410 hours on the hobbs - Replacement ribs and spar arrived

Finally got my replacement E702, E703, and E704 replacement parts from Vans yesterday. I ended up having to re-do about a half a page of prep steps in order to get everything back to where it was before the riveting blunder described in my previous post. When the parts arrived, they were in a very thick cardboard tube. I removed the spar only to find that the flange on the tip of the spar had been badly bent over during shipping. Upon close inspection, and after bending the flange back into place, it looked like the rivet holes were not compromised, and the skin was not creased in any way, so I was able to flatten everything back out with the rivet gun, a flush set, and a back rivet plate. I was beginning to think that this elevator is becoming a bad omen for some reason, but elected to try to push through it and keep working on it.

I also managed to remove the former E703 tip rib from the former messed up spar. Unfortunately the rivet holes where very badly mangled after attempting to set the rivets with a flange that had become badly deformed after screwing up the E704 counterbalance rib (see previous post). I tried to take my rivet gun with the mushroom flush set and lightly bang out the mangled metal around each hole using a back rivet plate, which seemed to work OK, but the rivet holes still appeared to be a bit oblong from attempting to set the rivet in a badly bent flange. I had originally thought I might be able to re-use the tip rib so that I would have less fabrication to do on new parts, but that turned out not to be the case.

Here is a list of all the things I have done in the past two evenings to get all three parts back to the state where I am ready to attempt riveting again:

1. Flute both ribs and straighten the edges with my edge bending tool. I found another tip on a builder web site after searching VAF that reminded me that the real purpose of fluting these two ribs is to make absolutely certain that the webs of both ribs are flush with each other with no gaps. This makes attaching the E713 counterbalance skin a much easier task, since th holes line up pretty well if the ribs  both fit together properly.
2. Remount the E714 lead counterweight so that I could re-drill the bolt holes in the forward flanges of each rib. With the bolt holes already in the counterbalance skin and the lead counterweight, I was able to take a number 10 drill bit and lightly mark the forward flange of each rib by turning the bit by hand. Then I disassembled the rib assembly and step drilled the holes in each rib flange to the proper size using the same technique described in earlier posts when I originally performed the counterweight preparation steps. These new holes actually turned out much better than the previous holes. It's much easier to mark the flange when the holes in the E713 counterbalance skin and the E714 lead counterweight have already been drilled. The new holes ended up much closer to the center of the flange this time, so that was a good thing.
3. Match drilled the rivet holes in each rib web attaching the E703 and E704 ribs together. Also match drilled the flange rivet holes in both ribs. (You know, the ones that totally screwed up when attempting to rivet them previously).
4. Clecoed the entire elevator frame to the elevator skin and match drilled all the remaining spar-to-skin attach holes, including drilling the 4 holes that are not predrilled on the ends of the E703 tip rib. Match drilled the counterbalance skin holes to the holes in both ribs.
5. Disassembled everything, deburred all the holes in the ribs and the spar, and dimpled them.
6. Countersunk the 4 holes on the inboard section of the spar that attach the E705 root rib to the back of the spar.

Now I just need to finish edge deburring the parts, and clean, prep, and prime them, and I will be back where I was a week ago, supposedly ready to rivet. I will tell you that it was not fun trying to cleco and match drill the new frame parts to a skin adn other parts that had already been dimpled. I am a little concerned that the holes and dimples may not line up as well as they did before, but I have done this sort of thing in the past and not had any problems with the parts fitting together correctly, so we shall see....

I went on VAF in search of info about how others had tackled the end rib riveting problems. Not surprisingly,  I found many others that have had similar problems with this part of the assembly going back as far as 2005. Most were saying that the solution is to hand squeeze these rib flange rivets, and to use the tip of riveting the flange of the E704 rib first, followed by the E703 rib, before attaching the two ribs together via the rivets in the webs of each rib. Van's instructions still say to attach both ribs together first, and then attach the whole assembly and rivet the flanges to the spar, which just does not work out if you try to do it that way. The problem is that while most were describing using the workaround, I could not find any pics of the yoke, rivet sets, and positioning they used to set thse rivets. Then I finally found one. You need to use a flange yoke, a 1/8 inch x 3/8 inch AN 470 round head rivet set, and a 1/2 inch x 3/8 inch flat rivet set on the other end. It is always a little harder to squeeze 1/8 inch rivets with a hand squeezer, but it can be done, and you have much better control with the hand squeezer. You have to leave the tip rib off when you set the flange rivets for the counterbalance rib, because the thickness of the squeezer prevents you from being able to get the round headed set over the head of the rivet due to lack of clearancefrom the tip rib. All you have to do is flex the counterweight rib out of the way just a bit, adn you can set the rivets correctly.

I bet I could convince Vans to give me job where my sole responsibility would be to evaluate and identify all of the latest build issues from their current set of plans for every airplane kit that they provide, determine the work arounds that are being used to correct the problems, and update all of the plans for each aircraft to incorporate the new and better building techniques. The fact that they seem to have no interest in receiving this info and making the changes to their aging sets of plans really pisses me off.

Anyway, I digress. For the record, I wanted to include some "before" pics of the fit of the flanges for both tip ribs against the spar before I rivet them together. If you compare these to the pics at the end of the previous post, you will see just how messed up the flanges of both of the ribs are. The way they appear in these next pics is exactly the way they should look after the flange rivets are set:

Notice that there are NO gaps in between the flanges in the above pics. Everything is nice and flush. Should be ready to try this again tomorrow, after verifying the correct rivet lengths, ensuring the parts are clamped tightly to the table, grinding down my yoke just a bit more, and borrow another set of hands to help hold the rib out of the way. Maybe this time it will work out......MAYBE.

370 hours on the hobbs - Starting on the Left Elevator

SO I installed 4 MK319BS pop rivets in the trailing edges of both sides of the right elevator as shown below:

I may need to order some more of these rivets from Vans before the left elevator is finished. I also need to order an E703 tip rib from Vans as I will be using that for the inboard riblet on the trim tab.

Time to put the right elevator up for a bit and start on the structure for the left elevator. As I look back on it, not a very good track record of working on the plane. I "officially" started on October of 2009, and after enduring about 6 months major home improvement delays and a host of other interruptions, including cold weather, major screw ups requiring major repairs, etc., here I am 2 years later, still trying to finish the tail. Hard for me to swallow, especially when you consider that there are others that have managed to finish the tail kit in about 9 months or less, and at about half the time hour-wise. Oh well, it is what it is. A "one day at a time" approach will net a completed airplane one day, so you just keep at it.

One more pic of the right elevator in all its riveted glory. Had to move it off the tables and benches so I could start working on the left elevator skin. So here it is on the dimpling table. Can't wait to get both of em attached to the HS.

Now on to the left side. This skin is a bit difficult to handle because part of the trailing edge is removed to allow the space for the trim tab. What is a trim tab you may ask? The best way to describe  it is that it is basically a small elevator within an elevator. Thus the use of the word "tab." It's main function is to allow the pilot to make small adjustments to the control surface to lessen the control forces that need to be applied to the elevators to maintain a given pitch attitude for straight and level, climbing, or descending flight.

It does this by changing the amount of force being applied to the horizontal components of the tail. To accomplish this, it moves in the opposite direction of the elevator, which basically makes the elevator move in the opposite direction. For example, if I want to move the elevators up to establish a climb, and I want to hold that attitude for relatively long period of time, your arm may get tired of holding the amount of force it takes to keep the airplane's nose in that attitude. So to fix this you "trim the airplane up," which basically means that the trim tab moves down, which actually adds lift to the elelvator, forcing it to move UP, which raises the nose of the airplane.

The way that I describe this to my flight students is that it is basically a poor man's autpilot, allowing one to fly the airplane essentially hands off of everything is set correctly. So it is a very helpful thing to have on any airplane. In fact, when it is all said and done, I will be able to trim the elevators and the ailerons. Unfortunately Vans does not include a trim tab designed for the rudder, but it looks like this is something that would also be handy, as many pilots report having to hold the rudder just a bit in level flight due to a variety of different factors.  There are other means of addressing any rudder trim issues, and I will cross that bridge when I get to it.

Confused yet? Don't worry, it be more clear as the components are completed. Why am I devoting so much to explaning what a trim tab is? Well, a recent event at the Reno Air Races involving the crash of a modified P-51 resulted in death and severe injuries to many many people. Thus far the pictures and initial investigation as to the cause of this tragic accident appear to be focused on the apparent failure of the trim tab on that airplane. Jimmy Leeward was the pilot, as well as a fellow EAA member, and so this trategy has affected us all. It leaves you wondering how such a small part on the airplane could be responsible for such an accident, but it can.

While I have no aspirations to modify my airplane to go 500 MPH (200MPH is quite enough for me, and is a realistic cruise speed for my airplane), the trim tab system is still a very important one, and so it bears spending the time to ensure that this assembly is done correctly. Failure of any component of an aircraft that directly affects the controllability of that aircraft is one of the continuously sobering thoughts that one has as you embark on a project such as this.

Back to the build.....
This is the left elevator skin with a trim reinforcement plate clecoed to the bottom. This plate serves as the mounting platform for the electric trim servo. The big cavity in the back is where the trim tab will be located.

And another shot of the back side of the left elevator skin clearly showing the cut out for the trim tab. When finished the tab will fit neatly in the space created by the cut out, and when everything is aligned, it will look as though it is just a normal part of the elevator. Here the vinyl has not been trimmed yet.

And a pic after the rivet lines for the stiffeners and spars has been trimmed away with the soldering iron. This is a real crappy job of cutting the vinyl, but the side shown was the last of the 4 that were trimmed, and by that time I was getting tired.

Next is the trim access reinforcement plate after match drilling, deburring, and dimpling, including the skin area to which it is attached. I used my 3 inch yoke to reach all but 2 of the holes that needed to be dimpled. For the remaining 2, I used the flange yoke, which allowed me to insert the yoke inside the hole in the skin in order to reach the last couple holes.

I am using two of my support blocks to hold up the upper skin where the trim tab cavity exists. One problem I found with this skin is that when it is left unsupported in this area, the corner on the end will bend down and it contacts the skin on the opposite side, and this causes scratches and gouges. So you need to be careful when prepping the skin during these times so that you don't damage the skin.

And finally, a pic of the frame parts. I have drilled and deburred the holes for the two rod end bearing support brackets that attach to the forward spar, and I have fluted the two end ribs, exactly the same as was done for the right elevator. The skin for the trim tab is also shown here. Lots of work to do yet.

All for now.

Fluting and straightening the ribs

These are fluting pliers and the resulting fluted rib. What is fluting you may ask? This is a process where small crimps are made in the flange of each rib to help bring the flanges to 90 degrees perpendicular to the web or main flat part of the rib, and to correct the bow in the web or flat part of the rib that results from bending the top and bottomflanges of each rib. The process of attempting to bend two 90 degree flanges on a thin piece of aluminum causes the larger flat part of the metal to bow in one direction. Fluting the flanges is necessary to straighten the bow in the metal by counter-acting the bending moment that occurs. Easier to see than to explain. Since I have already straightened all the flanges and fluted all the HS ribs, I will try to show a pic of the Vertical Stab ribs later on so you can see how pronounced the bow really is, and how fluting works to straighten it out. It really does work nicely.