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Old 01-21-2019, 08:17 PM
rnewcomb7797 rnewcomb7797 is offline
Join Date: Mar 2015
Location: Ft Leonard Wood, MO
Posts: 18
Default elevator fairing countersinking

I need to countersink the elevator fairing tips. Any recommendations on how to keep the countersink cage flush with the fairing since there is that slight flange just to the side of the hole?
RV 14A tail kit done
QB wings in the crate
QB fuselage done
finish kit in progress
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Old 01-21-2019, 11:22 PM
lr172 lr172 is offline
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 5,072

Eirther free hand it or make a plate from .125 and drill a 1/2" or 5/8" hole in it. Space the hole edge to piece edge to accomodate you joggle. 063 migth be enough depending upon the joggle height.

learning to free hand a countersink is an important skill. Its not that hard.

N64LR - RV-6A / IO-320, Flying as of 8/2015
N11LR - RV-10, Flying as of 12/2019
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Old 01-22-2019, 04:34 AM
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mulde35d mulde35d is offline
Join Date: Dec 2017
Location: Lithia, FL
Posts: 217
Default Countersink

+1 for what Larry said about free hand countersinking. I used a 100 degree deburr bit to countersink all my fiberglass. Rather easy once you get the sequence down.
RV-14A Sold
RV-10 Research In Progress
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Old 01-22-2019, 08:14 AM
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kiljoy kiljoy is offline
Join Date: Sep 2014
Location: Alameda, CA
Posts: 181

I did mine by hand as the force of pushing the countersink cage down on mine was bending the fiberglass. I wound up using my drill with countersink bit while using two fingers on either side from the bottom to support the fiberglass.
Dues paid (2020)
RV-14 #140394
Empennage - done(ish)
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Old 01-22-2019, 02:06 PM
MED MED is offline
Join Date: Jul 2015
Location: Aiken, SC
Posts: 569

As an alternative to using a drill, I put my bare countersink bit in my electric screwdriver. The slow speed made it very easy to control depth.
Miss March 2020
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Old 01-22-2019, 05:22 PM
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az_gila az_gila is offline
Join Date: Jan 2005
Location: 57AZ - NW Tucson area
Posts: 9,991

I like doing it freehand as others have mentioned, but with the countersink in an extension. It's easier to handle...
Gil Alexander
EAA Technical Counselor, Airframe Mechanic
Half completed RV-10 QB purchased
RV-6A N61GX - finally flying
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ
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Old 01-22-2019, 06:59 PM
Breezy Breezy is offline
Join Date: Nov 2011
Location: Okeana, Ohio
Posts: 99

The quick way is to free hand the countersink. Use a scrap and practice, the bits can grab with little pressure so get a feel for it. A sharp bit requires very little pressure. Use a very low speed on fiberglass.
I often free hand in aluminum as well if only needing to do one or two holes.
A ready extension for threaded bits is a cable turnbuckle center. The clockwise end is a match to the bit threads, also drill bits. If you have the equipment lathe the unused end for easier chucking to a drill.
Good luck!
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