Saturday, October 12, 2013

More Wood Work

The month of September was spent working, mostly, but with a few days to finish woodwork on the lower wings.

Both lower wings were unfinished in that they had no nose ribs from the walkway inboard. This involved making several nose ribs with leading edge strips to complete the inboard portion of the wings.

The root nose rib had to be made with extra bracing as the fabric, once on and heated, will stretch and pull the root rib inward. I made too many ribs, so I just doubled the root rib and made a couple of "knee braces" to give them some extra strength to resist this inward pulling force. Once given the once-over by Bill Hammond, and receiving stamp of approval, I felt that part of my fabrication was done and could move on.

One item that the original builder installed was a little 1/4" thick piece of spruce behind every nose rib to smooth the flow of the fabric once it is shrunk. I don't think they have a name other than "little strips of wood that smooth the fabric." The lower wings didn't have these on the bottom surface and since Mr. Rowe installed one of these little guys behind every nose rib, I decided to carry on and make a bunch of them to complete the wings as he had started them.

One last item remained: the leading edge strips on all wings had too little material protruding forward to allow for shaping the leading edge into curve that would match (or complete) the curvature established by the nose ribs. I ripped thin strips of spruce about 3/16" thick and glued them to the leading edges. Clamping that length of thin material requires lots of clamps. I used a few strips of scrap steel to provide some rigidity to the strips during curing. These will be sanded into the required shape using a belt sander.

After all the wood parts were fabricated and glued/nailed into place, the wings were essentially finished. It was time to put the woodwork aside and deal with engine parts.
Bad news here:
The engine shop where I took the steel parts to be magnafluxed, gave me the very bad news that the master rod had a small crack, which essentially doomed that whole assembly. The master rod is the main piston rod in a radial engine, from which all others are attached and articulate. This item is very expensive to replace, and if it failed in flight would result in catastrophic failure of the engine with no hope of salvage, most likely. This was very bad news, indeed. Now to call Jim Friedline and inquire as to my options. That turned out to be the only bright spot in the whole process. Jim said he had several master rods! Wow, what a life-saver! I was hoping he had retained a few parts from the sale of his inventory, but was surprised to learn how much he had left. There were several master rods that appeared okay, but as we learned from my own, looks can be deceiving. He also had one tank engine master rod with the other six rods still attached. We checked them with micrometers for wrist pin bearing wear and main bearing wear. The tank engine assembly seemed to have the tolerances nearest to standard (new), so I opted to purchase that assembly. In fact, I like the tank engine assembly better due to the fact that there are two oil gallery holes in the main bearing instead of one. There are also pins installed in the wrist pin bearings to prevent rotation of the bearings during operation. Metalurgically speaking, there is no difference, so it just seemed prudent to go with the parts which appeared newer. In fact the manufacturer's stamp is still plainly visible on these parts as are the original machining marks. Jim believes there is an STC somewhere for the tank engine parts, which there should be. The only reason they were not approved during manufacture is that they didn't have the required part number which received the FAA approval for aircraft use. The fact that they came off the same assembly line makes no difference to our paper-work addicted government representatives. After speaking to a radial engine expert, who recommended magnafluxing, we decided to have this assembly done, as well. Again, only prudent. Once the engine is together, this type of inspection would be impossible, so the peace of mind is worth whatever time and expense I incur. The engine shop guys wanted to apologize for finding the crack in my master rod, but I wouldn't hear of it. I told them that they saved my ass with that discovery, so no apology is required. This little disappointment is overshadowed by the what would be felt if the engine came apart in flight. I've seen a master rod failure and it isn't pretty. While waiting for the new master rod assembly, there's time for some more wood work.

The fuselage is on the gear and rolling around the hangar, which sure makes it easier to work on. One of the main items needed to fabricate is a set of bulkheads which hold the stringers that form the shape of the fuselage. I don't have a reliable set of drawings to go by, only an overview of the fuselage components which includes scaled down drawings of the bulkheads using four inch squares for enlargement onto plywood. I tried making a set of these without much success. I may have the shape right, but the size doesn't fit the fuselage at the various stations where they will be attached. I inquired around as to who might be able to provide assistance and Clay Hammond recommended Mark Lightsey of Aerocraftsmen, of Flabob Airport in Riverside, California. I got his email address from their web site and sent an email explaining the situation. Mark's company has restored many Travel Airs, Wacos, etc.—you name it. Their expertise is impressive. As it turns out, he is also  very nice guy—willing to help a builder/restorer in need.

Mark made copies of tracings they used in their last Travel Air restoration, put them in a tube and mailed them to me without even mentioning reimbursement. Hopefully, the Irish Whiskey I sent him will be sufficient to say "Thank You" to a real gentleman.
I transferred his tracings to poster board and then used that to trace the shapes onto the 11/32" mahogany plywood I'm using for the bulkheads. Each one came out perfect! They fit the width of the fuselage at every station, and the cut outs for the stringers line up very well.
This was quite a bit of work on the drawing table as well as the bandsaw. They look good attached to the fuselage. It's beginning to look like an airplane!
Mr. Rowe built the fuselage with little tabs welded to each station where a bulkhead would be attached, which sure lessened the work load, but the last two stations at the aft end didn't have them. I fabricated two little adel-style clamps to attach the next to last bulkhead as it would butt against a crossmember. The last little bulkhead, which forms the end of the fabric covering area, will need a clamp with a 90° flange so it can be clamped to the side tubing. This bulkhead is in two parts like the first one behind the cockpit. One piece of plywood has the stringer cut outs while the outer one is flat so it will present a smooth face to the outside.
One more thing: it sure is nice to have a companion in the shop. This is Bella, our 1 1/2 year-old Boxer. Great dog!