Riveting the Rudder Trailing Edge

Tonight. I decided to take on the most difficult part of the empennage:  The Rudder Trailing Edge!  This one simple little piece of kit causes the most headache and heartache out of the entire tail section, and for good reason.  If you can’t get a good straight trailing edge on the rudder, you will have a hell of a time trying to get it all trimmed out and flying hands off.  I followed the Van’s recommendation (see previous posts) about using a piece of angle aluminum and Pro-sealing the trailing edge wedge into place and clecoing the trailing edge onto the aluminum angle to help it bond into a nice straight piece. That worked wonderful.  Then I used Van’s suggested method of double flush riveting the trailing edge.

To start off, I had to remove the angle that has been holding the trailing edge in its curing position for the last 18 or so days.  The Pro-seal had squished out a bit, and bonded the trailing edge to the angle, but it was pretty easy to separate and remove the angle. 

Once I had the angle off, I used a #40 drill bit in my hand to clear out the Pro-seal from al the rivet holes.  On quite a few of these holes, I had to use the deburring tool with very light pressure to remove some of the Pro-seal that oozed out into the dimple.  I also tried to clean up the edges and skin surface so that no Pro-seal would cause the trailing edge to not sit flush against the back riveting plate. I used some acetone to clean off the skin surfaces, because Pro-seal is some sticky stuff! Once it was all cleaned up, I inserted the AN4263-3.5 rivets and used some masking tape to hold the manufactured heads of the rivets into the dimples.

You can also see in the photo above, I numbered every rivet on the tape, and then wrote in my riveting sequence just above the numbers.  Van’s tells us to start off by half-way setting every 10th rivet using a back rivet set.  I started in the middle, and counted every 10th all the way to the top and bottom and marked the with the number “1”.  These would get set first.  Then I counted every 5th rivet and marked its sequence as number “2”.  Then I tried to roughly put my third sequence, number “3”, in between the 1’s and 2’s.

Just like the plans tells us, I flipped the rudder over and used my back rivet set on the tails of the rivets and the manufactured heads on the backing plate.  I have a longer backing plate so this made this part go really smooth.  I started out by half-setting all the number 1’s, then going back and doing the number 2’s and so on by working from the middle out on each sequence. Once I had them all half- way set, I flipped the rudder up to make sure the trailing edge was still perfectly straight….it was!!!

Now, I flipped the rudder over so that the tails of the rivets were facing the back rivet plate, and switched out the back rivet set on my rivet gun, for a mushroom style flush rivet set.  I used my same sequencing, and set the rivets fully by using the flush set against the manufactured head, and the tails were driven into the back rivet plate until they were nice and flush.  I only used the corner of my back rivet plate so that I could fit JUST the rivet I was working on against the plate, this would keep the other rivets from holding the trailing edge up away from the plate and causing it to bend.  It took a lot more fiddling to do this, but I think it made it turn out really straight.

After I had worked my way out from the center of the rudder, using my riveting sequence, I turned the rudder up to make sure it was straight:

Yeah….I am definitely happy with that!! It’s not exactly perfectly straight, but it is WAY closer than the 0.100″ than Van’s says is tolerable.  I held the trailing edge against my aluminum angle to get a comparison, and to measure against my dial calipers, the worst I could measure was only about 0.05″ to o.075″ which is perfectly acceptable.

Once I had the trailing edge done, I had a few more rivets to squeeze on the top and bottom ribs.  I had left these out to make it easier to apply the pro-seal, so its time to set those babies.  I was able to use my squeezer on all of them except the very last one closest to the trailing edge.  Vans’ says its fine to use a MK-319-BS blind rivet in these last holes because of the super tight clearances.  I decided that’d be the route I’d go, because I did NOT want to mess up this beautiful rudder with trying to squeeze or rivet that very end rivet!  So, I stuck in a MK-319-BS blind rivet, and carefully set it using a pop rivet tool.  They came out really nice, and are almost perfectly flush with the skins. When she’s painted, this will get a little bit of filler and you’ll never know it 🙂

The rudder is now 100% riveted together!  All that was left was to clean up the edges of the trailing edge with some scotchbrite pads to break the edges, as well as to knock off any squished out pro-seal.  Then I rounded off the corners of the trailing edge using a file and scotchrbite pads.  That’s it for tonight! I am happy to have this part behind me now.  I have been dreading it for a while, but it actually wasn’t to bad to do.  I set aside a day when I’d have plenty of tie to concentrate and get it done slowly and correctly. This rudder will fly straight as an arrow!

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Google photos Link: https://goo.gl/photos/auZhkD8hAYvLhdiH8

Hours Worked: 2.5

Building the Trim Tab

I started this session by first dressing the edges of the left elevator skeleton parts, but that only took about 30 minutes, so I decided to find something else to work on.  Since those parts are waiting on priming, the only thing I have left to start on is the trim tab.  I read the plans and decided to give it a go and try to get the end tabs bent, and some work done of the trim tab itself. I managed to almost finish the trim tab assembly tonight 🙂

After dressing up the edges of those left elevator parts, I laid them up on the shelf and dug out the trim tab parts.  First we have to start off by bending the trailing edge of the skin for the trim tab, and this is done exactly like the elevators.  So I set up my bending brake  and put a very smooth and gradual bend on the trailing edge, and made sure it was straight with the spar in place.

Granted, I took my time on this, I got it done in about 20 minutes or so.  I have been reading up on bending these tabs for a while now, and watched the Orndorff videos, so I was pretty prepared to begin.  I started out by making some bending blocks that fit into the end of the trim tab.  I used the tab itself to draw an outline on a piece of 2×4 and then cut the shape out on my bandsaw.  I made two sets because the bends on each end are at slightly different angles.

With the bending blocks made up, its time to get to bending the trim tab! I start out by inserting the blocks and clamping everything down to my work table nice and tight so it doesn’t move during bending.

We start out by bending the bottom tab first, and overlapping it with the top tab, so that the top tab folds over the bottom, helping to keep water and debris from getting into the trim tab.   I used a block of wood in my hand to get the bend started and once I had it at about a 45 degree angle, I use a small hammer against my wood block to help shape the metal.  This way, I am using the soft face of my wood block against my tab and the bending block instead of the hard metal face of the hammer.  This keeps from dinging, denting and scuffing the aluminum.  I took lots of time and did this very slowly, using small light taps with the hammer against my block to bend the metal.  Once I had the bottom tab bent up to a 90 degree bend, I did the exact same to the top tab, bending it to overlap the bottom.   I am really happy with the results.

Now that we have the inboard side of the trim tab bent, it time to move to the outboard.  These tabs are MUCH smaller than the inboard side, so I had to take extra caution on these little suckers.  They would be easy to crack if you work the metal to much.  Eventually, I got them folded up, overlapping the bottom tab with the top just like on the other side.  I stuck the spar into the trim tab and clecoed it in a few spots to check my work, and I am happy with how it turned out!

Outboard Tabs

Inboard Tabs

After having a good victory on the tab bending, I still felt good enough to continue on working. The plans have us mount the E-717 and E-718 trim tab horns to the bottom of the trim tab.  E-717 has 3 of the 4 holes pre-drilled, so its easy to line up.  Then I just clamped E-718 to E-717 with some side clamps, and then use one of the clevis pins and hinges from my electric trim kit to make sure the holes were lined up properly in the trim tab horns.  Once everything was lined up, I back drilled both of the trim tab horns to the trim tab.

So, next up was to fully cleco on the spar, and then attach the hinge bracket so it can be back drilled.  I studied the plans and made a few alignment marks on my E-721 trim tab hinge.  Vans gives the measurements to the center of the hole in the skin/spar so its easy to mark the hinge with a sharpie, and then line up the cross hairs with the center of the hole.  I also marked the entire centerline of the hinge to the measurements Vans gives with a sharpie so I could align every single hole.  Once I had them all aligned, I used some cleco side clamps to hold it all together.  Once I had the hinge clamped on firmly, I started back drilling using the holes in the E-619-PP trim tab skin as my guides.

Once I had the hinge back drilled, I flipped the trim tab over and match drilled all the holes on the bottom to the spar.  Now, the plans has us disassemble the trim tab, so that we can trim off any excess from the trim tab horns, as well as the excess from the inboard side of he E-721 hinge.  I went ahead and trimmed off the very little bit of excess on the E-718 and E-717 trim tab horns, and smoothed the edges with a scotchbrite pad, and then did the same to the little bit of excess on the E-721 hinge.  I figured this was a good place to stop, so I called it a night.  I still need to deburr the holes, dress the edges of the trim tab parts and then dimple it all.  I am contemplating if I should prime the trim tab or not, not sure yet.  Here’s all the photos I took tonight:

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Heres the Google Photos Link: https://goo.gl/photos/nFHQysMhoQBFDwdJA

Hours Worked: 4

Bending the Left Elevator Trailing Edge

I spent about 20 minutes bending the left elevator trailing edge in the bending brake tonight.  I figured since I already had my bending brake setup on my bench, I might as well go ahead and bend the left elevator as well.  Since this elevator doesn’t have as much trailing edge to bend (due to the trim tab), it was really easy to get bent to the right shape and only took about 20 minutes counting checking it with a straight edge. It came out great, and then went back on the shelf until I get ready for it.

I decided to do a little more work on the right elevator since it took less than a half hour to bend the left.  I thought I would go ahead and get the right elevator assembled so I could match drill the skin to the skeleton and get it ready for dimpling.  While I was assembling the E-713 counterbalance skin to the E-703 and E-704 ribs I realized I made my first mistake, and one so bad I would need to order some new parts 🙁  I made the mistake last month during the initial assembly  which you can see by this photo. Notice the counterbalance skin, I have it flipped over in the wrong direction.  This cascaded down to when I drilled the lead counterweight.  So, essentially what happened is I assembled everything with that skin flipped over, and then match drilled the counterweight to it.  Tonight, when I started assembling everything together, I noticed the counterweight holes were not lining up, which is when I noticed that I messed this part up.  You can see from these photos how the parts were drilled:

That counterweight should be on the OTHER side of the rib and you can see the sharpie marks I made tonight to see just how bad it would be to re-drill.  These holes are too close so re-drilling them is not an option.  But, it looks like only the counterweight and its skin are needing to be replaced, and since the kit came with two (one for the left and another for the right) I can just use the remaining  E-714 and E-713 that would have went on the left side,  to keep working until the replacement parts come in. Both the left and right parts identical.

Thank goodness that I only need to replace two parts, the E-714 counterweight and the E-713 counterbalance skin for a grand total of about $40 from Vans.  I am so glad I caught this now, before I wound up having to replace more parts!  Oh well, I guess its good that my first mistake was something that is easy to fix and cheap to replace.  Luckily it won’t hold up any progress while I wait on the new parts.

So, I pulled out the E-714 and E-713 from my stock and re-drilled the skin and counterweight MAKING SURE the orientation was correct this time :-).  Drilling lead is a pretty rough task on a drill bit, so I kept it slathered up in Boelube.  With that squared away, I decided I’d go ahead and assembly it to the skeleton and then match drill the left elevator skin to the skeleton to get it ready for dimpling.  This was pretty uneventful, and went quickly.

Lasty, I figured I would get the last little step done tonight which was to match drill the WD-605-R elevator horn to the inboard side of the rudder.  I cleco’ed it on to the inboard R-709 rib, double-checking its orientation (I bet this part is expensive to fix, compared to the counterweight ha!), and then drilled it with a #40 drill bit.

And with that, the right elevator is ready for disassembly, dimpling and then riveting. That will be in another work session, I was a bit frazzled after worrying about messing up the counterweight, so I called it a night.  Here is the album for all the photos:

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Google Photos Link: https://goo.gl/photos/2i6PtVKFbjNHSrat8

Hours Worked: 2.5

Bending the Right Elevator Trailing Edge

I built my bending brake / jig for the trailing edge of the elevators tonight, and decided to give it a whirl on the right elevator.  It came out really good, and it looks like the trailing edge is going to be straight as an arrow.  I had been working on the plane earlier today, but took a short little break and started back at it.  First up, I had to build my bending brake / jig using some 2×6 boards that I picked up a couple of weeks ago from the Lowes Aviation Suppy here in town.  Van’s has some directions on how to build a simple little brake, but I have modified it very slightly per some suggestions from Vans Air Force members.  Instead of hinging the 2×6 boards so they fold width wise, I hinged them so they fold on their narrow side, which should make the break much more sturdy.

This lets me clamp the brake to my work bench so I can use it easier, and gives a nice flat surface for the elevator to lay against during bending. It also lets me use more leverage.  Bending the trailing edge took a bit more work than what I was thinking.  It takes quite a bit of force to get this thing to lay down! I did my bending in short easy bends so I didn’t over do it, checking as I went to make sure the elevator is bending straight.  After several rounds of applying pressure, removing the elevator and checking it, I finally started to get it close to being bent.

Once I get the skin to the point that it laid naturally across the front spar, I clecoed the front spar and the end ribs in place to get a better idea of how it was turning out.  I was pretty close at first, but had to put it back in the brake a few more times to get it perfect. I used my square to check that the bends were complete.  What we want to see is the skin flat against a straight edge, all the way from the front spar, down to the trailing edge, where the bend sharply drops off to a perpendicular to the square.  If the skin sort of “falls” slowly away from the straight edge, you haven’t bent it enough.  If the skin concave’s away from your straight edge, you have to much bend.  Too little bend is WAY easier to fix than too much, so I did this in small steps to make sure I didn’t over do it. I checked the skin from the top to the bottom at every stiffener and in between the stiffeners using my square and its looking really great:

However, I think I have a very slight twist in the elevator somehow.  When I laid a straight edge (4 foot aluminum drywall ruler) across the trailing edge from top to bottom I noticed that the trailing edge bowed about 3/32″ around the middle.  I thought I had a photo of that, but it was overexposed from the flash reflecting off the ruler.  But, I decided to call it a night at this point.  I am fairly happy with the trailing edge, and I’m going to post a question over on the forums about the very slight bow.  It’s probably easily fixable seeing as how I haven’t riveted the elevator yet. Heck, the 3/32″ may actually be in spec for the rudder, I’m going to do some research and find out.  Here’s all the photos from this build session:

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Google Photos Link: https://goo.gl/photos/NrH78YdKxtHENdNV6

Hours Worked: 1.75