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Center Section Bolts

Freemasm

Well Known Member
Taking the advice of those before me, I’m installing/aligning/etc the wings before the HS; advice being determine the actual angle of wing incidence. Then set HS to match. The first wing “inserted” without a lot of fanfare. Aligning and temporarily installing CS bolts is being painful. Any advice that can be shared there would be appreciate. Thx.
 
1. Usual advice is to use hardware store bolts for temporary installations. Save the expensive bolts for final installation.
2. Chill the bolts to shrink them. Ice works, dry ice better. Use a little lubricant on the shank but clean the threads before torque.
3. Some encouragement from a rubber mallet may be needed.
 
I made up a number of drift pins out of tapered hardware store bolts and used those when I was test fitting the wing. There is need (IMO) for close tolerance bolts and the like for temporary wing fitting.
 
Too used a tapered and polished standard diameter bolt for fit up. This was satisfactory for alignment. It was rechecked with final torqued fasteners installed and did not change.

For the final assembly: I don't know about the Rocket, but the 7 spar has relatively thin shear webs and thick bars for the tension members. The bolts must go though all. The holes are not perfectly aligned, so I made slightly tapered pins to press through the holes prior to using the NAS bolts. The bolts were measured and sorted as well as the holes. The pins always went though the heavy sections with finger forces.

The generously lubricated pins burnished the misaligned layers, and were several sizes in .0001" range. No NAS bolt was loose but they all were inserted and could be removed without gritting of teeth and a grimace.

The burnishing pins were short so they exited within the center spar sections.

YMMV, as well as your design, but you get the picture.
 
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Right or wrong, but done

For what it’s worth. The holes were already reamed and dimensionally verified. I had already made drift pins (long taper and very even/smooth before you ask). Even with no perceivable/measurable hole misalignment, lubed shanks, etc. I still couldn’t get more than one bolt/pin in. I tried persuading such with a rubber mallet. The structure laughed at me before calling me names.

The center section, and spar caps for that matter, are quite flexible without the layers fastened together. Tightly clamping would have probably been beneficial if I’d continued with the mallet. An air hammer/rivet gun with a fairly low pressure setting provided enough impulse to install the pins and bolts. Yes, there’s some burnishing. The cad layer was basically removed from the bolts. I don’t foresee the high shear bolts going in with finger pressure. Maybe this will help somebody down the road.
 
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