Final bending and match drilling elevator skins

The bends put into the elevator skins were close to where they needed to be, but they still needed some persuasion. Each skin needs to be flat from the spar to the start of the radius on the trailing edge, and mine were both still a bit ballooned. At first I tried using the small oak bending tool with some pliers to bend the trailing edges more, but it didn't seem to be making much of a difference. Either I wasn't using enough force or the tool just wasn't working very well.

It frustrated me for a bit before I read somewhere on the forums about using a hand seamer here instead. I put some duct tape on my hand seamer to keep it from scratching the skins and I tried it out. Starting at one end I carefully worked my way down the trailing edge of the right elevator, squeezing every inch or two at a time to ensure the bend stayed consistent. Lo and behold, it worked!

A word of caution, it may work too well. It's easy to put a lot of force into a smaller area than the wood bender, thus it's easy to overbend the skin in some places.

A little overdone here...

It takes some trial and error to figure out how much force is necessary, but I was eventually able to (mostly) get a consistently flat skin on each elevator. It's not 100% perfect but it will be easy to make any necessary adjustments even after the airplane is flying.

Just about perfect!

With the bending pretty much done, I clecoed the skeleton into place on each elevator and match drilled all the holes.

Rudder complete! Final riveting and rod end bearings

I would have called the rudder complete a while ago had it not been for the fact that there were eight rivets I couldn't yet finish.

The rivets in question were for the eight holes on either side of the horn brace. Initially I wasn't able to set them since neither my regular 3 inch squeezer yoke nor my bucking bar would fit in the tight space, so I ordered a 2.5" flange yoke (often called a longeron yoke) to squeeze these.

For the tight space around the rivet closest to the horn itself, I had to flip the sets so the larger one could reach the shank inside the horn to form the shop head. 

Nice! I could have used pulled rivets here, but the solid ones look a lot better in my opinion.

The absolute final step for the rudder was to put the rod end bearings into place. It takes a significant amount of force to screw these in, so I covered each with a cloth and used a vice grip to gain some leverage.

The lower rod end bearing should have its center at 1 1/16". Looks good to me!

With that, the rudder is finished for now. I took my vertical stabilizer off the wall to check the fit and make sure there wasn't any binding as the rudder is moved side to side.

Thankfully the travel was smooth throughout the rudder's entire range of motion, so no adjustments to the rod end bearings are needed at this point. I did temporarily put the fiberglass pieces in place to get an idea of how everything will look after it's done.

It's a tail!

After many months, the rudder is done! I couldn't resist taking a couple glamour shots in the polished skin.

I probably won't keep the aluminum polished (paint is a must), but it's fun to take advantage of the reflectivity while I still have it.

Into the stand it went, and it's now safely tucked away next to the horizontal stabilizer already hanging on the wall. 

Rudder done, elevators next!

Fixing left elevator rivet and bending left elevator skin

It was my day off, which turned into a nice long day in the shop getting lots of things done. The first task to tackle was fixing the bad rivet on the left elevator skin. I hadn't yet messed up any holes enough to require any oops rivets, but this was the first hole that would definitely need one.

Above: a normal dimpled #40 hole.
Below that: the enlarged mess made from three attempts at drilling out bad rivets.

I enlarged the hole to #30 with a reamer (it didn't need much since the hole was basically already at a size 30) and stuck in an oops rivet. It looked much better than the previous attempts.

It finally looks nice. These oops rivets are nice to have!

I put the skin into the bender and went to town.

Before...

...and after.

Somehow I managed to get the bend almost perfect on the first try. It still required a tiny bit of persuasion with the hand seamer, but getting things within spec was easy. Most likely because there's less metal to bend on the left elevator compared to the right one.

Building a rudder stand

With the rudder mostly complete sans a few rivets on the horn brace I needed to place it out of the way so I could have more room to work on the elevators. Up until now I had either stored it flat on a workbench or propped it up using some wood blocks:

Either way, I was taking up an entire workbench. Storing the rudder on the wall with the other empennage parts wasn't really feasible since the control horn at the base sticks out so much, so I made a stand out of some spare 2x4s. Design-wise I elected to follow the above logic of having the rudder rest on its front spar with the counterbalance as low as possible so it wouldn't be as likely to tip over.

I didn't want to remove the rod end bearings once they were installed, so I made a cutouts in the blocks just large enough to accommodate each. The rudder rests securely on its spar on each block.

The rudder is stable enough sitting in the stand that I won't have to worry about it tipping over or coming loose. It will sit next to the horizontal stabilizer until I find a better place for it.

The stand is just tall enough that the rudder can stay level without touching the ground.

Drilling elevator counterweights and bending right elevator skin

The counterweights for the elevators don't come with pre-drilled holes like the rudder counterweight, so I needed to match drill the counterweights to the skins in which they were nested. This would be pretty straightforward if not for the fact that the weights themselves are made of lead. The plans mandate using cutting/drilling oil while drilling these.

Looks like some kind of eldritch-horror tentacle monster emerging.

Oil is definitely needed here. Without it the drill bit is quick to bite into the lead and pull the drill down rather than pulling the material up and out of the hole. I would drill maybe a quarter of the way before having to re-lube the hole and the bit.

A couple notes for this step:

1) Make sure the drill is actually perpendicular to the assembly during drilling. The underlying E-703 and E-704 ribs are getting match drilled along with the counterweights, so if the drill is held at even a slight angle then the resulting hole in the ribs may be off center. Worst case, the hole ends up too close to the web or to the edge and both the rib and the counterweight need to be replaced.

2) Remove the blue vinyl immediately after the drilling is complete or the oil will probably be trapped under it. I didn't remove the vinyl until a few days later and the skin ended up slightly discolored around the drilled holes. If left on for too long this could probably cause some corrosion.



The second task of the day was starting to bend the aft edge of the right elevator skin. I followed the plans and made a bending tool out of some 2x8s and door hinges, with a scrap 2x4 put in the middle to gain some leverage.

The right elevator has the longest folded trailing edge in the build at around 5 feet, so I made sure to make the bender long enough to accommodate it. I should be able to fit the entire edge of any parts that need to be bent from this point on.

Also at the behest of the plans, I went ahead and used some oak and steel welding wire to make a smaller bending tool for fine adjustments later on.

The edges are sanded smooth enough to prevent any creases in the skin when pressure is applied.

I put the right elevator skin into the bender and made sure it was butted up against the hinges as closely as possible, then started the bend. Holding the skin in place is crucial to prevent it from slipping out of the bender; the skin slipping out of place during the bend causes the bend to occur well forward of the trailing edge and the skin becomes ballooned rather than folded.

Not bad!

Just like rolling the leading edge of the rudder skin, it takes a lot more force to get the skin to bend than I was initially comfortable with. It's still good to take it easy at first to get the bend started, then increase the pressure as the skin gets more folded. By the end of it I pretty much needed to make the stiffeners touch the opposite side of the skin to get the bend to where it needs to be. The skin is bent enough when you can insert the spar, hold down the skin against it, and there's little to no springback when the skin is released.

No springback, and the skin rests almost completely on the spar. Success!

I've seen some builders insert dowel rods into the fold to make sure the edge stays straight. This isn't really necessary as long as the bending tool itself is straight and you're holding the skin tight against the hinges on the bender itself. Not to mention, I've seen builders that have used dowels that slip out of place during the bend (completely negating any benefits of the dowel) or cause the bend to not be sharp enough (the dowel prevents the skin from bending far enough at the inside of the trailing edge). I ended up with a perfectly straight fold without using any dowels at all.

Match drilling elevator counterbalance ribs and skins

Each counterbalance is composed of two ribs, a counterweight, and a counterbalance skin. The ribs get clecoed together and match drilled first, then the counterweights are nestled into place in each skin. The skin with integrated counterweight then gets stretched over the rib assembly and clecoed into place for drilling.

Just like the rudder counterbalance skin, the skin for each elevator counterbalance takes some coaxing to get into place. It's a tight fit with the counterweight in the way. There will be bolts installed to hold the counterweights in place, but the super tight fit almost makes them seem unnecessary. Alternating between clecoing each side as you work your way up the ribs is a good way to approach this task without too much headache.

Finishing rudder leading edge

It felt like the right time to come back to my neglected rudder, so I returned to the soul-crushing process of rolling the leading edges. I managed to bend the top part as closely into place as I could before I went mad.

The rivet at the top of the small section is tricky. It's so close to the horn that there isn't enough room for the rivet puller to fit while keeping the head of the rivet flush to the skin. I fabricated the pulled rivet wedge mentioned in the manual and used that to get this rivet set.

I cut off a piece of the trailing edge wedge included in the practice kit (I haven't touched it since I started working on the empennage) to fabricate the wedge.

A slight bend to the mandrel allows the puller to stay flush with the wedge, which keeps the rivet head flush with the skin.

Not bad! Although all that bending and rolling seems to have scratched off a little primer from the counterbalance rib...

The most difficult part of each bend is knowing how far to roll before you've rolled enough. Too often I'd use a ton of force and bend the part way further than it looked like it would need to go but it still wasn't enough. 

Bends with just the pipe...

The manual does say that the pipe is just to get the bend started and you're supposed to complete the bend by hand. I finally went at it with bare hands and brute force and managed to get it roughly into position.

...and after further coaxing.

At this point the holes were close enough that I could pull them a just a bit closer together and cleco them in place.

After hours of struggling, the bottom part was finally in place.

The rivets gave me a little trouble when initially fitting them into their holes. I had reamed the holes to #30 before priming, so primer had since gotten into the holes and reduced the diameter enough to make it a tight fit for some rivets. After struggling with one rivet for a couple minutes I took it out and noticed how scuffed up it was getting.

Scuffed rivet on the left, fresh one on the right.

Instead of messing up the rivets any further by trying to force them in, I did what I should have done from the beginning and reamed the holes to ensure an easy fit for each rivet. Many pulled rivets later, I had a (mostly) completed rudder!