Tuesday, May 3, 2016

Bottom Cowling Tweaked For A Better Fit

After getting the fit of the bottom cowling in the ballpark the previous work session wanted to make sure the proper clearances would be achieved when the upper cowling is installed. After cutting the aft edges of the lower cowling to the scribe lines, decided to use duct tape to hold the positioning of the lower cowling so the upper cowling could be mated. This reveled the left side of the lower cowling needed to be made a little shorter to achieve the desired clearance around the spinner back plate. So the aft edges on the left side of the lower cowling received a little more sanding to pull the lower cowling away from the spinner backing plate.

Not sure all this work was necessary, because I have read where builders have not had the optimum clearances between the backing plate and cowling and Van’s provided a spacer plate to pull the backing plate forward to obtain the clearances. However, decided to try making an attempt to just shorten the left side a little so a spacer would not be needed … plus it will remove the slightly askew from center issue as well.
A piece of 1/8" aluminum was placed between the cowling and spinner back plate to use as a visual reference for achieving the desired clearances. I was working by myself so the yellow strap was used to catch the cowling if the duct tape gave way.

After removing some more material from the aft edges of the left side of the lower cowling, it was clamped in place then taped once again with duct tape so the clamps could be removed to test fit the upper cowling.
After removing material from the aft edges of the left cowling, it was taped back in place and the upper cowling was set in place and Clecoed to the bottom cowl for a test fitting. Now there is a good clearance between the spinner backing plate and the cowling. The metal spacer is not being pushed on as it was prior to tweaking the lower cowling.

Looking at the above photo, one can see the upper cowling which was trimmed to the cut line is just a little too long now and will also need to be trimmed back a little. To gain an idea of where to mark the cut, Bernie came up with the idea of placing blue tape on top of the hinge so it would show through the fiberglass allowing for the cut to be marked from above.
Looking closely at the photo, one can see the aft edge of the blue tape through the fiberglass. This is the cut line and was marked with a red sharpie.

This actually worked out quite well and after a little conservative sanding, the cowling was fitting nicely on the right side. The sanding began on the right side because that side started out not needing any sanding for the first inch because the upper cowling is slightly askew due to the left side of the lower cowling being pulled back a little. Ran out of time so will finish the sanding during the next work session.