Countersunk a Million Rivet Holes

Well, it felt like a million holes at least. Tonight I worked on the Main wing spar to get the remaining main wing spar flange holes countersunk for the dimples in the main wing skins, which I am going to start on tomorrow. Yesterday I also edge-deburred 3 of the 4 sides of the top outer wing skin. I also filed away those pesky points on the edge of the skin where it separates from the metal sheet that it is cut from on the CNC machine at the factory. These are potential sources for stress risers in the skin that could lead to cracks and fatigue. I think some builders leave these as is because they probably don't even realize they are there. I can feel them with my finger. Chalk that up to years of building plastic models where you had to remove each part from the plastic tree on which each part is molded. You had to clean up those edges to.

SO now most of the rivet holes in main wing spar flanges have been countersunk. I also called Vans today to ask about the corner of the skins that overlap when you form a lap joint with the inner and outer wing skins.This corner gets filed down so that the edges of the overlapping wing skins butt up flush with the fuel tank skin. I needed to find out if I am still dimpling those skins where they get thinned down quite a bit. The answer was yes.

Now for more about Dan's method to "remove" the LE assembly, which caused me such grief the other day. In fairness to Dan, when he came up with his idea to properly position the tank baffle to ensure that the skins all butt up to each other properly, which Van's instructions would NOT guarantee, he was experimenting with this for the first time. Dan did his Right wing first, followed by his left wing.

What I found out after I read ahead in his build log and reviewed how he did this for the left wing, was that he DID detach the clecoes holding the 408 LE rib and joiner plate to remove the LE from the wing spar while still leaving the fuel tank firmly attached to the wing spar. So the problem was that the first time he did this on his right wing, he did not  post anything about that crucial step in this process. However, for his left wing, he not only wrote about this critical step, but he also took a picture of it.

SO as with all experiments, you learn a bit more each time you repeat the process. Had I been smart enough to read ahead to his left wing assembly, I would have seen this and not tried to destroy my LE like an idiot.

I also wanted to mention that Vans was absolutely no help in this department, but not for the reasons I mentioned in an earlier post. After I re-read their instructions today, they basically have you attach the LE to the wing spar, and then they tell you to laeve the LE there  and "get to work on the fuel tank." then after you do all fuel tank work, you don't see another word about the Le until AFTER ALL of the fuel tanks assembly is complete. I mean sealed, riveted - COMPLETE. Then the next thing they tell you is to rivet the LE in the cradle OFF the WING - but they NEVER tell you when to 'remove the LE from the wing spar after you left it there. typical Vans instructions severely lacking in critical points of the build. Ridiculous.SO if you followed their method, you would still end up scratching your head about how and when to remove that LE assembly.

Lastly for tonight, before I can start riveting the LE together, I have to perform the final steps to make the cutout of the LE skin. I called Jim Elliot to discuss this with him again. The main questions were if I should leave enough outer skin in between the ribs of the bay in question that I will be cutting so that another line of rivets could secure the outer skin to the subskin to secure that area from bending or twisting and possibly cracking. The answer was yes, and use the same rivet pitch as was done on the rivets that attach the skin to the rib flanges and the subskin. SO I will be leaving about 1.5 inches or so of extra outer skin next to each rib to provide enough room for a line of rivets relatively close to the existing rivets that attach the skin to the ribs and the subskin. And then there will be enough rove to install a line of K1100-8 nut plates along the sides as well. this is consistent with information about this sort of things in AC43-14 for lap joint types of "repairs" which is similar to what I would be doing.


I also took a closer look at the lap joint or splice joint that is used to join the outer and inner wing skins, and noted the spacing and rivet pattern that they used  for that area, again which is very similar to what I will be doing with the LE. SO this gave me something to measure and to look at so I could see how this setup might look when I do it on both sides of the skin next to each rib.

The next decision was what type of radius to use for the rear part of the cutout. After using the 1/2 inch radius or the new access panel, I think I am going to stick with that for the transition of the cutout from along the sides to the rear portion on the top and bottom of the outer skin. this makes a nice large transition that won't load up the corners as much as a smaller 1/4 inch or 1/8th inch radius would. It also makes for a nice wide round corner to fit the removable LE skin up against when you mount it the LE.

SO I think I am very close to making some final measurements for cut lines and rivet lines, spacing adn patterns,as well as the number of nut plates and screws to use. I have also decided that the cutout will go back as far as the 4th or 5th rivet along each rib. Since the RV wing is very thick wing plan form, this means that the size of the removable LE that I will be making is still going to seem pretty large as it wraps around the subskin from top to bottom. And there is something to consider about how cutting away a smaller size is safer because I can always make it larger if necessary. But it is impossible to go the other way. If I remove too much, I can;t get it back. So this is that last nerve racking decision to make to determine the ultimate size of the removeable LE.

This is also where I had said that I would make a mock up of the assembly to get a feel for how this go, but the fact of the matter is that I think I have planned and researched this whole thing out to the point where I feel pretty comfortable with all the remaining steps that need to be completed to make this monster idea into a reality.

Anywhoo, I'm rambling about all this again just to make sure I capture it in writing. When I am ready, and the layout is drawn out and measured, it will be time to remove the 2 ribs and the subskin for one last final time, and make the cuts in the outer skin and finish trimming up the subskin to its final form.

KPR