Phil, After rereading your message, I guess you meant to use the firewall "flange" to fasten the cowling to as well, so obviously .040" thick material may not be enough for that job. I'd use something like 3/4"x3/4" .060" thick 6061-T6 angle (each only an inch long at the most...not continuous) would work fine...with nutplates on the back side, spaced about 6" apart. Another option for fastening the firewall stainless around the edges is just a narrow strip of something like .040" aluminum screwed on top of it, conforming to the outside shape of the firewall. Lots of ways to do it, for sure.
What I did on N56ML to retain the cowling was six of the little .060" 1" wide angles (lightened and rounded) across the top (turtledeck), and a piano hinge on each side with half screwed to the firewall and half riveted to the cowling. Again, narrow and light, not big fat hinge material. The narrowest hinge (1/2" or so) is plenty good for that job. Pull the hinge pins and you can get the cowling off in a hurry. The top and bottom of my cowling was done the same way...piano hinge halves. I much prefer that to the many screws that hold the cowling onto to N891JF, and when armed with only a screwdriver, I can get the cowling off of N56ML in about a minute and a half, vs about five for N891JF. This may sound insignificant, but if your engine was on fire due to a backfire you'd care! -- Mark Langford ML at N56ML.com http://www.n56ml.com
