Cowling Installation Problem
From Russ Erb:
The obvious statement: 0.016 stainless steel firewalls are flimsy, move around, and cannot be expected to maintain their position without external support.
Lesson to be learned from this: When building your cowling, build the boot cowl first (the sheet metal skin between the firewall and the front doorpost/instrument panel). Then make sure the COMPLETE boot cowl, including the exhaust tunnel, is in place to support the firewall in it's proper position while you build the cowling. Since the back edge of the boot cowl is supported by 4130 flanges welded to the structural tubing, it won't move around. You'll note that the cowling is supported mostly by the boot cowl, not by the firewall.
"Hmm, Russ, what gross buffoonery occurred that made you think this was worth mentioning to the group?"
Funny you should ask...
I built the boot cowl, then removed the two side pieces thinking I would need access to the back of the firewall while building the cowl, or some other stupid reason that I don't recall that turned out not to be true. I built the whole cowling and had it working nicely. Then I tried to put the boot cowl back on. One side was so misaligned it had to be totally redone. The other side wasn't aligned, but was close enough the problem disappeared when I drilled out the #40 holes to the screw holes. While I was at it, I redid the top portion of the boot cowl because of some edge distance problems.
Finally, I'm waiting to get yet another "last" aluminum sheet to redo the cowl doors. When everything else moved around and became rigid, they didn't line up anymore (about 1/4" off), so the camlocs won't go in their holes. I think I would have avoided all (most?) of this if I had applied my own advice above that I learned to late to be of use to me the first time.
Now YOU have no excuse.
#164, Rosamond CA