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  #1  
Old 02-24-2017, 09:52 PM
TimO TimO is offline
 
Join Date: Feb 2005
Location: Wisconsin
Posts: 341
Default Baffle Clearance to Cowl

I don't remember who tipped me off to this, and I couldn't find it on a forum search, so I started a thread about it for everyone else.

Someone told me that they had worn thru or almost thru their cowl because the aluminum engine baffling was rubbing on the cowl top. I just put it on my checklist for the next time I had the cowl off. This week I did, and sure enough on both the left and right sides, I have spots on the cowl top that are wearing in pretty harshly. If I had to guess I'd say I'm worn in maybe .030 or so.
The locations are, if I measure from the front outer corners of the cowl by the air inlet, about 9 or 9.5" in from the front corners of the cowl. The groves run maybe 1.5-2" long and then skip about 4" further back and then there is another spot that hits. With the baffle seals installed, it's tough to get a file on without wrecking the baffle seal, but I did manage to file it down in those areas slightly.
I put some gorilla tape over the spots and flew it for a couple quick flights, and yesterday I pulled the top cowl to check it again and it's still hitting a little. It's pretty good now in most locations with just one really heavy hitting area. I would suggest maybe when you do your baffles, you look at those areas and maybe about 8.5" to 15" back from the front corners of the cowl, I'd lower the baffle sides about 1/8". That should help eliminate the issue. You could go even further lower perhaps.
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  #2  
Old 02-25-2017, 12:22 PM
Gahannaflyer Gahannaflyer is offline
 
Join Date: Aug 2013
Location: New Albany, Ohio
Posts: 49
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I have to agree with Tim's assessment. I found the same thing.

Good call.
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  #3  
Old 02-25-2017, 05:43 PM
BillL BillL is online now
 
Join Date: Sep 2007
Location: Central IL
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Tim, what was your original (static) clearance? i.e. - how much was the engine moving - was it under torque conditions? I am still trying to document how much the engine moves and where the motion is the greatest.
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  #4  
Old 02-26-2017, 03:03 PM
TimO TimO is offline
 
Join Date: Feb 2005
Location: Wisconsin
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Bill,

To be honest I don't know what the measurement was there before the cowl went on. With the pre-cut baffles and pre-cut seals, I did not do anything but line up the cowl and install it as best I could so that the prop was as centered as I could get it in the propeller hole of the cowl.

I can tell you that the wear marks are very thin grooves, so there is not a lot of back and forth action to the movement. It's wearing in a very sharp line on the cowl. With the nice thick silicone seals that we get with the kit, we should easily be able to expand that gap, so if I could do it over again, I would trim them down a little. In fact, my seals got slightly damaged by the file, so I may end up eventually having to replace the seals along the side. Hopefully they sell just the seal kit.
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  #5  
Old 02-27-2017, 07:02 AM
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f1rocket f1rocket is offline
 
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A quick tip when fitting your baffles to your top cowl, line the sides of the baffle with paperclips and lower the cowl into place. This will give you a great indication of the gap between the aluminum baffle and fiberglass top. Make this consistent and don't let the rubber seal get too long and you will have a great seal.
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  #6  
Old 02-27-2017, 07:46 AM
BillL BillL is online now
 
Join Date: Sep 2007
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Quote:
Originally Posted by f1rocket View Post
A quick tip when fitting your baffles to your top cowl, line the sides of the baffle with paperclips and lower the cowl into place. This will give you a great indication of the gap between the aluminum baffle and fiberglass top. Make this consistent and don't let the rubber seal get too long and you will have a great seal.
Yes, for us "builders", but it sounded like the 14 you just fasten them on!
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  #7  
Old 02-27-2017, 03:57 PM
salto salto is offline
 
Join Date: Apr 2015
Location: Wee Waa Australia
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Originally Posted by f1rocket View Post
A quick tip when fitting your baffles to your top cowl, line the sides of the baffle with paperclips and lower the cowl into place. This will give you a great indication of the gap between the aluminum baffle and fiberglass top. Make this consistent and don't let the rubber seal get too long and you will have a great seal.

What a great tip for us assemblers!
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  #8  
Old 03-02-2017, 09:26 AM
GigAir GigAir is offline
 
Join Date: Apr 2013
Location: Gig Harbor, WA
Posts: 41
Default Baffle Clearance to Cowl

Tim. Once again, great post. I am finishing all the FWF items and this is very timely. Is there anyway you could post a couple pictures of the specific cowl areas where you are experiencing this issue? Thank you.
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  #9  
Old 03-02-2017, 02:51 PM
TimO TimO is offline
 
Join Date: Feb 2005
Location: Wisconsin
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Maybe soon. I don't have pics that I took already so I'll try to remember to do so when I remove the cowl again.
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  #10  
Old 03-08-2017, 11:22 AM
TimO TimO is offline
 
Join Date: Feb 2005
Location: Wisconsin
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I took some pics today. Slightly larger ones on my website. The pics aren't great but at least you can see the locations of where the concern is. The pics here are *really* pretty poor, resized to 800 wide. The lighting was bad, too.











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Tim Olson - CFI
RV-10 N104CD - Flying 2/2006 - 1300+ hours http://www.MyRV10.com
RV-14 N14YT - Flying 6/2016 - 170+ hours http://www.MyRV14.com
RV-10/14 Transition Training: http://www.RVCFI.com
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