ultimate in easy repairs, The

Try this strong, light technique

So many articles detail all sorts of methods to create a model; this one details and documents a fairly major repair. I hope that it will inspire those with limited building experience to repair their models rather than just trash them. Last flying season, I was practicing inverted flat spins with my Sig Ultimate Bipe (my favorite plane), and the engine flamed out. Without power, it descended evenly but steeply and, needless to say, I did not quite reach the runway. When I picked up the Ultimate, my heart sank; the plane had landed hard enough to break the fuselage in two. It was a long, quiet ride home.

The next day, I cleaned the model and thought about rebuilding it. New decals, covering and glue didn't amount to much expense, but I cringed when I considered all the time it would take. I decided there had to be a better solution.

Any good work begins with a careful assessment of the job ahead. I considered four options: scrap the fuselage and order, build and cover a new one; glue the two pieces together with CA and hope for the best; use dowels to align and reinforce the break (fairly complicated); or glue the joint with CA and reinforce it with plywood doublers. The last option seemed the least complicated and most likely to be successful. The following photos detail the work done to the left side of the fuselage; I used the same procedure on the right side.

1 I decided to remove and reuse a portion of the trim sticker that runs the length of the fuselage. Also, I wanted to remove only the covering around the area of the break. On this particular model, the 1/16-inch-thick plywood sheets form an angle on both sides of the fuselage. This angle runs in roughly the same direction as the break. I made the second parallel cut several inches back and beginning at the base of the windshield.

Most of the wood on both sides of the break was attached to one side or the other. Those pieces would help me to join the halves back together. The pieces of wood that were flaking off were of no real use, so I removed them to help ensure the tightest fit possible.

2 This step was one of the most critical because after its completion, there would be no going back. I carefully pieced the halves together, making sure that they fit as tightly as possible and were aligned. Because the front of the fuselage is thicker than the rest of the model, it would be really easy to end up with a banana if I just laid the halves on a table and glued! I added CA slowly, drop by drop, and continued to check for straightness as I went along.

3 I continued to fill in the areas where wood had flaked off until the surface was reasonably level. Before I made the plywood doublers, I cut a template of two pieces of scrap paper and laid them over the break, covering as much of the work surface as I could.

4 I transferred the template shapes to the plywood and cut them out on a jigsaw. To help smooth out the transition, I feathered the top surface of the doublers with a palm sander. I epoxied them into place so that I would have time to recheck the alignment and adjust it as needed. As the epoxy set, I used as many clamps as I could to ensure that all the excess epoxy was squeezed out. After the epoxy had fully cured, I removed the clamps, and the surface was ready for covering.

5 From this point, the job became like any other project wrap-up. I peeled back the covering ever so slightly on the nose side of the repair to slip the new covering under it. This would help to prevent "peel-back" later on.

6 The portion of the yellow trim sticker I had removed earlier was torn by the break, but it flattened out nicely when I reapplied it and carefully sealed the edge with thin CA. I have to say that I'm pretty pleased with the results. If you look closely, you'll see the tear in the yellow trim sticker around the "L." You'll also see the doublers under the covering, but this is an everyday fun-flyer and not a scale show queen! All that was left to do was to put the parts back on and go fly.

The entire repair project took only a few hours over a few days. The plane performs as well as it did before with maybe an ounce of added weight just behind the CG. All in all, I am really pleased with the decision to rebuild.

This approach can also be used to repair other broken airplane parts. Just remember to check the alignment and ensure that the repair is at least as strong as or stronger than the original parts without adding too much weight.

Copyright Air Age Publishing Oct 2003
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