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  #1  
Old 08-20-2020, 09:22 AM
KayS KayS is offline
 
Join Date: Jul 2009
Location: lake constance
Posts: 324
Default Cylinder 3 and 4 lower baffles

Hi All, didn't find what i looked for in this forum... In preparation for first flight i sealed all that small leaks in the upper and lower baffling. Then i recognized a huge gap on the rear and lower part of cylinder 3 and 4. It's hard to see, I even had trouble to get my cell phone into place to make a pic.

The gaps are between the crank case and the lower "circle shaped" baffles that cover the inner portion of the cylinders. The gaps protrude pretty far to the top. I could throw at least three tubes of RTV on the problem but not sure if that is the correct way to deal with it. I see no chance to rivet something on.

What did you guys do here?

Any help is very appreciated.

Cheers
Kay
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  #2  
Old 08-20-2020, 12:25 PM
fixnflyguy fixnflyguy is offline
 
Join Date: Jan 2006
Location: Winston-Salem, N.C.
Posts: 1,325
Default Leave them..

No real need to seal the lowers in my opinion. The just direct flow out of the high pressure area around the cylinders.. see mine.
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  #3  
Old 08-20-2020, 12:33 PM
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SeanB SeanB is offline
 
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Location: Colorado Springs
Posts: 587
Default

I think I understand which area you are descibing. Believe I've heard of a few builders placing foil heat tape there to cover. Can carefully lay in some RTV on top.
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  #4  
Old 08-20-2020, 03:57 PM
OZCleco's Avatar
OZCleco OZCleco is offline
 
Join Date: Dec 2018
Location: Maylands, Western Australia
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I ended up lining the lower baffling in its entirety with high temp silicone sheeting, and RTV everywhere else. The engine was operating far too hot so this was one of many mods that intended to make sure every molecule of air was passing through the cooling fins.

The lower inter-cylinder baffles had astonishingly large gaps. They also had substantial fretting marks from wearing against the cylinder fins. The silicone sheeting put an end to that. The cylinders wraps received the same treatment.

Worked a treat. I'll attach some examples.
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Last edited by OZCleco : 08-20-2020 at 04:40 PM.
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  #5  
Old 08-20-2020, 04:30 PM
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Foghorn Foghorn is offline
 
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Location: Virginia Beach
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This thread has some great baffle/cooling info.

https://vansairforce.net/community/s...hlight=Baffles
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  #6  
Old 08-20-2020, 05:08 PM
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DanH DanH is online now
 
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Quote:
Originally Posted by KayS View Post
Then i recognized a huge gap on the rear and lower part of cylinder 3 and 4.

The gaps are between the crank case and the lower "circle shaped" baffles that cover the inner portion of the cylinders.
That spot is often overlooked. Take a look at the tab in the red circle below. See how it has been bent 90 degrees to the rear baffle wall? It's flat when it comes out of the box, and lots of baffles get installed without that section being bent to fill the giant gap at the cylinder base.
.
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  #7  
Old 08-20-2020, 09:15 PM
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OZCleco OZCleco is offline
 
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Location: Maylands, Western Australia
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Quote:
Originally Posted by DanH View Post
That spot is often overlooked. Take a look at the tab in the red circle below. See how it has been bent 90 degrees to the rear baffle wall? It's flat when it comes out of the box, and lots of baffles get installed without that section being bent to fill the giant gap at the cylinder base.
.
I'll add to the chorus of voices confirming how effective Dan's advice was in that thread!

Last edited by OZCleco : 08-20-2020 at 09:19 PM.
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  #8  
Old 08-21-2020, 07:34 AM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
Posts: 5,745
Default No magic, just a little difficult.

Quote:
Originally Posted by KayS View Post
Hi All, didn't find what i looked for in this forum... In preparation for first flight i sealed all that small leaks in the upper and lower baffling. Then i recognized a huge gap on the rear and lower part of cylinder 3 and 4. It's hard to see, I even had trouble to get my cell phone into place to make a pic.

The gaps are between the crank case and the lower "circle shaped" baffles that cover the inner portion of the cylinders. The gaps protrude pretty far to the top. I could throw at least three tubes of RTV on the problem but not sure if that is the correct way to deal with it. I see no chance to rivet something on.

What did you guys do here?

Any help is very appreciated.

Cheers
Kay
RTV might go farther than you think. This is an often unseen, and large loss area. It was the worst I found the Vans M1B. I had the luxury, and luck, to find it early and removed the intersection fairing to bend and shape to get it a little better. You can (and should) make an extension for the RTV tube and get up in there more easily. Not going to be pretty, but unseen anyway. Anyone who knows to look will appreciate the challenges.

Another thought - that intersection baffle is held up with a spring. IIRC, it is "stopped" by an edge up against the top fins of the cylinder. You might look straight from the side and see if that is too far out. If the gap is really big then it has to have shifted. If so a screwdriver could push it back towards the case and balance the gaps. It does float around quite a bit until held with the spring. You could release the spring and do a better job, just don't let go of that "s" piece that holds it up, out some safety wire on it.

Good luck!!
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Last edited by BillL : 08-21-2020 at 07:46 AM.
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  #9  
Old 08-21-2020, 11:34 AM
KayS KayS is offline
 
Join Date: Jul 2009
Location: lake constance
Posts: 324
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Thanks for the inputs folks! Will order some more tubes of RTV and see how far that brings me.

For me it's to late now but i strongly advise others to seal all that gaps right after installation of the baffles. Should be pretty easy as long you have access and nothing is obstructed by exhaust pipes, oil filler tube and stuff. Now it's more of a horror story. But we'll survive that too.

Does anybody have an opinion on using heat resistant aluminum tape for baffle sealing?
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  #10  
Old 08-21-2020, 04:00 PM
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DanH DanH is online now
 
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Quote:
Originally Posted by KayS View Post
Does anybody have an opinion on using heat resistant aluminum tape for baffle sealing?
It's fragile. Permatex Ultra Black (aka Loctite 598) is the hot ticket.

http://tds.henkel.com/tds5/Studio/Sh...EN&plant=WERCS
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