Thursday, January 21, 2010

I finally got around to finishing my ( new style ) cowling.

The current version of the manual is incomplete and incorrect. I used a combination of advise from Roger at Zenith, the forum and the HBH video.

Here is how I did it:

1) Fit the top and bottom halves together, sliding the top half into the lip. I then made sure the the seam between the top half and the recessed lip of the bottom half was OK.
2) Clamped and taped it together.
3) Determined the center of the top half of the cowl and the center of the airplane. I then extended forwarrd the rivet lines on the side of the fuselage to use as reference for getting it even.
4) I then determined the angle of the cowl and got it centered and even. I used the seam lines on the cowl in conjection with some rivet lines on the fuselage to get it even and centered.
5) Once I had that I then marked where I neeeded to trip the cowling to clear the gear leg and windshield. I only trimmed the gear leg hole a bit, the molding supplied a large amount of clearence. I trimmed a small a amount of the top cowling to clear the windshield and sealing.
6) Once I had the the cowl trimmed I then drilled and clecoed the front four holes to join the top and bottom halves. I determined my safe area of the fuselage flange taped the cowling into place and drilled the cowling into the fuselage flange. I made the holes A4 sized.
7) I removed the cowling. and clecoed the nutplates onto the bottom cowl for the forward holes. I put the nutplates on the "wrong" side so the barrel was pointing away from the plane.
8) I got each plate parallel with the lip of the cowl and drilled one hole with an A3 bit and clecoed. I then drilled the remaining hole.
9) Removed all the nutplates and drilled the center hole out to AN3.
10) Cleaned & deburred the holes
11) I applied a slight countersink to the A3 holes that hold the nutplate using a hand reamer. Use A3 blind rivets to secure the nutplates. Do not drill out the holes on the nutplates.
12) I drilled out the holes on the top cowling to AN5
13) Using a flat riveter head I riveted the nutplates to the inside lip of the bottom half so the barrel pointed into the airplane.
14) I clecoed the nutplates to the fuselage flange where the cowl met and used a similar technique.
15) At this point I did not install the left and right nutplates where the top and bottom halves of the cowling connect to the fuselage.

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