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Baffle Rubber Done Perfectly Wrong

DanH

DanH

Legacy Member
Mentor
Walked past this Cessna in a maintenance hangar the other day.

The only baffle rubber not pointing the wrong way apparently never touches the cowl at all. However, some genius did give it a tuneup with a spray can of silver paint :rolleyes:

amfwon.jpg


1z1bckj.jpg
 
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Well, it probably starts out pointing the right way... Those Cessnas fly at such a blisteringly fast speed, they couldn't hold up and just flipped over the other way... :)

On the other hand, maybe this is why it's in the maintenance shop in the first place...
 
" . . . but it was signed off by an A&P!? "

Just sad.
 
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Well, since...

Those Cessnas fly at such a blisteringly fast speed
Click to expand...

:D That's it! It IS pointed the right way - the high pressure area is below and the air comes up and exits through the front!! :D
 
Winter Opps

It is fliped that way to bleed off excess cooling air to help the CHT's get up into the normal range as it is getting cooler here in the south ;)
 
Clearly the bad baffle sealing has been found acceptable during several past annuals. This sort of non-sealing is very, very common in certified GA aircraft, which is why I don't give much weight to RV builder statements like "My CHT's are high, but my mechanic has checked the baffles and says they are fine". You've seen my usual response: "Post pictures".

Please allow some clarity; I don't wish to paint all A&P's with a broad and ugly brush. However, I do have a question, and it's just as applicable to RVs as any other bird. Is this or is this not considered an airworthiness issue? Is the mechanic who signs off such an obvious fail putting his license at risk? Or is this just something a mechanic must sell to an owner to get it done?
 
When I purchased my Midget Mustang in [marginally] flying condition, the baffles were the same way--didn't even touch the cowling. Not to worry, however, as the prior owner/builder opened up the aft side cowl cheeks at the firewall to provide better flow and "it completely solved the oil temperature issues."

Some people's children...
 
..what A&P?

...this all looks like the kind of fine work I may have done when I first worked at a local maintenance shop. I was 15, and I thought I knew all about aircraft, ('cause my Dad built one!)
Of course the engineer should be looking at all this prior to the cowls going back on, but just saying that a LOT or work is not done by him/her. Often they simply say " clean that engine, touchup the paint, and put those baffles back on..."
and walk away for the rest of the day.
 
Some times when i think my work isnt perfect I take a look on the Certified planes at the hangar and always feel beter, it is very noticiable tha quantity of cessnas and pipers that have deficient baffle installations, but all that airplanes dont have complete cil by cil engine analyzers so they dont know that is bad, and the most important is they never have a problem in 20-30-40 years, so as a friend told me some time. "I only believe in God and Lycoming":)
 
I know this is obvious to you guys, but for those of us that haven't been in the guts of cowl can you clarify further the proper install details. I think I get the idea but it would be good to have the specifics. I had assumed that the baffle material was just flat material. I'm now getting the feeling that is not the case and that the curvature should point inward, the higher pressure area then forming the seal against the cowl.
 
I was introduced to the importance of baffle sealing when I witnessed the A&P who worked on my dad's 172 reach his arm through the cowl hatch doors and then through the cowl inlets to make sure the baffle seals were turned the right way (toward the airflow). Those baffle seals were much stiffer than what is shown in Dan's photos. They didn't appear to be factory original.
 
Yep

....and if you guys still getting to the baffling stage, cut it across the short width from the roll, you'll already have that 'built-in' curvature...installed curving inward.

Best,
 
DanH said:
Clearly the bad baffle sealing has been found acceptable during several past annuals. This sort of non-sealing is very, very common in certified GA aircraft, which is why I don't give much weight to RV builder statements like "My CHT's are high, but my mechanic has checked the baffles and says they are fine". You've seen my usual response: "Post pictures".

Please allow some clarity; I don't wish to paint all A&P's with a broad and ugly brush. However, I do have a question, and it's just as applicable to RVs as any other bird. Is this or is this not considered an airworthiness issue? Is the mechanic who signs off such an obvious fail putting his license at risk? Or is this just something a mechanic must sell to an owner to get it done?
Click to expand...

Why I've never understood aircraft owners who weren't extremely hands on in the maintnenance of their birds. Much more likely for you to be killed by a mechanics mistake in your plane than in your car.

I knew nothing about aircraft when I bought my first one the year after I graduated college. But I did every bit of work on every aircraft I've owned (under supervision when required). Sure, I paid more for the first few annuals or the first time I pulled a jug off than I would have to just pay someone else, but I figured i was paying for education and peace of mind. I still seek out and pay for that knowledge 23 years later.
 
understanding

I understand after reading Walkman and Roy's post that there are a lot out there putting together these and other "E.H.B's" who may not have a good grip on this one. It reminded me this is why we have "FAR's" and "AC" like part 23 and 41-13. Some of these came at grate cost to people and property. I have always liked the idea of the 150% rule and find myself using it for a lot of other thing other than aircraft. Helps keep my cost down in the long run and things just seam to last longer. I don't have any good "J.P.G.'s" of a seal installation. But if any one dose it would be nice to post them with a short how you did it.
Yours as always R.E.A. III #80888
 
rapid_ascent said:
I know this is obvious to you guys, but for those of us that haven't been in the guts of cowl can you clarify further the proper install details. I think I get the idea but it would be good to have the specifics. I had assumed that the baffle material was just flat material. I'm now getting the feeling that is not the case and that the curvature should point inward, the higher pressure area then forming the seal against the cowl.
Click to expand...

The baffle seal material should be riveted to the inside of the baffles and curved towards the engine. Thus, when air enters the cooling inlets, it pressurizes the baffles and they seal against the inside of the top cowl forcing the air down between the cylinders, not past the fabric.

Here is a diagram I found on the net:
Cowl-Saver-Art-Web.gif
 
Thanks for the clarification. Nice graphic Bill. You learn something new every day. I must admit I've never thought about this, but it might have been something you figure out at the time. However it does appear that many people haven't.
 
N941WR said:
Bill R.
Astronaut Candidate Trainee Assistant Third Class
Click to expand...

Agreed, that's a helpful graphic for those of us not-yet FWF. Thanks, Bill.

[and nice to see you "owning" that title Paul gave you in another thread; it's like you were "tapped" with a knighthood! I'm seriously jealous.]

--
Stephen
 
Flash light

How many of you are looking at the baffles with the cowling installed (can you? as I don't have the benefit of an RV nearby) A couple of properly places "snips" cured a hot cylinder on a lycoming/maule installation. You can actually rely on air pressure to aid in a "shingle" overlap to seal well. Having a few pieces overlap at the aft end seal better than one waved piece.
 
Sample of perfect baffle seals

Would anyone like to show us a really good sample of his RV9/RV7 baffle seals? My ones are worn out (I bought a flying RV9 ) and I would like to redo them ... but I haven't got any picture how.

Does anyone would show us a photo how they should look like especially the difficult spots at the front of the cowling and the air inlets? Thank you so much for your help and your advice. :cool:

Pit
 
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N941WR said:
The baffle seal material should be riveted to the inside of the baffles and curved towards the engine. Thus, when air enters the cooling inlets, it pressurizes the baffles and they seal against the inside of the top cowl forcing the air down between the cylinders, not past the fabric.

Here is a diagram I found on the net:
Cowl-Saver-Art-Web.gif
Click to expand...

And the first few times you fly with your plane, you'll be peeking inside through all sorts of convoluted means to make sure the baffle material has fallen the correct way.
 
Nose & Air inlets

Thanks Bob,
unfortunately this drawing doesn't show the lining of the baffle seals around nose and both sides of the air inlets, thats why I am asking again, sorry. Any help with a picture of your RV7 / 9 baffle seals ?
Thanks Pit
 
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Nose & inlet images

Ditto.

Searches of this site have turned up a number of bad examples, identified as such; I'd appreciate any "this setup worked well, and my CHTs are XXX" images, especially of those *&%#@ inlet baffles.

Thx!
 
Pictures please

I have been working on inlet ramps and baffles as well any inlet area pictures "done right" would be appreciated.
 
Speed mod

DanH said:
Clearly the bad baffle sealing has been found acceptable during several past annuals. This sort of non-sealing is very, very common in certified GA aircraft, which is why I don't give much weight to RV builder statements like "My CHT's are high, but my mechanic has checked the baffles and says they are fine". You've seen my usual response: "Post pictures".

Please allow some clarity; I don't wish to paint all A&P's with a broad and ugly brush. However, I do have a question, and it's just as applicable to RVs as any other bird. Is this or is this not considered an airworthiness issue? Is the mechanic who signs off such an obvious fail putting his license at risk? Or is this just something a mechanic must sell to an owner to get it done?
Click to expand...


Clearly you guys know nothing about the TRANS-SONIC speed envelope of this airplane. It's like the cones on the SR-71. This thing is so fast, they have to move the baffle position so the shock wave flows correctly past the benson refradulator and the canuter valve. This set of baffles has been designed for a particular resonate frequency to allow the pilot's wife less leeway in his spending. That or a pencil has a neck brace from whiplash..... Dan is right.... not cool
 
Dan,

Do you have any images of baffles done perfectly? I'm redoing mine and have bounced back and forth on the proper way... Straight piece with bends and cuts where it mounts to the metal, curved piece that has slits where it touches the cowling or multiple straight pieces with overlaps.
 
Sid Lambert said:
Dan,

Do you have any images of baffles done perfectly? I'm redoing mine and have bounced back and forth on the proper way... Straight piece with bends and cuts where it mounts to the metal, curved piece that has slits where it touches the cowling or multiple straight pieces with overlaps.
Click to expand...

Sid, mine are darned good. Drop by and take a look. They are made of multiple pieces with overlaps.
 
Thanks Kyle. I remember helping you put the cowling on once a few years ago. Yours were tight for sure. Is your cowl off now?
 
Sid Lambert said:
Thanks Kyle. I remember helping you put the cowling on once a few years ago. Yours were tight for sure. Is your cowl off now?
Click to expand...

Nope, it's attached right now, but if you're around the airport later this week, we could pull it off and you could take a look. I've got a couple of wires to run FWF anyway.
 
Walked past this turbo Continental on a Cirrus last week.

The contact pattern at "A" is what you want to see on all your seals.

"B" illustrates why overlaps should be minimized. Every overlap allows a leak, so use as few as possible.

The fastener at "C" appears to be digging into the inner surface of the cowl. Some RV installations can have a similar problem, the left side of an angle valve motor in an RV-8 being a good example.

iy23rq.jpg
 
I put wax paper and a dab of black RTV at some of my overlaps then put the cowl on. The -3 and -4 cowl has too many curves across the top for no overlaps.

Once the engine is broken in I will do more scientific speed runs but right now it appears 5-7 kts fast with the new engine and new baffles. I think most would be baffle since the engine just went from 8.5 to 9:1.
 
baffling overlaps

Dan:

Thanks for the image of - and comments on! - Cirrus baffling overlaps.

The more I see, the more I realize that thinking before wrenching goes a long way.
 
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