I spent way too much time on this! I took the Melville cowl and prepared to trace the outline on my existing layout of the firewall done using the plans pattern. I set up some fence blocks to postion the cowling for tracing. The second pictures shows the slight mismatch in radius that I had previously notice, which is why I was bothering with this detail in the first place! The Melville cowling requires that the firewall extend down further than the plans pattern. Basically the bottom of the tracing need to be at WL 0.9 which is the bottom of the flat part of the fuselage. The plans pattern stops at approximately WL 5.125. That means that the bottom edge of the lower cowl outline needs to be placed 4.225 inches lower that the stock pattern. I spent a lot of time figuring this out! For the upper 2/3 rds of the firewall I will use the stock pattern and for the lower third I will use the actual cowl outline which I transferred to plywood and cut out. I noticed that the tracing (and the actual cowling) is slight different from right radius to left radius, so I am using the full tracing rather that the symetrical half style. Hopefully all of this effort will result in an easier time fitting the cowling, rather that having to add or subtract material at the firewall/aft fuselage at the late stage of cowling fit up
Lower Cowl and Fences In Position
Mismatch of Plans Pattern to Actual Cowling Outline
