I began installation of the LH lower engine cowl section and spent quite a bit of time getting the placement just right considering the size of the cowl door, visual asthetics, and making sure there was room to complete routine maintenance such as spark plug removal/installation.
Once I had identified where I wanted the top edge of the cowling to be located, I drilled a single hole in the forward and aft edges to secure its location. I then marked and trimmed most of the excess length off the aft section of the cowl to permit it to roll better as I continued the drilling process.
Next I located and trimmed the "U" channel support that will be located along the top edge of the lower cowl. After laying out the rivet pattern, I first drilled the holes into the "U" channel, then back drilled them onto the lower cowling. By installing this support at this juncture I added stability to the lower cowling and eliminated the possibility of waviness being inadvertantly induced to the cowl during drilling.
Initially, while locating the cowling for trimming, I had used clamps to secure the cowl but noticed the nose bowl would flex about 1/16" and I did not like that movement as I feel it might induce stress or change the front gap. To avoid this flexing, I switched to using a seat cushion as a wedge to help roll the cowling into place and hold it while I marked the areas which needed trimming.
I continued by carefully trimming the forward edge of the cowl a little at a time until it perfectly rested into the nose bowl flange.
With the cowl still supported with the cushion wedge, I clamped the inboard edges (forward and aft sides) and proceeded to drill the fastener holes in a sequence of two holes on the aft edge followed by two holes on the forward edge and so forth.
I did not drill the two inboard-most fasteners on the front edge as I wanted to wait until I locate and drill the RH cowling and determine where the overlap of these two pieces will occur.
Supporting cowl with cushion to avoid stress on nose bowl
"U" channel located along the top edge of lower cowl
