Smooth cowl, Rotax 912, IV-1200 fit..HELP!

[GWright6970]

After exhausting all of my efforts, I can't get the top and bottom sections to be 5/8" from face of cowl to face of prop flange ON THE TOP AND THE BOTTOM to save me. (See photo) I have the aft end of the top of the bottom cowl at 17.5 inches up from the bottom longeron, etc...

The cowl came from the factory two months ago, and was already pretty much trimmed.

I even tried taking the aft end of the top cowl, and pulling it down 1.5 inches SUPER TIGHT over the sides aft end of the bottom, and even that extreme measure did not fix the angle.

PLEASE.. what am I missing gents??!! Thanks!!!

[Geowitz]

Mine was the same and I tried the exact adjustments you did without any luck. This is a problem with the mold.

What I did to get it closer was to use a cutoff wheel in the dremel and cut out a wedge behind the top flange into the top of the cowling, but still leaving the flange attached at the bottom. Then I when I pushed the top of the flange back it brought the angle closer into alignment and I hysoled the back of the flat part of the flange to the cowling. Kinda hard to explain.

It wasn't perfect, but I just ended up just going with it. Overall alignment of the cowling to the plane and windshield trumped spinner alignment. Using the adjustments you already tried will give you problems with the windshield later. Just adjust the flange with a little fiberglass work using the joggle joint to align the cowling with your thrust line and it'll be fine. No one ever notices and it functions perfectly fine.

[GWright6970]

I think I understand.... let's go for a picture!

After looking at it, did your wedge cut further down around the sides also? I'm trying to figure out how that cut blended with the air intake openings. Seems they need to be "shaved back" and new glass put in.

I just wish that we didn't have to do this!!! (Like fix the mold) You know something is up when looking at the top mold's overlap flange with the bottom joggle edge and it does not have the same match angle... a good 5-8 degrees off.... The bottom is ok.... its the top that is bad.

In any case, we need a fix... is this what you did George?

Thank you!!

[mr bill]

I mounted the engine on the fuselage before doing anything with the cowl. Then drilled and clecoed the top and bottom halves of the cowl together, before mounting on the plane. Then removed the fuel pump from the engine and centered the cowl opening relative to the prop flange and moved the cowl back 5/8" and clamped the cowl to the fuselage tubing. Then I drilled holes in the cowl to match the tabs in the fuselage, clecoing as I went along. Lastly, I trimmed the rear edges of the cowl to match the door opening. I had none of the problems you have mentioned.

[Geowitz]

Mr Bill - your cowling is slightly different. The latest mold sold for the IV's has this problem.

[GWright6970]

Bill,
I am envious!! This one is nothing like that in fit!

Thanks for trying!!
Cheers,
Grover