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Friday, March 25, 2011

Progress this Week

Well I did manage to get some work done this week on 53T.  Most of the progress was in the department of sanding and filling and more sanding.  As mentioned before I put some filler in a few spots on the stringers where we had pulled a little wood up with the fabric.  Hey I guess we just got a little excited tearing off the fabric.  Other places that needed some help were on the wing center section and the coaming around the cockpit.  The epoxy filler (best guess) that was originally used to fillet the transition from the wing to fuselage had gotten soft in a few places and was pretty easy to chip away.  I removed everything that seemed to want to be removed and filled in the gaps with Super-Fill.  The coaming around the cockpit is skinned with Balsa and seemed to have had some sort of epoxy coat over top of it that had chipped off in large areas when removing the fabric.  This also happened on the balsa leading edges on the wing roots.  Anyway I used some super fill in those places too to fill in the holes and keep everything as smooth as possible.  There also is a fairly large area on the right wing root that is sort of flat on top.  It had a bunch of filler there before, some of which came up with the fabric.  So I slopped a bunch of super fill on there in hopes of building it up to a more appropriate wing profile.  Here are a bunch of pictures of various areas in various states of fill.

Visited with a few of the experts about the left wing this week.  Basically there are two options.  Option 1 is to get good measurements on the material that was removed and then figure out the bending stresses through that area using good conservative assumptions.  At max weight and max G if we still have a positive margin on the spar then we'll just smooth it out, varnish, and carry on.  Odd's are this will be the case, I think.

Of course if that is not the case then the only option is to scarf the spar with new spruce.  The repair would look something like this:

That is easy enough, the problem is getting to the spar.  To do that I'd have to cut out three bays of leading edge skin, remove at least a couple sets of cross members, and take out at least a few ribs.  Then scarf the spar and put everything back together.  Not impossible of course.  Harry and Neal have and will continue to do much more complicated repairs.  It's not really anything that I think is outside my abilities either, but i'm not so excited to test those skills that I'm looking for an excuse.  So, hopefully tomorrow I can get some good measurements and start crunching numbers, then go from there.

I spent some time last night doing some more looking around the tail area and trying to visualize and determine the best strategy for the repair before I got too crazy and cutting wood.  I think I have a plane so the next thing I do on the fuselage will probably be to remove the aft bit of each lower longeron along with the lower part of each beam on the vertical stabilizer and some of the plywood sides of the box spar.  Here are a couple pictures of how that area looks now.  I used some rough chisel work previously to remove the bad portion of the aft beam and plywood cover on the aft side as well as the plywood along the inside of the lower longerons.

That's all for now.  Tomorrow is supposed to be club cleanup day at the Gliderport and if we make it out there I plan to return with 373Y.  However the forecast is looking pretty crummy so we'll see if it happens.  The temperature is down for the weekend and beginning of next week but I think I will have the heater operational tomorrow at some point which is fantastic! Of course then I'll need to finish a few spots of sheetrock and insulation in the ceiling and walls.

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