Transferred all Holes in the Access Panel Mounting Flange to the Subskin

If you have not quite figured out what I am doing in this series of posts (join the club!), I am basically eliminating the need for a separate access panel mounting flange by creating one out my existing subskin. I originally was not planning on doing this until I realized that the subskin was already going to be there, and would serve as an access panel mounting flange just as well as the other one.

Picking up where I left off yesterday, the next step was to match drill the #30 pre-drilled holes in the other mounting flange, through the predrilled holes in the access panel cover plate, and finally into the subskin at the proper locations. By placing the mounting flange over the LE skin, there is a gap between the subskin and the mounting flange that is filled by - you guessed it, the thickness of the access panel itself. it is pretty much the same process that I had to follow to cut the hole in the outer skin. Everything gets mounted in reverse order. The access panel goes under the mounting flange and over the LE skin as shown below:

My first step in transferring all the holes to the subskin was to match drill the predrilled #30 holes. to start this, I first clecoed all the #40 holes around the perimeter of the LE skin. I then had to line up the access panel cover with the predrilled holes in the mounting flange by hand, because remember, the #30 holes do not exist yet in the subskin, so there is no clearance for them yet. I think I started with the upper middle hole and worked my way around, drilling the hole through all 3 layers of metal, clecoing it, and moving to the next hole. The pic above shows what it looked like after drilling adn clecoing everything. The next pic shows the resulting holes after removing the assembly:

Now I needed to match drill the #40 holes on either side of the #30 holes. These are the rivet holes for the nut plates that will ultimately be installed under the subskin. The #30 holes will eventually be drilled to a larger size to accept the mounting screws for the panel cover.

After having a hard enough time with trying to line up the holes of the subskin, ribs, and leading edge skin, I wanted to make sure that all of these holes were as spot-on the mark as possible. The problem now is that I cannot drill the #40 holes through the access panel cover. Those holes only exist in the mounting flange, or in my case, the subskin. If I don;t use something underneath the mounting flange to fill the small gap between the subskin and the mounting flange, the holes might become misaligned during the drilling process.

So I came up with a plan - I decided to sacrifice the panel cover that Vans provided to supposedly fill their pre-drilled access hole in the LE skin. I used it as a "filler" to fill the void between the subskin and the mounting flange so I had solid layers of metal to drill through.

I started with the lower right corner area by placing the Vans-supplied cover panel over their precut opening as follows:

This allowed me to be able to drill most of the $40 holes in that quadrant into the subskin.Here is the post-drilling pic for that section:

Then I relocated the panel cover to the upper right section and drilled as many of those holes that I could:

Every time I finished a section I had to uncleco everything and reposition the access panel to the next section.Took a little time to do this but wasn't that bad. Next was the upper left quadrant:

And then finally down to the lower right quadrant:

I was able to get all the holes from the mounting flange drilled except for one, which unfortunately is located on the left side just below the middle, right where the Vans hole and my new hole merge together. If I were to drill match drill this hole it would just hit the corner of the outer LE skin. So I have to put some thought in to this hole, which I will probably re-position slightly AFTER I figure out how I am going to fill the remaining area of the original Van's hole.

Anyway, after all this was done, I removed the entire panel assembly again to check my handy work and verify if I successfully transferred all the holes to the subskin. I think it came out pretty darn well:

As further proof, I placed the new access panel cover in its position and, now that all the holes have been drilled in the subskin, I was able to cleco it into position to check the fit:

The inner and outer edges of the panel cover are right up against the edge of the outer LE skin, so I may have to do some trimming to account for vibration and airflow pressures causing the two edges to rub and wear against each other. Vans panel cover was WAY undersized for the hole that they made, and I still can't understand why it was cut so undersized. Anyway, he fit of this new, slightly larger acess panel is pretty darn good, and I am pretty happy with these results.

The last pic is of my now machine gun holed Vans access panel cover. It turned out to be a really good back plate for the drilling that I needed to do. I was OK with doing this because, as you can tell from the above pic, I will need to fabricate a rather odd looking piece of metal to cover up the remaining portions of the old hole. Hopefully the pics make this a bit clearer now.

Next step is to drill the two holes in my custom flanges of my custom rib. I am really dreading this for reasons that I mentioned in my last post. Once these last holes are drilled, I need to fabricate that weirdly-shaped piece of metal to fill the remaining void from the Vans pre-cut hole, and come up with a rivet pattern to attach it permanently to the subskin. I will probably treat it like a patch again to ensure that sufficient strength is added back to that area that has been substantially cut away now.

Then I follow the remaining SafeAir instructions to mount the nut plates and drill the screw holes to the required size. Then I still need to decide how much of the subskin to leave in tact, and how much to remove around this entire area.Luckily I managed to check the right wing LE, and was relieved to find out that there is NO Vans precut hole on that side. I don't think I could go through this fiasco again!

Then the whole LE comes back off the wing and gets disassembled yet again (sigh), so that the subskin and other holes can be deburred, and then the dimples will be applied to every hole that needs one. Never thought I would be using the word "dimple" this soon. I wonder if I even remember how to do that?

Progress.........

KPR....