Cowl Flange

When I built the diffuser, I used the cooling inlet cutout as an endpoint. The intention was to use it as a mold for the cowling flange.

To create the flange that maintains the duct shape and matches the baffle, I used the inside of the baffle as the mold. After trimming the aluminum baffle flush with the rough opening of the inlet, I taped off both the inlet and the cowl with tape and then waxed it for a mold release.

I made the layup in multiple stages. Since this was the case, I used West Systems epoxy so that did not need to sand it between layers. This could have been done with vinylester but I wanted a long working time to make sure things were right. The first step was to glass the corners with glass cut on a bias.

After the corners were mostly cured (using a radiant heater to speed the setup), I went  back and glassed the sides, top and bottom.

Using an Exact knife, I trimmed the the fringe back flush with the cowl.

The next step was to create a reference flange so that I could line things up in the same location once the cowl was off. For this I used a lighter glass cut on a bias so that it would follow the sharp curve of the cowl. I used polyester resin for this step to speed up the cure time.

After it all set up, the cowl and baffle were remove and this is the result.

Next step is to put the cowls together off of the airplane and glass the flange into place from the inside of the cowl using the reverence flange to align everything. From there the flange needs to be trimmed to its final size and the aluminum baffle needs to be cut back to meet it.