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Baffle Seal Gaps...a Problem?

rockitdoc

Well Known Member
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Are these baffle seal gaps going to be a problem re cooling? They were cut per the template except for the notch to clear the nut plate in the rear one. When folded down, as when the upper cowl is installed, gaps remain at these two locations, albeit small.
Baffle Seal Gap Aft Engine.jpg

Baffle Seal Gap Port Engine.jpg
 
Leaks are cumulative. A little here, a little there..

The finning on the angle valve engines will let you get away with murder...CHT will fall in the acceptable range, even if higher than other installations with good sealing. Oil temperature will be the wildcard.

Don't take this the wrong way, but you're asking for validation of work you know is not as good as it could be. When your heart says it's not great, do it over.
 
gap seal

Yes.

Its not going to cause CHT to be dangerous high but it could be better.

Take a 3rd piece of seal and close the gap.
 
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baffle seal gaps

The advice I got way back when was;
if air gap area in the baffles total more than the area of a 25 cent coin, you basically negated the effectivness of differential air pressure between the top & bottom cowl...

With that in mind, I always strived for the tightest seals I could get.
pictures right themselves when expanded...
 

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The advice I got way back when was;
if air gap area in the baffles total more than the area of a 25 cent coin, you basically negated the effectivness of differential air pressure between the top & bottom cowl...

And what's the diameter of the opening for the cabin heat air flow? And any blast tubes installed?
 
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Can't speak to the back baffle as it is hard to see enough detail in the picture. The gap on the side is not correct. On the -14 there are is a strip on each side that are mislabeled. Left is right and right is left.
 
Which are planned for & useful air bleeds.
The point is that you should make the baffle seals as effective as you can.

Yes, assuring a good seal is definitely the thing to do. I was only questioning the validity of the advice someone gave you that an opening the size of a quarter completely negates the entire pressure differential top to bottom. Especially since plenty of installations have 1, 2, 3 or more blast tubes in addition to the heater SCAT tube.

That said, the OP's baffles should be redone...they can be done without any gaps, and the builder should take the time to make that the case.
 
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I agree with what Ralph said. I was trying to improve the baffles on our C-170 years ago, and read an article about how to do this. They said that a 1 square inch opening (leak) in your baffle seals could cause a cooling efficiency loss of as much as 20%. I try to make mine as tight as I can too - a flashlight in a darkened hangar with the cowling on helps. In your first picture, you could add a piece of seal to close the gap like others have suggested. If you look to the left of that gap in your picture, it looks like there’s a wave in the baffle seal. When the top cowl is on and the baffle seal is curved forward as it should be, if that wave is still there, that’s a leak also. Sometimes you can just slit the fabric in that wave and the separated halves will overlap each other. Maybe there’s a little too much material in that area because of the variable top cowl curvature.
 
The advice I got way back when was;
if air gap area in the baffles total more than the area of a 25 cent coin, you basically negated the effectivness of differential air pressure between the top & bottom cowl...

With that in mind, I always strived for the tightest seals I could get.
pictures right themselves when expanded...

Ralph,

I couldn't tell from the photos, but do some of the seals share rivets?

Scott
 
No, my rivets were evenly spaced. Areas that overlapped were shaped with a tab (as pictured). I use the seal material supplied by Vans, I find it easier to seal, it comes rolled up, I use that natural curve to initiate the inward bend of the seals that makes installing the top cowling easy, it also helps with the sealing.
I tried to picture how I cut pleats(?) to help pinch the strips to the top contour of the inner cowling. I cut all the pleats (flutes?) the same distances but either compress or expand the distance of the rivet spacing to help mold the seal to the convex or concave cowl contours
Hope this makes sense...
 

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… I tried to picture how I cut pleats(?) to help pinch the strips to the top contour of the inner cowling. I cut all the pleats (flutes?) the same distances but either compress or expand the distance of the rivet spacing to help mold the seal to the convex or concave cowl contours…

Re post 12:

One might call those triangular cuts “darts”, perhaps “open darts”. Thanks for the idea! And the sketch!

https://en.m.wikipedia.org/wiki/Dart_(sewing)
 
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No, my rivets were evenly spaced. Areas that overlapped were shaped with a tab (as pictured). I use the seal material supplied by Vans, I find it easier to seal, it comes rolled up, I use that natural curve to initiate the inward bend of the seals that makes installing the top cowling easy, it also helps with the sealing.
I tried to picture how I cut pleats(?) to help pinch the strips to the top contour of the inner cowling. I cut all the pleats (flutes?) the same distances but either compress or expand the distance of the rivet spacing to help mold the seal to the convex or concave cowl contours
Hope this makes sense...

Total sense. Thank you. My whole day is set for tomorrow. And, maybe my top cowl will go on easier! :D
 
Is Van's no longer supplying pre-cut and punched baffle seals for the RV-14 FWF kit? It should be plug and play except for the 2 mislabeled pieces.
 
Is Van's no longer supplying pre-cut and punched baffle seals for the RV-14 FWF kit? It should be plug and play except for the 2 mislabeled pieces.

They are. But, the gaps I showed still occur. I’m replacing four of the offending bits to alleviate the holes.
 
Baffle Seals Revised for Better Sealing

It took all morning, but I finally got the revised seals in place. I made templates out of cardboard to get the curvature right before cutting the silicone. I probably need to do it again in order to try to get rid of the buckles at the 'darts', but overall, I'm pretty happy. All the seals curve inward as they should. Maybe if I widen the 'darts'?

Before:

Baffle Seal Gap Port Engine.jpg

After:

Baffle Seals Revised Port.jpg

Before:

Baffle Seal Gap Aft Engine.jpg

After:

Baffle Seals Revised Starboard.jpg
 
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Not Taken Wrongly

Leaks are cumulative. A little here, a little there..

The finning on the angle valve engines will let you get away with murder...CHT will fall in the acceptable range, even if higher than other installations with good sealing. Oil temperature will be the wildcard.

Don't take this the wrong way, but you're asking for validation of work you know is not as good as it could be. When your heart says it's not great, do it over.

Don't worry about offense, Dan, this is my first rodeo. All advice, critiques, scolding taken the way it should be....with thanks.

But, I wasn't looking for validation, I just didn't know if the gaps I had were acceptable since I used the precut seals supplied in the FWF kit and followed the plans. Van's is usually so good about accuracy (like 99.9% of the time) when things like this come up, it usually means that is the way they designed it. In this case, not so much. Rare occurrence. Easy fix, though. Thanks.

Scott
 
Looking good.
Finish off by shooting a bit of black silicone sealer in between the aluminum & rubber strips to close up any leakage there.
 
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