Fuel Tank Bay Cover page 1

July 25, 2010

The fuel tank bay cover comes with about 100 holes pre-drilled to the wing.  The tank cover must eventually be attached using #6, flush head machine screws. To accommodate these screws, we need to install nutplates (also called "Anchor Nuts") in the wing. There are several varieties, but the lightest and least expensive are the K-1000 or MK-1000 anchor nuts. The MK-1000 are miniature versions of the K-1000. I went with to MK-1000 ones to save weight and they allow me to get into those inside corners easier.

You can buy a special jig for drilling for anchor nuts, but I have found over the years that the following technique works just fine. Here is a step-by-step description of how I install anchor nuts.  You will need a #40 drill bit, some silver clecos (3/32"), a countersink attachment for your drill and a rivet squeezer along with some #3 flush rivets.  

We start with the drill, anchor nut and clecos:

To give better clearance for drilling, reach under and run the cleco up through the hole from the bottom, clecoing the anchor nut in place through the center (threaded) portion.

To save time, you can do it like a production line, clecoing a whole row of anchor nuts at once:

Now drill just one side:

Put a cleco in that one side to prevent the anchor nut from moving while you drill the second side:

Now remove the anchor nuts, and use a countersink tool to countersink the rivet holes just enough that the rivet will sit in the hole and be flush with the surrounding skin.  Here is a closeup of the countersink tool:

The outside frame does not spin and is adjustable to control the depth of the countersink.  You can also just countersink by hand with a debur tool but it takes awhile.

Here is grandson Cole demonstrating the proper technique for countersinking a hole. Note that he is keeping the tool from spinning and marring up the wing skin. Also note that the proper concentration technique involves sticking out your tongue. He got that from his Papa 8^):

Can you tell he's a big New Orleans Saint's fan?

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