Baffling critiques?

[crabandy]

Almost done with my baffling, at least I hope so. I traced the front center metal baffling on the cowl and extended the inlet ramps via foam/glass/filler to the line I traced. After a few hundred put the cowl on, fit baffle material take cowl off iterations the fabric seems to hug the cowl fairly well. Critiques before I seal and rivet it?

Outside inlet #1 cyl

Behind spinner #2 cyl inlet ramp

Inside inlet ramp #2 cyl

I had to stretch the metal on one side of the center baffle

[crabandy]

Has anyone added a stiffener above #1 cylinder? The screw orientation of #1 cylinder's baffling leaves it kind of "flexible" at the top of the rocker cover. I think there would be enough pressure to push it out slightly and leak air. Thoughts?
Thanks,
Andy

[LettersFromFlyoverCountry]

You're going to want to cut those air dams down.

[DanH]

(1) You must arrange unattached seal rubber so that plenum pressure pushes it against the mating surface, not away from it. In the photo below pressure will push the rubber away from the back side of the fiberglass...a big leak. Attach the rubber to the fiberglass. Plenum pressure will hold it against the aluminum.

(2) Looks like you have 12, maybe 13 overlaps around the perimeter. Each overlap is a leak area 1/16" high and a 1/2" to an inch wide. It adds up. Some overlaps are necessary, but.....

Leaked mass flow contributes zero to cooling and 100% to drag.

[crabandy]

Thanks for the critiques!

[LettersFromFlyoverCountry]

It's up to you but you might want to wait until you've flown it a bit. It doesn't take long for the rubber to "imprint" on the fiberglass, you can see where you're getting a good seal and where you're not.

[scsmith]

Originally Posted by LettersFromFlyoverCountry

You're going to want to cut those air dams down.

I have trimmed my air dams twice, 1/4" off each time, and they are still too big. It is hard to trim them while installed. I wish I had made mine removable with bolts and plate nuts instead of riveting. See Ironflight's post about doing this. at least, I think it was him.

[LettersFromFlyoverCountry]

Stein Bruch gave me a good idea when I was trimming mine (and I'll be trimming them again). He had a small piece of stainless that you put behind the air dam to protect the fins on the engine and then carefully cut with a dremel and a cutoff wheel. It worked great.

[Flying Scotsman]

Not flying yet, but very close...second the removable air dams. Not much additional work, and I can remove them and do a nice job of cutting them down if/when I have to.

Also, had many, many fewer individual pieces of baffle material...basically two down each side from front to back, two across the back, two on the front by the prop.