Step 2: Preparing and fitting the bottom cowl

Mark a centerline on lower cowl for the notch you will cut for the nose gear. Measure out a 1 3/8" wide notch and about 12" deep and remove the material.



With the notch cut out in the lower cowl you can now slide the lower cowl in place and begin fitting the bottom to the top. You will need to improvise ways of holding the cowl up from beneath. Fitting the lower cowl to the top is a LONG process. Be patient and take your time. Stop every now and then to make sure you haven't forgot anything.

On my cowl, the lower half of the cowl around the spinner area and air inlet holes, I needed to trim about 1/4" off. You want to make sure the inlet holes are concentric and of the right size as well as having a 13" diameter area where the prop spinner goes. I almost didn't notice this until I had the bottom cowl in position the first time and saw that there was a good portion of the cowl below the spinner.



With the front edges trimmed to produce the right diameter holes and a straight fit, I positioned the cowl and marked trim lines along the aft edge where it hits the firewall. Use the same method as the top cowl, drawing a line back from the firewall 2" or so and then measuring forward from that line. Do the same for the bottom edge. Remove cowl and trim.

While the cowl is off for the first trim, go ahead and install the vertical hinges along the firewall. This will help hold the cowl in place when fitting.



Reposition cowl and check for fit. I used cutoff wheel to take bulk of material off initailly, staying back from my line about 1/16" and then sanding down towards the line using some 40 grit paper. Note adjustments on cowl, remove, sand, repeat. I probably removed and sanded 15-20 times working on a good fit. When sanding the aft edges, watch the front area of the cowl to make sure everything lines up well. I used clamps on the front in alignment.



When you get close to getting a good edge along the aft edges it is time to trim the sides where the top/bottom meet. Use some duct tape to hold the top/bottom together. Instead of using the measure method, I reached inside the inlet hole with my arm and marked a trim line with a fine tip marker using the edge of the top cowl as the reference. Towards the aft end, I did have to measure since my arm isn't long enough to reach all the way back.

Remove cowl, trim, sand, reposition. Here is another spot where you'll take the cowl off a dozen times make small corrections, sanding high spots, getting a good split line.

When you've finished sanding and have the sides lined up, the aft edges fit well, it is time to drill the vertical and bottom hinges to the cowl. The bottom you can do yourself by laying on the floor and with one hand reaching in the outlet area to hold down the hinge and drill with the other. For the sides you really need a partner. One to reach in the outlet and hold the hinge while the other drills/cleco's 3 or 4 holes.







(My time to fit the bottom cowl was about 10 hours or better over two days. I went slow and took lots of breaks, stepped away for awhile. You could probably do it faster.)