N83002 Fuselage Repair

bsafran · Post by **bsafran** » Wed Jan 18, 2012 02:31

Tubes 11L and 12L run between the gear fittings. The book gives them different numbers, but it is all one tube. This plane has had tube 12L repaired with an larger tube inserted in the damaged area. This not only screwed up a pretty smooth line where the fabric will wrap around, but it also pulled the rear fuselage to the side a little bit. We are going to "repair the repair" by cutting it out and replacing it with a different type of fix. The rear splice is kind of close to a cluster of tubes which might not give us enough room to splice in an inner tube which would clean up the fabric line. If we have to cut out and replace tube 12L back to where it joins with the longeron, there is a lot more work involved (and extra work equates to extra cost to the owner). You can see in the last picture where I cut the repair just forward of where the original tube was cut. You can see the one tube inside the other. I am going to try and grind down and remove the exterior tube without damaging the inner original tube. That way we can make our repair splice far enough in front of the cluster to conform to AC 43.13-1B.

bsafran · Post by **bsafran** » Sun Jan 29, 2012 10:24

Tube # 6 and # 7 (once again, all one piece of tubing) make up the top spine of the rear fuselage. Obviously, when the tail is broken off the plane, a splice has to be made somewhere. It's difficult to replace the whole tube because it goes through a real complicated area where it connects to the fixture that hold the front of the horizontal stabilizer. There are seven different tubes that weld to # 7 in the span of just of few inches. Grinding tube # 7 from the inside out within that cluster is a pain, so using a splice just forward of the cluster is always preferable. This plane's # 7 tube is not only broken, it is also bent very close to the cluster. We probably could get by with a splice, but since we have to replace 4 of the 7 tubes that are in the way, it gives us cleaner access to make a complete replacement. This picture shows the bottom of tube # 7 with three of the seven touching tubes cut away. We haven't decided whether to splice or replace yet. That decision will come later.

bsafran · Post by **bsafran** » Sun Jan 29, 2012 10:36

The easiest part of repairing tube # 7 is removing the metal piece that makes up the curve where the vertical fin meets the top of the fuselage. Just like the door sill material, this curve is held in place by small welds. The last picture shows the owner removing the curve using a dremmel cutter. When cutting off these welds, make sure you err on the side of caution. If you grind away the weld material where it contacts the curve, any mistakes will only damage the curve. That's easy to fix. However, if you nick the tube it's attached to, now you have another repair to do.

bsafran · Post by **bsafran** » Wed Feb 01, 2012 21:43

We are getting into an area that most Champ rebuilders might be faced with - replacing the longerons. This plane has severed longerons - the tail was torn off! A simple slice to rejoin the front and rear fuselage halves is not possible in this case, so some sort of longeron replacement is needed. The best repair would be to completely replace the entire longeron (left and right) from where they join into the landing gear area all the way to the tailpost. You can see how a new longeron set can be made with Mr. Pancake's jig in the restoration posting of "Fuselage Jig/Brian Safran".

However, there is some good longeron tubing in place in N83002 and removing it and welding in new pieces would just add cost for the owner. The decision on how extensive the longeron replacement will be will come later. Right now we know that the bottom tubing on the severed tail has to come off. Just like we showed in previous postings, the tube that makes up the longeron must be cut back to the contact point of the tubes that join it. The first impression when the decision has been made to replace the longerons is to cut them completely out. Please don't do this. The bridge type frame of the fuselage makes for a very strong structure as long as that structure is rigidly in place.

If you cut too many tubes out, the rigid framework becomes a wiggley worm that is easy to damage while moving or working on. We need to cut out the longeron contact point with other tubes, but we want to leave the basic longeron intact down the line to the next joint to help keep the fuselage from flexing. If you eliminate the strength of the fuselage while you are repairing it, you just might twist or bend something that will add to the repair list. When all the grinding out work is done we will then cut off the remaining longeron tubing giving the "wiggley worm" the least chance to jump up and bite us!

bsafran · Post by **bsafran** » Wed Feb 01, 2012 21:59

The first picture shows the hard part for an Aeronca owner - taking a hacksaw to his fuselage! Donnie is hacking off the longeron just in front of where the lower tail wire attach fitting is. It would have been preferable to make a splice forward of this area of the longeron, but the damage was too close to make that possible. Several thing are happening in this part of the longeron, not the least is that the tube takes a bend towards the tailpost. Most people I talk to think that the tail wire attach lug is just a tab welded on the exterior of the longeron. Aeronca knew that this was a major safety area and had that tab triple welded. It actually passes through the longeron and is welded on both the exterior and the interior of the longeron tube. For extra safety, the cross tube (number # 60) that goes between the longerons at that point joins across the inner welding to hold it in place for a third weld.

bsafran · Post by **bsafran** » Wed Feb 01, 2012 22:17

It's time to remove the longeron tubing, but we want to leave as much of the tube intact for as long as possible to maintain the rigidity and strength of the fuselage structure. Once the fuselage loses that connected support, it becomes easy to twist and damage. At each joint where the longeron contacts other tubes, the object is to cut out a section that allows access to the inside of the longeron tube to grind away to the contact tubes and still allow the longeron to remain connected through the weld material to maintain the fuselage strength for as long as possible. I don't have a good picture to demonstrate this since N83002 doesn't have a complete fuselage. It is actually in two pieces. You can see where the owner has exposed the inside of the longeron tube near a cluster and is grinding away from the inside out to remove the longeron but leave the connecting tubes intact. The longeron will only be left connected by a small portion of the weld material between the longeron and connecting tube. This is just enough to give the fuselage some remaining strength to protect it from jerks like us who bump into it or lift it the wrong way and it takes a horrible twist. Later, the remaining longeron material will be cut off and the weld material it was connected to ground down to make room for the new tubes.

bsafran · Post by **bsafran** » Thu Feb 09, 2012 19:45

When so many parts of the fuselage need repaired, sometimes it's difficult to decide what to work on next. Today, I went back to tube # 70 which holds the door hinges. That tube has already been cut out and the area it contacts other tubes ground down. This grinding was only basic shaping and careful filing remains to be done to prepare the area for joining in a new tube. The first picture is a copy of one earlier in this thread where the top part of tube # 70 was removed and ground down close to where it contacts the surrounding tubes. The last two pictures shows where we have filed down the material even closer to the contact tubes. This gives us enough clearance to start mating up a replacement tube. Once everthing is cut and shaped like we need for welding, the final bit of filing off the remaining weld material will take place.

bsafran · Post by **bsafran** » Thu Feb 09, 2012 20:08

The step is going to be replaced on this plane along with the streamlined tube that attaches it to the fuselage. We have a die where we put in a slightly thicker plate than is specified in the Aeronca step cup drawing and then shape it to the die with a hammer. I'll probably make the cup for this plane using the die just so everyone can see how to make one yourself. However, American Champion offers a new replacement part (or parts) so you don't have to go through the bother. You can order each individual piece or purchase a completely assembled unit from Chad at American Champion. His phone number is 262-534-6315. The flat cover plate (the part you step on) is part number 1-2407 and it lists for a whole $18.16. The step cup is part number 3-465 and it costs $20.85. If you want the whole unit which is the cover plate welded to the step cup and then attached to the streamlined tube, just order step assembly part number 4-588 for $181.55. It comes with a gusset (part number 1-10506) to help strengthen the joint.

bsafran · Post by **bsafran** » Tue Feb 14, 2012 22:19

When I started this topic, my main intention was to illustrate to rebuilders what they might come across when repairing their Champ fuselage. About a month after I got started showing the work on N83002, I called Bill Pancake and invited him to comment on what was on the website. I thought he could add some remarks pointing out things to look for, how to avoid mistakes and add some insight into how a fuselage repair should go.

His first suggestion was to spend more time discussing the area where tube # 7 (the top longeron of the tail section) butts into the fitting where the front of the horizontal stabilzer joins the fuselage. He wants everyone to really inspect the bottom of the tube at the very aft end. He has seen several cases of water creeping in from where the wing fairings screw through the fabric and travelling all the way back to this point. Then rust sets in and over time the tube needs repaired. I have seen several instances that back up Bill's claim.

Since this section is not the easiest to fix, I have seen many different patches that don't really comply with AC 43-13-1B. This picture shows the area to inspect. No killer rust exists in this tube, but you can at least see the area that Mr. Pancake wants everyone to pay close attention to.

bsafran · Post by **bsafran** » Sun Feb 19, 2012 09:35

The step on N83002 needs replaced. Earlier, I had posted pictures of the new individual parts and the complete unit available from American Champion. A friend of mine wanted two steps for his planes, so he ordered the top and bottom pieces. They came to him already welded together. Here are a few pictures of what he received. Compared to what it takes for us to make a replacement step, these new parts seem to be the right way to go.

bsafran · Post by **bsafran** » Wed Feb 22, 2012 11:16

N83002's fuselage is broken into two pieces and our original plan was to splice the two halves back together with a lot of new tubing. It's time for a change in plans. I have another rear fuselage section that at first glance looked to need more work than the original. It turns out that we will spend a lot less time repairing and splicing the spare instead of fixing the first one. When you look at the pictures, it seems obvious that the green primered one looks better than the lighter colored replacement.

However, when you visualize what tubes come out of both for the repair, you can see why the one on the right is the best choice for the owner. Less work means less cost and Mr. Gunkelman seems agreeable to less cost. Both tail sections need to have the longerons replaced so its a wash there as far as time and material involved. The lower tailpost is severed on the tail piece on the right and intact on the left, but that really doesn't make any difference. We would have to do major work on both bottom tailposts anyway.

The bottom of the tailpost rusts away from the inside just like the rear longerons do and you can't inspect this area very well with the fabric on. When your Maule tailwheel does that violent shimmey (I don't like Maule tailwheels) the weakened tailpost snaps at the bottom. Go out to your hangar, lay on the ground, grab your longeron handle on the right side and watch the tailwheel when you wiggle the plane side to side. If your whole tailspring system rocks back and forth, you have a broken tailpost.

We reinforce every tailpost that comes through the shop, even if it appears okay. You don't want to cover the fuselage just to have to cut the fabric back in five years because the tailpost cracked. Now you can see why it is easier to repair the fuselage tail on the right as opposed to the one on the left. The right side one will just have a new tube welded in. The one on the left needs a lot more labor to fix. You can't remove fitting 1-2318 (the tailwheel leaf spring plate) without destroying it or the tailpost. We have to cut a hole in the bottom of it to match the inside diameter of the tailpost, insert a smaller tube up inside the tailpost and properly weld the reinforcement in place. Then you have to weld in a washer or such in the fitting to close back up the hole.

What really swayed the decision to use the tail on the right over the one on the left was the fact that tube #7 was straight where it comes into the area by the front horizontal stabilizer attach tube. The original was bent back in this area requiring that we replace the tube all the way back to the attach tube. (Look at the pictures posted previously to see this) Since the other tail has a nice straight tube #7. we can make a splice in front of that complicated area where all those tubes come together.

Post by **joea** » Sun Feb 26, 2012 17:02

Finally found the time to read this entire thread.

Very good work and excellent documentation!

Joe A

bsafran · Post by **bsafran** » Sun Mar 25, 2012 08:35

The airplane owner has cut out the tailskid leaf spring fitting (1-2318) and it is being shown by his son William. Just like all of the other tubes and fittings we have removed so far, the metal is removed down to the point that only the weld material remains. That last bit of metal will come off later using a less abrasive and slower meathod (so we don't screw up a part we need). Leave kids alone in the shop and they will find something to play with. William mistook the fuselage for a jungle gym set of monkey bars. He can't wait for his first ride in N83002.

bsafran · Post by **bsafran** » Sat Mar 31, 2012 18:26

This fuselage has had many repairs that have thrown it out of whack and then there is damage that needs to be addressed. We finally had a day where we could take the fuselage (or should I say - pieces of the fuselage) out of the shop and sandblast the areas where the major repairs will be made. The paint and rust needs to be eliminated so that a good bonding of new tubes and weld can be accomplished. Before sandblasting, some preventive measures should be taken. There are places where screws attach to the tubing which have left holes. The area where the left and right sides of the windshield screw into the fuselage are prime examples. If these holes are left open during sandblasting, some residual sand will be left inside the tubes. The first picture shows the screw holes in the tubing on the right side of the plane where the windshield attaches to the frame. The second picture shows how we cut an "O" ring so that we can stuff it inside the hole to allow sandblasting right up to the edge of the hole, but prevent any sand from entering the tube where it will be impossible to remove. The last picture shows how to take an awl to push the "O" ring segment into the tube to block any sand infiltration.

bsafran · Post by **bsafran** » Sat Mar 31, 2012 19:14

I hate doing the sandblasting, but it needs to be done. Luckily for me, N83002's owner was willing to step in and help out, which keeps his costs down. The front half of the fuselage has been sitting in the built up front section of the jig. That portion of the jig must now be dismantled so we can take the fuselage outside for specific sandblasting. We need to clean the area around the tubing clusters that will require repair so that a good weld material to tubing bond can be made. Doesn't Donnie Gunkelman look like a Carhart Storm Trooper from Star Wars in his sandblasting uniform?