More workbenches

With the increasing number of bench-attached tools in the workshop, I realized we'd need more benches. We bought wood and hardware and built 2 more using the same EAA project (which is really easy to build), again just adding casters to make them easier to move around.

The result is much more actual workspace, where I can leave the bench tools attached and use the two new benches for assembly:

Time lapse:

Total workshop time (approx): 16.5h

Rudder and horizontal stabilizer skin priming

With only a few unprimed parts from the rudder, we spent most of Friday priming parts, including all the smaller remaining parts of the rudder (2 tabs, the horn and 3 stiffeners), both rudder skins and both horizontal stabilizer skins.

For the horizontal stabilizer skins, I used my super-advanced method to keep the markings after the PreKote etching - that is, taking pictures then re-marking before applying the primer. The marks were still visible through the primer.

Markings before priming

Faint marking after priming

Now after the primer cures I'll go back to riveting the rudder, including installing the static wicks.

Time lapse:

Total rudder time: 24.6h
Total horizontal stabilizer time: 69.7h

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

Rudder dimpling, riveting and more deburring

We dimpled all the rudder parts which were already primed:

I'm not Santa, but I  had a little helper

Lots of dimpled parts

Riveted rudder rib

Spar nut plate for attaching rudder to vertical stabilizer

Before I could continue the rudder assembly, I needed to prime a few remaining parts (3 stiffeners, the side of the other spar doubler and the rudder horn) - another post will cover the priming.

Time lapse:

Total rudder time: 23.6h

Research: static wicks

Since I do plan to fly my RV10 under IMC, I decided to have static wicks installed, specially after hearing multiple reports of PFD "white-outs" on planes without them (apparently the LCDs we use are very sensitive to static charge and eventually just stop working).

I started my research by looking at what other builders did, and found the very useful post by Mouser and another similar one by Tim Olson. Both of them used Dayton-Granger 16165, which sounds like a safe bet since Dayton-Granger themselves provide proposed installation instructions specific to the RV10. As much as it would be fun to remember Maxwell's equations to do the electromagnetic calculations myself, I thought I'd trust a company that does this as part of their business :)

I'm going to follow Mouser's suggested bill of materials, so I ordered the parts for the rudder and elevators:

• 6 Dayton-Granger 16165 static wicks
• 12 MS35207-261 screws (equivalent to AN515-10R6)
• 8 AN366F-1032A nut plates (the inboard elevator mounts use 2, the others use 1)
• 4 MS21080-3 one-lug nut plates for the aft rudder and elevator outboard screws

The next step is to make sure the electric charge can flow all the way to the wicks. Since I'm priming the parts, the surfaces are not conductive, so I measured the resistance of the skin from distant rivets on and got good results (1-2 ohms). For inter-part conductivity, I mounted one of the rudder attach bolts to the VS and saw that it's a poor conductor, meaning I need to do additional bonding there. The standard way to do bonding is with a braided strap. I also looked at pre-assembled straps with holes (such as this, this, this, this and this), but found that most come in inconvenient lengths and/or hole sizes, so I ended up ordering the braid plus 33457 terminals from Aircraft Spruce.

To attach the bonding strap to the parts, I'll add a nut plate to both parts (e.g. rudder and vertical stabilizer), for which I picked the same AN366F-1032A nut plate and MS35207-261 screws. The FAA AMT Airframe handbook (chapter 9, figure 9-146) shows the recommended sequence of washers, nuts and their materials for the case where you can install a screw + nut on the same side (but not for using a nut plate). Some more searching found me the Australian AC 21-99 which happens to have that same figure/table (not sure which government copied from which), but also has the equivalent for nut plates (chapter 13, figure/table 13-2):

Since the braided strap is tinned copper and the structure is aluminum, this gave me (for each bonding / hole pair):

• 2 MS35207-261 screws (cadmium-plated steel, same as for the static wicks)
• 2 MS35338-43 lockwashers (cadmium-plated steel) - options where the MS35338 or the MS35335, but since the Australian document mentions the MS35338 several times, I picked that
• 2 AN960-10L / NAS1149F0332P washers (cadmium-plated steel, for washer A)
• 2 AN960JD10L / NAS1149D0332J washers (aluminum, for washer B). The FAA AMT book mentions the AN960JD10L as a suggestion, and I was tempted to replace these by AN960PD10L available at Spruce, but a quick look at the coating codes shows that J is MIL-C-5541 class 3 and P is MIL-C-5541 class 1A - according to the MIL-C-5541 standard, class 3 is really what I want ("where lower electrical resistance is required")
• 2 33457 terminals (tinned copper)
• Tinned copper braid - I ordered a few different sizes and will see which one fits better.

Now I'm waiting for the parts to arrive, and will make a new post with results afterwards.

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:

Finally, I deburred all the edges and holes then cleco'ed the whole thing together to see what it looked like, and I'm happy with the results:

Conduit passing through the vertical stabilizer

Doubler to support the conduit

Conduit sticking out the top (needs some finish after assembly)

Time lapse:

Total vertical stabilizer time: 27.7h

Horizontal stabilizer ready to prime/rivet

This one took a lot longer than the previous sections (partly because I had to study for two exams in the meantime), but it's finally done!

The last part of the work was a LOT of deburring and countersinking, which overall took me over 13h of work (for all HS parts).

Lots of machine-countersunk holes

Time lapse:

Total horizontal stabilizer time: 65.9h