Started drilling flap hinges to wing
November 7, 2011 – Over the last week or so I set up to drill the flap hinges to the flap brace on the wing trailing edge.
I decided to cleco the bottom wing skins into place. I’m REALLY glad I did because I found out that the flap braces are not necessarily in the correct position to align the flaps with the ailerons when attached, as seen below:
If I had clamped the flap to the brace, then adjusted to the aileron, it would have been way off.
My next problem was how to hold the skin and the brace together so I could also clamp the hinge in place to correctly drill it. I had read about how other people used rivets to temporarily hold everything together, but it seemed that some of those people went overboard on the size of rivets they used for this. I picked four spots along the brace where it seemed that a cleco did the most good keeping everything tight and aligned, and I laid out rivets at those locations. I’m just using the same -3 rivets that will be used to rivet everything together at the end. I countersunk the skin and used a short rivet to hold the flap brace in place.
When I rivet the hinge in place, I’ll just shoot these like all the others. I don’t believe the countersinks in the skin will pose a problem, because those are surrounded by regular dimpled holes, and I’ll also be putting a strap on the backside. More on that later.
A friend of mine from work, Carlos, came over to see the project and to give me a hand with the alignment of the flaps for drilling. I tried to handle it by myself, but the fine adjustments were a pain, and I was afraid I’d drop a flap.
I had drawn the line along the hinge at 1/4″ as a guide for edge distance. With the trailing edges aligned, we were on the low (edge) side of that line. A little less edge distance than I would like, but again, I’m going to put a strap behind everything, so I’d have extra structural support. We placed a small c-clamp at each end and did the adjustments as needed.
The plans call for a 1/4″ gap between the flap and the aileron; other people have gone with 3/16″. I decided to split the difference and got a nice 7/32″ gap.
The trailing edges in that picture don’t appear aligned because the flap is not held in trail with the aileron.
When we were happy with the positioning, I drilled a couple of holes on each end, just to hold it all in place. Here’s the outboard and the inboard clamp setup:
I removed a flap to expose the hinge and make it easier to drill the rest of the holes.