I decided I wanted the inside of my cowling to be as smooth as the outside. I first sanded the raw weave with 80 grit. I then did 2 coats of SuperFil, sanding between each application. This is the first coat of Evercoat Uro-Fil primer. I've sanded most of the cowling at this point. I'm going to hold off on doing the lower cowling because I plan on some major modifications.

I still have the original spinner backplate. I won't be using it on the new installation because it's got nutplates installed for a 2-bladed prop. My new Catto prop is 3-bladed so I'll need a new spinner and a new backplate.

I decided the old spinner would work perfectly for fitting the cowling. The consensus among my friends is that I don't want to go crazy trying for a VERY tight fit between the cowl and the spinner. Everyone said a 1/4" was close enough. I had some particle board sitting around so I decided to make a ring that was thicker than the flange--in fact, just enough thicker than the flange to provide a nice, uniform gap between the cowl and the spinner.

Normally, the prop bolts go through the prop and through the backplate. You can't see it in this picture, but there are prop studs that actually fit inside holes on the backside of the prop. These studs hold the prop in place from a sheer/twisting perspective. I made the particle board circle spacer so that I could bolt the backplate firmly to the prop extension without actually installing the prop. I just bought hardware store bolts to hold the combination onto the prop extension.

Here's a picture of the cowling held in place against the particle board ring which is mounted to the back of the spinner backplate.

Before I put the bottom cowling on, I was able to reach inside with an angled drill motor to drill through the fiberglass flange on the cowling into the particle board ring. I clecoed it in place and carefully marked the position of the lower cowling. I then took both halves off the plane and then set them face down on the ground resting on the spinner back plate. I then drilled and clecoed the bottom cowling to the spinner back plate.

Once this was done, I picked up the whole assembly and re-installed it on the airplane via the spinner backplate.

I used blue masking tape to define the line to be trimmed from the bottom half of the cowling. I just used a die grinder with a cut-off wheel to trim the fiberglass.

My Hobby-Aire respirator system really saves my lungs for these types of operations!

Here's the lower cowling re-installed after trimming and a little sanding.

In this case, I used the blue tape to define the spacing for my attachment holes. I first marked where the engine mount interfered with backside access I then marked the desired spacing on the tape and drilled. I carefully peeled this piece of tape off and used it on the other side of the cowling so that the holes would be perfectly symmetrical.

Don't worry, I don't plan on leaving that jog in the fiberglass. I just didn't want to trim any more than was absolutely necessary. While it's possible to graft on additional fiberglass if you get it too short, it's a waste of time and really not a lot of fun!