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Showplanes Cowl w/o Plenum?

claycookiemonster

Well Known Member
Working on the baffle and of course, with the prop extension, the forward "ramps" will be a bit short of the actual intakes. Also the round intakes do not exactly match up. Did you extend the ramps forward to seat below the intakes? Something else?
 
Did you do anything to address the round inlets, since the ramps and baffling assumes rectangular inlets? I'm looking at where we are, and I can see aligning the bottom and outboard edge of the baffles with the inlets, and then going to town with those conical corner gussets to approach a circular shape internally. Something like that?
 
Did you do anything to address the round inlets, since the ramps and baffling assumes rectangular inlets? I'm looking at where we are, and I can see aligning the bottom and outboard edge of the baffles with the inlets, and then going to town with those conical corner gussets to approach a circular shape internally. Something like that?

That’s about right. Mine still a work in process. Email Bryon at Showplanes, he has good pictures for reference.
 
Yes - extended the bottoms and sides of the ramp sections and terminated each with 3/4 of an inch or so of the flexible baffle seal material. Just make sure all the terminations are "outside" of the round openings within the cowl and there's enough flex material to facilitate easy cowl removal. Approaching 600 hours on a -8 and CHTs and oil temps have never been an issue.
 
baffle extensions

Not flying yet but here is mine.
 

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Vbug, I'm right there with you. I got Bryan from Showplanes to send me some photos and you are doing it as he did. I'm following right in your wake. We have fabricated both ramps and ended up with a much cleaner entry area. I was afraid of air leakage and was trying to come up with complicated ways to get from square and flat to round at the intakes. Bryan was very helpful, saying that the cowl cools just fine, and a bit of leakage wouldn't be a problem.
 
baffle seals

Yeah I spent too much time creating templates for the compound curves but I think it's gonna work. Not too difficult to install the lower cowl with the baffle seals extended forward. Good luck!
 
Inlets

Not a showplane cowl, but I took a slightly different approach. Vans cowl and Fiberglass baffle.
I bonded the inlets, secured the cowls then allowed it to cure. Inlets were cut away from the top cowl.
Fab a foam plug for each side. Forward end matches the shape of the inlet then transitions to the shape of the baffle.
Layup fiberglass and attach them to the plenum. Trim the cowl imlets so there's clearance to remove the bottom cowl. When it's done the bottom cowl goes on first. Plenum is installed. Seals are neoprene or silicone wrapped around the imlets. Top cowl installed. I've seen variations with inlet seals inserted from the inlet openings as well
When it's all done, the plenum fits pretty snug to the metal baffles and the inlet gaps are sealed.
It's a lot of work though.
 
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This is a James cowl so not sure how much it helps. I did a plenum but you might get some ideas on how I did the circle to square transitions. It was work for sure but came out pretty nice and works well.
 

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