It's finally time to start fitting the baffles to the top cowl. The upright baffle parts all start life being extra-tall, and then they get trimmed down so they end just short of the top cowl. You don't want too small of a gap between the fiberglass cowl and sheet metal, which could cause the shaking engine to damage the cowl; you also don't want too large a gap because it prevents the rubber air seal material from doing its job.
But, since the cowl isn't transparent, how do you know where to trim without a lot of tedious trial and error? I used a method suggested by someone else, which begins by using wood strips to elevate the top cowl some known distance above its usual position:
After making sure the gap is even at each corner, you then reach through the gap to trace the contour of the top cowl onto the baffles.
It just happened to work out that a popsicle stick is just the right length to give me a 3/8" offset from the inside cowl contour. I notched the end to locate the tip of a sharpie, then used this contraption to draw a line on the baffles inside the cowl.
This is a picture looking in one of the cowl inlets, showing the line I traced. This worked pretty well and wasn't too difficult, other than requiring some painful contortions to get the pen onto every corner of the baffles while working in a limited space.
After removing the top cowl, I retraced the wobbly line so I could see it while cutting:
Then I removed all the baffle parts (quite a chore).
This is the first time in quite a while that the engine has been baffle-less:
The bandsaw made quick work of the initial trim cuts. I stayed outside the line, since there is some error inherent in this process, and I didn't want to cut off too much too quickly.
Everything goes back on for fitting, for the nth time:
After only one cut, it almost fits! Still a little trimming left to do in the aft corners, where I had a hard time making sharpie marks.
Here's a view into the right inlet, with the top cowl in place. I'll have to trim the cylinder baffles down a lot further once I glue the upper inlet ducts in place, but that will come later. For now, I'm glad I haven't attached them yet, since they would just be in the way.
Next: Yet more trimming…