and 46R have to be cut out and the contact point with tube 47 ground down. The point where both tubes were cut in these pictures is not where we will make our splices. That will be farther up the tube close to where the rudder pedal and brake pedal fittings are. Right now we just want to expose the area where the three tubes join so the weld material can be removed. Only grind down to where you are close to the tube. The final material removal will have to be done with less aggressive meathods so we don't make more work for ourselves. Trust me, you do not want to cut out and replace tube 47 which dives in between the front gear fittings!