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  #1  
Old 06-03-2018, 08:16 PM
Drifteral Drifteral is offline
 
Join Date: Nov 2016
Location: Battle Creek, NE
Posts: 36
Default Cowling Dilema.

After mounting the engine and mount to the firewall, I temp installed the cowling to the airframe and noticed there is about 1/2" from the front of the ring gear to the front edge of the cowling.

I noticed my cowling has the "CS" marked on it and i'm using a wood prop.
Is it normal to have to trim the back of the cowling to get the fit needed for the prop/spinner?

I was under the impression that most 6's needed a prop spacer of some kind.
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  #2  
Old 06-03-2018, 08:49 PM
N941WR's Avatar
N941WR N941WR is offline
 
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Location: SC
Posts: 11,532
Default

You need to get one of these spacers from Saber Manufacturing:

(Click to enlarge)

Then install the prop and spinner. Once they are in place, you fit the cowl to them, starting with the top cowl. Set it slightly low (About an 1/8" should be fine) so that when the engine sags, it will fall in line.

This picture is me fitting the bottom cowl.

(Click to enlarge)

Good luck!
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Last edited by N941WR : 06-03-2018 at 08:55 PM.
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  #3  
Old 06-04-2018, 05:42 AM
Drifteral Drifteral is offline
 
Join Date: Nov 2016
Location: Battle Creek, NE
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Default

Bill thanks for the reply.

I should have done a better job of explaining. In my situation any kind of a spacer more than say 3/4" the cowling will be to short.

In starting to think i have the wrong cowling.

Al
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  #4  
Old 06-04-2018, 06:09 AM
Rv3Dave Rv3Dave is offline
 
Join Date: Jul 2016
Location: Florida
Posts: 31
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Originally there were two cowls offered, one for constant speed props and one for fixed pitch. At that time the fixed pitch cowl used a 4” extension. At some point Van’s switched to a 2 1/4 inch extension for fixed pitch which allows for the same cowl to be used for either type of prop. If you have a very old cowl it could be the shorter constant speed version. However, it sounds like any extension would be an issue with your setup. Maybe the back of the cowl was trimmed incorrectly at some point.
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  #5  
Old 06-04-2018, 09:58 AM
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
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Quote:
Originally Posted by Drifteral View Post
After mounting the engine and mount to the firewall, I temp installed the cowling to the airframe and noticed there is about 1/2" from the front of the ring gear to the front edge of the cowling.

I noticed my cowling has the "CS" marked on it and i'm using a wood prop.
Is it normal to have to trim the back of the cowling to get the fit needed for the prop/spinner?

I was under the impression that most 6's needed a prop spacer of some kind.
Is this a new cowl installation that you are just starting?

The aft edge of the cowl always requires some amount of trimming.

A cowl labeled CS means it is the constant speed or fixed pitch version (VS fixed pitch only) and requires that a fixed pitch prop be installed using a
2 1/4" prop spacer. Until that is done, you wont be able to accurately evaluate the fit of the cowl.
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  #6  
Old 06-04-2018, 04:28 PM
Drifteral Drifteral is offline
 
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Location: Battle Creek, NE
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I see no evidence that the cowl has been trimmed or otherwise modified.

With a 2 1/4" spacer the cowl will be 1 1/2" to short.

Right now if I remove approx. 1/2" from the firewall side of the cowl it will be even with the face of the ring gear.

Maybe that's the way it's supposed to be. I don't have a problem with trimming the cowl to fit and also not having to use a prop spacer.

The only concern I have would be with clearance inside to cowl such as starter, alt and exhaust. So far it looks like there are no problems with the starter but I don't have an alternator or exhaust yet.
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  #7  
Old 06-04-2018, 05:34 PM
rvbuilder2002 rvbuilder2002 is offline
 
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Location: Hubbard Oregon
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Quote:
Originally Posted by Drifteral View Post
I see no evidence that the cowl has been trimmed or otherwise modified.

With a 2 1/4" spacer the cowl will be 1 1/2" to short.

Right now if I remove approx. 1/2" from the firewall side of the cowl it will be even with the face of the ring gear.

Maybe that's the way it's supposed to be. I don't have a problem with trimming the cowl to fit and also not having to use a prop spacer.

The only concern I have would be with clearance inside to cowl such as starter, alt and exhaust. So far it looks like there are no problems with the starter but I don't have an alternator or exhaust yet.
Your clearance concerns are valid, but your description of the mis fit makes no sense.

The original (non constant speed) cowl used a 4 inch thick prop extension vs the 2 1/4 that is used with the CS cowl. What you are seeing makes it sound like you either actually have a 4" extension or you fwd fuselage was built incorrectly (doesn't have the fwd tilt of the upper firewall).
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  #8  
Old 06-04-2018, 05:34 PM
Rv3Dave Rv3Dave is offline
 
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Location: Florida
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Not using a spacer is not normal, either the cowl is too short or the engine mount is non standard, assuming you are using a lycoming 4 cylinder engine.
If you can make it work without a spacer go for it.
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  #9  
Old 06-04-2018, 05:46 PM
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az_gila az_gila is online now
 
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Quote:
Originally Posted by rvbuilder2002 View Post
...... or you fwd fuselage was built incorrectly (doesn't have the fwd tilt of the upper firewall).
I wouldn't call it incorrect...

The original plans had the firewall with no slope in the upper area. I had to splice metal on my F-646 parts to get the slope.

F-646 was significantly redesigned in 1999 (R7 on Sheet 30).
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  #10  
Old 06-04-2018, 05:53 PM
elev666 elev666 is offline
 
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Location: Kincardine Ont,Can
Posts: 77
Default Check your engine mount

Just a guess , but is there not two different lengths of engine mounts ? One that gives you a 8.5 firewall to isolator mount centers and the other is 11 off the firewall for the lighter 0-290/ 235 powered RV 6s,,,, you may have the long one !
Scott may enlighten us on the history here !
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