Prep for Final Assembly and Riveting of the LEFt wing LE

As mentioned previously, the next step was to remove the vinyl inside the LE skin that I have left on all this time to protect the metal. I do not prime the entire interior surface to try to save some weight. The epoxy primer overspray and cold temps have left this remaining blue vinyl in a state that is very difficult to remove. Here is one of the problem sections that I needed to remove:

I was not able to take my finger nail and lift up the edge to peel it away like I normally can. The primer hardened onto the metal next to the vinyl making this difficult. So what to do? I still need to remove this protective vinyl because if left on it can cause corrosion to occur by trapping moisture and debris between the vinyl and the metal. Unfortunately the vinyl only chips away and it won't peel off as one piece. 

After pondering this for a bit I remembered that I have a heat gun around here somewhere. I thought that maybe I can use that to heat up the glue on the back of the vinyl to at least soften it up a bit and see if that would allow it to separate from the metal easier. So I got this bad boy out and gave it a whirl:

After mucking with the setting son the gun and experimenting with how hot things could get, I finally came up with a procedure that involved holding the gun at a safe enough distance and heating up the entire surface of the vinyl as well as the edges until the vinyl softened up enough for me to peel it away. What I found out real quick is just how fast and how hot that heat gun can heat of the vinyl AND the metal. SO after figuring out how not to burn myself too much, this actually started to work pretty well:

Here is the sheet removed from the inside of the LE skin:

And here are some shots of what happens to some of the remnant primer 

It separates from the vinyl and rolls up into little flakes that have either a positive or negative charge that causes them to stick to the LE skin. After I got all the vinyl sections in between the ribs removed I had to use a shop vac to remove all the primer flakes.

The next task was to remove the red ink with the metal specification information. Normally isopropyl alcohol removes this very easily, but it has been baked on for so long that t was no longer doing a very good job, so I switched to using acetone, which worked very well. I was not too worried about wiping the acetone on some of the epoxy primer because that stuff, once hardened, is almost impervious to anything, and is very hard to remove with anything but acetone rubbed very deep and hard into the primer to soften it. What little acetone did come into contact with the primer evaporated away before it did any harm to the primer. I used paper towels and small dab of acetone to remove the red ink on the metal. Why remove this? Well some say it can lead to corrosion over time as well, but others say it doesn't harm anything. UP to now I have always removed it from the metal as part of the final assembly prep, so I did it here as well.

Once this was all done, it was time to final assemble the LE for what I hope will be the last time. the subskin and two inboard ribs were re-clecoed to the LE skin again, and the entire LE was placed back on the wing spar due to one thing I read in the instructions about making absolutely sure that the rear edges of each LE rib were exactly straight. The only way I knew how to ensure that was to re-cleco the LE back onto the wing spar again so that all the rear rib flanges were in alignment with the spar web, and then I can remove it again and start riveting the entore LE together. 

I also needed to put it back on the wing spar because I wanted to screw down the new removeable section using those new nutplates I just riveted to the subskin, so that I could check the actual "installed" fit of everything. As with everything else, I found out that after I screwed down the removeable section, all of ONE of my screws sat nice and flush to the skin exactly as planned. One of the screws was not laying flat on once end, suggesting that either my screw dimple or the hole or the nut plate was not properly oriented for the screw. It is not so bad that I feel that absolutely must fix it, but it may end up bugging me enough to the point where I am going to fix it anyway. This means removal of the subskin again to reset another nut plate, and of course it is one of the corner nut plate that are difficult to set.

I may actually try to set the new plate with everything mounted on the wing, but I am still debating that with my self. Here is the string of pics showing the part as originally envisioned, planned, and realized:

And finally, the same non-matching fit that I have been dealing with shows up once again after the part is screwed down onto the subskin, but the inboard side is quite flush and looks really good. I think I can still flush out the other side with the LE by applying a little fiberglass magic later on. 

Overall I am happy that it seems to have gone together pretty much how I envisioned it. Here are some final shots of the screws through the nutplates on the inside of the subskin:

More Nutplate Hell and Creative Clamping

After several days I was finally able to finish riveting all 20 nutplates to the subskin. Man did that turn into a royal pain in the ass. As of the previous post I had made it to the last side and had messed up the rivets on the last, most-forward nutplate along the edge. This is where the skin starts to curve at the very front, which makes trying to set straight rivets with a rivet squeezer a bit of a challenge. I think I managed to finally get it after drilling bad rivets out a couple of times.

With the side nutplates installed, it was now time to tackle the hard part - the remaining rear-most nutplates on the top and bottom sides of the subskin. I could not use a rivet squeezer on these because they are too deep into the center section of the subskin for any of my squeezer yokes to reach. SO that meant that it was time get out the rivet gun and the bucking bar - something that I have not done for a very, very long time.

I decided I did not think I needed to practice on anything, because I was able to get the air pressure setting correct for the rivet gun. Looking back I wish I would have been more experienced about that when I riveted the horizontal stabilizer skins onto the frame. It hangs up on the wall in my garage so that every time I walk in I have to look at it, and I cringe every time that I do. That is because I literally beat the shit out those skins because my pressure was too high, and almost every rivet attaching the skin to the forward spars has this large skin dimple from over hammering the rivet gun on the skin. By the time I got to the elevators I had pretty much figured that out, but I literally pounded the HS skins almost to death..

Anyway, with the air pressure set on the gun, the next step was to figure out how to clamp everything down tight. I ended up deciding that using my bench vise should allow me to set everything up to use both hands to buck these rivets without needing to worry about securing or holding the part. Here are some pics if what I came up with. IT involved the bench vise, a small 2x4 for the smooth front side of the skin, and a custom sized much smaller piece of 3/4 inch plywood for the back side. All of this had to be positioned very carefully to ensure that there was enough space for the rivet gun and bucking bar, and to allow everything to be clamped tightly down without deforming any dimples in the skin. With so many dimpled rivet holes in this custom part, this became a challenge at times.

The top part of the skin was easier because there were not as many holes to dodge while clamping it all down:

I used a bar clamp to provide stiffness and resistance on the top part of the skin. This was the difficult part of trying to use the bench vise for this large piece of aluminum. The vise only provides a small amount of depth, so the top part of the skin remains very flimsy unless it reinforced with something such as the wood that I used.

On the front side I had to make sure there was enough room for the rivet gun:

And here is shot of the back showing how I had to be careful about the size of he wood  used and how it was positioned to avoid smashing or deforming any existing dimples. The other concern was of course making sure that I had enough room to use the bucking bar. This did not prove to be much of a problem until I got to the corners where the first side nutplate is located relatively close to the rear-edge nut plate in the corner. 

And here is yet another creative clamping method where I was able to use the access plate hole on the bottom side to insert another bar clamp for added stiffness. 

The stiffness is needed because, regardless of who you may talk to or what you may read in a book, you HAVE TO apply some pressure on the rivet gun and the skin to ensure that it will NOT bounce when the rivet gun is activated. This is what directly causes badly set manufactured rivet heads where they sit noticeably proud of the dimple because the underlying skin was allowed to flex and bend each time the rivet set was pounding against the skin. The part needs to be clamped in such a way that any movement of the part is severely restricted. This is the only way that you are able to buck good quality rivets. Sometimes the temptation is such that you do not take the necessary steps to ensure that everything is properly clamped. Then you basically pay the price for the mistake, and you have to drill out bad rivets and try again.

I was able to get all of the nutplates riveted in place, except of course for the very last one, which was a corner nut plate on the bottom side of the subskin. This one proved to be so difficult that I think I drilled the rivets at least 4 times and replaced the nutplate once because it was deformed beyond acceptable limits on one side or the other. I think I must have drilled out no less than a dozen rivets and replaced 3 nutplates during this whole exercise. The top side ones went pretty well, but the bottom side was another story. In fact, I had screwed up the rivets on the last nut plate so many times that the shape and condition of the dimples in the subskin. it was so bad that I was now unable to secure the nutplate in place with a cleco so that the flange on the nutplate would sit flush against the skin. I had to start using tape to hold it in place. When this did not even work, I had to take out my other arsenal of tools. Luckily I was able to use my 4 inch no hole yoke on the bad nutplate on the bottom of the skin. I mounted it on the hand squeezer because I was not having any luck with the gun and bucking bar, and the pneumatic squeezer was too bulky to fit as well. 

So my only choice was to use the hand squeezer so that I could position it and take my time to set the first rivet to make certain I did it correctly. I was able to set the first rivet on one flange just enough to hold it in place where I could then finish it up with the gun and bucking bar. The manufactured head of the rivet ended up sitting just proud of the skin on one side, but I had a plan for addressing that. Part of the plan was to try to use the rivet gun to move it a bit more flush to the skin - this only partially worked.

With the first rivet set as well as could be expected, I then was able to properly set the second rivet with the rivet gun and bucking bar. The corner rivets only allowed just enough room to insert my small tungsten bar in between the two nutplate flanges on the corner. One slip and the rivet, skin, and nutplate would be history. In fact, he bar did slip one time and slightly creased the skin, but I deemed it as OK since it was a dull crease with no apparent stress risers, which means I just barely stopped the rivet gun in time. Had I not done so this entire subskin and the planned project would have come to a screeching halt.

Here re the pics of the finished nutplate rivets on the ear side of the skin. First the nicely set ones on the top side:

And then the less-nicely set ones on the bottom side. Some of the primer was knocked away from all the repeated pounding from multiple attempts to set the rivets, and if you double click on the pic you can see it in more detail and tell very easily which rivets caused me the most trouble. 

And here is the back side of the nutplates all riveted together.

Now, remember that slightly proud rivet I mentioned earlier? Well, here was my solution for that. A long time ago I was at Harbor Freight, an I just happened to stumble on this next little gem - a watchmakers hammer. I used the round headed side of this hammer to lightly tap on the edge of the rivet that was sitting proud, and I was able to get it to sit much more flush after just a few taps with this hammer. This hammer was critical for this because the small size and weight of the ball end of this hammer was just about perfect for ensuring that it only contacts the surface of the rivet head and not the surrounding skin. If it was too large it would dent the surrounding skin, but I found this little hammer to work exactly as I thought it would:

And finally, here is just a small sampling of all the tools  ended up using to accomplish this seemingly small task. As I said before, most of this was pleasant to work on, but those few times when things got difficult, they got VERY difficult. I could not risk damaging or screwing up the subskin because it has required so much customization that there was no way at all that I would be able to take the time to try to fabricate a new one, nor would I even want to. If that part were to be compromised beyond use or repair, I would abandon the entire modification and return to a stock LE without even looking back. Too much time and too many delays with this to even think about starting it all over again.

And here is he pile of drilled out rivets and damaged nut plates that I had to drill out and replace, sometimes repeatedly:

So yeah, I got really good at drilling out AN426 rivets again, too. Anyway, I was able to pound some rivets again, so that is always good. And, more importantly, that step is now complete, which allows me to move on to the next step. 

So next up s to remove all the remaining internal sections of vinyl covering on the inside of the LE skin that I have left in place all this time. Unfortunately this is proving to be difficult, because some of he overspray from the epoxy primer that I used has hardened the vinyl in those areas, and as a result is very difficult to pry up a corner of the vinyl and keep it going so that I can remove the entire thing without it breaking apart. That vinyl has also been stuck to the skin since 2010 when I ordered the wing kit, and I already know that the longer it stays on the glue makes it harder to remove as it gets older.

After that vinyl gets removed it is finally time to rivet the left wing LE together. Great  - more curved surfaces t deal with. I can hardly wait...….

KPR

Finalizing the Scarf Joint and remounting the LE to the Wing Frame

Been a while since I last posted. Snowblower repairs, bad weather, and a wonderful cold have kept me at bay for a while on the project. Finishing the scarf joint turned out to be royal pain in the butt. I thought I had finished the joint, had a pretty good fit between the wing skin edges and the fuel tank skin edge, and then I final sanded everything with 320 grit aluminum oxide sand paper to remove the deep scratches. Then I took both wing skins off of the frame set all the remaining dimples with my squeezer, masked off the sanded areas of the wing skins where I formed the scarf joint, and primed them all with NAPA 7220 self etching primer.

Then I reapplied both wing skins to the frame to check the fit, since this was the first time that the dimples were added to that entire area. To my utter disappointment, the skins looked like they had not even been touched. The edges stuck out like sore thumb. My friend Mike had warned me about this a while back, but I thought that was because of the skin edges not being slightly bent, which I had already addressed. However, it became apparent real fast that the newly dimpled skins and the added primer were both causing the skins not to ft very well against the wing spar flange.

SO I called Vans about this. they said that you really can't judge how they will go together until you actually rivet them to the spar, and not to worry about it too much. Well, I decided to try to alleviate at least some of this ill-fitting issue, so I took off the inner skin, noticed that the edges of the skin were quite thin, but that the rest of the metal moving away from the edges still seemed to be a bit thick - indicating that I had not removed enough metal on the inner portions of the wing skin. So out came the file one more time. This time I focused ONLY on the inner portion of the skin, staying away from the edges as much as possible.

Then I re-sanded the deep scratches from the file and re-primed the small 1 inch square area that I was working on. Then I rechecked the fit and decided that enough was enough, and it was time to move on. I think I pretty much realized at that point that it was the dimples and how they were fitting into the countersunk hole of the spar flange, that as causing the fit problem, even though the hole has been countersunk a little bit more than flush per Van's instructions.

When this areas gets riveted to the spar that metal will be forced into the spar flange hole and hopefully will smash down a bit more with the force from the rivet gun. If I don't like the fit after that, I can drill the rivets out and figure something else out. OH - but wait -  by the time you get to this joint in the wing for riveting, you have already done the rest of the holes in the skin, because per the plans you save this lovely area for last. So I'll be damned if I am going to rivet everything else just to find that this area is still not seating properly. Others don't seem to have problems with any of this, so why the hell am I?

Time to move on. The scarf joint is as done as it is going to get. I am pretty certain that all that I will get for my efforts on this is a cracking wing skin in this very area once I start flying. If I do, you can bet that I will be asking myself why I even bothered with this stupid scarf joint - which some builders have also decided not to do, since it is "only cosmetic" per Vans.

I re-inspected the state of the leading edge assembly after my near disastrous and stupid attempt to force it off of the wing spar with the fuel tank mounted next to it. (See my Stupidity label to find the post). I tweaked the rear flange of the inboard 408 rib a bit more with the handseamer, and I checked for cracks or fatigue, and did not see any evidence of that. I removed the fuel tank assembly from the wing spar and remounted the LE assembly, all the while having flashbacks to my stupidity from before. I re-secured the LE assembly to the wing spar with clecoes and then added the fuel tank assembly. That's when I got my next head scratching moment - when the edge of the fuel tank skin and the LE skin did not line up correctly.

Initially I had a situation where there was no gap at the very tip of the LE and the fuel tank skins, but as you went further aft, this turned into at least a 3/64s inch gap. WOW! I thought I had everything here all matched up nice and neat - so once again I foud myself asking what the ^&*O&%$^! Obviously this was some sort of angular issue between the wing frame and the LE and Fuel tank assemblies, which I had verified long ago were butting up to each other with no gap whatsoever - so I knew that something just "wasn't right."

So I'll cut to the chase. There were two things that found that I needed to do. The first is a long standing problem that I have had ever since I put the frames on the wing stands. I used a hydraulic jack to support the center of the wing frame, which does sag under the weight of the wing assembly when mounted on the stands at both ends. I thought that this would be a great method - but found out long ago that these jacks do NOT hold their pressure forever, and they start to slip. As a result, I have had to continuously reapply pressure to the jack to lift the center section to keep everything aligned.

This time I wanted to be sure to recheck the "level" state of the frame by using a fish line strung across the rivet holes of the spar flange and held in place by two clecoes - one at each end. Then you apply the pressure from the jack until the fish line cuts through all the rivet holes evenly. Works great, and I found that I needed to apply more pressure once again to level everything out. The only problem with this is that to do it correctly you need to remove the wing skins from the frame. I did all this in warm weather, before the cold snap hit over the past couple of days. Seemed to level everything out again.

Today is the first day since I got sick that I have been able to go out and check on things in the garage. What I found this time was even more shocking. This time the gap between the LE and fuel tank skins was consistent from top to bottom, and was quite large on both sides. So once again I am asking what the ^&%^%#%$!. I rechecked the jack, but after leveling the center again I still had this huge gap.

The Le had been firmly reattached to the wing spar several days ago, so it was not moving. That meant that something was up with the fuel tank for some reason. When I put both assemblies back on the wing spar, the fuel tank was butted up against the LE skin and then I clecoed the inboard-most holes in the baffle and Z bracket on that end. Then I put #30 clecoes back in each screw hole through the nut plates, just as I had done many times before. None of the other fuel tank ribs, including the outboard-most rib, were clecoed, because at the time I did not think I had access to those holes since the LE an fuel tank are now butted up against each other.

So while scratching my head about this latest quandary, I came up with a plan, based on the only thing I could think of that was causing this gap problem - the clecoes I used to attach the fuel tank assembly to the spar were not allowing the skins to line up correctly for some weird reason. So I came up with a brilliant idea - make absolutely sure that the center of the wing frame was level (again), remove all the fuel tank attach clecoes, slide the fuel tank assembly over till the skins are snugged up against each other, and re-clecoe the fuel tank to the spar again. Then check the fit and go from there. I was skeptical about this whole thing, because I thought that the rib to Z bracket holes would now be out of alignment after sliding the skins together to "make" them fit. I found myself asking - "did I really mess up the whole fitting process and drilled the wrong holes in the wrong places, and that is what is causing all this?" Could I really be that stupid - again?

However, much to my surprise, after I re-clecoed the inboard rib to the inboard Z bracket, and then started carefully applying #30 clecoes to the screw holes through the nut plates again, the skins magically all lined up like they were supposed to, and they stayed that way as I added each cleco. Thank goodness for that is all I can say. Then I saw that I could still apply the clecoes to the outboard fuel tank rib and Z bracket through the access panel opening of the LE. And the skins stayed flush together after I did that. How bazaar is that!

The only thing that I can conclude from this is that I think there was some misalignment of the inboard and outboard ribs when the rest of the fuel tank assembly was removed to match drill the baffle to Z bracket holes for the remaining fuel tank ribs. It could also be that the sagging center section of the frame, combined with some slight shifting of the screw hole clecoes, may have caused the misalignment occur. Putting #30 clecoes in the holes intended for the screws in the fuel tank skin, which have yet to be dimpled, is a bit out of the ordinary. Normally you put clecoes through matching holes in two or more pieces of metal.

However, in this case, until the fuel tank skin holes are final drilled to size for a #8 screw, and dimpled, you are inserting a clecoe into a hole in a flat skin, and then in turn the rest of the cleco must extend further than normal, all the way into the end of the nut plate on the inside of the spar flange. This results in a clecoe that is under higher spring tension than usual, since it has to be extended more than usual, and the flat skins are then being pulled slightly into the large countersunk hole in the wing spar flange, causing some uneven tension on the fuel tanks skin. When you combine all this with an unsupported center section of the wing frame, it is not hard to see how things might not line up correctly.

The lesson learned from this is to make sure that parts that you know are supposed to fit together are actually mated that way first, and THEN you cleco everything in place - NOT the other way around - i.e. clecoe everything and then check the fit. Clecoes that are inserted into places where they may be allowed to shift or distort the assembly a little (flat skin screw holes into countersunk holes  nut plates for example), can cause such a mis-alignment of closely fitting parts like skins. The second lesson learned here is that I need to replace the STUPID hydraulic jacks with a 3/8 inch threaded shaft with a small wood support on one end, and a large washer and nut assembly on the other end, inserted into a solid wood base with a hole slightly larger than 3/8 inches for the rod to freely insert into, and adjusted so that the center section of the frame remains level ALL THE TIME! Don't use stupid hydraulic jacks unless you want to feel my pain.

So I already have one screw jack assembly from another builder, which I obviously never used, and I'll need to fabricate another one for the other wing stand. That is my mission for tomorrow. SO in short I have been on a bit of wild ride ever since the time came to remove the LE from the frame to start working on the fuel tank assembly on the wing spar. It's been one wild thing after another ever since.

The last thing for tonight is that I finally have the LE back on the wing frame, which is the point that I was trying to get back to ever since this latest round of madness began. I needed to get the LE back on the frame one last time for it is final-assembled so that I can get down to business and make those final decisions about cut lines and new rivet holes and locations for nut plate and screw holes, all in preparation for the big "cut your LE to pieces" exercise. I worked out some final measurements tonight and will elaborate more on all that in my next post. I am very close to being ready to make the cut in the LE skin once these measurements are finalized.

Continuing with Dimpling and CounterSinking holes for the LE

Starting with some pics from the dimpling of the LE outer skin mentioned in my previous post:

This was a bit of a chore that required me to clear away a large area of the work bench to be able to maneuver it so that each hole could be dimpled. This was complicated for me because my dimpling table is on the bench, the back side of which is right up against the wall. So this restricts my ability to position the parts and also to position myself so that I can hold and hit the ram with both hands to properly form each dimple. Since space is restricted I found that I have to get very creative about how I position myself to be able to set these dimples. Translated another way, it means that I have to bend my body in some very unnatural and uncomfortable ways to be able to do this.

SO I can tell you right now that I am not looking forward to dimpling the larger outer wing skins, and I may go ahead and try to set up a level method on the garage floor, away from the work benches, just so it will be easier to move both myself and the sink around on the dimpling table without risking throwing my back out of whack. Not fun.

The next 2 pics show my re-assembly of the LE after I got most of the skin dimpled, except for the several holes that I missed match drilling as I mentioned in my previous post. I started reassembling by clecoing the subskin to the outer skin first, just to try to align the dimples. then I decided to reattach the center ribs first, followed by the outer ribs and then finally the inner ribs. I had numbered each rib with a piece of tape to ensure that each rib was reassembled in its proper place. (Read on for a humerous blunder that I made regarding the rib position).

Some complications arose:
1. I discovered that I had not dimpled two of the forward most holes in the subskin - I just missed them after I finally decided to dimple all the holes. So I had to detach the subskin, dimple the holes, and reattach it again - more wasted time.
2. After the LE was completely reassembled, it was time to put it back on the wing spar so I could match drill the remaining skin holes to the wing spar that I missed, and to match drill the W-423 joiner plate holes for the nut plates between the fuel tank and the LE. The only problem was that when I tried to reattach the LE rear rib flanges to the main wing spar web, I would not get the clecoes inserted into the end-most holes in the #3 rib position.

I removed the LE several times trying to figure out what was wrong. the first time I thought it was excess primer in the holes, so I ran a #30 drill bit through each rib hole.Then I put it back on the wing spar, but still had the same problem. SO I took it off again. This time I noticed that one of the rear rib flanges had 2 extra holes in it, and I remembered that one of these ribs had rear flanges that were pre-drilled from the factory, but they must have been a different hole pattern for an RV-6 or RV-7. SO for the RV-8, they tell you to match drill 2 new holes in this rib and to disregard the other holes.

It was then that I realized that I must not have the right rib in the right location. And sure enough, when I checked the rivet hole pattern for each rib flange on the main wing spar, that was exactly the problem. The funny thing is that I think I messed this up clear back to when I primed each of the LE ribs. I remember picking them up from my priming table when I was all done, and I was all but certain that I had picked them up in the proper order. it just so happens that this number 3 rib has a slightly different rivet pattern that the rest of the ribs. SO once I switched the #3 and #4 ribs to the proper locations, everything magically fit back together again properly, but NOT before I had removed and replaced the LE assembly on and off the wing spar about 4 times. So that was last night's big blunder:

After resolving that problem, all the ribs seemed to fit nicely in the dimples with the skin. The next step was to set my microstop countersink tool to the proper depth by testing it on some scrap pieces. it is amazing that you can set this tool to provide a countersink that is accurate to 1/64th of an inch. I put a piece of angle between 2 drill boards and marked several holes that are far enough apart for the frame of the countersink tool. then drill drilled the holes and used a rivet to check the depth.

This procedure is also perplexing to me, because I am able to set the tool so that the rivet heads do sit perfectly flush in the holes. But the problem is that every time I actually set rivets in these hole to attach parts together, the rivets seem to end up slightly proud of the top part being riveted. This happened quite a bit when I did the holes for the fuel tank nut plates long ago.

So then yo are left with a decision to make - if you should counterskink just a little bit deeper or not so that the rivet truly does end up flush. The question then becomes, how much deeper do you countersink? SO I did some tests with a few different settings and decided which one I wanted to use, and proceeded with the holes in the wing spar flanges.

The other piece of metal in the top pic was a test piece that I made with one dimple in it to check the depth against the spar flange after the countersink holes was drilled. The test is to see if the dimple fits correctly in the countersunk hole so that the skin then sits flush with the spar. My past experience with this is that the parts tend to get slammed together pretty good with you actually  rivet them together, so if the trial fit with the test piece looks good then it should definitely be that way when everything actually gets riveted together.

With the depth set, I went ahead and countersunk all the spar flange holes for the LE skin. About 128 per side for the LE. I think they came out pretty good, and the real test was clecoing the LE in place again. The skin seems to butt flush against the spar flange along the entire span, so I am happy with the results.

I then match drilled the missing holes, which I will have to debur, dimple, and countersink when the LE comes off for what should be the final time.

The last thing I did was to secure the fuel tank assembly next to the LE, so that I could FINALLY match drill the joiner plate screw holes that secure the tank to the LE skin. I was a little surprised that after dimpling and securing the LE and then butting it up against the tank that the bottom side skin has a small gap, but the edges from the middle to the tip of each skin seem to match up just fine. The top side of the skin does not seem to have this gap. I was a little disappointed, because prior to dimpling the LE this joint was completely perfect, with no gap. I guess I will have to wait until I dimple the tank skin screw holes and get it ready for riveting until I will no for certain if there is still a gap there or not.

Here are the shots of the bottom and top side skins of the tank and the LE with everything tightly secured with clecoes. The holes for the screws for the fuel tank skins that attach it to the wing spar flanges are secured with #30 clecoes that go all the way through the #8 nut plates that were attached to the wing spar flanges a long time ago.

The last pic is of the end of the wing along the wing spar flange line, showing the flush fit between the LE skin and the wing spar flange. Although this pic only shows the very tip of the skin, I checked it along the entire span for both top and bottom skins, and the fit between the dimples in the skin and te countersunk holes in the spar flange seems to be good enough for me.

One last note: In order to countersink the LE attach holes in the wing spar flange, the bottom and top skins need to be removed, so that the countersink tool can rest on the spar flange properly. The bottom skins had been removed a long time ago, so that was not an issue. However, the top skins remained on to provide strength and stability to the frame. Since they needed to be dimpled anyway, I removed the top outer skin so that I could countersink the holes for the LE on that side. This was the first time I had removed the top skins in a very long time.

Next steps:
Measure and mark the cut lines and rivet/nutplate hole locations for the removable LE. Then drill #40, followed by #30 holes for the primary rivets and screw holes along the left and right edges and the top and bottom rear edges. This needs to be done with the LE secured in place.

Need to decide what to do with the Stall warning holes. IF these will be removed by cutting out the skin section that I plane to use for my removable skin, I need to do nothing. If they will remain, I need to prep them to close them up, as they will not be used for anything in my plane.

1. Match drill the joiner plate holes to #30 only. Need to be careful not to drill into the spar bars of the wing spar so a drill stop is a must have for this. You don't drill the #19 holes for the screws until AFTER you remove the assemblies from the wing spar, for the same reason.
2. Remove the LE assembly and dimple and countersink those few remaining holes after deburring them.
3. With the fuel tank and Z brackets secured to the spar, match drill the inboard fuel tank rib, baffle, and Z Bracket rivet holes.and cleco them in place. Use a long, 12 inch #30 drill bit with a drill stop securely attached to prevent drilling into the wing spar.
4. With the LE removed, you can also access the outer-most tank rib, baffle, and Z bracket holes to match drill those.and cleco them into place. Use the same drill bit as before.
5. Remove the fuel tank skin and inner ribs from the wing spar, leaving only the baffle plate and the inner and outer-most tank ribs. Then match drill the remaining inner tank rib Z bracket rivet holes through the rear baffle plate.
6. Place primer in all the countersunk holes in the wing spar flanges for the LE
7. Dimple the top outer wing skin
8. Countersink the remaining wing spar flange holes for the top outer wing skin.
9. Apply primer to those countersunk holes
10. Reattach the outer wing skin and check the fit against the spar flange.
11. Make the stiffeners for the fuel tank, match drill them and cleco to the tank skin
12. Match drill the fuel tank skin and rib holes. Disassemble and debur all holes
13. Final drill and dimple all nut plate and screw holes in the joiner plate.
14. Final drill and dimple the screw holes in the Fuel tank skins.(top and bottom)

And then I need to disassemble the LE subskin and ribs, and make the necessary cuts to the LE outer skin.

Then we go from there.

Did the Drilling and Deburring, Now Back to Dimpling....

After a long period of time, the length of which I can't even recall, I finally got to dimple some metal last night and tonight. It started last night by clearing off the work bench to make room for the dimpling table and C-Frame tool. Here is the table with the C-Frame in place and the subskin ready to go. After I countersunk the rivet holes for the nut plates that surround the access panel hole, my next task was to dimple the Screw holes with a # 8 dimple die, which is visible through the first of several holes in the subskin in the next pic after this one:

In this next pic which is a close up, see if you can find the problem that almost cost me months and months of work:

Do you see it? Before I divulge the answer, I just have to say that it was such a joy to setup my dimpling table on the "new and improved" work bench, where all the table legs fit on a truly flat workbench, without the need for a hinged extension like the one I had to use so many times before while building the tail section. I was waiting for the day when the decision to go with the solid core door as mt new bench would pay off. It is still a pain in the ass to have to adjust all the adjustable table legs to get the table correctly leveled with the dimple dies, since I do not have "easy" access to the rear of the table, which is up against the wall/pegboard. This makes it a bit difficult to adjust the rear leg height, but I managed to get it done. Another challenge is that with the wing currently on the stand, and the bench being a few inches wider than before, I have less effective space to work with when lifting the table onto the work bench. it wasn't too bad to get it up there, but I still had to be careful not to hit the wing.



Now, back to the pic, do you see it yet? Or rather, I should be asking, do you NOT see it yet? The male dimple die is mounted on the bottom of the C-Frame, and the guide pin from that die is visibly sticking up through the hole. BUT..... To make a dimple, you need to have both a male AND a female die. If you guessed that the female die is not mounted on the ram just above the hole, then you were correct.


In my haste to get to dimpling I had set up everything else correctly, but I forgot the final step of inserting the female die into the ram. And then, yes, for that first hole, I held down the ram over the pin of the male die, and whacked it a few times. After removing the ram I inspected the "dimple" and found it to be very shallow and it did not look right. It also had a very strange looking rim at the bottom of the so-called dimple. It was then that I realized what I had done. (Or not done in this case).



The good news is that, after I inserted the female die into the ram and struck it again, this time the dimple looked like a dimple, although it still has the funny looking edge at the bottom. I test fitted it with the nut plate, and everything fit just fine. So then I finished dimpling all the remaining #8 screw holes.



With the screw holes in the subskin done, the next step was to dimple the access panel cover plate.

And here is the result of the cover plate dimples. Turned out pretty good I think:

And I got the same results for the matching subskin dimples:

I trimmed away a little too much metal in one corner of the opening, so I took a couple of files and radiused that corner just a bit more, and then I trimmed away a little more excess metal on the straight edges. SO what do you do when you finish dimpling two parts that are supposed to fit together - trial fit them of course! This next pic has a #8 screw in one of the holes to see how it will look with the plate secured to the subskin:

Next came the final prep of the rivet holes for each K1100-8 nut plate. After countersinking the holes for the NAS 1097 rivet heads, this exposed some unprimed metal. So I needed to perform the same trick I came up with  a long time ago when I countersunk all those fuel tank nut plate holes. I used a tapered Que-Tip  (NOT the standard round-headed ones, but specifically tapered and cone-shaped), and some NAPA 7220 self etching primer in a cup, to lightly coat each of the countersunk holes with some primer.



IN this next pic, pay close attention to the white plastic cup in front of the box of Q-Tips:

I shook up the spray can of primer really well, and sprayed some excess primer into the bottom of the cup. I sprayed just enough to allow the Que tip to get enough primer to cover each rivet hole as shown below (pic is a bit blurry - sorry bout that!).

Just insert the primer soaked Q-tip into the rivet hole, remove, and move to the next hole and do it again. After doing a few holes, you figure out how much pressure to apply to deliver the right amount of primer on the edges of each countersunk hole. Excess primer is not much of a problem - you just scrape it away from the edges as necessary. it is also important to test fit the rivets in the hole after you do this. If you get too much primer in there then you can take a deburring bit and run it just enough to either reduce or eliminate the primer, and re-fit the rivet and reapply primer as necessary.



Now for the rest of the story. I almost had another "accident" here that could easily have caused several nasty problems. Luckily, I managed to "escape" relatively unharmed. This next pic shows the bag of the plastic "bath" cups that I used. I guess these are supposed to resemble the old paper Dixie cups, and are designed for holding small amounts of water for rinsing after you brush your teeth, etc.

I primed a few holes, and then paused briefly to check the holes with the applied primer, and I set the cup down on the bench for only a minute or two. Also note that I am doing all this right on top of my carpeted dimpling table. (Not a good idea). When I went to pick up the cup again to saturate the Q-tip one more time, the entire bottom of the cup completely separated from the rest of the cup, and started spilling any remaining liquid primer that was still in the cup.


Most of it ended up dripping on the subskin and my hands and fingers, and luckily there was not very much liquid remaining in the cup. I also thought that some of it splashed onto my work clothes, which I was still wearing for this event, but I seemed to have escaped that disaster as well. But I still had several more holes to prime, so what was I going to use for a container, knowing that using this particular cup was now out of the question?



I had also purchased some different condiment cups a long time ago, as shown in the next pic, that I had also never used before.

Now that I was much more alert as to the potential problems that a plastic container and highly volatile primer might cause when combined together, I knew that I would test this situation out for several minutes by keeping the container on the work bench the entire time, sitting on top of several paper towels - just in case. This time, though, after several minutes, nothing bad happened, and the container seemed to "hold its own" with the primer:

So, several lessons learned (or re-learned) here -
DON'T use the first cups for any type of chemical mixing without testing it first.
DON'T wear your good clothes when priming stuff.
DON'T pick up the cup and hold it near critical tools or parts unless you are certain that retains its viability as a container. (And is not melting away in your hand or smoldering, etc.)


I think that each different cup is made with a different type of plastic, and one is obviously more resistant to the chemicals in the primer than the other.




The next task was to dimple the permanent cover plate with my 3/32 inch dimple dies. So I had to change out the dies in the C-Frame for the smaller holes in the patch plate.

I could have used the pneumatic squeezer for all of the cover plate holes, but I wanted to continue to practice with the C-Frame, since I am going to be using it for quite a while in the near future to dimple the LE, Fuel tank, and main wing skins and ribs. Lots and lots of holes to dimple and countersink. So the more practice I get with the C-Frame the better.



And now the results:

Then it was back to the subskin to dimple all matching holes in that part:

I had been trying to decide if I was going to dimple one final hole that ended up being very close to another hole for the permanent patch plate. This was just the result of a measuring issue where I had already drilled a hole that matched an existing hole in one of the mounting plates that I decided to use as a template for the subskin. Afterward, I decided that I also needed rivet holes about 1/4 inch away from each of the edges. So this resulted in two of those holes being very close together. Anyway, I finally decided to go ahead and dimple it, after seeing that the dimples were far enough apart so that they would not interfere with each other. I did this in the holes for in the patch plate and the subskin.
I will also need to dimple this hole in the outer LE skin. Hopefully it all comes out OK. I think it will.



Tonight I finished (almost) dimpling the remaining 3/32 holes for the subskin for the perimeter holes for what would have been the mounting plate for each access panel, and all but 8 of the most forward LE holes in the subskin, which will need to be dimpled with the close quarter dimpling tool, since the bend in the skin is too stiff to dimple them safely with the C-Frame. I will also need to use the same tool for dimpling the rib flanges that correspond to these same holes.



I also need to scuff, clean, and prime each cover plate. This last pic shows the fit of each plate against the subskin after the dimples were formed. Everything fit together amazingly well. I won't set the rivets on the permanent patch plate to the subskin until I have reassembled the entire LE again, to make sure that the fit between the patch plate and the outer skin is also good.

Everything aligned really, really well after setting all these dimples, and there was not much distortion or bending of the parts either, so I am happy about that.


Another "next" step is to rivet my nut plates for the access panel to the subskin (Yes, another thing I have not done in forever). I spent some time today trying to figure out how to secure the subskin to the bench for this. Anytime I have to do this for some sort of pre-bent skin, you have to get very creative about how you secure and stabilize the part. I'll elaborate more on my thought process for that tomorrow.


One thing you can count on, is that it will involve a lot of clamps and a lot of uniquely shaped and positioned clamping blocks to ensure that I have the security, rigidity, and stability that I need to properly rivet them in place. I also want to make sure that I position the part so that I can apply pressure on the pneumatic squeezer on the non-moving part of the yoke against the manufactured head of the rivet, so that the moving part of the squeezer will be against the rivet stem. Then, once I get all that figured out, I try to position everything so that the squeezer is in my right (dominant) hand, and my left hand is free for holding the part, etc. That bit of wisdom comes from a lot of learning about riveting from actual experience, which you just can't find in any of the text books or the classes. Thankfully I still remember how to apply those experiences.



More tomorrow

KPR