So, last night I grabbed the booster rocket off the bench and headed for the 'BlastFromThePast Vehicle Finishing Facility' (a large cardboard box in the corner of the back yard), to apply the first coat of primer.
When I tried to insert the engine casing on the end of the painting wand into the main tube, I found it to be exceedingly difficult.
Here's why:
In this photo, it can readily be seen that the main tube is a distinct oval shape, and one of the fin units is somewhat warped.
How did this happen?
Here's the answer:
After assembling the three tubes, I had applied a very liberal set of fillets using Elmer's white glue to hide the big gaps and bubbles that invariably plague parallel-glued tubing.
This attempt to make things pretty led directly to the dreaded 'Elmer's Effect' - severe glue shrinkage that warped the body tubes completely out of round. Things are so bad that one of the gliders will no longer fit between the fin projections. To make it fit in the present condition would require inner surface of the fins to be sanded down to 1/32" thickness.
No good.
I have a couple of options here. The first is to use the 'Forced Air Thermal Alignment Apparatus' (my wife's hair drier).
The idea is to insert engine casings into all three tubes for support, then heat up the joints with the hair drier to soften the glue and allow re-alignment. It is hoped that, when things cool down, the components will retain the proper position.
If this doesn't work, I am afraid the only other course is to scrap this booster, buy another BT-20 tube, and start it all over.
Sigh.
Live and learn.
In the meantime, the filling and sanding of all those balsa glider parts is still progressing.
