Brief Description: Drilling Spar for Tank Nutplates
If I recall correctly, there are about 72 screws holding the tank onto the spar. Nutplates for every one. I drilled for the K1000-08 nut plates today. The order will be to use the #30 holes in the spar flange to hold the nutplates in place. Match drill the two #40 rivet holes in each. Take off the nutplate and countersink all the #40 rivet holes. I used a backing plate predrilled to #40 behind the #40 holes in the spar flange so when I countersank the #40s the pilot end of the countersink bit would hold firm rather than wobbling around in the small spar flange holes. This made for very nice countersinks. No chatter gouges. Very nice. After I mount the tank and hold it on with #30 clecoes, I will enlarge all the #30 holes to #19 so the flush mount screws will fit through the holes. Then I will take the tank off and rivet on the nutplates now that the center holes have been enlarged to the correct width. Once the rear fuel tank baffle is prosealed and riveted onto the tank. I can countersink the forward most of #19 holes on the top and bottom of the tank because the metal will be thick enough now that the tank baffle and tank skin are prosealed together as one. The rear most row of #19 holes in the tank skin will be dimpled. The matching surface on the spar flange will be either dimpled where possible, or machine countersunk. There are several places where you cannot dimple the spar flange due to interference. On the tank, all the dimpled #19 holes will screw into the K1100-08 counter sunk nut plates. On the tank skin, all the machine countersunk #19 holes will screw into the K1000--08 nutplates.
