Scribe Lines

[lewy]

Hello, We are installing the lower and upper cowls, I have sanded just past the scribe line on the firewall fit of the cowl and the front of the cowl is still touching the spinner back plate. Do I keep sanding until I get the desired gap between the cowl and spinner plate or have I made a mistake some where?? Anyone else go beyond the scribe line to get a good fit. Thanks D. Lewis

[rsipp]

We had the same issue. We had .125 machined off of the spinner backing plate, good clearance now. That was the factory suggestion. We have had to do that on a 4 as well years ago.

Dick Sipp

[rvbuilder2002]

The scribe lines are the true proper trim of the cowl when it is in it's proper shape. Because it is flexible until fully installed, the front portion can push forward towards the spinner.
The danger in continuing to trim is that once finished, you could end up with internal clearance issues (exhaust to cooling duct, oil cooler to muffler, etc). This is likely the reason trimming the spinner later was suggested, instead of shortening the cowl
To gauge where the cowl will actually be when finished, you need to at least start the installation process so that the top and bottom are somewhat clecoed together.
This can be done by drilling only a few strategic holes so that positions can be changed later if needed.