cowl inlet - airseal gap

[Paul Eastham]

Hi everyone,
What have you all done for the upper inboard corners of the cowl inlets? I am having trouble getting a reasonable-looking seal in this spot, upper left in this photo:



You can see the inside of a gap there. I can add another flap lower down on the baffle, but it seems that the incoming airstream would just push it away from the cowl.

I have also tried adding a little glass fairing and running a strip inside the cowl, which seemed to work better but still not perfect. It also makes putting the top cowl on rather tricky.
(undersized test strip shown here)



Is this worth trying to get perfect? What have others done?

Thanks,
Paul

[osxuser]

Plentum

[dan]

Paul, yours looks pretty much just like mine. The airseal/garlock material doesn't mate up all that well in that inboard top area. In fact, I never even had any material there until about 6 months ago! Cools just fine and the plane ain't no slouch speed or economy wise.

If I were doing it over, I'd mold the inlet ramps into a continuous ramp dealie that goes all the way across the top cowling. Then I'd chop the "hump" baffle (front center) down pretty much flat. Don't know if the words I'm saying actually make sense...lemme know if you want a sketch or something.

[Paul Eastham]

Originally Posted by dan

Paul, yours looks pretty much just like mine. The airseal/garlock material doesn't mate up all that well in that inboard top area. In fact, I never even had any material there until about 6 months ago! Cools just fine and the plane ain't no slouch speed or economy wise.

Ok, cool...thanks for the data point. I was thinking this might be a neutral pressure area anyway due to the apparently high airspeed in this spot. That's my rationalization anyway

Originally Posted by dan

If I were doing it over, I'd mold the inlet ramps into a continuous ramp dealie that goes all the way across the top cowling. Then I'd chop the "hump" baffle (front center) down pretty much flat. Don't know if the words I'm saying actually make sense...lemme know if you want a sketch or something.

I was considering that too, but I am trying really hard not to do any more fancy mods and just get it flying...plenty of time to tinker after phase 1.

[Ironflight]

Originally Posted by Paul Eastham

I was considering that too, but I am trying really hard not to do any more fancy mods and just get it flying...plenty of time to tinker after phase 1.

Paul -

1) I agree with Dan's observations - my baffle seals look odd there as well, and things cool and run just fine. Based on what I have learned on other threads about tuft testing actually showing reverse flow Pu the inlets at times, we might sometimes put too much emphasis on the tight seals...

2) Forget about having time to tinker after phase 1....I finished phase one in six weeks, and have been flying for 9 months now, and can't stand the thought of taking the airplane out of service for tinkering! (The month in the paint shop nearly killed me!)

Best of luck - finish it up, and go fly!

Paul

[vlittle]

Originally Posted by dan

Paul, yours looks pretty much just like mine. The airseal/garlock material doesn't mate up all that well in that inboard top area. In fact, I never even had any material there until about 6 months ago! Cools just fine and the plane ain't no slouch speed or economy wise.

If I were doing it over, I'd mold the inlet ramps into a continuous ramp dealie that goes all the way across the top cowling. Then I'd chop the "hump" baffle (front center) down pretty much flat. Don't know if the words I'm saying actually make sense...lemme know if you want a sketch or something.

Dan, I did something like this, adding wings to the cowl ramps:


This allowed for a good seal across the front.

Your idea of making them contiguous would make the shape of the front center 'hump' baffle even simpler, and easier to seal.

Vern Little

[dan]

Originally Posted by vlittle

Your idea of making them contiguous would make the shape of the front center 'hump' baffle even simpler, and easier to seal.

That's what I figure. I'm trying to determine if there's any down-side to doing it. I assume it would shrink the volume of the "plenum chamber" slightly, but I find it hard to believe that would have any measurable effect. As in, the benefit of a better seal would probably outweigh that "loss" anyway.

If anybody actually tries the one contiguous inlet ramp approach, please report in on your findings!

[sf3543]

On my RV8, I built a plenum by creating an aluminum "lid" over the normal baffle kit. I have about a 3/8" gap between the cowling lips and the front edge of the plenum...no seal material at all. Cooling is exceptional. I think it is a little better than the normal baffles were on my RV6. Also, I don't think there is much, if any, leakage around the edges since the top of the cowling doesn't puff up like it did on the -6. I always noticed this on the -6, because I could see that the back of the cowling was lifting a little in flight so that I could see the edge of the fiberglass. Parked, it was perfectly flush. The -8, with the plenum, doesn't do this. So, I would say that the seals aren't quite as important to get perfect as you might think, unless you are racing or are having cooling problems of some kind.
Just my observations.