I did something rather stupid that has caused me to rebuild my lower cowling. In the lower corners I had used a metal shrinker to form the metal to hug the curve. I had wanted to use all flush screws so dimpled the screw holes. I soon realized that was a big mistake as after a couple times on and off with the cowling I was noticing incipient cracks in some of the dimples. I tried drilling small holes to stop the cracks, but one cracked through to the edge. If it was just one I would just try to patch it, but there is a total of 6 screw holes I dimpled in the shrunk metal and will probably crack through. Remaking the lower cowl is about twice as hard as the initial build. All the screw holes on the firewall, cowl doors and nosebowl need to line up. As it turns out while remaking it, I discovered that I had interference between my cowl flaps and exhaust mufflers. I modeled my cowl flaps after Battson's and didn't have the exhaust system on the engine when I built the first cowling. I believe I know why I have interference and he didn't. Due to my cold air intake, Clint built me an exhaust system with the two back cylinders dumping into the pipe that sweeps back from the front cylinder to fit the cowling. Looking at pictures of the 3 into 1 system I now realize that my exhaust moves the mufflers back 5 to 6" in comparison. Consequently, I will be relocating my cowl flaps up the side of the cowling versus in front of the tunnel. I measure about 90" of outlet area at the tunnel, with a lot of that partially blocked by the mufflers. Planning on about 40" of cowl flap outlet, will see how that works before enlarging the tunnel outlet. I'm glad I found this out now before I had everything painted, put together and thought I was close to flying.
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