Thursday, September 24, 2020

Cowling part 1

I never do things the easy way....

I started the cowling a week or so ago.  As is my standard I feel I need to "improve" things a little.  In the case of the cowling I am using quarter turn fasteners (I did this on the 9 as well and was glad I did) and I'm doing some cosmetic alterations as well.  This cowling is much larger than the one on the 9 and there were times when it was difficult to get the lower cowling on and off.  For the 10 I decided to cut the snorkel section out to make it easier to work with while installing and removing.  That requires lots of work and a bunch more quarter turn fasteners.  You will see what I mean below.  Once that is complete there is a strong possibility that I will split the lower cowling in half so that I can install/remove one side at a time.  more fiberglass work and more quarter turn fasteners.  I'll make that call once I have the scoop complete.

The top cowling half gets fitted first.  You can see the overlap with the skin.  If you look closely you can see the blue line I drew 3" back from the firewall edge.  This line helps me measure forward to determine the precise cut line.  Actually it wasn't one single was one big cut and a bunch of iterations of sand, install, measure, remove, sand, get the picture.

There are actually many steps in the process before we get to this point but in this picture you can see I am using my laser level to set the horizontal line.  You can also see the wood disc that I made to simulate the back side of the prop spinner.  This helps me set the gap between the prop spinner and the forward edge of the cowl.

Both cowl halves fitted to the airframe.  You can see the line on the upper cowl where I measured forward 3" from the blue line for a cut line.  The bottom cowl will get cut once I have fitted the top cowl.

This picture shows the method I used to locate the quarter turn fastener holes.  I taped those aluminum scrap pieces to the fuselage skin in such a way that I could fold them back once the holes were aligned with the receptacle location.  This worked quite well but I still have to go back and adjust hole positions.

Here both the top and bottom cowl halves have been fitted to the firewall.  I still have some work on the horizontal line but its getting close!

Using these aluminum scrap pieces I positioned them such that I could hold the scoop in a precise position.  Then I used my dremel and a hacksaw blade to cut along the blue line.

Skip ahead several hours and this is what it looks like.  The scoop has been cut out and the flange has been glassed in under it.  (See picture below)

This is the inside of the lower cowl where you can see the fiberglass flange being worked on.  I still have two layers of glass and lots of sanding/filling/etc to do before this is done.