Brief Description: Cowl Fitting - Hinge Drilling Mistake
Removed the cowls and found that most of the rivet holes drilled yesterday are too close to the hinge barrels. I obviosly misunderstood the plans note to drill the holes 5/16" from the edge as I measured from the back edge of the cowl, not from the edge of the hinge that is hidden beneath the cowl.
Remeasured and layed out new holes on the fuselage to put the holes about in the center of the hinge mounting flange (5/16" from the hinge edge). Re-installed the cowl and clecoed it back in place using the incorrect holes. Drilled new holes by removing one cleco at a time, drilling the new hole and then inserting the cleco into the new hole.
Removed the cowls. Removed the hinge halfs and debured both the incorrect original holes and the new holes. Found that in some cases the orignal holes actually penetrated the hinge barrels in a few spots, and were too close in almost all the other cases.
After talking to Van's Builder Support, they confirmed my assumption that there was no safety reason not to use the hinges with the original holes left open, but that there was a risk in doing this that sometime in the future cracks could start at one or more of the original holes and if so would require replacement of any sections of hinge with cracks. Since future replacement of these hinges would require drilling out rivets from a painted cowl and likelly require some repainting, I decided to order new hinge from Van's and use new hinge halfs and redrill the correct holes into the new hinges.
Filled the incorrectly drilled holes in the cowls with epoxy with Cab-o-sil mixture. Placed packing tape on the inside surface of the cowl to keep the epoxy from contaminating the side where the hinge will need to lay flat.
