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  #1  
Old 08-17-2017, 11:28 PM
E. D. Eliot E. D. Eliot is offline
 
Join Date: Dec 2005
Location: San Pedro
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Default Cowlingfront/spinner clearance

I'm interested to know what you have found the measurement between the front of the cowl and the rear of the spinner to be. I suppose that this will be self evident when I get there in the cowl assembly but I am just curious. I'll be there tomorrow.

By the way, I am blown away by the fit that is produced by exactly following the instructions for cutting and sanding the edges of the cowl down to the scribe lines in the instructions. Wish that the scribe lines were a little more prominent though.

I believe that the cowl can be trimmed - fit in place and anchored to the piano hinges in the span of about 6 hours. Just amazing. Takes two people to do it easily.

Thanks for answering
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Last edited by E. D. Eliot : 08-18-2017 at 09:29 AM.
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  #2  
Old 08-18-2017, 01:52 AM
rgmwa rgmwa is offline
 
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Have you hung the engine yet? I had to do a lot more trimming than that suggested by the scribe lines to get a good fit. At one stage I even wondered if the engine was misaligned on the mounts, but it worked out fine in the end. My cowl to spinner clearance is about 3/16", but 1/8" would be OK.
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  #3  
Old 08-18-2017, 06:25 AM
John-G John-G is offline
 
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Location: Northeast Ohio
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I used a long piece of 1/8" thick aluminum bar stock as a spacer taped so it was tight to the prop backing plate and adjusted the fit of the cowls accordingly. Also waited until the engine was hung rather than relying on blind faith that the clearances would be correct. The links below have photos of what I did .... the second link has a photo that shows how the final gap turned out.

http://www.dogaviation.com/2016/05/b...etter-fit.html

http://www.dogaviation.com/2016/05/m...s-cowling.html

Happy building,
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  #4  
Old 08-18-2017, 09:26 AM
E. D. Eliot E. D. Eliot is offline
 
Join Date: Dec 2005
Location: San Pedro
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Default Thank you

Many thanks to both of you who took the time to answer my question. Yes, we really go 'all in' when we trim the fiberglass to the scribe lines! I have the bottom one half cut and sanded to the scribe lines and the fit to the fuselage is amazingly good, Haven't measured to the back plate yet this morning and your answers are very helpful.

Now, I have to make a guess as to how much of a 'gap' to allow between the fuselage sides and the fiberglass edges - for paint. I'm guessing that 1/16" is about right?

Thanks again - Ed Eliot
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Last edited by E. D. Eliot : 08-18-2017 at 09:58 AM.
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Old 08-18-2017, 10:22 AM
sblack sblack is offline
 
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Location: Montreal
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If the gap is too small, won't it create a nightmare for installing and removing the cowling without scratching it? I have not got to that part of my construction yet, so I would defer to those who are flying for advice. Certainly a small gap looks great and it is good for drag, but if you end up gouging the paint everytime you remove the cowling it will look awful before long.
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Old 08-18-2017, 10:47 AM
rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by sblack View Post
If the gap is too small, won't it create a nightmare for installing and removing the cowling without scratching it? I have not got to that part of my construction yet, so I would defer to those who are flying for advice. Certainly a small gap looks great and it is good for drag, but if you end up gouging the paint everytime you remove the cowling it will look awful before long.
Can't consider all RV's the same....
On the RV-12, the cowl to spinner gap has no influence in cowl removal / installation difficulty.
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Old 08-18-2017, 11:10 AM
AeroDog AeroDog is offline
 
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Is is safe to assume that cutting to the scribe line will not remove too much material. In other words, does a builder typically cut to the scribe lines, then remove additional fiberglass to fine-tune the fit?

Jerre
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  #8  
Old 08-18-2017, 03:15 PM
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scottmillhouse scottmillhouse is offline
 
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Quote:
Originally Posted by AeroDog View Post
Is is safe to assume that cutting to the scribe line will not remove too much material. In other words, does a builder typically cut to the scribe lines, then remove additional fiberglass to fine-tune the fit?

Jerre
I would NOT cut exactly to the scribe line and I would NOT even consider anything more than a very rough trial fit before you install the engine. For my 12 for the first cuts I was always about 1/4" outside the line first and then trimmed, filed or sanded to fit. I used 1/8" cowling to spinner gap and to center the cowl to the spinner I needed about an extra 3/16" on the left side. If I cut to the line the cowling would have been off center with a 1/4" or so gap. It could just have been my cowl but why risk trashing any parts by cutting too close.
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  #9  
Old 08-18-2017, 04:24 PM
DHeal DHeal is offline
 
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I cut and fitted my circa-2012 RV-12 cowl before mounting the engine. By following Van's molded-in trim lines I ended up with a very nicely fitting cowl. My cowl-to-spinner clearance is @ 3/32" with no rubbing. That being said, I think having the engine in place would alleviate some builders' cowl fitting concerns.

As rvbuilder2002 noted, this cowl-spinner clearance is not a significant factor for cowl removal. The significant factors are 1) providing an appropriate shape around the exhaust pipe-cowling exit hole and 2) ensuring that the long thin longitudinal slot along the bottom of the cowling is sufficiently wide to readily clear the nose strut with nose strut fairing installed. With these clearances, the lower cowling can be easily removed by slightly lowering it vertically and then sliding it aft and off.
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  #10  
Old 08-18-2017, 05:27 PM
rgmwa rgmwa is offline
 
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Quote:
Originally Posted by E. D. Eliot View Post
I'm guessing that 1/16" is about right?
That's what I did.
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