While I wait for my dimpling pliers to turn up, I thought I'd move on with the next step...countersinking relevant holes in the spars and spar doublers.
First I found myself a piece of scrap aluminium and practiced with the microstop countersink cage (having never used one before). The spar flange holes sit underneath the dimpled wing skins, so they actually need to be over-countersunk by 0.007" (or seven clicks on the microstop cage). The picture below shows my test piece.
When it came to countersinking the actual spar flange holes I found that I needed to adjust the countersink depth slightly. Also, as I worked my way along each spar I stopped every 3-4 holes and rechecked the depth with a rivet. Seemed to go okay.
Not shown in photos, but I also countersunk relevant holes in the spar doublers, being very careful about which holes, and on what side.
Spent quite a bit of time doing this, but hey, I'm in no rush.
