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ARTICLES
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It seems like every time I
build an airplane I make at least one major mistake. Most of the
time these errors can be fixed easily. One of the great things
about model airplanes is that the materials they are built of are
usually not as strong as the glue that holds them together, so it's
simple enough to glue pieces of wood into damaged areas and move on to
the next step. Currently I'm building a 40 sized Telemaster from Hobby Lobby plans by Joe Bridi, which I purchased at a swap meet. I decided to power the plane with an OS 52 Surpass mounted on a Dave Brown mount, with the cylinder pointed to the right. It seemed like a pretty good idea to mark the firewall and drill it for screws, throttle cable and fuel lines before gluing it to the front of the airplane. Unfortunately I was having a little bit of trouble with my clamps shifting around, and in the momentary confusion I ended up attaching the firewall upside down. I didn't want the engine mounted at the bottom of the firewall, pointing left. And I didn't want to remove the firewall from the airplane because it would destroy the front of the fuselage. I figured that the most practical solution would be to fill the holes and drill new ones. Here's what the firewall looks like after the repair.  You can see the incorrect throttle location on the left side of the firewall (your right, the plane's left). This got filled with epoxy when I added the triangle stock. The new location was drilled on the right side of the firewall (your left, the plane's right). The screw holes and the fuel line holes were drilled to the next larger size to match standard 1/4" and 3/16" dowels, then quarter inch pieces of dowel were pushed into the holes. The plugs were glued with thin CA, and then any remaining cracks or spaces were filled with thick CA. The whole firewall was then sanded smooth, marked and drilled for the correct mount location. You can use similar tricks to fill voids and other shortcomings in balsa wood. Sometimes I receive some very flattering compliments on my Monokote work. If only they knew what was underneath. I don't take a lot of trouble to get things perfect on the inside where they won't be seen. For example, when I was putting wingtips on this same Telemaster all I could find in my balsa stash was an old piece of narrow but very thick aileron stock. Unfortunately the stock was just 1/16" short of being the same thickness as the wings. Instead of buying a bigger stick, I simply filled the remaining gap at the thickest part of the airfoil with a very small piece of 1/16" balsa wood.  It's a pretty simple improvisation, and you'll never see it after the plane is covered. When I joined the wing halves I noticed that I had gotten a bit carried away sanding the last 2 inches on the inboard end of one of the leading edge sticks, and it was about 1/16" shy of the other leading edge's size. I went ahead and joined the wings so they would line up at the trailing edge, then I used a piece of 1/16" balsa wrapped onto the thinner leading edge to fill it back out. A sanding block brought it down to the correct level to match the other panel. If you look carefully at the panel on the right side of the photo, you can see where the wood grain doesn't quite match right next to the center line. This is where the extra piece of wood got wrapped around the leading edge stick.  |