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  #1  
Old 09-30-2018, 04:36 PM
JDA_BTR JDA_BTR is offline
 
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Location: Baton Rouge, LA
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Default Baffle RTV

I ran into the step asking me to put RTV on to seal the gaps between the baffle and the engine. I assume that is everywhere on top where air can go out without going past a cylinder fin. There are places where the baffle does a good tight fit at the fin edges and I wonder if I really need RTV there.

Or is this intended to be mainly sealing the baffling interface to the engine CASE? If I did RTV between engine case and the baffling, along with sealing some small holes in the baffle joints, that would be pretty efffective. In that case no RTV on any cylinder, just baffle/case and some baffle corners.

Anyone have any pics with arrows of what to seal if doing it perfectly by the plans?
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  #2  
Old 09-30-2018, 04:44 PM
Kyle Boatright Kyle Boatright is offline
 
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Generally, you are sealing the baffles to the case, but the objective is to close any airpaths that don't push air through cylinder fins, the oil cooler, blast tubes, or SCAT going to heaters, carb heat, etc.

Even if you don't see a gap between the aluminum baffles and the case, a bead of RTV is a good idea to eliminate relative motion between the two, preventing fretting and wear on the baffles or case.
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  #3  
Old 09-30-2018, 04:56 PM
JDA_BTR JDA_BTR is offline
 
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Should I steer clear of the baffles around the cylinder covers? Or is everything fair game?
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  #4  
Old 09-30-2018, 05:05 PM
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Ironflight Ironflight is offline
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Quote:
Originally Posted by JDA_BTR View Post
Should I steer clear of the baffles around the cylinder covers? Or is everything fair game?
Anywhere an air molecule can escape is fair game....
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  #5  
Old 09-30-2018, 10:24 PM
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RV-14E RV-14E is offline
 
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Default

Help keep that precious air going over the cylinders.

Here's part of what the plans specify, from when I placed the baffles:

Left aft baffle.



Forward baffle.



Here you can see various nooks and crannies sealed (from when I installed the control cables). Note the forward area along the forward of the crankcase, the areas around the blast tubes, prop cable and other little areas.



Here you can see the rear of the crank case sealed as well as some areas along the rubber seals (from when I riveted the upper forward fuselage skin).

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  #6  
Old 10-01-2018, 05:02 AM
JDA_BTR JDA_BTR is offline
 
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I see it better now. Thanks!
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  #7  
Old 10-01-2018, 05:08 AM
BillL BillL is offline
 
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Default They are hard to see and access, but . .

Don't forget to look closely at the intersection baffles between the lower cylinders. They were a huge leakage area for my factory M1B.

Edit: and . . did you check for the flashing on the through fins around the spark plugs?
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Last edited by BillL : 10-01-2018 at 05:26 AM.
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  #8  
Old 10-01-2018, 05:08 AM
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DanH DanH is offline
 
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The sealant you want is Loctite 598.

https://www.henkel-adhesives.com/us/...te_si_598.html

Available in a 300ml caulk tubes or small squeeze tubes. In the US, Permatex Ultra Black is the same product. In additional to not being monkey butt orange, it is remarkably tough, oil resistant, and has a good temperature rating.

It's not hard to understand what you want to accomplish, which is to make sure every molecule of cooling air (1) remains in close contact to hot parts, and (2) actually gets to the hot places.

A light bulb held under the engine will highlight gaps.











The problem with wraps is usually air leaking from the sides, which means it does not cool the area around the lower spark plug. There are a whole lot of fins down there, but they won't do you any good if the air gets sidetracked.

BTW, Lycoming places a rubber comb between the fins, which blocks some flow and often worsens the wrap fit problem.

Along the same lines, engine shops often add a bead of silicone across the baffle in an attempt to stave off chafing wear. However, if the silicone is up between the fins, it blocks flow.







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Last edited by DanH : 10-01-2018 at 06:07 AM.
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  #9  
Old 10-01-2018, 05:37 AM
Kyle Boatright Kyle Boatright is offline
 
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Quote:
Originally Posted by DanH View Post
The sealant you want is Loctite 598.
The general description of the product is RTV. What makes this RTV different than the black high temp RTV from the parts aisle at Wal-Mart?

For what it is worth, I've been using the high temp black stuff from Wal-Mart/NAPA/Wherever for 20 years without any problem...
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  #10  
Old 10-01-2018, 05:42 AM
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Larry DeCamp Larry DeCamp is offline
 
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Default Dan H question ?

3M Fire barrier 2000 really sticks to aluminum well and is GRAY. Any reason not to use it for sealant ?
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