What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Fitting cowl

Phantom30

Phantom30

Well Known Member
I guess I'm brain dead....but for the life of me I can't find info on clearance between front of cowl face and rear of spinner. My top cowl (cut to scrib lines), when laid butt up to top skin comes in contact with rear of spinner.

Anybody happen to know which plans page # this is covered on?
 
IMHO no less than a 1/4 inch. Keep in mind that the engine moves around a lot more in flight than on the ground. Also it's mounted on those nice thick rubber lord discs. Think light turbulence!;)
 
The design nominal on an RV-12 is 1/8"

I have seen as little as 1/16" work fine with no sign of any spinner contact.

The engine does move around, but nothing in comparison to a Lyc.

Builders that install to have 1/4 clearance or more would be one explanation for reduced clearance of items inside the cowl.
 
Thanks guys....I had already placed a 1/8" thick paint stir stick across rear of spinner. Looks like that will work fine.
 
Stir Sticks, Yeah!

Bingo Ric,
I taped pieces of stir sticks to the spinner and left them there throughout the fitting. Also "clean up" the overlapping contact areas along the front between the lower and upper cowling for a nice tight fit.
Have fun,
Dave
 
You know....I've been dreading this work...but like the rest of the kit....once you tackle it, not really bad.

It's also nice having the feed back of this forum...Scott, much appreciate your input keeping us fledgling in step....when I get this bird in the air I'll stop by your "towered strip" and buy you a cool one of choice.😎
 
Mount Engine/Prop/Spinner First

I was surprised to see the KAI called for fitting the cowling before mounting the engine. Other projects I have worked on always mounted the fixed engine before fitting the somewhat adjustable cowling.

On our -12 project, I cut the cowlings to the scribe lines and test mounted them with the engine and spinner back plate (bulkhead) in place. At the upper left side the top cowling almost touched the edge of the back plate, perhaps 1/32 clearance. Ultimately I removed 1/16 to 1/8 from the rear edge of the top cowling to pull the front surface of the cowling away from the back plate to an eventual .15 to .18 inch space.

That said, I may have contributed to the problem when I prepped the cowlings. The scribe lines were faint to nonexistent. I used reflections and a horizontal flashlight to trace them in black ink before cutting, but still had to interpolate in places. Perhaps the molds had worn by the time kit 921 was produced.

Recommendation: Mount the engine, back plate and rear prop hub first!
 
Mount engine first if possible.

I did the install in the KAI order and found that my spinner was too close to the cowl after I mounted the engine. Needed to fabricate a spacer and also ordered longer bolts for the propeller install. Not overly difficult but tasks that could have been avoided. If I build another -12, definitely would mount the engine before finishing the cowl.
 
Mine is at least 1/4 or more. I made the mistake on my first RV build of getting it too tight. Almost impossible to get the cowl on and off without chipping and scratching the paint. I would suggest 1/4 inch.
 
Last edited:
Pat Stewart said:
Mine is at least 1/4 or more. I made the mistake on my first RV build of getting it too tight. Almost impossible to get the cowl on and off without chipping and scratching the paint. I would suggest 1/4 inch.
Click to expand...

I would recommend against that.

There is no comparison of cowl removal on the RV-12 to the other RV's.

1/8" is more than enough clearance, more than that actually starts to negativelyreduce clearance in other areas.
 
rvbuilder2002 said:
I would recommend against that.

There is no comparison of cowl removal on the RV-12 to the other RV's.

1/8" is more than enough clearance, more than that actually starts to negativelyreduce clearance in other areas.
Click to expand...

Sorry must disagree, I have taken my 12 cowling on and off many times. 1/8 is too tight. Mine is 1/4 and there is no internal clearance issue. The 12 cowl has exactly the same problem as the other RV,s with getting the fwd section behind the spinner in place and off, exactly the same.
 
Last edited:
Sure, I'll join in -- I have @ 1/8" gap and removing / installing my cowl is a relatively easy one-man job. I think that the clearance around the exhaust pipe exit hole is more of a factor in how easily / difficult it is getting the cowling on /off.
 
DHeal said:
I think that the clearance around the exhaust pipe exit hole is more of a factor in how easily / difficult it is getting the cowling on /off.
Click to expand...

And whether the exhaust pipe has been trimmed.... the earl version exhaust with the slanted pipe needs to be trimmed ~ 4 inches....

There is really no comparison between cowl removal on a 12 and the other models (I have worked on every model ever produced). There is no inlet seals that you have to fight passed the inlet ramps of baffling, etc. As long as you learn to navigate the exhaust pipe (which is even easier with the later version with the vertical exit pipe), the RV-12 cowl could be any easier.
Proper positioning of the oil cooler hose fittings (described in the KAI) can make the oil cooler pretty much drop into place on its own also.
 
rvbuilder2002 said:
And whether the exhaust pipe has been trimmed.... the earl version exhaust with the slanted pipe needs to be trimmed ~ 4 inches....

There is really no comparison between cowl removal on a 12 and the other models (I have worked on every model ever produced). There is no inlet seals that you have to fight passed the inlet ramps of baffling, etc. As long as you learn to navigate the exhaust pipe (which is even easier with the later version with the vertical exit pipe), the RV-12 cowl could be any easier.
Proper positioning of the oil cooler hose fittings (described in the KAI) can make the oil cooler pretty much drop into place on its own also.
Click to expand...

Brilliant, no ramps. Still must get the cowling up and behind the spinner.
 
My only point here is 1/4 works fine with no internal clearance issue and also improves the ability to get the cowling on and off. I have no issue with anyone wanting to use 1/8, builder choice.
 
You must log in or register to reply here.
Back
Top