To drill the holes in the cowl for the F-12118 cowl attach plates, Van’s instructs the builder to run a #30 drill through the hole in the nutplates and drill lead holes in the lower cowl from the backside. I ran into a small issue here, in that, the stiffener riveted onto the right side of the firewall prevented my drill from squaring up with the nutplate. I tried to use my angle drill with the short threaded drill bits, but the body on it is so long that the slope of the lower cowling interfered. Next I tried my Harbor Freight 90 degree drill that has a much shorter body and was surprised to find the drill bit does not go very deep into the chuck, making the drill too tall to clear the stiffener.
The drill clearance issue was solved by using the Dremel outfitted with a cutting wheel to shorten the drill bit. After about 10 seconds of cutting, the drill bit was shortened enough so the body of the drill would clear the stiffener.
Shortened #30 drill bit in the small 90 degree air drill ready for
action.
The #30 drill bit was run down through the nutplates on the F-12118 cowl attach plates from the top to drill through the lower cowling. The four #30 holes will need to be enlarged to #19 after the cowling is removed.
#30 holes drilled through the nutplates on the F-12118 cowl attach plate
into the lower cowling.
The F-1285 cowl bottom close-out was worked on next. The F-1285 cowl bottom close-out is a plate that hangs from a bracket and covers the long slot for the landing gear. Instillation involves bending the closeout to match the curve of the lower cowling and mounting it onto the F-1285B-1 bracket which is hung from the center landing gear mounting bolt. Typically, a nut and screw are used to attach the F-12118 close-out to the bracket … but think the nut is going to be changed to a nutplate at some point in the future. During the initial test fitting, it was determined the mounting hole in the F-1285 cowl bottom close-out did not align with the hole in the mounting bracket. The close-out needed to be moved forward a little more … to accomplish this, the aft edge of the landing gear cutout was elongated a little allowing the plate to move forward so the mounting holes would align. After the mounting bracket issue was resolved, tape was placed on either side of the cutout to be used as a visual reference for positioning the F-1285 cowl bottom close-out for clamping so it would be centered on the slot when drilling the holes into lower cowling.
With the F-1285 cowl bottom close-out now attached to the F-1285B-1 bracket and centered over the slot in the lower cowl, the #19 holes were drilled into the lower cowl. A combination of #19 Clecos and screws were used to hold placement as holes were drilled into the lower cowl using the nutplate holes in the F-1285 cowl bottom close-out as the drilling template.
#19 holes drilled into bottom cowl using the F-1285 cowl bottom close-out
as a drill guide after the slot aft of the landing gear tube was elongated a bit allowing the close-out to be moved forward so it could be attached to the bracket not in view.
All that is left to do is install the eight nutplates onto the F-1285 cowl bottom close-out, enlarge the four holes for the F-12118 attach plates to #19 and the lower cowl mounting system will be finished. Later in a few days a fiberglass air duct will need to be bonded onto the inside of the lower cowling by way of a fiberglass layup. This duct will supply cooling air for the oil and water coolers.
