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Permalink Reply by John Austin on April 1, 2020 at 6:45am

Although my build was years ago, my cowl oil filler door opening was similar.  I did not use the supplied fiberglass door, however.  It did not have the slight compound curves necessary to fit nicely in that recessed opening.  I tried heating it and bending it, but never got satisfactory results.  So, I instead used a piece of aluminum for the door. The aluminum allowed me to bend the curves into the door to match the cowl - the final fit was even better than the first picture below.  I used a recessed button latch as many aircraft do, and rather than the included piano-hinge, used a "hidden hinge," available from Cleaveland Aircraft Tool,  that allows more clearance when the door swings open and has a spring to hold it open.  I also safety-wired a piece of soft vinyl tubing to the inside of the hinge's swing arm (not pictured) to act as a bumper when the door opens so it doesn't swing too far and hit the cowl.  In the last picture of my painter holding the upper cowl, you can see the frame I built around the underside of the oil door opening to stiffen and reinforce it and provide a secure mount for the spring-loaded hinge.  Click on the picture for an enlarged image that shows the detail better.  Works great!

John

N750A

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Permalink Reply by John Burns on April 2, 2020 at 11:38am

Thanks for the great pictures.  Exactly what I was looking for.  You probably saved me from wasting some time with that fiberglass piece.  Using aluminum makes a lot of sense.  I think I can even manufacture a hinge like that.  THANKS

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Permalink Reply by John Austin on April 2, 2020 at 11:43am

I think I can even manufacture a hinge like that.

Yes, those "hidden hinges" are rather pricey!  You can probably find a suitable spring at a local hardware store that will allow it to spring open/hold it open.  As you can see, I mounted it with the hinge-forward so the door would tend to blow shut in the slipstream if the latch failed.

BTW, as you can see in the last picture, I laminated a strip of 0.025 along the inside back edge of the upper cowl and the inside rear side edges of the lower cowl to reinforce the areas where the screws and Camlocs attach the cowl to the fuselage.  I used West System's G-flex epoxy and scuffed the metal wet with epoxy (as West recommends) and used a bunch of clamps while it cured.  8 years and 635 hrs and it has never delaminated.  The attach holes have no deformation or cracking of the paint.  My painter recommended it and I'm glad he did!

John

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