Continued working on fitting the cowling:
1. Filed and sanded some more on the flange part of the cowl halves. When they seemed like they were fitting reasonably well, I clecoed the upper cowl into position, then hoisted the lower one using a pair of adjustable straps.
2. This led to a long series of filing and sanding, then putting the lower cowl back on, then taking it off and filing and sanding some more, etc. for hours and hours.
3. Gradually, things started fitting better and better, until I was confident enough in the fit that I drilled and clecoed the top and bottom cowls together at the inboard side of the inlet holes, and also drilled and temporarily clecoed the lower cowl to the fitment jig. The fit I achieved was not exactly what I initially wanted, because it leaves a bit of a flat area showing on the lower cowl, below the spinner. But this really couldn't be helped, because I'd long ago fitted the upper cowl based on where I thought the spinner would fall. This assumption was driven by the fact that I couldn't actually fit the lower cowl at the time, nor even simulate it. If I had been able to fit it back then, I would have found that even with the cowl halves assembled as tight together as possible, the "spinner circle" of the cowl is about 13.5" vs. the 13" diameter of the spinner. The only way I could have made the front propeller hole any smaller would be to cut away in inordinate amount of the cowls, which would have a). made the two inlet holes too small for good cooling, and b). would have interfered with the installation of the horizontal row of Skybolt fasteners. So I will just live with the small flat area.
4. Removed both cowls and prepared to install the hinges and Skybolt fastener plates for the lower cowl.
5. Cleaned the firewall edges and firewall flanges with mineral spirits, then dried them and applied globs of Fire Barrier 2000 into about 2/3 of the holes along the flanges of the firewall. Smoothed them with my finger. I also added the sealant to the holes where the magneto leads pass through, and also to a "Y" in a wiring bundle that seemed to need it.
6. Trimmed two Skybolt tabs to fit on the lower left edge of the firewall. These will be installed tomorrow, after the sealant dries.
7. Took careful measurements of the cowl split-lines, extended these measurements onto the sides of the fuselage, then spaced the last remaining three Skybolt fasteners on the left side. I then positioned, clamped, drilled, and clecoed them in place. The lowest Skybolt fastener on the firewall edge should now be exactly in line with the horizontal row of fasteners on the cowl. Fingers crossed.