(page 21-02, step 7) What wing spar?......                                

Step seven says "File the curved  recess of both wing spar receptacles to closely fit the rounded mating ends of the rear spar assemblies of both wings."  The problem is, contrary to what most people apparently do, I bought the fuselage kit before the wing kit, figuring that it was quite important to finish the fuselage first in order to accommodate my sitting in the fuselage, grasping the stick, and making airplane noises.  Little did I know that I'd need something from the wing kit in order to complete some task in the fuselage kit.  After my initial panic, I solved the problem by ordering the rear stub spars from the Mother Ship (parts shown on right) for the grand sum of $31.00.  Problem solved.  I'll simply delete these parts from the wing kit when I order it.  The plans say to identify the top of the receptacle by the flat spot machined there.  It appeared to me that both ends of the part had a flat spot, and I initially mis-identified the top and filed the inner contour to match the stub spar upside down.  Fortunately, the rivets only match up in the correct orientation, and I discovered my error.  Doubly fortunately, the contours still matched when I turned them upside down, so all was well.

I was delighted that the plans called for pulled rivets for these parts, so I broke out my favorite tool: the pneumatic rivet puller (shown at the top of the picture).  When the wings are attached, the stub spars fit into these receptacles and carry the torsional loads from the wings.  The wing spars (which, of course, I don't have yet) support all the bending, most of the shear, and none of the torsion load.  There's a similar stub spar at the front of the wing which I haven't encountered yet.