Damazio family's RV-10 project: section06

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Vertical stabilizer completed, again

In my first tech counselor visit, quite a while ago, they identified that the rear spar caps in the vertical stabilizer were not properly deburred (not surprising, it was the first part I ever made):

Vertical stabilizer's poor deburring from 2014

After much hesitation, I decided to redo that rear spar and its attached parts, so I had a lot of rivets to remove:

Vertical stabilizer skin rivets to remove

For the 1/8" rivets that attached it to the ribs, I had to remove them through the shop head, but that turned out to work well with exactly the same technique - drill to some depth, break the head off, and then the actual rivet hole is evident to finish drilling:

Vertical stabilizer attachment to middle inspar rib being removed

After just a few minutes (easier than I expected), I had the whole thing off:

Old rear spar removed from the vertical stabilizer

I got the new parts from Van's, and got to work like it was 2014 again:

New rear spar being drilled

Since I already have the completed tailcone, I skipped ahead and final-drilled the VS rear spar into the tailcone now, so I could countersink the bottom holes and prime the whole thing:

Rear spar attached to the tailcone

Rear spar match-drilled and bolted onto the tailcone

Like before, I added a nutplate for the grounding strap, slightly closer to the brackets this time:

Grounding strap nutplate

After primer, I riveted everything back together:

Rear spar riveted together

Vertical stabilizer completely riveted again

The holes that attach to the middle inspar rib got cherry rivets (CR3213-4-2) instead:

Cherry rivets attaching the middle inspar rib to the rear spar

Overall, the results were a lot better than before (who knew, 5 years of building experience makes a difference :) ):

New (left) and old (right) rear spars

Time lapse:

Total vertical stabilizer rivets: 350 (I didn't count repeat rivets again, so no diff from last time)
Total vertical stabilizer time: 76.1h

Large batch of fuselage primer

We primed quite a few parts from various fuselage sections (and even some from the empennage attachment, and for rebuilding part of the vertical stabilizer):

Various fuselage parts after scrubbing with Prekote

Primed fuselage parts on the floor (ran out of space elsewhere)

Primed fuselage parts on the workbench

Primed fuselage parts on top of the fuselage

This unblocks a ton of work, so expect many more posts in the near future.

Time lapse:

Total time: 6.5h (but I'll count it towards each section instead)

Hiatus, then vertical stabilizer completed

I had a brief hiatus while (1) waiting for more rivets to arrive; (2) spending some more time with my wife; (3) taking some vacation time traveling to Oshkosh Airventure:

I'll later post a summary of RV-relevant things I saw and found out at Airventure.
Now that I'm back and I have rivets, finishing the vertical stabilizer was pretty quick, and consisted of riveting the rear spar and the top and bottom ribs:

Minus some rough edges (hey, it was the first airplane part I ever built), I'm quite happy with the results, and eager to complete the next parts (rudder is not far from completion).

Time lapse:

Total vertical stabilizer time: 63.6h
Total vertical stabilizer rivets: 350

Out of rivets, but making progress

I've riveted more than half of the vertical stabilizer:

But then, sadly, when it was time to rivet the top rib, I ran out of AN426AD3-3.5 rivets (probably because I stepped up a half size from -3 when doing the rudder stiffeners due to the dimple depth):

Out of rivets :(

Were it not for this, I might have finished the VS today, since the remaining rivets are all squeezed and thus easier to set. I have more rivets on order (of multiple sizes, just to be sure), and meanwhile the progress on the rudder is also stalled (since the counterweight rib was the next thing to rivet, which also takes -3.5s) - I guess it's time for another round of priming to start riveting the horizontal stabilizer together.

Meanwhile, the inside rivets actually came out quite good (only 3 needed replacement, which has been amazingly easy to do since I got this tool), except for a few scratches on the primer from hitting it with the bucking bar:

Time lapse:

Total vertical stabilizer time: 58h
Total vertical stabilizer rivets: 234

Vertical stabilizer skin riveting started

Now that I know a bit more about antennas (lots of thanks to Don from Delta Pop Aviation for the patience explaining a lot of it), I've decided that I don't want to add a whisker-type antenna to the vertical stabilizer (more on that later), which means the VS is ready to be finished!

Before taking any other steps, I studied the best place to attach the bonding strap (which bonds the VS to the rudder), and decided to install a nut plate for it close to one of the hinge brackets (about the same height as in the rudder):

I then clecoed the skin on and double-checked that everything looked right:

I started riveting in the order suggested by vans - with the middle nose rib, followed by the top rib forward of the front spar:

The conduit proved to be annoying, as it got in the way of holding a bucking bar against some of the holes (tungsten bucking bar to the rescue!):

I got so far as to do the bottom nose rib and rivet the front spar as far as the squeezer would go (but it was late so I didn't want to annoy the neighbors by bucking any more rivets) - more to come later!

Time lapse:

Total vertical stabilizer time: 54.2h
Total vertical stabilizer rivets: 141

Vertical stabilizer corrections

I had a few coworkers who are also builders review my riveting work so far, and that led me to make some fixes - mostly squeezing a bit more on a few undersqueezed rivets, replacing one rivet, and to be more careful with edge deburring in the future.

I mounted the conduit mod by using RTV black glue on the top attachment and fastening the conduit:

Conduit attachment to rib

Conduit attachment (bottom)

Conduit attachment (top)

Rivet that had to be replaced (cracked head)

This time I used a different squeezer, borrowed from a coworker, and it made all the difference - I'm definitely ordering one of these for myself:

The Main Squeeze

I also realized that I have one more missing detail before I can rivet the VS skins - I need to attach a VOR antenna to the top of the VS (the conduit will be helpful after all), so I'm researching antennas (post on that later) and will finish the assembly after that.

Time lapse:

Total vertical stabilizer time: 48.2h

Vertical stabilizer skeleton riveting

Today I set most rivets on the vertical stabilizer skeleton:

Vertical stabilizer skeleton riveted (except for bottom ribs)

Conduit for running wires up the stabilizer

Being my first big riveting job, it took some trial and error - for instance, I put all the clecos in, then realized that the rivets wouldn't go into the holes (tiny misalignment) - removing the clecos, putting some rivets (without setting them), and then putting the clecos back worked perfectly with no misalignment. Also, I tried to use my mighty pneumatic rivet squeezer, then realized (and forums confirmed) that the AD4-7 rivets I was trying to squeeze are too long for it - it only has maximum force at the last bit of its travel, and with a long rivet it just never gets there. I ended up setting most rivets with the hand squeezer, and only using back riveting for the rivets closest to the hinge brackets (where the squeezer doesn't fit).

I also realized that I need a better rivet squeezer - preferably lighter and that can access tighter areas such as the junctions of ribs and spars - those were more challenging than they should have been. I'm considering the Main Squeeze.

Other than that, the skin is fully dimpled, and as soon as I finish securing the conduit (need to buy supplies for that) I can start riveting the skeleton to it.

I also broke my big toe on Friday, so the next few sessions will be slow at best.

Time lapse:

Total vertical stabilizer time: 46.1h

First rivet is in! (plus VS dimpling)

Now that the main structure of the vertical stabilizer is primed, I went ahead and dimpled it:

Lots of dimpled holes

I later found out about Cleaveland's substructure dimple die, which makes a lot of sense to use, so I ordered that and will use it instead of the regular die in the future (I may or may not redo these using that one).

After the dimpling, I decided to go ahead and follow the next step in the instructions, which is to rivet the rudder stops to the upper hinge bracket:

First 6 rivets! Only 102938102938 to go :p

It even turned out to be the correct size for the shop heads :)

I could have gone on riveting the other parts, but there's a small primer fix needed on the rear spar (somehow I forgot to deburr the flange edges, so had to redo it which removed the primer) before I can continue.

Time lapse:

Total vertical stabilizer time: 34.1h

Vertical Stabilizer priming

We finally got to the point of priming the vertical stabilizer. We realized we needed a larger table/bench for this, so we used the lid from the empennage kit box.

Wife mixing the Akzo

For all the markings that could be unambiguously redone, I simply took pictures to make the process easier:

Markings to be preserved photographically (i.e. I can redo them easily from the picture)

I also found a few holes and edges which I had not deburred properly, so I did that before priming.
We started getting a good sense of how much primer is needed for the parts - we mixed 4oz and that covered the parts just right, on a single side - so another 4oz was the right second mix to do the other side.

Primed parts

While the skin wasn't primed yet, this is enough to assemble and rivet most of the VS structure. More priming to come soon...

Time lapse:

Total vertical stabilizer time: 31.2h

Vertical stabilizer conduit mod

As I mentioned before in Empennage Mods, I made the changes required to run wires through the vertical stabilizer. For now this will be an empty conduit, but at some point in the future I may decide to run wires for e.g. a camera.

This was strongly based on Mouser's mod, with a few changes: I didn't add a plate to the bottom, I'll rivet the top doubler to the bottom of the top rib and I'm only running one conduit (I'm assuming that whatever power I need will not be enough to produce interference on data cables).

Before I did anything, I went through the Standard Aircraft Handbook - which didn't say anything about conduits - and the Aviation Mechanic Handbook - which lays out the rules for how much you can fill the conduit and their minimum bending radius. I'm not filling conduits now, but the bending radius got me thinking how I'd route it from the bottom of the stabilizer into the fuselage, so I decided to look at how the connection is made - as seen on manual page 11-6, the vertical stabilizer sits over part F-1014, near two big holes. To make the smallest (biggest radius) bend possible, the best thing seems to be routing closer to the VS spar (the forward side of the aft hole through the ribs):

For the bottom rib, unlike Mouser's, I decided not to use a mounting plate/doubler, since that nose rib has to be removed and replaced during assembly, and I'd rather not add much slack to the conduit (the above book does say that the reasonable slack is 1/2"). I also considered adding one of the MIL-style circular connectors at the top, but as cool as it'd look, decided against it for simplicity, sanity and weight.

I started by marking the corners of the flanges of the top rib over a thicker piece of aluminum (blue markings below), then drew lines and the respective rounded corners to cut the doubler from. Resulting dimensions are annotated below:

Markings for the doubler

I cut the doubler into the rough shape I had outlined, then found its center (midpoint on each edge) to mark the point of the center (conduit) hole. I also marked rough locations of the locations for AN470-AD4 rivets near the corners:

I drilled the rivet holes with a 1/8" bit, then drilled the center hole and enlarged it to 5/8" with the unibit. It fit nicely under the rib as intended:

I then clamped them together and match-drilled the doubler holes into the rib, using a #30 bit for the rivet holes, and the same unibit for the conduit hole.

At this point I grabbed the conduit to check that it fit through the hole, which it didn't - silly me, 5/8" is the measurement for the inside of the conduit, so I went back and enlarged the conduit holes further to about 1/16" short of the external diameter (to give a tight fit in addition to the silicone glue to hold it in place). With this, the conduit fits just right.

For the lower ribs, the work was simpler - just adding something to hold the conduit, for which I followed Mouser's suggestion and used the Panduit LHMS-S5-C cable ties. I held them into the lightening hole, marked the hole position, then drilled it to #30: