308 hours on the hobbs - Back to the Rudder (UGGGHHHHH!)

Had a bit of a scare the other day that I might have ruined both my VS and Rudder. Before I get into that, let's pick up where we left off before Oshkosh. I was almost done with the leading edges of the rudder. Lessons learned were:

The bend that was made with the bar  as described in my previous posts is only an INITIAL bend. You still have to do more bending (most end up doing this by hand) to get the holes in the edges to line up with each other so they can be pop riveted into place.

The plans clearly show that you MUST bend the leading edge skin near the edge of the spar flange in order to close them up so that the nicely curved edge is the proper distance away from the spar web. Very confusing since they spend so much time telling you how to bend the skin so that you DON'T end up doing exactly that.

Anyway, I used a techique of pushing down on the outside and up on the inside of the skin on the top to try to keep from creasing the skin next to the spar flange. Creases in the skin right next to the spar flange cause stress risers when flight loads are imposed on the control surface, which can cause crackes to form. I know this sounds confusing to you other builders out there. Just think of it this way. The initial bends were made with the skin down or on the surface of the board with the J bolts. The final bends are done in the opposite manner, pushing down on the skin on the top side to close the gap.

Here is a pic of all three sections closed up and pop riveted.

That pic does not show the crappy way that the middle and bottom skins turned out. To put it simply, the initial bend method that used (with the J bolts holding the bar and skin down flat on the table, worked SO well that I actually over bent the edges of the skins. They were initially bent so that the edges were almost at a 90 degree angle to the spar web. which the way that they should END UP when you are FINISHED bending everything. UNfortunately, as I stated previously, I still needed to finish bending the skins to close up the gap that still existed after the initial bends on both sides were completed. this ment that the edges of both skins ended up being well OVER 90 degrees to the spar web, causing them to curl up adn back toward the spar web just enough to caause me some severe headaches. This next pic shows the outcome. Notice the stressed edges of the inside skin in between all the pop rivets. This is the inside skin still wanting to curl back toward the spar web, but I am effectivey forcing the inner skin to attach to the outer skin. The result is that the edges of the skin are not flush with each other throughout the entire length of the edge:

I had problems getting some of the pop rivets to grab the inner skin so that it could be pulled tight against the outer skin. This was because in some areas the inner skin was curled inward  a bit more than the rest of the edge. So I was left with a decision, Replace the entire rudder skin since I had streched it too far, as one tech counselor told me, or devise a way to get the inner skin close enough to the outer skin so that the pop rivet would grab it. I chose the latter. I've spent way too much time on this damn thing already to even think about replacing the otherwise nicely attached rudder skin. I came up with a sort of lever that used 1/4 inch thick by 1 inch wide steel bar from HD, and a couple of small wood dowel sections, one taped to the end of one side of the bar, adn the other taped to the opposite side of the bar in a location where it could be used as a lever to push the inner skin outward after inserting it inside the curved section. Again, confusing as hell, I know. I forgot to get a pic of the lever so I will do that post again tomorrow. It actually worked fairly well, but required three people to get it to work correctly - one on the lever, one on the pop rivet gun, and one holding the rudder down so it would not move. Quite the operation but it did the job.

The LE skins are now all pop riveted into place. The only problem is that the middle and lower sections of the rudder LE are a bit concave when you look at them. This is due to the outer skin being pushed into the inner skin, and being drawn closer to the Spar web due to the over bent inner skin. Not happy with the outcome, but I have learned my lesson, so the elevators adn airlerons should come out looking very pretty.

Now on the next problem. After getting the LE skins closed up, I wanted to see that baby all hinged up on the VS. So I pulled down the VS from the garage shelf that I built, pulled out the 3/16" aluminum temporary hinge pins that I purchased, installed the rod end bearings in the rudder per the plans, and proceeded to insert the rod ends into the hinges. I found that the hinge holes were not quite large enough to fit the pins, After some research, I arrived at the conclusion that a 3/16 inch reamer would clear out each hinge hole enough to insert each hinge pin., and this seemed to work OK, but I noticed that each pin did have a little bit of resistance when going through the hinge holes. Then I swung it back and forth, with the RV grin all over the place, with the knowledge that had just completed my first full assembly of a stabilizer part and its corresponding control surface.

Then came time to remove the pins so that could move on to the elevators. Well, the bottom and middle pins all came out fine. but the top hinge pin would not budge. Short story is that a ridge had built up on the hinge pin due to inadequately reaming out the hinge holes, and this prevented it from coming back out of the holes. I ended up taking a small cold chisel that would fit in the confied space where the hinge is installed, and avery hard hammer, and banging the living hell out of it until it finally came out far enough for me to bend te hell out of the steel hinge half so that the bearing of the rudder would finally be free so that I could get he rudder off. Then I had to take my dremel cutoff wheel and leterally had to cut the tip of the hinge pin off in order to get it off of the hinge. I'll just close by saying that this ruined a perfectly good evening, and I almost ruined both parts in the process.

Further inspectiosn revealed that the hinges were still in good shape, and the rod end bearings on the rudder appear to be OK as well. SO I think I averted disaster yet one more time. The moral is that 3/16 " is a bit too SMALL for the 10/32 bolts that will eventually fit in them, as well as the 3/16" hinge pins that used. What I really needed was a number 12 reamer, which I did not have (have one on order as I write this). I did, however, have a number 12 drill bit. SO I used that to further ream out the holes. Just trust me when I say that the amount of material that was being removed by both the 3/16" reamer and the #12 drill bit, were basically dust particles, but apparently this was enought to make the difference in the pins fitting correctly or fitting too tightly in the hole.

Pics will help clarify this mumbo jumbo I hope:

Look towards the top of the pic on this one to see the sligt divet or inward bend of the skin. This is that concave result I spoke about earlier:

While I really wanted to try to put solid rivets in everything on the rudder, the trailing edge finally beat me into submission. You are given the option here to use pop rivets since the clearance in this area is so small. I was in the process of making a small bucking bar out of the 1/4 inch thick steel bar I mentioned earlier, but I finally caved in and said WTF and took the easy way out by using the pop rivets. Nice hole, eh?

Here is the original "happy moment" when I thought everything was coming to gether nicely. The hinge pins are in place and the two assemblies are now joined into one.

Next is a pic of the bottom temporary hinge pin in place.the temporary pins are used so that you do not put unnecesary wear and tear on either the hinge hole or the threads on the actual bolts that are used. the pins are smooth and are soft aluminum so they are not supposed to cause any damage or difficulty. (HA!)

And another seemingly happy moment, all before I realized I could not remove the rudder due to the stuck hinge pin:

And one last shot of the hinge pin assembly before I call it a night. Tonight I reattached the lead counterweight to the top of the rudder, hopefully for good this time. Torqued it to 30 inch pounds. Just a little powder coat touch up on the hinge brackets, and the VS and rudder can go to sleep for a while while crank out the elevators. 'Gnight all!

Attaching the rear spar

A nice shot of the rear rib flange of the bottom rib that attaches to the rear spar. I was able to use my pneumatic squeezer to set these three round headed AN470 rivets. Another tip that I was reminded about after reading several posts on VAF was that you generally want to put the manufactured head of the rivet up against the part with the smaller thickness. In this case the metal for the rear spar and the rib are supposed to be the same I think. SO then the only rule would be to pace the manufactured head on the part where it is easier to access with the rivet set. I will go one further by adding my own little rule that I intend to stick with for the rest of the build. I will also apply the manufactured head of the rivet to the part that is more flexible than the other part, assuming it can be accessed with the rivet set adn bucking bar correctly. What I mean by that is explained in part by looking at the photo. The rib flange is the part that is able to bend and flex a bit. The rear spar web, on the other hand, is absolutely stiff, and will not budge very much, if at all.

Sometimes the flanges do not sit exactly flush the the part that they are being riveted to. In this case that is the rear spar. The only way to seat the rib flange so that it is nice and flush with the rear spar is to put the manufactured head of the rivet against the rear flange of the rib, so that the cup set on the squeezer can be placed over the head, and then enough pressure can be applied against the head to push the flange up tight against the rear spar web. This rivet clamping techique worked rather well, and helps prevent rivets from creating or "filling" the gap in between parts that may not be mated very well for one reason or another. Clecoes only hold parts together in these situations marginally well (not very well at all in my experience), which is why I have also ordered three 1/8 inch screw clamp clecoes, which should help cinch down the work pieces a bit better during riveting. Can't wait to try those out on the next rib-to-spar assembly!

Not as bad as the HS, but not good either

This was a result of getting tired and choosing to continue on with riveting the skin, rather than taking a break from riveting. This is called a smiley, and when they go deep enough, they can become a structural concern. Luckily these are not very deep, and some filler will take care of these small dings in the skin. This occurs when the flush rivet set in the rivet gun is not held straight up and down on the skin while bucking a rivet, and is tilted just ever so slightly while pressure is applied to the skin and the trigger is pulled. It happens in less than a blink of an eye, and really sucks when it does, especially after doing a much much better job on the entire VS skin up to this point than I did on the HS. Oh well - ya keep learning as ya go sometimes.

What happens when you don't get it quite right

This pic is oriented similar to the pic in the previous post, but shows the opposite side of the middle rib of the VS (VS707). If you double click on the pic to expand it to full resolution you should be able to see the slight deformity of the spar flange (near the center of this pic, on the bottom side of the spar, just to the right of the rib). I am still not totally certain how it got bent that way, but it obviously occured when the bucking bar either slid off the rivet, and perhaps was combined with the rivet gun continuing to hammer on the rivet on top of the skin. Only the spar flange appears to be bent, and thankfully there is little if any damage to the skin. I dressed out adn re-primed the flange as best I could.

I also spoke to Vans about this, and explained that I was thinking about placing a back rivet plate in there to try to pound out the bend in the spar flange. They said that as long as the bend was not compromising the rivets ( it is in between them), and there was not apparent damage to the skin itself, then it should be OK if left alone. There is a risk that any additional attempts to pound out the bend in the flange might also stretch, distort, or weaken the skin. So I decided to dress it out as best I could, leave it alone, and build on.

Riveting the VS skin to the forward Spar

This pic shows the inside of the skin after most of the riveting of the skin to the forward spar has been completed. The right side of the VS skin is on the bottom, and the left side is on the top. This pic also shows rivets of the skin to the middle rib of the frame (VS707). The camera is looking forward from the back of the VS where the rear spar will go, once all of the forward skeleton is riveted in place. The rivets actually don't look to bad here. I used both of my tungsten bucking bars and the flush set in the rivet gun to set these rivets. It is quite the trick, because you have to slide your bucking hand, in this case my left hand, under the skin, and hold the rivet gun with the right hand. You have to buck the rivets mostly by feel, and by learning how to position your hand and fingers around the bucking bar under the skin, and then focusing on the correct position of the rivet gun on top of the skin. Definitely takes some practice to figure out how to do it correctly.