VAF Forums

VAF Forums (https://vansairforce.net/community/index.php)
-   Traditional Aircraft Engines (https://vansairforce.net/community/forumdisplay.php?f=21)
-   -   Photos: Really good baffle seals (https://vansairforce.net/community/showthread.php?t=141528)

Mike S 03-11-2018 10:05 AM

Quote:

Originally Posted by DanH (Post 1245154)
Take a close look at the inlets on Rutan's Boomerang. The inlet lip and connecting duct you see extending out the front of the cowl is all hard glass, and part of the plenum. Sealing is around the outside of the duct, behind the lips.

This, I believe.


Snowflake 03-12-2018 08:02 AM

Mike, the photo doesn't come through.

f1rocket 03-12-2018 08:29 AM

I've posted this before but this seems like a good place to post it again.

Remove your existing seals. Place paper clips all along the perimeter of your baffling so they stand tall and will hit the cowling. Put your top cowl on. Remove it. There's the perfect outline for your seals. Get the red/blue silicone seal material and cut it about 1 inch longer than the paper clips. Carefully work the corners to avoid puckers or gaps and bingo, you are ready to go.

AviatorJ 02-15-2019 06:34 PM

Quote:

Originally Posted by bruceh (Post 1109218)


A lot of these photo's are missing. However I'm now suspecting that I may have some large leaks in my back corner seals. I don't believe mine fold over like this and I just assumed the air pressure pushed everything up and tight. Is it acceptable to rivet them in place with a backing washer if I can't get them to stay folded over?

bruceh 02-15-2019 06:42 PM

I have some RTV between the corner folds to keep it all air tight. If you look closely you can see just a bit of orange on that lower left corner in the picture.

Kyle Boatright 02-15-2019 06:58 PM

Quote:

Originally Posted by AviatorJ (Post 1325044)
A lot of these photo's are missing. However I'm now suspecting that I may have some large leaks in my back corner seals. I don't believe mine fold over like this and I just assumed the air pressure pushed everything up and tight. Is it acceptable to rivet them in place with a backing washer if I can't get them to stay folded over?

You can also (loosely) stitch them together with a loop of dental floss or similar. A little wear, a few heat cycles, and they will take the appropriate set.

RV10Pilot 09-25-2019 09:05 PM

I am just about ready to cut my baffle seals and drill the holes for the rivets to hold them on. Since there are no dimensions in the plans I am planning on starting with seals 3-1/4" high and setting them 1" down on the baffles. This will give 2-1/4" to seal against the cowl. The rivets will be 1/2" down from the top of the baffle. Does this sound like a reasonable starting point?

Kyle Boatright 09-26-2019 08:00 AM

Quote:

Originally Posted by RV10Pilot (Post 1376059)
I am just about ready to cut my baffle seals and drill the holes for the rivets to hold them on. Since there are no dimensions in the plans I am planning on starting with seals 3-1/4" high and setting them 1" down on the baffles. This will give 2-1/4" to seal against the cowl. The rivets will be 1/2" down from the top of the baffle. Does this sound like a reasonable starting point?

I think what you want is enough material to touch the cowl plus an inch or maybe a bit less. Seals which are too long will cause the seal edge to bend down and away from the cowl after the point of contact, creating a leak path.

So, you might start with your proposed length on a section, cleco the seals in place, and check fit looking in through the air inlets and oil door. Trim to length based on what you observe and cut the others to match.

Hartstoc 09-26-2019 09:33 AM

Quote:

Originally Posted by DanH (Post 1108945)
Considering all RV fabrication tasks, the thing I most often see done badly is baffle sealing rubber. Flap seals arranged so they blow open, seals that seal against nothing, puckers, gaps, overlaps, you name it...the list of sins appears to be endless.

However, I have seen some installations that were beautiful. Believe me, I look; I'm the nut case who walks around fly-ins while peering into cowl openings like some kind of airplane up-skirt pervert ;)

Builders need to see some really good seals. Who has pictures? Who can show us how it's done? Post those photos please. You'll help a whole generation of RV builders enjoy lower CHT and oil temperature, while going faster due to reduced cooling drag.

Great thread. I?ve got nothing to offer except an out-of-the-box thought. I have no photos but will try to find.

We did a lot of work on cowl design and cooling sealing on the CAFE Foundation test Mooney back in the 1990?s. That bird actually ended up with a huge spinner from a turboprop and a 360? annular cooling inlet. I'm not suggesting that path for RV?s but the baffle seals were something completely different.

We used thin, 10 mil, flexible, reinforced silicone fabric to create a baffle seal at the engine?s horizontal mid-plane. The seal extended around the circumference of the engine cylinder mid-point line with the outer edge of the fabric attached to the lower cowl inner wall and to the firewall itself below the oil filter. A bit of a hassle accessing the lower plugs, but when you removed the upper cowl you had full access to the
Entire accessory section and the top half of the engine, with no aluminum flanges need to support heavy baffling engaging the upper cowl. The beauty of this installation is that it provided for a much larger volume decelleration plenum, and the entire upper accessory section was was in the ice cold pressure section. It was essentially a hermetically sealed partition. If I were building new I?d seriously consider such an approach. Pressure recovery of that system was in a class by itself. I?ll try to dig up some photos.-Otis

RV10Pilot 09-26-2019 10:38 AM

Quote:

Originally Posted by Kyle Boatright (Post 1376107)
I think what you want is enough material to touch the cowl plus an inch or maybe a bit less. Seals which are too long will cause the seal edge to bend down and away from the cowl after the point of contact, creating a leak path.

So, you might start with your proposed length on a section, cleco the seals in place, and check fit looking in through the air inlets and oil door. Trim to length based on what you observe and cut the others to match.

Thanks Kyle. I was so Wondering if the could be too long and you answered that question. Always better to start too big and trim vs to short and starting over.


All times are GMT -6. The time now is 07:30 AM.