Here is the pic after I had finished setting all the remaining rivets. Call it being lazy or whatever, but once I had changed the setup to allow me to squeeze the most forward rivets - 2 nutplates on the bottom side and two more on the top, I decided that instead of switching everything back to the previous clamping and setting method, I would just keep going with the new setup. Why is this significant? Well, the change in the setup also meant that instead of pulling the stationary part of the yoke against the manufactured head of the rivet and the skin, and allowing the ram of the squeezer - the moving part - to smash the rivet tail, the process is reversed. So I had to place the moving ram over the manufactured head of each rivet, and try to keep it centered on the rivet head as it moved upward to close the gap with the stationary part of the yoke on the other side.
SO the difference is that when configured one way, you are holding the squeezer stationary against the rivet while the ram moves and sets the rivet. For the other configuration, the ram is moving upward and you have to try to keep the rivet set over the center of the rivet as it moves. THis is how I have messed up so many rivets in the past that I cannot even begin to count. Trying to keep a flat rivet set stationary over a small rivet head while the ram is moving is counter-intuitive, but the problems is that, as is the case here, sometimes you do not have much of choice as to how things need to be configured in order to get the job done. So you have to learn how to rivet using a lot of different techniques and setups - that's just the way that it is. In the above pic you can see how the ram will push on the skin and the rivet head as it moves up, so you end up developing this sense of allowing the ram to move up while the squeezer moves backward a bit, and, if everything stays in alignment, i.e.the rivet set on the ram does not slip off the center of the rivet head, the other flat set will eventually make contact with rivet stem and smash it to the proper size.
Fortunately I was able to set all the remaining rivets that way, and they all turned out fantastic! So I did not even have to drill out or reset any rivets. All 14 nutplates for the tank attach edge of the subskin were set successfully and correctly, and I was very pleased with that. it is not often that I engage in a rivet setting session and I do not have drilled our any rivets or fix a problem of some sort. I was glad to get that behind. me. Here are the finished nut plates - all riveted on.
With that done I decided that the next major task was to drill the corner holes in the LE skin to establish each corner radius as closely as possible and provide the relief holes for the straight cuts that I need to make to remove that portion of the LE skin that will now be "removable."
The steps were:
1. Clear off my work bench to allow the LE skin to sit on the top surface
2. DEtermine how high above the work bench I would have to stack other drill boards to account for the depth of the unibit to create a 1 inch wide hole with the necessary 1/2 inch radius that I designed each corner to have.
3. Charge my batteries for my electric cordless drill, which is once again the tool that ALWAYS use when drilling holes in metal with a unibit. NEVER use a high speed air drill with a unibit. I learned this lesson a very long time ago and have heeded it ever since. Air drills turn way to fast, and unibits cut much too quickly and efficiently, and the drills lack sufficient torque, to ensure that the hole will be drilled properly without distortion or without accidentally over-sizing the hole.
4. Install the correct unibit with a 1 inch diameter step in the drill
5. Stack the required number of drill boards on the work bench uner the Le skin to ensure that the unibit will not drill into the work bench top. IN my case I had to ensure that I had at least 2 inches of drill board under the LE skin.
6. Clamp the LE skin over the drill boards. Again, the idea here is that the unibit needs to drill into the thin flimsy metal of the LE skin and then into the wood underneath to keep from marring the hole in the metal and causing substantial burs. This is why you need a high torque drill - because you have to drill through so many layers or thickness of wood, in addition to drilling the hole in the metal.
7. Measure 1/2 inch x 1/2 inch from the cutlines on the rear and sides of the LE skin, mark that location and use the punch to mark that location. This is to be the center point of where the unibit must start drilling in order to achieve the 1/2 inch radius that matches the curvature of the skin that I had already drawn on the surface. I started out by drilling a #40 pilot hole, so the 1/4 inch wide center point of the unibit would be able to locate a good center without wandering. Then I just inserted the unibit tip in that hole and started drilling slowly to ensure that it was entered correctly. I did NOT drill the hole up to 1/4 inch before using the unibit, as I did not consider that necessary.
7. Drill the two corner holes on one side of the skin, unclamp, flip the skin over, reclamp, and repeat the steps to locate the drill hole and drill the two holes on the other side of the skin.
Here I am beginning to stack the required drill boards on the bench after determining that I will ned at least 2 inches of wood to prevent drilling into my work bench top.
I decided to use my Dremel tool and an EZ lock reinforced cutoff wheel to make the necessary straight cuts, and for this job I wanted a fresh wheel on the tool, so I changed out the old one which was about down to the shaft, with ab rand new disk:
Another blurry pic, but this is my harbor freight unibit that has a 1 inch wide step in it that is about 2/3 up from the tip. You can just see on the right side where I marked the step just above the 1 inch step with a sharpee so that I could tell which step I was on as the tool advanced through each step in the drill bit. I frequently stopped to clear debris from the drill hole and to check the progress of each step against the lines I had drawn on the LE skin, just as I had one before when I cut out the hole for the new access panel so long ago.
Next are the two holes on the bottom skin after I had drilled as close to the pre-marked lines on the skin as I dared. In fact I got a little too close on the first one.
And here is my clamping setup. I ended up using a 3/4 inch particle board, 2 2 x4s, and a 2x6 board on top of my work bench to provide the depth that I needed to keep from drilling into my work bench. Used a very haeavy can of clecoes and my clamps to secure the skin on the workbench. The top of the skin draped over the front of the work bench just fine while the bottom skin layed relatively flat. This setup worked great.
And finally a pic of all four corner holes drilled in the LE skin. I had hoped to also perform the big cut on the remove the section of the Le skin, but I was exhausted and needed to get some sleep first. Unfortunately the weather is going to change and get cold and snowy for the next two days, and I will NOT perform the cuts of the LE skin unless EVERYTHING is optimal. I have come too far to screw this up now, so I am not taking any chances. SO the best I could do for now was setup the LE sin for the next step, which is to FINALLY cut out the section that will ultimately be removable.
Here is the sequence of pics showing how I did that:
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