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Cowling dimensions

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n76lima(at)mindspring.com
Guest

Posted: Tue Mar 09, 2010 3:13 am Post subject: Cowling dimensions

 	  Quote: 	
		  Bob S, you're a font of knowledge on lots of things.  Do you know if there

  are differences between the installed heights of any of the engine mount

  vibration isolators?  I know there a a couple of different part numbers

  out there for Tiger/Cheetahs, do they have different installed heights?


	


I don't have any data on differences in height between the Lord and Barry 

mounts.  I have shimmed (and in many cased UNshimmed) the engine to mount 

configuration to get the spinner centered in the stock nose bowl.  IMHO, 

the purpose of the shims is to make up for manufacturing tolerances in the 

cowling, the mount, and the firewall.  Only the bottom shim washers are 

required to have the engine clear the steel mount, due to the diameter of 

the pressed steel cups that Grumman used.  Other brands (C, P, B) have 

different designs of steel mount pads, and don't require any lower shims to 

be standard.



It is interesting that the experimental crowd just bolts the engine to the 

mount, and then fits the cowl with the spinner in the position that it 

falls.  Could be some pretty large plane to plane variations as the exact 

position of the firewall varies, the mount varies, and if you listen to 

PowerFlow, even the Lycoming engine varies from unit to unit!  And this 

could affect the thrust line, which in turn changes the flight characteristics.



Given the problems I've had swapping cowl parts to repair crack damaged 

planes, I'd say there probably is AT LEAST 1/4" manufacturing tolerance in 

the area you speak of -- distance from firewall to crank flange.



My suggestion is to center the spinner in the stock cowl, and then install 

the Jaguar cowl and trim the trailing edge as needed to achieve a good fit.



Alternatively, you might have to construct some sort of jig/fixture that 

will confirm the crank flange position relative to the firewall for a 

"standard" installation, and then compare that to each plane before the 

gross trim of the cowl.



Best wishes, we are all pulling for you!



Bob Steward

Birmingham, AL

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GrummanDude

Joined: 15 Jan 2006
Posts: 926
Location: Auburn, CA

Posted: Tue Mar 09, 2010 8:27 am Post subject: Cowling dimensions

Bob, both this and the one you sent to TeamGrumman(at)aol.com come to the same mailbox.  

 

  

 

 

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_________________
Gary
AuCountry Aviation
Home of Team Grumman

GrummanDude

Joined: 15 Jan 2006
Posts: 926
Location: Auburn, CA

Posted: Tue Mar 09, 2010 8:53 am Post subject: Cowling dimensions

Bob, could you do me a favor and post this request on GG?  The more data the better. Thanks

  Gary

 

  

 

 

  --

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_________________
Gary
AuCountry Aviation
Home of Team Grumman

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