Cowl fit at bottom firewall

[Gary Wallace]

Im looking for some tips/advice on how to bend the bottom cowl skin in at bottom firewall corners to snug cowl skin into firewall/ boot cowl skin . Has anyone left the skin sticking out? Advice, tips and pics appreciated. Thanks. Gary

[alaskabearhawk]

Not sure what you are referring to. Can you send a picture?

http://www.mykitlog.com/users/display_log.php?user=yeeeha&project=527&category=3583&log=272647&row=16

http://www.mykitlog.com/users/display_log.php?user=yeeeha&project=527&category=3583&log=272684&row=15

I used a slip roller to form my panels.

[Battson]

I think those photos you linked to are 'boot cowl', as opposed to 'cowl'. Question relates to the cowl metal I think.

[Bdflies]

Gary,
I think I understand your question.. I used a shrinker at the corners, to 'tuck' the edge in, a bit. This allows the lower cowl to fit very nicely to the boot cowl. If you don’t have one, Harbor Freight sells shrinkers and stretchers for very reasonable prices.

Bill

[Battson]

I just left the sheet metal flat and let is assume the curve of the firewall. Obviously I put fastening screws close-ish to the edge of the cowl metal, to avoid the bottom cowl 'tabs' by the tunnel from standing proud.
It looks fine, the overlap is so short, it blends in perfectly - if I correctly understand what you meant.....

[whee]

I did mine like Battson. Looks fine. I wanted my tunnel opening tight and small so I used rachet traps and pulled the sheet pretty tight. Most builders don’t and probably shouldn’t do that if they aren’t installing cowl flaps.

[Gary Wallace]

[Gary Wallace]

Its a bit tough to see the gap with all the blue plastic but the gap there is what im referring to. I dont want ro make a mess of the cowl skin is all, tring to shrink it or bend it or whatever

[Gary Wallace]

And bdflies, i do have a shrinker but it takes a bit to get an inch to shrink up enough..it also chews up the skin more than i think i like..not sure yer if i want to ATTACK the skin with the shrinker yet....

[Bdflies]

Looks like you have more 'overhang' than I had.
Gentle nibbles with the shrinker and a light touch with a sanding disc, left it looking good.

Bill

[Battson]

OK - let's back the truck up here.

A tight fit is a problem for later, you want some flex here.
Tight cowl overlaps are hard to get reattached at maintenance time. They tend to scratch paint when you realign them (and inevitably misaligned them). Same goes for dimpled cowl skins at the overlap. At some time past, Cessna started leaving a 1/4" gap there all the way around, and packing the cowling with rubber isolators. It still looked great. Further, if the cowl and boot cowl are in direct contact, it increases vibration and that leads to 'smoking' i.e. corrosive wear, it also causes fretting. It took hundreds of hours of flying, but it happened. This looks awful and everybody notices the overhang because of the black 'smoke' streaming from it, especially when flying in rain.

I have glued cowl anti-chafe tape in that area, so the tape stays put when I remove the cowl. Makes it easier putting it back together. The tape goes all the way around the top of the boot cowl to the bottom (tunnel) on the other side. If you don't allow room for that tape when you build the cowl, you may not be able to add it later. The cowl will be too small / too tight fitting. I highly recommend doing this.

All that being said, the overlap doesn't need to be excessive. An inch is what I used.

[Gary Wallace]

I have a one inch overlap as recommended. Looks like more when hanging out I agree