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.

Update on 6 year old Akzo Nobel Primer and on to the next LE Challenge

I am happy to report that the 6 year old Akzo Nobel primer that I used the other day to prime several parts, including two of the LE ribs, seems to have worked just fine. There is no flaking or chipping, and adhesion to the metal seems to be just fine. So I think I can continue to use that $200.00 investment until it runs out. Good to know.

Now for the next challenge. As I previously reported, I can still remount the LE again and final drill the two rear rib flange holes, but before I do that I wanted to start the process of trimming down the subskin to its final form. I had this pretty much figured out until I encountered the next challenge:

What to do about the existing service hole that was pre-cut from the factory on the bottom of the left wing LE. the right side does not have this cut, and that is because the original plans located this hole for installing and servicing the stall warning kit. To further complicate matters, the access panel that is designed by SafeAir for allowing installation and access to the auxiliary fuel tank transfer pump is located in a slightly different location. Part of this location overlaps the location of the existing hole that Vans already cut into the skin. Each of these access areas requires installation of a backing plate/stiffener to serve as a mounting flange for each in inspection plate. Here is the pic that kind of lays this all out:

The unfinished parts are the access panel and mounting flange from the SafeAir kit, and the blue colored flange and access panel that overlaps the SafeAir panel are the ones from Vans. Almost immediately you can see the problems. The Vans access panel is more to the rear of the skin, closer to the wing spar. The SafeAir location is more forward (the flange is not in the correct location, which is where the unfinished cover plate is. I just wanted to separate them so that you can see that they are two separate parts. You can also see the size difference.

Since I decided not to use the Vans stall warning system, opting for an AOA solution instead, I would really rather use the SafeAir kit. But how do I get rid of the existing hole that Vans made, and then re-cut a new one to fit the  SafeAir kit? As you can see, I will have to cut out part of the existing hole, but not all of it.

To complicate matters even further, my subskin currently resides where either of these mounting flanges would need to be installed. This may actually turn out to be a blessing because I may be able to  use the existing subskin as the mounting flange for the new panel, and it will also serve as the mounting flange for the existing panel that will need to be permanently mounted, except for that small area that overlaps the hole for the panel of the SafeAir kit. Then there is the fact that the skin thickness of the SafeAir panels is thicker than the .025 LE skins.My caliper shows them to be about .0315 inches thick. My guess is that they were cut this way because this kit is designed for several different Vans aircraft models, including the RV-10, so they may be thicker because of that.

I purchased the Safe Air panels because even if I choose not to install their aux tanks right away, it will be nice to have these panels already installed, in addition to the bung kit on the fuel tank, so that all I will really need to deal with is the actual installation of the aux tanks and the transfer pump, and the hose fittings between the main and the aux fuel tanks and the transfer pump. So the more I do now the less work I have to do later.

Not only that, but I like the larger, and more centrally placed location of the SafeAir panel. A long time ago I tried to fit my arm and hand inside the smaller panel that Vans provides, and there just isn't much room for either. I could imagine having a very difficult time troubleshooting fuel leaks in this area or servicing the transfer pump.

So basically, I need to cover up the current hole and cut a new hole. I'll have to think on this one a bit to get the sequence of the steps down correctly, but I think I can do this smartly by using the subskin for the mounting flanges. Luckily, the right LE skin does not have this mess of an existing access hole, so all I have to do on that side is cut the hole for the SafeAir panel in the bottom of the right wing LE skin.

Did I mention that I will be glad when all the LE work is done, so that I can start on the fuel tanks again..... It just never ends. Whhhhhaaaattt????? Did I just admit that I am looking forward to working on my fuel tanks??? I must be crazy.

KPR.

Been busy preparing for more metal work

For the past week and a half I have been "re-acquainting" myself with my build. I've been dong lots of research on various things, and I am getting ready to place an order with Vans and Aircraft Spruce for a variety of things. Other than getting my pitot mast resized and re-drilled, I have been:

• Researching and reviewing my SafeAir pitot/static line kit, and reading about all kinds of static source issues and solutions for various installations. I'm trying to figure out if I am going to use the supplied static ports from the SafeAir kit, or get the ones from Cleaveland Tools.
• Reviewing instructions for my SafeAir Bung kit for the fuel tanks, and my access panel kit for the leading edge. These are the line connecton ports on the outboard side of each tank that will allow me to connect supplemental fuel tanks after I complete the build
• Deciding if I am going to install the stall warning kit from Vans in the left wing. Right now I think the answer is no, as I will be using an AOA indicator with both visual and aural indications. I'm still conflicted by this a bit, since the AOA is a purely electronic solution, and susceptible to failures, and the stall warning vane is electro-mechanical.
• Deciding the location of my pitot mast on the wing and designing a backing plate for it
• Removed the leading edge from left wing to expose my modified LE rib, right where I left it almost 2 years ago. Lots of flange riveting to do yet.
• Finally determined what to do about the rib flanges that attach to the skin. My custom built rib does not have the same rivet pattern on the very last hole that attaches the skin to the LE rib closest to the wing spar, and then to the wing spar flange. Instead of making a flange extension using a dongle technique, (see my old posts on this) I just need to trim the last part of the rib flange off to remove the drill hole on the very end of the flange, and measure and drill a new hole in the wing skin and the rib flange, followed by one more additional rivet in the skin and wing spar. Basically I will create new rivet holes that match the hole pattern for that rib in its stock position on the inboard side of the LE. I know I know, pics of all this will be easier to understand. Stay tuned.
• Reviewed my landing, position, and strobe light assembly and wiring instructions. Posted to VAF to get pics of the inside of the wing tips with the same light and antenna setup that I am planning for my bird.
• Reviewed lots of VAF posts about antenna placement and wiring. I mean LOTS!
• Gonna order the composite practice kit from Aircraft Spruce, and some hinges and other assorted metal from Vans. Time to get the hands dirty.
• Starting to put together my list for a quickbuild RV-8 fuselage kit. That's gonna come in a really big box!
• Starting to measure out the cuts that I will need to make in my sub-skin mod so I can put that in its final form so I can finally prime and mount the left wing LE.  
• I need to recheck and correct for twist in the wing frames. Spot checks show that things are mainly level, but I think they need to be tweaked a bit. I may need some help with that.

The main goal of this was to re-address my issues with the LE from long ago, and make some decisions so I can move on. I think I have figured all that out now, so its time to measure, cut, file, and smooth some metal, and then drill and debur a few holes. Piece of cake man!

Left Wing LE Stall Warning Parts and Instructions

Yesterday I managed to start the process of fluting and straightening the flanges of the inboard W408-1 L rib. I am still not 100% satisfied with it, and it is  a little bit harder to work with since it is a thicker rib than the others, but a little more tweaking and I should have it just about right. The holes will be match drilled with the W423 tank attach strip I mentioned in the previous post.

Then I focused my attention on the stall warning kit that came with my wing kit. There are electronic and fabricated aluminum parts that make up the attach bracket for this assembly, which is basically a micro switch with a flat metal vane that sticks out of the LE of the left wing at an angle such that, when the angle of the wing against the direction of flight gets too steep, the vane will move causing the microswitch to close which then sends an elecrical current to an audible warning circuit that gets piped to the audio panel, and finally to your headset. It is an early warning system designed to tell you when you about to stall the aircraft.

The only problem with installing such a devise on an aerobatic airplane such as mine is that it will be going off quite a bit as you enter different attitudes during various aerobatic maneuvers. So it basically can become more of a nuisance and  distraction during aerobatic flight, and is not recommended. 

The one interesting thing about this kit is that it contains a short support rib for the extreme leading edge of the wing that I may decide to use to help support that area since it is the same part of the LE that will house the fake machine gun fairings. One other thing I found interesting is that there is a slot that has to be created right on the lower portion of the leading edge of the wing for the vane to stick out into the airflow. According to the instructions, the slot is made by drilling 2 holes in an exact location determined by a drilling template, and then enlarging those holes with a number 10 drill bit, and then cutting the slit in between the two holes. This is a rather large hole, and I think it is more than large enough to fit two 16 ga. wires for the lights. More importantly, I was a little worried about drilling extra holes in the LE of the wing until I started looking at the stall warning kit.

The whole reason I started reviewing the details of this kit was that the holes are already predrilled for the mini support rib as well as the starter holes for the stall warning vane. Most builders not using this system will simply close the holes with a rivet or some other means. Those that will do alot of aerobatic flight or that will use an AOA system for stall warning indication instead of this system are the ones that typically will not use this kit. Vans provides it as a standard part of the wing kit, and it still makes a good backup system, if nothing else, so I may still assembly it and run wires for it except for installing the vane. The other reason I started looking at it is that the access panel opening has also already been cut out by the factory, and I will definitely be using this panel for access to the wiring for the machine guns and also possibly the stall warning switch assembly. Another added use will be for access to the wiring and fuel pump assembly for the extended range fuel tanks should I decide to install those later on. All of that stuff will also live in the same bay in the wing.

Now for some pics:

Here is the mounting bracket for the access panel clecoed into position in hole that is already cutout in the bottom of the left wing LE. There are two tabs on the left side that line up with holes for the rib flange on that side. Only problem is the instructions show this incorrectly, or they cut the aprt and drilled it incorrectly. Either way, the instructions and the actual alignment of the part do not jive with each other. Just another opportunity for Vans to straighten out some of their instructions I guess. Another part is just barely visible on the bottom of this pic. It is the template for drilling the holes in the LE of the wing for the support riblet and the slot for the vane. I guess they provide this template for those that may decide to add it later if they choose not to install it during the initial build, but in my case the holes and access panel are already cut and drilled, so I really did not need the template, but I am glad they provided it. The reason is that this template is made from .020 aluminum (or perhaps even thinner), and so it wraps around the the LE wing skin relatively easily. I went ahead and installed it for 2 reasons:
1. To see if the template holes lined up with the predrilled holes in the skin, which they did
2. To give me  a sense for the same type of "boot" that I will be fabricating that will wrap around the top and bottom of the LE wing skin, jsut as this template does.

NExt pic shows the rest of the template as it wraps around the bottom of the LE wing skin. There are two sets if template holes - one for the RV9 and the other for the RV7 and 8. You need to be sure to use the correct hole pattern. You can just see the clecoes for the holes for the bottom of the support riblet on the bottom left side of the pic, adn the unclecoed holes for the RV9 on the right side.

Next is a side shot showing the clecoed template as it wraps around the nose. The bottom - most clecoes are for the two starter holes for the vane that sticks out into the airflow that actuates the micro switch when close to the critical angle of attack of the wing.

And finally the top side of the LE wing skin showing the last set of holes for the top of the support riblet clecoed in place. It was very easy for me to invision what the mounting bracket for the gun assembly will look like after viewing this template assembly. It will simply become a question of how many nut plates and screws to use on the top and the bottom, and how far back from the LE the mouting bracket will extend, and how wide to make it.

Here is the support riblet that mounts into the LE wing skin. The micro switch is assembled with some additional brackets, the microswitch, and mounting hardware that all comes with the kit.

And here it is clecoed into position. You can also see the two starter holes for the vane that actuates the microswitch. It's really kind of a neat setup.

And finally a couple of pics that show the template after I removed it from the LE (It was completely flat when I started):