Cooling air inlet duct opening.

[Flyboy66]

I am cutting the lower cowl for the radiator scoop. I would like to see the finished work (painted or not) of how people contoured the inlet, if anyone is willing to share. Did you use super fil on the edges? I was going to round the inlet. Do most make the transition a sharp corner, or a rounded edge? Does it affect airflow either way?

I did see tropicals work. If you did it same way as he did, no need to reply.

steve

[Dave S]

Here's some.....

Decided to reinforce the lower lip with a piece of aluminum

Also found later that the cowl behind the radiator/below the firewall was prone to flapping from engine vibration. Fixed that with a perpendicular aluminum bar riveted to the inside of the cowl behind the radiator/below the firewall.

[aviator79]

I don't have any good pictures on hand, but I used Super Fil and made smooth transitions. The newer versions of the lower cowl have a stiffener glassed in the location Dave mentions behind the radiator, and the instructions will have you bond in a scrap piece of fiberglass to reinforce the lower lip.

[efwd]

Yeah, that is what I was talking about adding Cowl Baffel. As you can see, in mine, I have restricted flow over the top of the oil cooler and I probably have significantly reduced that one inch worth of radiator between the oil lines. Wonder if it will matter when the summer arrives? I enjoy the fiberglass stuff so it will entertain me to make the correction.

[jrevens]

I left a gap between the bottom cowl & radiator... don't recall exactly how much. I sealed that gap with some nice soft silicone rubber "D" section that I glued to the cowl w/ silicone sealant. The cowl comes off & re-installs very easily.

Carl - I flew this morning when it was in the low 30's, and I was up to adequate temperature by the time I taxied to the run-up area, but I do have oil & water thermostats.

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[Flyboy66]

I am reconsidering moving the oil cooler to a lower position. Does anyone know the specifications of the stainless steel used to make the brackets? I might try to source locally if I can find some.

Steve

[Cherrybark]

As usual, a search of the forum turned up the answer to the next stage of my build - mounting the radiator, oil cooler, and getting the ducting set correctly. This thread answered my questions and I really appreciate Eddie's pictures.

[efwd]

My firesleeve is just wedged into the space and secured from coming back the way it went in by a piece of velcro. The gap is too close fitting to allow it to go through toward the exit.
The Rotax manual states that the engine should be run around 1800 for two minutes. I do that then bump up to 2200 and that is enough to taxi (too much) but like John, It is warmed up by the time I get to the run up area. It takes about 4-5 min run time.

[Cherrybark]

Thanks for the feedback on time to operating temperature. And I really like these ideas for closing the gap around the radiator.

[jiott]

I used fairly sharp edges, using SuperFill. I like the look of crisp edges for NACA ducts better than rounded. Personal preference. Be sure you have the duct glued in solidly with Hysol before starting the SuperFill; a friend has his crack loose after several hundred hours.