Chapter 23 – Bottom Cowl TDC

I started out today by marking and then trimming the top cowl aft left side where it curves into the vertical side of the top cowling.

Here’s the trim mark on blue tape (the aft mark).

And then how it looked after I finished.  This is fairly close to what I have on the right side as well.

I then Clecoed the aft-most hole on each side of the bottom cowling, where it interfaces with each wing.

I then drilled out the CAMLOC mounting hole for the second to the last hole on the bottom cowling interface with the respective wings.  I then mounted the second to the last CAMLOC receptacle on each side.

I then took the cowl off and drilled out the second to the last CAMLOC hole on each side.  However, before putting the cowling back on I filled the aft top center gap between the left and right new bottom cowl skins with CF.

After laying up 2 plies of CF on the inside I peel plied the layup.

I then added a ply of CF on the exterior side of the bottom cowl aft top center gap.

I then peel plied that layup as well.

I then remounted the bottom cowling… here you can see the new second to the last CAMLOC positions open . . .

I then determined that the left side gets a -5 stud while the right gets a -6 stud.

Here’s the gap fill layup at the top center of the bottom cowling.  It looks pretty good, although admittedly it may need a bit of clean up and tweaking.  We’ll see how it turns out.

And another side view of the top center gap filled on the bottom cowling. This provides a visual somewhat of how it will look in relation to the spinner flow guide.

I’ve spent a good bit of time over the last couple of days (when I could) searching through the old CSA articles dealing with cowl designs and configurations.

Based on one article in particular I decided to determine my cooling air inlet volume (opening) vs. outlet volume (opening) per side.  The CSA article on the subject mentioned that optimum airflow is attained when the outlet is no less than 1.6 times the size/volume of the inlet.

I made a template of the inside of the armpit scoop and then tested it out against the side opening part of the aft cowl opening template.  Even though comparatively narrow to the vast majority of Long-EZs I’ve seen, my outlet is around 27 sq. inches each side while my armpit inlet on each side is around 10 sq. inches.  If you subtract ~5 sq. inches for the exhaust pipes I’m still around 22 sq. inches for the opening each side.  Clearly that’s an outlet volume 2.2 times the inlet volume.

Based on that CSA cowling article, my cowl aft opening shouldn’t present a bottleneck in allowing cooling air to exit the cowling.

With my ‘fun with math’ part of the evening over, I called it a night!


Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.