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Rear Spar and Tie Downs

August 16, 2011

The rear spars are ready for initial assembly with the main spar. I got that finished the other night. Here’s a shot of that:

Finished part 1 of the rear spars. They are sitting on shelves used by my son for hockey gear.

The little pieces of blue tape are reminders of place not to put a rivet right now.  They will get riveted later once the ribs get put in and when the hinge hardware needs to be put on.  The hinges will for the ailerons.  Space is an issue with these multiple long parts.  I’m going to have to come up with some kind of storage for the wings as they get swapped out during the build.

On the main spars the last thing that needed doing (and I was waiting on) is the tie downs.  The tie downs are just an aluminum extrusion that is bolted to the spar.  On both ends there is a hole.  The instructions tell you to tap one of the holes appropriately with threads for a ring bolt you will install later (like right after your first flight).  I tried it on two holes and just kept screwing it up.  I think my Harbor Freight Tap and Die kit is rubbish.  I found out while researching that Cleaveland Tools has a pre threaded version of the same part.  So I just ordered it.  Sometimes doing things just to do them isn’t much fun.  A quality Tap and Die kit is going to be in the $200 range.

Here is the hardware for the tie down bracket.

The squares on the left are spacers that go between the tie down and the spar.  Vans has you cut 1″ lightening holes in the pieces.  Lightening as in make your plane lose weight.  Cutting the holes is a PITA.  The rig I had to build on my drill press to hold things in place was unsafe.  Drilling it is messy and uses lots of cutting oil.  In the end, I’m just not sure its worth the ~ 1/2 oz savings in weight that you realize.  The spacers also serve as the place where you bolt down the bell crank for the ailerons.  Its not like you can leave them off altogether.  I messed up 3 of the 4 of them so I”m waiting for a replacement piece of aluminum stock so that I can re-make them.  Once that is done it’s onward to prepping ribs….kill me now.

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From → Build Log, Spars, Wings

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