Deburring holes and edges, scuffing ribs and LE skin for primer

 First things first - a shout out to fellow RV-8 builder and friend Steve Riffe, now living/flying in the Dallas area. We started our tail kits at about the same time in 2009, and he just received his airworthiness certificate for his finished airplane. N ow he can take his first flight and continue with phase 1 flight testing. See post on VAF here , and his builders log is at this location 

Its really great to see another soon-to-be-flying RV-8 make it to the finish line. Way to go Steve!!!!

Over the past several days I have been taking care of several small jobs. The first involved more trimming of the Left wing LE skin edges for the new access panel. I discovered that one of the edges was decidedly not aligned with the corners and was not straight. So I took a straight edge ruler and marked "straight" with the sharpee, and then carefully took the file and trimmed down the metal, being careful not to dig any more ridges into the skin. This next pic shows the result:

If you click on the above pic and view it in a larger resolution and look at the left and right edges you can see the problem. What happened is I filed away a little too much metal on the skin edges. leaving a small gap between the access panel cover and the edge of the LE skin.This happened because I forgot to stop filing after reaching the INSIDE edge of my sharpee line. Instead I kept on filing until the sharpee line was almost gone. Even the ultra fine sharpee can leave at least a 1/32 or 3/64 inch wide line, so you have to remember where to stop removing the metal.

Here is a close up that shows the gap better:

The funny thing is that this gap is much smaller than the Vans access panel and cutout for the original access panel LE skin. I think I have seen posts from other builders where they actually fabricate a new panel cover so that it fits better. Perhaps I will do the same, but for now I will leave it. I still have a lot of surgery to do to figure out how to close up the original hole, and right now that is just a bit more important.

Next is a pic showing the vinyl that I removed from the tip of the LE and the outer races for the rivet holes for each LE rib.

As I mentioned before, I am pretty certain that leaving the interior and exterior vinyl on the pre-bent edges of any skins applies a bit of extra force away from the wing ribs, making them just a little bit harder to bend into position when assembling the ribs. If you remove the vinyl from this area it reduces that stress a bit. Works for me. YMMV.

With the LE ribs completely disassembled I starting scuffing them in preparation for primer. I still need to clean them, but at least the hard part is done:

A couple of important notes about this for other builders. even though I took the time 2 years ago to use a small jewelers flat file to remove the bumps that result from the factory bending of the tip sections of each rib, I found that all of the ribs still needed to be filed a bit more. You can see the file I used in the middle of the above pic.

I made sure I rechecked all of these on each rib, because I was surfing the web one day and found a PDF file link to what I presume to the the new Section 5 of the Vans manual for the RV-14, which is much more informative and contains a lot more tips and tricks than my older Section 5 contains. One of the sections specifically called attention to making sure you do whatever is necessary to remove ALL bumps on the front of all leading edge and fuel tank ribs to prevent bumps from appearing in the skin when you start riveting everything together. they even had pictures and diagrams of how this should look.

My litmus test for this is a little bit visual, but mostly by feel. I ran my fingers over the tops and bent sides of each cutout on each rib, and if my finger gets stopped by a ridge, I went to town on it with the file until is felt reasonably smooth. I was surprised by how much more I had to dress these edges out until I was satisfied that they were smooth enough. It will shock you just ho much you need to thin down the edges of some of these sections. don't be bashful about this trimming if you don't want bumps in your LE wing skins after riveting.

I should have mentioned that prior to scuffing everything I deburred all the rivet holes in each LE rib. I honestly do NOT think I had ever deburred any of these holes in the remaining ribs, while i definitely deburred everything involved in the area of the mod that I am doing, I don't think the LE holes had ever been disassembled beyond that. I was amazed at how much some of the holes needed to be deburred.

One of the hardest things I had to do was deburring the inside of all the rivet holes that attach the top and bottom of the LE skin to the wing spar. The outer holes were easy because they are right in front of you, but I must admit I was not prepared for the need to do all of the inner holes. These were a pain for several reasons:

- They are hidden under the wing spar flanges so you have to bend and contort your body in weird ways to get to them all.

- With one side of the main wing skins clecoed in place, I was not able to get my electric drill with my deburring bit into position to debur one side of the holes. The other side was easy because the wing skin was removed. While I suppose I could have removed the mounted wing skins, I did not want to do this because they do help maintain the structure and placement of the frame. So I took the deburring bit out of my drill as I have done before, and twirled it between my fingers, while contorting myself even more while trying to blindly fit the tip of the bit into each inside hole. Easier to demonstrate than explain, but lets just say it was a major pain in the butt, and it leaves my fingers in a rather raw state after doing this for about 100 holes or so. Anyway, the wing spar holes are now deburred as well, so mission accomplished.

Here is a pic that kind of shows the area that needed to be deburred. I only focused on the top row of rivet holes for now, since those are the holes for the LE skin. I will have to do the bottom row of holes when  am ready to finish prepping the main wing skins, but that can wait.

And then finally, after a bit more precise vinyl removal on the inside of the LE skin, I started scuffing the inside of the LE skin. What follows is a series of pics that shows the overall scuff job of one side, and what appear to be rather deep scratches from all the mod work and fitting, installing and removing parts multiple times, and how those scratches seemed to scuff out pretty well with the scotch brite pad, indicating that the scratches were probably only as deep as the alclad coating of the metal.

And finally, since I will be priming another small batch of parts in the near future, I needed to get two more turkey basters to measure out both parts of the primer, just as I did a few weeks ago. Here is the uncontaminated "new" turkey baster that I got from King Soopers.

Next steps are to finish scuffing the other side of the LE skin, then wash and clean the ribs and skin, then prime them. Once that is done I will reassemble the LE and attach it on the wing spar so I can mark up the subskin for the new access panel opening and start trimming that lovely piece of metal to its final form, whatever that may be!

KPR!