24 February, 2006

Day 2 with the Tern: Fuselage Part 1

Today was my day off, and I was much more productive than normal - mostly because the weather was not nice enough to golf.

I began with a quick finish of the tail feathers. I drilled the mount plate and rounded the forward and aft edges, and then took some care to mount the stabs at the same height on the plate and the same decalage. After that was done, I moved on to the fuse.

Nothing makes me revise my thinking like actually building a fuse. I had planned to use a thin spruce plate for the towhook, and run it through a mousehole in two bulkheads. I decided that this wasn't the best plan, so I eliminated one of the bulkheads and made the towhook plate out of basswood. Much as is done on the Spirit, I used 6-32 blind nuts in three locations to give some Cg flexibility for the tow point.

The only other change that I made was to use basswood for B4, which is the main loadbearing bulkhead. It takes most of the load from the hookplate, and is the tie to the wing bolt. The aft deck went together nicely, and the Magic Magnet system made the height offset a breeze.

The aft wing bolt point is just between the full fuse bulkhead and the first bulkhead on the aft deck. While the double triangle stock at the aft deck attachment point has stiffened that up quite a bit, I am counting on the wing box to carry some of the tail load for big positive moment maneuvers. Given the stiffness of the tailboom, this shouldn't be a problem.

Once everything was test fit, the assembly of the fuse sides with the Magic Magnet system was the easiest that I have ever seen. I used the vertical stands to provide pressure at each bulkhead (replacing my fingers), and was able to get it perfect in two shots (one for each side). As you can see, I used some presses to hold the fuse down in the center so that it wouldn't twist when I had only one side on. I have to say, that worked even better than I had hoped, and this seems a truly great tool for making slab sided fuselages.

Overall, I call this a pretty good second day. The only problem was a lack of planning that caused me to glue some bulkheads in place before I had made cutouts for the pushrods. That may come back to bite me, as I couldn't get the pushrod holes cut at the angle that I wanted, but I don't think it will be anything more than cosmetic.

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In fact, I just got off the treadmill...