Top cowl panel thickness

[Battson]

My cowl was an inch or so longer than the stock 2024 T3 aluminium templates provided with the kit, so I made mine from aluminium sheet. I measured a couple of panels for the right thickness adn ordered 0.025" sheet, but.........

I failed to notice that the top cowl is normally made of thicker metal than the other 4 panels. Bob has specified this somewhere.

As a consequence, my top cowl panel drums a lot. You can see this in any of my videos which show the panel, because the slower frame rate captures it. The oil dipstick door is the easiest place to see it.

What thickness metal have people used? Specifically those who are flying and know that it doesn't drum!!

[S Lathrop]

I made mine from .040 thick aluminum.

[whee]

In the 1999 Combined Beartracks Bob specifies 0.032 2024T3 for the top panel. The width of the top panel could vary which will obviously affect drumming. I'm pretty sure 6MKs cowl was build to Bobs spec and it didn't drum.

[Steve W]

Battson, if you want to stiffen a flat panel that's already painted, get yourself some 3M DP-190, an applicator and tip, make one or two 1/2" angle strips and glue them to the panel. Do this off aircraft so you can cure the assembly with some compression on the strips. I've used the stuff to attach the door skins to the steel frames, gear leg fairings and have used it on other projects. On my Glastar, I glued the trailing edge skins at the top of the cove skins. If you do it correctly with proper preparation, it is incredibly strong. It ends up with a straight edge without the puckering from all the rivets. When my boot cowl is in it's final place, I plan on forming a piece of angle and gluing it on the sides to stiffen the skins. Do the research on line. It's amazing stuff.

[bestbearhawk1231]

We used DP-190 at the FBO I worked at for interior work. Don't remember using it for metal to metal but I am sure it would work well. The applicator and mixing tips make epoxy very clean and convenient. There was another DP product that we used with a shorter curing time. All the 3m DP epoxies that I was exposed to worked well.

[Battson]

Battson, if you want to stiffen a flat panel that's already painted

I had some cracks developing as a result of the vibration in that panel, so I am committed to making a new one.

[Battson]

Results are in.
Using a 0.032 top cowl instead of the 0.025 one makes a huge difference. There is zero vibration by comparison, definitely always use 0.032 alclad for the top cowl.

I used even thicker metal for my oil access door, and that doesn't move at all now either. When it was made of 0.025 the air pressure and vibration used to play havoc with the oil door.

[Mark Goldberg]

We give that top center piece of cowling in .032 with our kits. Mark

[whee]

Out of curiosity what’s your bottom cowl made of? 0.032?

[Mark Goldberg]

The kits come with .025 everywhere except that top center piece of .032. MG

[Battson]

Out of curiosity what’s your bottom cowl made of? 0.032?

Mine are made from 0.025 Al