Baffling

ERJDriver · #1 06-20-2022, 09:42 AM

Question for the people smarter than me. Didn’t build my 8A, the lower cowl has no silicon baffling material to seal it to the aluminum baffling material mounted to cylinder 1/2. These cylinders run about 20-30 hotter in the climb. Is this why? Cooling ramps are installed in the top cowl and that baffling is new before I bought her

It’s just the lower cowl lip sitting on top of the aluminum, how much cooling/drag am I giving up?

Mike S · #2 06-20-2022, 09:58 AM

Are you talking about the cooling air inlets?

Photos would really help.

ERJDriver · #3 06-20-2022, 04:46 PM

Yes, the cowl inlets where the lower cowl sits on the baffling attached tot the front of cylinder 1/2.

Not my pic but here is an example of what I don’t have

blaplante · #4 06-20-2022, 05:06 PM

Well, ya, that's not going to help!!! A multi square inch leak from the upper (high pressure) to lower cowl. I am surprised you can maintain any decent CHT at all.

Carlos151 · #5 06-20-2022, 09:12 PM

Quote:

Originally Posted by ERJDriver

Question for the people smarter than me. Didn’t build my 8A, the lower cowl has no silicon baffling material to seal it to the aluminum baffling material mounted to cylinder 1/2. These cylinders run about 20-30 hotter in the climb. Is this why? Cooling ramps are installed in the top cowl and that baffling is new before I bought her

It’s just the lower cowl lip sitting on top of the aluminum, how much cooling/drag am I giving up?

Get yourself a copy of OP40-14 which is the baffle installation instructions and drawings. Should have baffle seal material on that lower cowling that will lay over the bottom ramps. That will definitely reduce your CHT’s on cylinders 1 and 2.

ERJDriver · #6 06-21-2022, 04:58 AM

Yeah giant PIA getting the lower cowl on and off with how the previous guy has it setup

olyolson · #7 06-21-2022, 05:22 AM

I don’t have any baffling material on my lower -8 cowl. The engine sheet metal baffles fit pretty tightly to the lower cowl with just a minimal gap. It is kind of a pain to get on but I figured out just the right amount of leaning, tongue wrist and stretching and of course a small amount of cussing to get it on. It’s not really that bad now that I know the right technique.

There was a dramatic effect on temps when I installed the upper inlet ramps which were not on the plane when I got it. The engine always had pretty high CHTs with #2 always about 20 degrees hotter. I had to pay attention on climbout but now with the upper inlet ramps installed I have no issues and can climb out on a hot day and not worry about temps, even at lower climb speeds. My CHTs are all normal now within about 5 degrees of each other. I also did a lot of sealing around the engine where I had some significant gaps.

I know a couple RV-8 guys and don’t remember seeing baffling material on their lower cowls.

ERJDriver · #8 06-21-2022, 05:55 AM

I have an A so the stupid nose gear is what makes it difficult. I guess I can try and tape them off and a what happens. I also don't have the material behind the spinner on that baffling.

Scott Hersha · #9 06-21-2022, 06:14 AM

Not having baffle seal material on the baffles behind the spinner can be a huge pressure leak, especially if you have the specified 3/8” - 1/2” gap between the metal baffle and the top cowl surface.
If you install the seal material on the cowl cooling inlets, you’ll need to trim the metal ramps back to give you about 1/4” or slightly more clearance from the cowl lip to allow you to get the lower cowl on. The surface of the ramp at the forward end should also be ~1/16” lower than the cowl lip to allow the seal to lay flat on the inlet ramp. If you can get that OP plans drawing as others have said it will help.
I just finished my baffle install on my RV6 yesterday so it’s fresh in my mind. I’ll try to remember to take a couple pics today, so you can see how I did my seals behind the spinner. There’s more than one way to skin this cat, but it has worked well for me on my other builds.

Carlos151 · #10 06-21-2022, 06:29 AM

Here’s a picture of the seals behind the flywheel when I was installing them per the baffle kit instructions. I ended up installing nut plates to make it easy to replace the seal material in the future. The more air leaks you seal, front and back, the better your temperatures will be.