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Sealing baffles

wirejock

Well Known Member
What's the best way to seal this area around the crankcase?
There are spaces on the forward area of the crankcase and aft area near #3.
I would prefer something that wasn't stuck to the engine so the baffles can be removed and replaced without reapplying a tube of RTV.
How did you do it?
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I think most of us start off with bold ideas of not gluing (w/RTV) our baffles to the engine, but quickly practicality and reality sinks in. And I'm a guy that made my VS top fairing removable, wingtips as well, etc., all in the name of servicability.

The problem is unless the stuff is RTV'd to both the baffle and to the engine, the vibration and air pressure just pushes stuff out of the gaps.
 
RTV

I think most of us start off with bold ideas of not gluing (w/RTV) our baffles to the engine, but quickly practicality and reality sinks in. And I'm a guy that made my VS top fairing removable, wingtips as well, etc., all in the name of servicability.

The problem is unless the stuff is RTV'd to both the baffle and to the engine, the vibration and air pressure just pushes stuff out of the gaps.

Guess I will goop those holes before first flight. Too much maintenance going now to do it.
 
Shop heads

Those three rivets around the doubler look a bit under-set to me...

Nope. I have measured every rivet on my bird from the start. Two holes in each rivet gauge. Min & Perfect (1.5D). If min fits, they get a bit more till they fit the perfect hole. Over 16,000. Baffle rivets are not structural. What else ya got! :D
 
Larry, I know u have spent a lot of time creating your special RV. I have 2 suggestions:
1 use HiTemp Clear. Not that orange stuff.
2 use blue painters tape to provide an outline or border rather than just gooping it on.
Both of these will make it look much better. Get another knot or 2 out of it also.
 
Nope. I have measured every rivet on my bird from the start. Two holes in each rivet gauge. Min & Perfect (1.5D). If min fits, they get a bit more till they fit the perfect hole. Over 16,000. Baffle rivets are not structural. What else ya got! :D

I'm just not used to seeing a gap between the rivet shop head and the hole...
 
Shop heads

Me neither! I reckon they need another hit (2nd picture). We also want your plane to be perfect. :D

Really? It's a doubler on a non structural part. You guys. I'll whack them again. Can we get back to sealing holes please?
 
Seals

Larry, I know u have spent a lot of time creating your special RV. I have 2 suggestions:
1 use HiTemp Clear. Not that orange stuff.
2 use blue painters tape to provide an outline or border rather than just gooping it on.
Both of these will make it look much better. Get another knot or 2 out of it also.

Sort of what I've been doing. I used Permetex Ultra Black per Dan's recommendations. Most of the seals so far were a strip of fiberglass impregated with Ultra Black.
Do you think the same technique would work to seal the gaps? Like a 1/2" overlap. Let it set up. Hopefully it lays against the crankcase and seals under pressure.
 
Larry, I know u have spent a lot of time creating your special RV. I have 2 suggestions:
1 use HiTemp Clear. Not that orange stuff.
2 use blue painters tape to provide an outline or border rather than just gooping it on.
Both of these will make it look much better. Get another knot or 2 out of it also.

I'd suggest the black high temp RTV and electrical tape, but that's quibbling. Either way, masking the edges with tape will make it look better.

And unless you want to take the baffles and other things on and off a thousand times, you'll find a few places where about the only way to seal them is a big 'ol blob of RTV applied with your gloved fingertip, and with no easy way to mask it so it is neat.
 
Sealing holes

Really? It's a doubler on a non structural part. You guys. I'll whack them again. Can we get back to sealing holes please?

Back on topic, apologies; if there is a clear or gray or even black high temp RTV that is available to seal those gaps then I too think that it would be better looking than roughly applied red (and also complement your beautiful plenum). How high does the temp rating really need to be though, we should ask ourselves?!
 
Looks like

Nope. I have measured every rivet on my bird from the start. Two holes in each rivet gauge. Min & Perfect (1.5D). If min fits, they get a bit more till they fit the perfect hole. Over 16,000. Baffle rivets are not structural. What else ya got! :D

Looks like the rivets are longer than necessary, making the appear under set. That is all I got.
 
Back on topic, apologies; if there is a clear or gray or even black high temp RTV that is available to seal those gaps then I too think that it would be better looking than roughly applied red (and also complement your beautiful plenum). How high does the temp rating really need to be though, we should ask ourselves?!

I used gray high temp (650*) RTV from O’Reilly Auto Parts. Looks good.
 
Permatex Ultra Black is available at auto parts stores everywhere. Loctite 598 is the same product. Looks good, tough, highly adhesive.
 
Ultra Black

Permatex Ultra Black is available at auto parts stores everywhere. Loctite 598 is the same product. Looks good, tough, highly adhesive.

It is a good product. Available in big caulk gun style tubes too. For anyone just starting the sealing process, prices are all over the place. Wally is cheapest on commercual packages. Buy about four. Auto part store near our house is double. Dan's method of using fiberglass impregnated with Uktra Black works great. Cut fabric to fit the cylinder area. Lay it on plastic. Smush the RTV on one side. Flip to clean plastic. Smush the opposite side. Trim off the excess plastic and apply to the cylinder fins. Allow to fully cure. Pull the plastic. Trim the excess fabric flush.

I'm going to try a similar approach to sealing these gaps.

Looks like the rivets are longer than necessary, making the appear under set. That is all I got.

Rivets are very slightly under set. 0.117"D. They will be hit again when the baffles are removed.
 
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I used the ultra-black stuff and really slobbered it on. Didn't try to get fancy. Also remember to goop up the little inter-baffle holes on the bottom. Only light that shines through from the bottom should go through the cylinder fins.



Have not flown yet, so we'll see how the cooling ends up with these seals. (also, yes I know the cylinder air dams are reversed in that picture--they were subsequently switched)
 
Dan's method of using fiberglass impregnated with Uktra Black works great. Cut fabric to fit the cylinder area. Lay it on plastic. Smush the RTV on one side. Flip to clean plastic. Smush the opposite side. Trim off the excess plastic and apply to the cylinder fins. Allow to fully cure. Pull the plastic. Trim the excess fabric flush.

What Larry describes is seen below, on my 390. The goal is to seal so air cannot escape out the side edges of the aluminum wraps. It must stay between fins all the way to the exit.

Be sure to run a tiny bead across the aluminum wrap when installed over the RTV/glass. Don't want air leaking between the aluminum wrap and the outside of the RTV/glass wrap.

This 390 has never exceeded 380 CHT, on roughly 46 sq inches of exit area with the cowl door open, or 30 closed when below 50 OAT.

I'm going to try a similar approach to sealing these gaps.

I have closed larger gaps with a strip of RTV impregnated glass fabric. That said, most leaks are best closed with a plain bead of sealant.
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I used the ultra-black stuff and really slobbered it on. Didn't try to get fancy. Also remember to goop up the little inter-baffle holes on the bottom. Only light that shines through from the bottom should go through the cylinder fins.

Ryan
What are the "little inter-baffle" holes?

Be sure to run a tiny bead across the aluminum wrap when installed over the above. Don't want air leaking between the aluminum wrap and the outside of the RTV/glass wrap.

I have closed larger gaps with a strip of RTV impregnated glass fabric. That said, most leaks are best closed with a plain bead of sealant.
.

Dan
I wrapped mine almost exactly the same as your photos. Thx
If I understand, you recommend a bead on the baffle that seals where the cylinder wrap begins. Correct?
 
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Be sure to run a tiny bead across the aluminum wrap when installed over the above. Don't want air leaking between the aluminum wrap and the outside of the RTV/glass wrap.



I have closed larger gaps with a strip of RTV impregnated glass fabric. That said, most leaks are best closed with a plain bead of sealant.
.

Yep. Good idea. I see a couple areas under the cylinders where there is a small gap between the metal baffle wrap and the cylinder fin, inboard and outboard where air can spill out before exiting at the end of the under cylinder baffle. I assume this is what you are talking about. Sealing those areas with RTV while being careful not to glob any of it into the fin inside the baffle edge might help a little. It all adds up.
 
What are the "little inter-baffle" holes?

Probably the gaps between the crankcase and the inter-cylinder baffle plate.

The hidden gap so often missed is between the rear baffle wall and the base of the rear cylinders. There's a little tab which should be bent forward and up, into the gap where there is no fins, just outboard of the cylinder baseplate. Then seal it with UltraBlack.

If I understand, you recommend a bead on the baffle that seals where the cylinder wrap begins. Correct?

Like the sketch below. Don't want air sneaking down between the RTV/glass "gasket" and the aluminum wrap.
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For the large gaps I mixed a dry epoxy and micro and added black and white pigment to make it Lycoming gray. Then I sealed it in place with high temp Gray RTV. It looks very nice and the the epoxy piece would be reusable if I ever disassembled it.
 
Just another data point - I didn't put a single dab of RTV anywhere on my baffles. I figured I'd do it after flying to see how bad my cooling was, but it turns out I have enough cooling without sealing between the baffles and the engine.

I realize that everyone's installation is different, and this might not work for others.

Where I spent my time was on ensuring that the lipstick red silicone baffle seals are smoothly against the cowl, and there are no leaks. I've tested with ground OAT of about 35c, and I hope to get further south this summer to test things when it's really hot.
 
Baffle seals

Just another data point - I didn't put a single dab of RTV anywhere on my baffles. I figured I'd do it after flying to see how bad my cooling was, but it turns out I have enough cooling without sealing between the baffles and the engine.

I realize that everyone's installation is different, and this might not work for others.

Where I spent my time was on ensuring that the lipstick red silicone baffle seals are smoothly against the cowl, and there are no leaks. I've tested with ground OAT of about 35c, and I hope to get further south this summer to test things when it's really hot.

Just to help the data, would you add Model, Engine, Induction, etc. Helps to compare apples to apples.
 
Just to help the data, would you add Model, Engine, Induction, etc. Helps to compare apples to apples.

Mattituck IO-360, cold air induction, standard cowl, AFP FM200, PMAGs with eicommander (timing: ADV max: 32.2, ADV shf: -1.4), NGK BR8ES, Hartzell C2YR-1BFP/F74972, Total Aero DM 15W-50 w/camguard

CHTs stay under 400F without trouble. My oil temps just barely get to 180F on a hot day (100F) with several turnarounds.

The only "non-standard" part of my installation is the very flexible silicone baffle seals. I was careful to make sure that they seal all around, and if I look at the wear pattern on the silicone and the cowl, looks good with just a couple of gaps.

Got some photos here but happy to take more if it can help. I have an oil change scheduled for today, if I can finish my honey-do list.

http://www.rv8.ch/more-baffle-work-rivets-and-silicone-baffle-seals/

http://www.rv8.ch/engine-photos-after-test-flights/

IMG_1637.jpg
 
I used gray high temp (650*) RTV from O’Reilly Auto Parts. Looks good.

+1 - Matches the engine color.

One could match cut the baffles and make it all removable, but then the movement can, likely, etch into the case. My choice was to seal and use the RTV to keep the edges of the baffles from etching into my engine case.

If you do a really good job of making all the air go through the fins people won't believe it and make funny sketches to represent your work. :D
 
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