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Questions about fitting the cowling, section 38, RV-12 Classic

Brett H

Active Member
I am in the process of starting to fit the cowling while I await the delivery of the powerplant kit in late February.

My concern is the alignment of cowling to the Spinner Back Plate. Namely, being centered and the gap.

What are peoples experience doing this before the propeller / spinner is installed? Should one really wait? What is the correct gap?

Thanks.

Brett H
Columbus, IN
 
Get the engine in place, and prop, and spinner, then fit the cowling. Follow the instructions.

I've seen one RV-12 where they didn't and the cowling was offset from engine, prop and spinner. A sign of poor fit and finish workmanship.
 
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+3 .... Wait

With the engine in place you can get a much better fit. I used a couple of 1/8" thick aluminum plates between the spinner back plate and the cowling to get a nice even fit.
https://1.bp.blogspot.com/-8sooYqEIvY4/Vyiq6hQVVbI/AAAAAAAALjk/miBaFzkzd0YrG74r3kypjo1gNl4iwMKCwCLcB/s1600/DSC01745.JPG

Edit:Added a link to a photo showing how the aluminum plate was used. The yellow strap is not necessary ... but I was working by myself, so used it as an insurance policy in case the duct tape securing the lower cowling to the fuselage give way.
 
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Thanks for the responses.

Based on the responses, I’ll wait until I can locate the cowling relative to the Spinner Back Plate.

Also, I’ll use 1/8” as the desired clearance between the cowling and spinner back plate. For the life of me, I was unable to find in the Van’s documentation what this clearance is supposed to be.

Brett H
Columbus, IN
 
For the life of me, I was unable to find in the Van’s documentation what this clearance is supposed to be.

I don't think the 1/8" clearance is referenced in the documentation. However, as you get close to the scribe lines you will see that the clearance ends up being around 1/8" or slightly more. Using the 1/8" spacer will get you in the ballpark and also help you get an even fit all around the back plate.

I'm not positive about this, but I do think I remember reading a post many years ago where Scott mentioned the gap should end up being 1/8" or a little larger. I tried looking, but couldn't get back that far in time with the search tool. If the gap is much less than a 1/8", you will likely have a hard time with cowl removal without damaging paint.
 
Wow. The procedure for installing the RV-12iS cowling differs greatly from that of the RV-12 Classic.

The RV-12iS locates the top cowl off of the Spinner Back Plate and the trims / locates the rest of the cowling from that.

Whereas, the RV-12 Classic cowling is trimmed to the scribe lines on the cowling and then installed on the fuselage prior the engine installation. The location of the cowling relative to Spinner Back Plate is a resultant of how the cowling was installed / fits.

The RV-12iS instructions state that the clearance between the Spinner Back Plate and Cowling is 3/16”.

Brett H
Columbus, IN
 
Hmmm. Guess it works, since a lot of others obviously used that method, but if it were me, I’d talk with Van’s Support and ask if the iS procedure could be applied to the ULS. I’m certainly not familiar enough with the ULS/iS differences to make a recommendation.
 
Well.

Yesterday I finished sanding the edges of the cowling to at or near the scribe lines. The weather the last few days was actually warm and very conducive to making the mess outside.

My plan is use the RV-12iS approach to locating the cowling to the spinner. Also, the iS instructions provide guidance if the edges of the cowling edges need to be trimmed further. Beyond that, I plan to follow the RV-12 Classic instructions after the engine has been installed.

Brett H
Columbus IN
 
Hey Brett
For what it’s worth when I built my RV12 classic I too waited till the engine was installed to trim and fit the cowl. And actually the trim lines where very close to where everything ended up. However I do recommend installing the engine then fit the cowl.
I’m currently helping a group build a RV12iS and with the engine installed,less the exhaust, I’ve been fitting the cowl. I been recalling how tedious this process can be.
 
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