Time: 7 Hours
Today I got to have my weekly breakfast with some fellow builder which included a lot of hangar talk. That always fuels my passion to build making my dream of flying an RV-8 coming true that much sooner. When I got home I started the next step of this service bulletin which was to begin riveting all the parts together. To start I decided to hit the tough rivets first. These would be the ones on the fingers of the new doubler. They are tough because you have to rivet inside of the wing skin where there isn’t much room and you have to use a double offset rivet set. This set makes a “z” shape sort of allowing it to get close to the skin and have the gun perpendicular to the work. With a straight set your gun would be at an angle since the gun is thick. I fabricated a shim of sorts out of 1/4″ flat stock and gorilla tape. This allowed the rivet set to rest on it and be at the right height for the rivet.
These , although difficult, went pretty fast. Unfortunately I had to do one side then set everything up for the opposite side. I then flipped the HS over and repeated the process. Here are the first 5 which all turned out perfect.
I realized on the first 2 rivets I set once I flipped the HS over that the 1/4″ flat stock was a little too thick by about a 1/16″ which held the rivet set up a little too high causing a smiley face on the rivet head. Not a big deal and certainly not worth drilling out. I created a new shim out several thinner pieces of aluminum taped together and the rest turned out perfect. Now I turned my attention to the main ribs I removed earlier. If you remember I cut off the forward flange if those ribs. That is due to now the spar area where those flanges sat is now thicker with the new doubler. This means that these would fit as they should. Van’s had a cure which is to take some thin angle stock and make a floating rib flange. Then you could get the fit just right and rivet that new flange in place making a perfect fit. I cut the stock and cleaned up all the edges. I then bent the stock to the 86.4° that is required for it to sit flush on the spar. I then grabbed some of my spring clamps and placed it into position on the rib.
Once you have that in place you can return the rib to its spot inside the skin. Once in position you release the clamps slightly and slide the angle up flush with the spar. Once there you can use some C clamps and tighten it down so that you can match drill the 4 holes in the spar and the 4 in the rib.
After all those holes were drilled in both ribs I cleaned up and deburred everything. A little scuffing and cleaner and they were ready for primer. I also cleaned up the forward spar areas where I nicked the primer and touched them up as well.
All that remained was to rivet the forward rib/spar/main rib holes, the main rib to rear spar holes and all the skin/rib holes. I used the double offset again for the rib/spar/rib rivets and the squeezer for the rest. Some may notice that I riveted every hole on the upper skin along the two ribs and spar. Normally you leave several holes open for future platenuts that will hold a fairing that ties the vertical stab and the horizontal stab together giving a clean look. I’m going to do the same but a much cleaned look with only 2 screws on top and 2 on bottom like my friend Glen did on his first RV-8. Since I’m not sure exactly where I will place those screws I filled in all the rivet holes and will drill out the ones not needed down the road.
This was an interesting project as it helped me understand how to disassemble a section, repair it and reassemble it. Something I’m sure I will have to do in the future. It took me 18 hours from start to finish to get this done. Not to bad considering the amount of work. I’m glad that’s done and now only have a few small tasks to complete and I’m officially out of work until my fuselage which should be 4-6 weeks away from delivering!!
Time: 6 Hours
The FedEx guy showed up at lunch time just as I got home from running my errands this morning. Since the SB parts are here so I jumped in the Hangar to finish up the work.
First task was to cut the angle off the end of the forward spar flanges. After thinking about it overnight I decided to remove 8 more rivets along the forward spar and skin joint. I also removed 13 rivets along the rear spar on the top and bottom. What this did was allow me to lift the skin away from the cut area and get a file and sandpaper along the cut. It wasn’t perfect but it worked.
There is a top and bottom of the doublers where the top is depicted by 1 offset rivet hole. I used all the other holes to make a straight line on the top and bottom of the fingers that extend off the doubler.
I also drew a line down the of the holes on the spar that will correspond to the ones on the fingers of the doubler. When I clamped the doublers to the spar by lining up the bends in the spar I also lined up the two lines I drew.
With the doublers clamped in their place I started drilling and cleckoing the 8 holes that the plans call out. I then checko’ed the two support angles that were on the spar originally and match drilled every hole. As I drilled 1 I would clecko and move to the next. There were several holes that get drilled from the doubler side and several that get drilled from the angle side.
Time: 5 Hours
Yesterday I received a new tool from Aircraft Tool Supply to help with AN470 rivet removal. This tool is like a countersink cage with a drill bit and a centering head on the end. The bit and head can be changed to accommodate various sized rivets. The problem with drilling AN470 rivets is they had a round head and getting a drill bit to stay centered is very difficult, resulting in a usual oblonged hole.
Here you can see the forward spar and it’s rivets that tie the left to the right. All these get removed and a doubler with extra rivets will get added. The doubler extends from center outward and required some modifications of existing parts. For now I’m just removing all the parts and taking care of the mods that are required until my parts arrive.
First task is to drill all the skin/rib rivets that hold the forward and aft inboard ribs. I marked all the rivets that I needed to get. These AN426 rivets need no special tool since they are flat and much easier to drill out.
Once the skin rivets were done I turned to the 470’s and started with the easier accessible ones. I set the gauge on the rivet remover to drill just deep enough to cut through the rivets head but no the underlying material. Here you can see how the drill is perfectly centered.
Once I drilled that hole I used a 1/8″ pin punch inserted into the drilled hole and snapped off the head. I then drilled a smaller #40 hole in the center of the remaining rivet shaft for just a 1/16″ or so. I then used my modified automatic center punch. This punch has a spring internally that snaps the pin as you push pressure on it. Normally used to mark metal so that your drill bit does not wander during drilling. I took the sharp point off and squared it off, I also narrowed the end to more of a straight but rather than a tapered one.
For the 4 rivets that tie the flanges of the forward rib to the spar and aft rib are too close to the rib web that my new tool wouldn’t fit. I had to turn to a borrowed part, thanks Glen, which gives your drill a 90° turn.
This drill was no perfect and drilled at a slight angle since it was so tight. So I drilled just deep enough to be able to snap the head off. I then repeated the process of punching out the rivet. The holes turned out perfect with no damage.
I then grabbed my 1/4″ round file to make relief notches in the spar, top and bottom, as per the bulletin. These need to be 1/4″ wide by 5/16″ deep and will help alleviate stresses in this area avoiding future cracks.
You can see on the left spar the lower middle hole that I buggered up during the initial build and had to go up a size in rivet to fix it. The hole looks worse than it is and is a lesson for me to not try to drill out a rivet just because it has a smiley face on it! The next mod is to trim the ends on the spar flanges at an angle. I took measurements and marked these cut lines.
Since I’m going to have around 6-8 weeks of down time before my fuselage is ordered I decided to comply with a service bulletin that Van’s out out. There were 2 new bulletins, 1 for the horizontal spar and 1 for the elevator rod end attachment. I’m going to do the spar bulletin and not the other. My training for not doing the other is it is more for already flying aircraft and was caused, from many sources, to be from the jam nut on the rod end not being tight. That nut transfers the loads and forces from the elevator rio end to the elevator spar. If the nut is loose it can cause the load to be applied to the wrong area causing a crack. These nuts will be on my preflight inspection on flights and I’m not concerned about them. On the other bulletin they have found cracks in the HS spar at a transition area from normal wear in flight. Many haven’t found cracks and only need to do the bulletin if cracks are found. I figured that I have the empennage in pieces now and can do it with a little less work compared to a built aircraft. This is not an easy bulletin to comply with once off the airplane as it has you partially disassemble the HS and drilling 470 type rivets is a pain in the best scenario. I will have plenty of time to complete it and no need to rush. The parts are only $15 from Van’s and will be here by the weekend I’m guessing. He is a link to the service bulletin.