Compared to mounting the a fuel tank, enlarging holes and setting M4 rivnuts seemed easy and definitely less stressful. Still, it was no time to be careless. The wing skin is easy to damage.
It took several steps to get the factory punched holes enlarged to letter number #A diameter, a perfect size to accept M4 rivnuts. I double checked my references and reviewed the process I would use. A series of increasingly larger straight-flute chucking reamers in my trusty lithium-powered drill did the trick.
All of the holes in the wing skin and the inspection covers were in the correct places and the alignments matched perfectly. The drill mounted rivet setting tool worked flawlessly. All rivets are consistent and tight. The screw clearance holes in the covers are ideal. Everything is fits together nicely.
There are several points in the build where short rivets are required. Sling Aircraft (TAF) has chosen to leave this task as an exercise for the builder, to adapt some from the ordinary ones supplied with the kit. Here I’m shortening 3,2 x 8mm rivets to about 5mm. These will be used to fasten the piano hinge and control horn to the elevator trim tab.
For some steps, I use a small box end wrench and a socket to provide support around the entire head of the rivet, as I drive the mandrel out or back in using a hammer. I use a cutoff-wheel in the Dremel Tool to trim the rivet body.
I’ve finally gotten to the point of acomplishing the very first step on page VS1 in the Empennage Construction Manual! I’d been worrying about it. Getting the rivnuts securely mounted calls for a rather deliberate process with good technique. It all went very well. What a relief.
Having an effective tool – Astro Pneumatic Tool ADN14 Rivet Nut Drill Adapter Kit – and practice made the day. I’ve seen a couple of other builders recommend this particular tool. Because it relies on a cordless drill motor and identification of an appropriate torque (clutch) setting, I felt there would be a good chance of getting consistently good results. This seems to be the case.
Practice! I got an assortment of metric rivnuts and used the tool to work with them until I knew exactly what to expect. Now I have 14 perfectly mounted rivnuts!
BTW – the KAI mentions using high strength Loctite to insure that the mounted rivnuts don’t slip in their holes. I say – learn how to mount them firmly and they won’t slip. No Loctite is needed. Because IMO – if they’re not tight enough to stay put, then they’re not satisfactorily mounted.