Baffles combing?

RV8Squaz · #1 05-01-2009, 08:21 PM

Hey Guys,
I was wondering if you know of any tips or techniques to prevent the cylinder cooling fins from wearing through the baffles, particularly the curved parts that wrap around the bottom half of the cylinders. I have 350 hours on mine and I removed some of the baffles for some minor repairs and noticed the combing. I was thinking about gluing or pop riveting some baffle seal material on the inside of the curved pieces to prevent further wear. You guys got any other ideas?

Jerry
RV-8 N84JE

aerhed · #2 05-01-2009, 08:41 PM

I've seen RAM engines etc. with a layer of RTV laid on the chafe area and cured before installing. Seems to kinda work, longer than bare aluminum. I suppose you could painstakingly make them out of stainless.

scsmith · #3 05-02-2009, 12:03 AM

I've been thinking of putting a 1/4" wide by 1/16" high bead of RTV across the curved part, maybe 1/4 the way from the bend to the end. Can anyone report whether this helps? I suppose the small gap to the ends of the fins will affect cooling a little? Maybe made the bead thinner so it doesn't do that.

DanH · #4 05-02-2009, 06:01 AM

I'll be lining the inside surface of the cylinder wraps with a sheet of fiberglass fabric impregnated with black Loctite 200F silicone. It will reduce baffle wear, but the real goal is sealing the wraps to the fins...a gasket of sorts.

A bead of RTV across the wrap and installed while wet may squeeze in up between the fins and block desired flow area.

An RTV bead across the wrap and cured before installation will space the wrap away from the fins. Air that leaks out the side of the wrap does no cooling.

If the "comb" wear pattern is limited to the area where the wrap goes around the lower square edge of the cylinder head fins, you need to bend the wrap to match the square edge. Van's baffles straight from the box are not bent to match. The detail is often missed by builders.

The Lycoming-installed rubber strips intended to eliminate fin ringing often space the baffle wrap away from the fins. More cooling loss.

panheadmark · #5 05-02-2009, 06:34 AM

Dan, I'm interested in using the technique you describe, I did a search for Loctite 200 and it comes up as a thread locker and not a silicone. They show other high temp silicones, just wanted to get the right stuff. Sounds like a very good way to do the lower baffles. Thanks.

Mark Erickson
RV 9A #91317
finish kit

DanH · #6 05-02-2009, 02:45 PM

<<I did a search for Loctite 200 and it comes up as a thread locker and not a silicone. They show other high temp silicones, just wanted to get the right stuff.>>

Whoops, I dealt you a typo. "200F" was a reference to a temperature rating. The typo was substituting 2 when I meant 5; the actual temp rating is 500F. Sorry.

I can make it right <g> The material is Loctite 598. Here's the Loctite .pdf:

http://tds.loctite.com/tds5/docs/598-EN.PDF

drill_and_buck · #7 05-02-2009, 04:26 PM

I remember reading that Vans uses UHMW TAPE on the curved part of the baffle to prevent, or at least retard the combing effect.

I put some UHMW tape on my baffles, but am not flying yet.

Mike Draper
RV-8, CS, TMX0360
N468RV
Fiberglass and fairings.....

az_gila · #8 05-02-2009, 05:44 PM

Quote:

Originally Posted by DanH

<<I did a search for Loctite 200 and it comes up as a thread locker and not a silicone. They show other high temp silicones, just wanted to get the right stuff.>>

Whoops, I dealt you a typo. "200F" was a reference to a temperature rating. The typo was substituting 2 when I meant 5; the actual temp rating is 500F. Sorry.

I can make it right <g> The material is Loctite 598. Here's the Loctite .pdf:

http://tds.loctite.com/tds5/docs/598-EN.PDF

...have a 500 F, even from the aero aisle of Ace hardware....

http://www.acehardware.com/product/i...id=PPC:2074229

I've seen RTV (usually clear) used to make a thin film - and cured before installation - where the cylinder fins are.

I have also seen a PHX overhauler delivered a certified engine with baffle material on the inter-cylinder engine baffles contact area to prevent wear.

Andrew M · #9 05-02-2009, 07:11 PM

chafe when its bonded to the fins (or anything else for that matter) I use a small bead of red high temp rtv cured, then install the baffle with a fresh line on top to bond.

AWM

DanH · #10 05-02-2009, 09:59 PM

<<even from the aero aisle of Ace hardware>>

Well, they're both black and rated to 500F, but the Loctite 598 specification is specific for exposure to engine oil and fluids. The Permatex 81158 is not recommended for engine gasketing. It appears to be intended primarily for seals and weatherstriping.

http://www.permatex.com/documents/td...tive/81158.pdf