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  #1  
Old 09-17-2020, 10:48 PM
Stewbronco Stewbronco is offline
 
Join Date: Sep 2019
Location: Langley BC
Posts: 156
Default Spinner to cowl gap

Ok. About to mount new CATTO 3 blade and spinner . Definitely going to be using plane for Aerobatics and I remember how much the spinner in old Decathalon would move when rolled inverted . My gap right now (Sensenich metal prop varies from about .525" at bottom to about .255" at top of spinner to front of cowl . Obviously the less gap looks better but how much is enough to allow for engine movement? ....mounts seem to be in good shape I just think it was built this way as the gap difference would be the other way around if sagging mounts .
I am leaning towards the 1/2" gap as much as I don't like the look of it ...seems the safer option ??
What is experience out there with this ??? Perhaps not the issue I think ??
Thanks in advance. Stew
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  #2  
Old 09-17-2020, 11:17 PM
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rv8ch rv8ch is online now
 
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Location: LSGY
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Default gap

Interesting question - most people want a very small gap for looks, but then complain about how hard it is to remove the cowl. I've never heard of someone who got it too tight and then had rubbing on the cowl, but clearly it could happen.

Based on my reading and looking at hundreds of RVs at KOSH over the years, I think 1/2" is at the higher end of the gaps most people have - and the lower target seems to be 1/8". I have not measured mine after paint, but I have enough to get a thick microfiber cloth in the gap before I remove the cowl to protect the paint.

Let's see if someone reports a problem rubbing with a too tight spinner to cowl gap.
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  #3  
Old 09-17-2020, 11:34 PM
Stewbronco Stewbronco is offline
 
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Location: Langley BC
Posts: 156
Default Cowl removal

Agreed ...cowl removal is a definite consideration for me...especially with the composite prop
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  #4  
Old 09-18-2020, 05:07 AM
fixnflyguy fixnflyguy is offline
 
Join Date: Jan 2006
Location: Winston-Salem, N.C.
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Default My thoughts..lots of variables

Mine is a little over 1/4" all the way around, and cowling removal must be done very carefully..the top cowl is no issue as it lifts straight up, however the bottom has to be rotated down and forward. I always keep a roll of cheapo vinyl 2" tape around that I apply around the lower cowl lip and gear fairings for cowling removal. It protects paint and allows the cowling to bump the spinner with no damage..10 years and not a scratch on my cowlings. Also, before you paint, make SURE you can get the cowling on and off WITH propeller, spinner and gear leg fairings all on the plane. The leg fairings are also a trickery spot for the cowling trim/fit. Make sure the spinner backplate and spinner are super smooth and true all the way around..I have seen some that are like hacksaw blades!
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  #5  
Old 09-18-2020, 05:26 AM
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Larry DeCamp Larry DeCamp is offline
 
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Default Gap adjustment ?

Stew, how do you propose to adjust the gap ? I have two 3 blade Cattos and the rear plate seats on the crank extension and thats it. Are you proposing shimming the spinner back plate or adding some filler to the cowl ?
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  #6  
Old 09-18-2020, 08:14 AM
Stewbronco Stewbronco is offline
 
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Default Adjust cowl

Add filler to cowl ....I would never shim the spinner....

Last edited by Stewbronco : 09-18-2020 at 08:21 AM.
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  #7  
Old 09-19-2020, 05:21 AM
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MikeyDale MikeyDale is offline
 
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Location: Garden City Texas
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Default

Mine is 9/32". I wished I had 3/8" or at least 5/16". Bottom cowl is a little irritating! I shimmed the engine mount down then removed the shims after 150 hrs as the engine sagged.
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  #8  
Old 09-23-2020, 09:53 PM
1flyingyogi 1flyingyogi is offline
 
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Location: Long Beach, CA
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Default

I had a 1/2" gap before and hated it. Finally, I machined down the prop extension by about 1/4" and it looks a whole lot better now, but as many have pointed out, taking the lower cowling on and off takes more effort and finesse now. I put some tape on the cowling to protect it when removing/ reinstalling. Engine movement is not enough to cause any rubbing at 1/4" gap. Aerobatics and all.

Of course, check your prop bolt clearance and make sure they are not going to bottom out if you decide to mill down your prop extension. Removing 1/4" from mine was not an issue.
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  #9  
Old 09-25-2020, 12:56 AM
Stewbronco Stewbronco is offline
 
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Default going to fill cowl

MANY THANKS to all for responses .....going to fill cowl front with flox/ resin over some exposed screw heads to 1/4" gap and try cowl on/ off a bunch . Will leave filter at least 1/8" over screw heads in case I feel the need for 3/8" for cowling removal without jeopardizing my new CATTO 3 blade . Pretty sure cowl re/re will be two person job
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  #10  
Old 09-25-2020, 03:14 AM
YvesCH YvesCH is offline
 
Join Date: Feb 2015
Location: Basel, Switzerland
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Default

Quote:
Originally Posted by Stewbronco View Post
MANY THANKS to all for responses .....going to fill cowl front with flox/ resin over some exposed screw heads to 1/4" gap and try cowl on/ off a bunch . Will leave filter at least 1/8" over screw heads in case I feel the need for 3/8" for cowling removal without jeopardizing my new CATTO 3 blade . Pretty sure cowl re/re will be two person job
I also do have a 3B Catto and I have approx. 1/4" clearance. The only thing which is bothering is the rubber flap attached to the lower cowl. As I am in Phase 1 I am taking off the cowl quite often. To remove the cowl I put several layers of tape over the backplate of the spinner to avoid scratches.
To reinstall I fold those rubber flaps around the cowl, fix them with some tape and then install the lower part (I manage meanwhile to do it alone but its better if you have someone with a helping hand). After the lower part is fixed I remove the tape...
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