Matt's RV-8 Project



Matt Dralle's RV-8 Project
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Date:  2-15-2010
Number of Hours:  1.00
Manual Reference:  
Brief Description:  Cowling Pin Retainers - Part 1

In my estimation, there isn't a clear recommendation in the plans on how to hold the long, cowling side pins in. They take a drill to actually get them all the way in, but they could definitely work themselves out with vibration, so some method of holding them in with a screw or something is necessary. The pins are about 3 feet long and join the upper and lower halves of the cowling together through a piano hinge. Its a pretty slick system, but can be a little frustrating at times trying to get them in and out. Van's offers replacement hinge pins with pre-welded "tabs" that are about 1" long and about 1/2" wide with a single hole for running a screw through and into a platenut mounted inside the cowling. While that would certainly be functional enough, it just lacks something in the elegance department.

A couple of weeks ago, I happened to notice these little airfoil-shaped retainers on a fellow RV-7a builder's plane. I decided to try to make a set of my own. I started with a sheet of .063" 2024-T3 and the laid out the shape I had in mind in CAD on the computer and then printed it out on some adhesive backed paper. I added a center, front hole to allow the angle on the hinge pin to poke though and be held from going in or out. I then added a couple of #6 counter sunk holes for mounting the retainer to the cowling, and then added a couple of platenuts mounted on the inside of the cowling. I got the bend in the retainer by putting both the left and right piece together in the vice and gently "pounding" a series of small bends until I had a shape that matched the contour of the cowling perfectly. I used a belt-sander to get the final outside shape of the retainer, and then surfaced the top side to remove any of the bend marks.

All-in-all the whole thing came out pretty nice. The retainers hold the pins securely, and more or less look like they were suppose to be there.
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Airfoiled Retainers Done On CAD

Airfoiled Retainers Done On CAD

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Holes Drilled, Screw Holes Counter Sunk

Holes Drilled, Screw Holes Counter Sunk

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Contour To Match Cowling

Contour To Match Cowling

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