Of course as soon as I thought I was out of the woods with respect to countersinking and platenuts, along came more platenuts. This time it was the inspection panels. There are 3 inspection panels on the underside of each wing. Each panel screws into the spar in 4 spots, so there are 12 nutplates per spar.
Here's an inspection plate as it comes from Van's...pre-cut and pre-punched. However, the pre-punched holes aren't ready to be dimpled...they need to be bored out. But be careful...the spar takes #6 screws and the skin takes #8 screws.
I used the ScotchBrite wheel on each of the 6 plates' edges, which were pretty rough out of the box. Then I dimpled all the #6 and #8 holes on each of the plates.
Yet again, this countersinking thing. The screwed up thing is that the spar comes with #30 (1/8") screw holes...and that's not big enough for #6 screws. So first I bored out the holes to 9/64", and then I drilled out the rivet pilot holes to 3/32". On both spars. Deburred the holes. Then I made an alignment tool for countersinking the screw holes. This time I put a #30 hole in the tool...it was either that or #20, since those are the pilot sizes of my countersinks. So #30 it is. Anyway, I countersunk the 12 screw holes on each spar. This went more quickly than the tank attachment screw holes since there are way fewer of them.
A quick check to make sure the dimpled inspection panel rests flush against the countersunk spar. Yep.
Next step was to countersink the 3/32" rivet holes. I won't bore you with any more details. If you don't know how to prep a flush screw nutplate attachment by now, go back to square one, dude. Anyway, the inspection panel nutplates are all on there now.
The next step was to attach some nutplates to the spars where the center spar sections attach. I won't bore you with details or pictures.
The next phase of construction involves fabricating the tiedown bracket spacers. The tiedown brackets (I'll show you a picture of those tomorrow or something) bolt directly to the spar and spar doubler. You need to make four spacers to go between the spar and the brackets. Too difficult to explain. Just look at the picture below and you'll see the dimensions of the spacer. You get aluminum bar stock from which to make these, but the ordeal is cutting out the circular holes. Not really difficult, just a time sink, since the holes need to be deburred and all that. I seriously considered not bothering cutting out these holes, but I guess every ounce counts, so lighten these suckers up or whatever. If I took a 3-ounce shortcut 50 times on this kit, that would make the plane 10 pounds heavier. Gotta do it.
It's tough to see here, but I used an adjustable hole cutter in the drill press. Its smallest diameter is 1", which is exactly how big the holes needed to be.
Boom. After about 45 minutes I had 4 of these suckers. I still haven't deburred or polished the insides of the circle cutouts yet...it was too late at night to have the die grider going nuts.
