Prep for new SafeAir Access Panel

Not too much done on the plane today due to Mother's Day and extensive yard work. I made preparations for cutting the new access panel opening in the bottom of the left wing LE outboard skin. Took the following steps:

Measured location and traced the outline of the new panel per instructions from SafeAir. The measurements are 2.25 inches from the edge of the LE skin where it butts up against the fuel tank skin, and 6 inches from the rear edge of the LE skin (the part that attaches to the wing spar.) This is where one corner of the panel is located.

Determined that the diameter of each nicely curved corner of the new panel is 1 inch, so the radius is .5 inches. This is a rather large radius for a piece of metal, and is much larger than the radius of the corners on the Vans panel.

Measured and marked 3 of the 4 corners of the new panel with the .5 inch radius. I could not mark the 4th corner radius because that space is already missing on the LE skin due to the pre-cut panel hole for the Vans panel.

I'll have to come up with a way to cut a 1 inch hole in the skin to match the radius of each corner of the new panel. I don't have a wide-enough unibit with a 1 inch section on it, so I may need to go buy one. Don't want to use a hole saw on this aluminum, especially not the LE skin for fear of damaging it. Might be able to use a flat blade one inch hole cutter/drill bit, but will need to practice on something before I commit to that. I think that a one inch hole is too small for my flying wheel cutter that I have yet to use on anything.

The 1 inch holes need to be drilled in each corner of the skin to serve as starter holes for cutting out the square pattern for the new access panel cutout pattern. They also serve to bring the cut line very close to, but not quite directly on the corners of the panel cutout. This allows one to cut the panel space so that it is close enough to the drawn edges of the pattern so that they can be filed to the final fit for the new access panel. You need to creep up on the final lines for the access panel so that it has the proper seamless fit on all edges and corners. Otherwise it looks ugly and causes drag if there are any gaps between the skin and the panel cover.

Next steps:

Will probably need to remove all the other ribs from the LE skin and clamp the skin down on a drill board so that the unibit holes can be drilled cleanly. The area of the skin to drilled needs to be flat against the drill board, and the only way I can do that is to remove the other ribs.

Use my center punch to mark the center of each hole to be drilled by whatever drilling method I come up with.

Drill each corner hole in the LE skin.

Use a cutting wheel on the Dremel tool to remove the rest of the pattern from the LE skin.

Note that doing this will leave this area looking like a bit of a mess, with part of the new panel hole overlapping the existing hole from the other panel, which will eventually need to be covered back up. That will be remedied later.

File the edges until the new panel fits perfectly in the new panel hole in the LE skin.

Proceed with the rest of the SafeAir instructions for fitting the new attachment flange for the new panel cover. Somewhere during this step I have to figure out how to cover up the old panel hole while retro fitting a way for the subskin to act as the mounting flange for the new panel. There's lots of geometry involved here, as well as figuring out where to drill rivet holes for old panel, and how to design the subskin to act as the mounting flange for both panels.

Confusing? It is to me too. So I have to go slow here to make sure I don't mess this skin up so bad that I will need to order a new one.

KPR...