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  #1  
Old 10-05-2021, 11:45 AM
PBell PBell is offline
 
Join Date: Mar 2018
Location: Granbury Tx
Posts: 17
Default Check my thinking before I make a mess

Trying to finish up my -9 o-320 FP. The cowling was sent in early 2019 and because of a move and family problems shortly after delivery, my inventory check was not thorough. Not really knowing that much about cowlings, I saw a cowling and checked the box on the inventory. Fast forward a year- trying to install over a FAB, hmm, doesn’t fit! Looking closer, tag that is glassed in the corner of cowling says “IO360”. So seeing $$$ signs trying to figure out how to ship back to Vans for the correct cowling, I called Vans, tech support told me to cut out the bottom of the cowling and drop in the -6 scoop and glass it in. I’m fixing to make the final mating cuts. Was going to cut each piece within a quarter of an inch of each other then grind a scarf angle on each piece so the scoop fits slightly into the cowling then start glassing them together. Does this seem like the right thing to do? What should I use to make this scarf joint? Thanks in advance!
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  #2  
Old 10-05-2021, 12:24 PM
Ralph Inkster Ralph Inkster is offline
 
Join Date: Feb 2008
Location: Calgary, Alberta
Posts: 1,534
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You have trial fit the cowl & scoop in reference to the carb & where the FAB air cleaner will be? Don't guess positioning it or you might have clearance issues later.
-Cleko or solidly tape a spreader bar across the aft edge of the cowling to preserve the dimensional shape of the cowl in general.
-Mark a center line in the scoop and cowling to establish positioning while you work.
-don't trim the overlap yet. maintain about a 1" overlap with the scoop laying in place outside the cowling (laying inside compromises effective interior vertical clearances)
-drill a series of cleko holes all around the scoop & cleko in place.
-trial fit again, be sure you are happy with clearances before gooping things up.
-grind a taper to the external scoop surface edge, as well as roughing up the surface of the cowl in the gluing area. grind the mating surface where needed to get a snug fit
-with a flox slurry, glue & cleko together, let set
-later with flox slurry, smooth out exterior surface, than apply 2 layers of glass to join and smooth the exterior, final shaping can be done with micro balloon slurry, fill, prep for priming
-inside, use dremmel to trim back inside joint. also grind inner honey come back a bit to smoothly transition the inner surface followed with one or two layers of glass to seal it.

This is one way to do it, other ways will inevitably be suggested as well.
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Last edited by Ralph Inkster : 10-05-2021 at 12:29 PM.
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  #3  
Old 10-05-2021, 12:40 PM
PBell PBell is offline
 
Join Date: Mar 2018
Location: Granbury Tx
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Thanks Ralph, yes i did trial fit. I had planned to mount inside the cowling, but the clearance and thickness of scoop outside mounting does make more sense.
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  #4  
Old 10-05-2021, 01:45 PM
BillL BillL is offline
 
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Location: Central IL
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Quote:
Originally Posted by PBell View Post
Thanks Ralph, yes i did trial fit. I had planned to mount inside the cowling, but the clearance and thickness of scoop outside mounting does make more sense.
I had the same dilemma with a 7 cowl and found it worked to mount to the outside you may need the clearance inside. Be sure there is no gel coat where you mount, then you can grind off the excess internally and make it nicely contoured.

I wish I had just spent the $$ in the end and swapped cowls. But . . . this works too. Flying now with 200+ hrs. :-)
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  #5  
Old 10-05-2021, 08:36 PM
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9GT 9GT is offline
 
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Location: Southern Michigan
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Your at that point now where you need to bond, re-glass, and finish the snorkel to the cowling. With a little more work, you can make that snorkel removable and thank yourself every time that lower cowl comes off.
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