Horizontal Stabilizer Construction
Current status: Riveting in progress.
Time invested on this sub-assembly: 64 hours (56 by me)

The only customizations I'm adding to the horizontal stabilizer is grounding straps connecting to the outboard end of each elevator.

Updates regarding the horizontal stabilizer
3 Jan 2010
Quick progress on the horizontal stabilizer today and yesterday. I'm doing some things slightly out-of-order. The plans call for primer on different subassemblies at three different times. I'd like to get all of the really long parts out of the way in one pass, if possible. And really, if I can get away with it, I'd like to do all of the HS priming in one shot so that's what I'm currently going for.

However, this means that some steps have to be skipped. particularly the riveting together of the two spar assemblies. Additionally, I've decided to use the aftermarket HS-1008 brackets from iflyrv10.com, and I'm still waiting on them to arrive, so the steps involving those parts can't move forward. Luckily, the HS-1008s only attach to the forward spar assembly and don't prevent work on the rest of the HS. I did go ahead and rivet together the center hinge bearing for the rear spar assembly, since none of its components get primer anyway

Hinge Bearing

The rest of the rear spar components were quick to process and they are now ready for primer. Likewise, the forward spar goes pretty quickly. With the exception of the HS-1008 brackets, the components of this sub-assembly are ready for priming.

Front Spar Doubler

With the spars as far as they could go without the arrival of my additional alodine and alumiprep (I need twice as much as I have to make a deep enough pool in the dunk tank for parts this long), I started deburring the edges and lightening holes of the ribs. Using the scotchbrite wheel, this went pretty quickly. So I continued on to make the 9° bends in the inboard ribs and also to ream out the trim tab control cable hole in the inboard nose ribs.

Rib Processing

The next step is to construct cradles for the skins, which I started yesterday but was unable to finish because I don't have a jigsaw. I went ahead and cut one of the side pieces from the empennage kit delivery crate into appropriately sized pieces and drew the rib template on them. That was it for last night.

Making Cradles

This morning, I picked up a jigsaw from a friend and cut out the interior pieces from the cradle boards. A bit of duct tape to pad the inner surface and they were ready to go. Here's one in a test-fit:

Cradles in Action

Before populating the skin with parts, I had to match-drill the ribs into the forward spar. This was easy, but with the skins and cradles and plans sitting on my workbenches, I was really starting to run short on space.

Horizontal Stabilizer Skeleton

Luckily, once the internal match-drilling is complete, everything starts to get piled together inside the skins and it takes up a lot less space. Getting clecos into the nose ribs was considerably more easy here when compared with the vertical stabilizer. Probably I just know more about what I'm doing than I did back in October, but this was really a snap.

Filling the Skins

The stringer assemblies are trivial to assemble, but be sure to put the clecos holding the two parts together on the top (longer) side, so that they don't stick down into the curvature of the HS skin. Note that this is the opposite of what is shown in the following photo. I had to reverse them or risk marring the skin.

Stringer Assemblies

Also, I somehow managed to insert one upside down and didn't notice until I got the skin cleco'd up all the way down half of one side. Oops... Not a big deal, just had to remove all those clecos and flip the stringer over. It is a bit unwieldy lifting the entire HS out of the cradles to pull the skins back for this operation. I'd recommend having a helper for that, though I was able to accomplish it alone.

Once the stringers are in, the skin can be cleco'd to the inspar rib flanges and then aft spar assembly can be inserted.

Fully Assembled

This is where I left it for tonight. The next step is to match drill the skins, a task that should take some time and be boring. One additional task I skipped was to match-drill the stringer web. This requires a #30 bit in a right-angle drill and I was somewhat surprised to find that my tight fit drill kit that I bought from Isham didn't include a #30 (it has a #40, the rest are standard multiples of 1/32"). I've ordered the bit from Cleaveland and will do the stringer web when it arrives.

Center Structure

4 Jan 2010
Split up the skin match-drilling into four segments to keep it from being too tedious. Managed to get all four segements done today. One in the morning, one at lunch, one at dinner, and one just before bed. No pictures; it doesn't look any different than it did yesterday. I'm glad this is out of the way, though it really just means that I'm one step closer to deburring all of these holes (twice, once for each side). Boo.

Progress is basically stalled right now awaiting the delivery of several items. The match drilling of the stringer web requires a drill bit that shipped overnight from Cleaveland today. The forward spar assembly requires the aftermarket HS-1008 brackets which have been on order from iflyrv10.com for over a week, but they haven't given me any indication of when they'll be arriving. How long do I wait before giving up and manufacturing my own?

I can't alodine the long parts until I get my additional alumiprep and alodine, which are scheduled to arrive on Wednesday from Aircraft Spruce. However, this is a ways off anyway since this step comes after deburring and dimpling.

18 Jan 2010
It has been a bit slow the last couple of weeks. I'm still waiting for my HS-1008 parts to ship, though Steve at iflyrv10.com assures me that they are shipping today. In the meantime, I've been getting everything ready that I can without these parts. Since my last post, I have completed all deburring on all parts, all dimpling on the nose and inspar ribs, and all countersinking of the spar and stringer flanges.

I also acquired some additional tools and supplies. Got a second gallon each of Alodine and Alumiprep, more buckets to mix them in, a bench vise (need this for some of the early operations on the tail cone), and some compressor oil (I think its about time for an oil change on this guy).

Just a few things left to do before I enter the chemistry stage of the horizontal stabilizer:
  • Scuff and clean the inner skin surfaces
  • Remove the vinyl from the rivet lines on the outer skin surfaces
  • Dimple the skins
  • Match drill and deburr the HS-1008 holes.
Once these tasks are complete, it'll be a full day of Alumiprep/Alodine/Akzo, then the riveting begins.

Last night I met another RV-10 builder in my home town and we got together at my place to talk about our projects, etc. He's just finishing up his vertical stabilizer, so I'm a bit farther along than he is, but its good to have a local who is familiar with the kit to bounce ideas off.

24 Jan 2010
A few days ago I heard from Steve at iflyrv10.com that my parts had actually shipped and would be arriving yesterday, so I started finishing up all tasks that could be done in anticipation of some real progress yesterday and today. This included scuffing the inner surfaces of the skins so that they looked like this:

Horizontal Stabilizer Skin Post-Scuff

And then removing the vinyl from the rivet lines on the outer skin surfaces, leaving them looking like this:

Vinyl Removed From Rivet Lines

I went snowshoeing yesterday morning, and when I got back there was my package from Steve. I immediately set about match drilling the 18 holes into the HS-1008 brackets. Used a piece of angle stock to keep the brackets square during this operation.

Preparing to Match-Drill the HS-1008 Brackets

The last thing to do before entering the chemistry phase was to dimple the skins. Due to a dinner party last night, this was put off until this morning. Nina helped me run the skins through the DRDT-2 dimpler and we knocked the skins out reasonbly quickly.

Nina Gives the DRDT-2 a Try

With that, all horizontal stabilizer parts were ready for alumiprep, alodine, and akzo. I spent several hours today getting all non-skin parts run through the alumiprep and alodine washes. Got to use the full 12' of my dunk tank for the spars, which was somewhat unwieldy but fun.

Pipelining the Chemistry

Had to use a big keg bucket to drain the tanks because there was more than five gallons of each solution, and I was storing them in five gallon buckets. The alodined parts look good, as always. We decided to watch a movie tonight, so the Akzo primer will have to wait for another day.

Solid Gold Airplane

27 Jan 2010
Primed the horizontal stabilizer parts!

This has been ready to happen for a few days now, but I haven't had the time. Tonight I had nothing planned after work, so when I got home and got a quick dinner out of the way, I hung up the plastic, suited up, and primed all of the parts. It went reasonably quickly, taking about 2.5 hours for the whole routine. I used exactly 3 cups of primer (1.5 cups of each component), if you're interested. When I finished, there was just a little puddle at the very bottom of my HVLP hopper.

Primed Parts Drying

Once the primer had dried, I was anxious to start riveting because that is my favorite step. So I got right to it, beginning with the rear spar assembly. I got the rear spar doubler riveted on to the rear spar, all of the rivets were squeezed easily with the longeron set.

Rear Spar Doubler

Also got all of the hinge brackets riveted in place with the squeezer:

Elevator Hinge

I did not, however, get the central hinge bearing installed. This is the first component of the plane that requires bolts torqued down to a particular torque, and this the first time I've tried to use my torque wrench. Only this evening did I discover that my torque wrench has a 3/8" mandrel and my socket set is all 1/4" sockets. Time for a new socket set! I'll be heading to the hardware store over lunch tomorrow, with any luck. For now, I left the central hinge bearing off and just set the rear spar assembly aside.

Started riveting the foreward spar assembly together, including the spar doubler, the two spar caps, and the two HS-1008 brackets. Ran out of time after the AN470AD4-7 rivets and stopped for the night.

Forward Spar Doubler Rivets

I noticed that the AN470AD4-7 rivets are so long that they required the entire longeron set travel to compress correctly. No spacer washers. This means that when I go to longer rivets (like the AD4-9 and AD4-10 rivets used in the 18 holes common to the HS-1008 brackets), I won't be able to use the squeezer and will have to resort to the gun. Boo.

28 Jan 2010
The skeleton of the horizontal stabilizer starts to take shape.

On my lunchbreak I picked up the socket I needed to torque down the AN3 bolts on the center hinge bearing. I promptly over-torqued the first bolt and totally stripped the threads on the nyloc nut. Ugh. Managed to get the other three torqued properly and marked with torque seal, but had to wait until after work to free the borked bolt and replace it. In the meantime, the aft side looked finished:

Center Hinge Bearing

I solicited advice from some of the local EAA guys on how best to remove the stripped bolt, since turning the nut (in either direction) did nothing to either loosen or tighten the grip. Their suggestion was to put vice grips on the bolt head and pull while turning the nut with a electric drill. Didn't work at all. I ended up drilling it out.

Take That, Nyloc

With the offending bolt out of the way, I put in a new one (with a new nyloc) and torqued it properly, marked it, and that was that for the center elevator hinge bearing.

All Four Bolts Properly Torqued

With that step done, I skipped ahead to riveting the stringers, stringer web, and inboard inspar rib assembly. The outer rivets connecting the two halves of each stringer can all be squeezed easily. So can the rivets that connect the inspar ribs to the stringer web. In order to use the squeezer for the rivets that connect the stringers themselves to the stringer web, you have to get a little creative. I was able to do all of the rivets on the first stringer by using a 4" thin-nosed yoke and coming at them from the far side of the stringer web. I had to use a few too many shim washers to make the spacing work out... but it seemed to work well enough.

Ridiculous Overuse of Shim Washers

Using the thin nose was nice, because it allowed me to get the corner rivets without any difficulty at all. The only problem is, once the second stringer is in place, the thin nose yoke is out of the question. In fact, you can't even fit the longeron yoke over the double-flange of the stringer... unless you remove both sets first. So I had to thread the yoke onto the part, then stick the sets into the holes in the yoke. This was a bit unwieldy, but allowed me to get most of the rivets in the second stringer with the squeezer. The only exceptions were the two in the corners, which I had to do with the gun.

Second Stringer Riveted On

The next step in the plans is to attach this assembly to the forward spar assembly, so I went back and finished up the rivets on the forward spar that I had skipped. The really long rivets that are used to attach the HS-1008 brackets required the gun, the rest were done with the squeezer.

I actually ran out of the AN426AD4-7 flush rivets used in the upper and lower pairs of the central rivet columns. I was two short. I had used some of these rivets back in the vertical stabilizer as oops rivets when I had accidentally countersunk some holes I wasn't supposed to. I guess I didn't have too many spares of this size. Anyway, it gave me an opportunity to use my rivet cutter for the first time, shaving down some AN426AD4-9s to fit. I wonder if I'll run short of these in the future?

The last step on the forward spar assembly was the addition of two snap bushings for the elevator trim tab control cables. I added a fillet of black RTV silicone to the aft side to keep them from vibrating loose.

Front Spar Rivets Complete (for now)

With that, the forward spar assembly was complete and I could move on to the next phase which was to build up the inspar skeleton onto the aft side of the forward spar. All rivets in this section were squeezable with the longeron yoke. This went reasonably quickly and that's where I called it a night.

End of Today's Progress

The next step is to put the skins back in the cradles and start riveting the skeleton parts into the skins. The horizontal stabilizer should be complete in reasonably short order!

31 Jan 2010
On Friday before heading down to Albuquerque for the weekend, I got a bit of work done on the stabilizer. The first step was to get the skins set back up in the cradles and to cleco in the nose ribs. This wasn't difficult and went very quickly.

All Eight Nose Ribs Cleco'd In Place

Here's an inside view:

Nose Ribs Cleco'd Into Skins

The inboard and outboard nose ribs can be riveted with the squeezer and go very quickly. Here's a view of one of the outboard ribs all riveted in:

Nose Rib Rivets Done

The middle nose ribs require bucking and the rivet gun. I got Bob to swing by after work and help me knock these 40 rivets out. No big deal. Once that was done, the entire forward spar and inspar rib assembly that I had riveted together earlier gets set on top of the nose ribs and everything gets cleco'd together.

Forward Spar and Inspar Ribs In Place

That's where I left the project on Friday. When I came back into town today, I started doing all of the rivets that connect the nose ribs and forward spar. The outboard nose ribs can be squeezed and look like this:

Spar Riveted to Nose Ribs

The middle pair of nose ribs just gets LP3-4 blind rivets. Here's a view looking down on the rivet heads holding one of these nose ribs on:

Blind Rivets for a Middle Nose Rib

Next I cleco'd in the remaining inspar ribs and go those riveted to the forward spar. The outer ones get solid rivets, the inner ones blind rivets. At this point, the next steps required bucking and I waited for Bob to come over for that. In the meantime, I set about putting the bonding strap attachment hardware in place for the braided strap connecting the horizontal stabilizer to the elevators.

To match the connection on the elevators, I needed the attachment to be just to the outboard side of the outboard hinge. During my EAA technical counselor visit, my counselor advised me to just use AN3 bolts and anchor nuts instead of the elaborate aluminum threaded rod setup I had been using. So I'm going to try that here. I went ahead and drilled a #12 hole through the center of the hinge bracket, then put an AN3 bolt through the hole and threaded on an anchor nut. I matched drilled the holes for the anchor nut rivets through using the nut itself as the template. I made sure to cleco the first hole before drilling the second to make sure all three holes line up.

Anchor Nut for Bonding Strap

The next step was to countersink the hinge bracket for the AN426AD3 rivets, but while countersinking the first hole, I snapped the pilot tip off of my 3/32" countersink bit. The rest of this modification will have to wait on my replacement bit from Cleaveland.


Switching gears, I added the snap bushings to the aft spar and put a black RTV fillet on the forward side to keep them from vibrating loose. Having run out of things to do, I waited for Bob to show up again and then we set to work riveting.

The first thing we did were the rivets that hold the inboard ribs and forward spar together. These are in cramped quarters and cannot be squeezed. They required the long offset set for the rivet gun and were made much easier with the addition of a second person to buck.

Tricky Rivets

Then we set about doing the top side forward spar skin rivets. There are a lot of these, and they take a long time. It took us about two hours to do just the top side (and we didn't do any of the stringer or inspar rib rivets, just the spar).

Forward Spar Skin Rivets Done

When we were done with that one long-ass rivet line, Bob had to go so I drilled out two rivets we had borked and fixed them, then called it a night. Here's a time lapse movie I made of the activity starting with the inboard rib rivets. Thrill to the excitement of watching us rivet and eat pizza. Woo!

Good times.

8 Feb 2010
A bit of work has occurred in the last week. First, Bob came by on a lunch break and we did the 120 bottom side forward spar skin rivets. The next day, my replacement countersink/deburring bit arrived from Cleaveland so I finished off the K1000-3 anchor nuts for the bonding strap attachments. Here's the aft view of one of the two:

Anchor Nut Aft View

And here is the forward view:

Anchor Nuts In Place

With that, the rear spar customiziations are complete and it is ready to be riveted onto the rest of the horizontal stabilizer. However, before that can happen, I need to finish all of the inspar and stringer rivets. And I wanted help with that. I've been trying to get an assistant for several days now, and finally this evening Bob was free again and we spent three hours tonight knocking out all of the remaining bucked rivets in the horizontal stab. We did 384 rivets tonight, and at some point we put in the 3000th rivet in the plane!

Bucked Skin Rivets Complete!

As you can see in that picture, I also finished off the squeezed inner and outer inspar rib flange rivets, so now the only rivets left are those attaching the rear spar. One more thing before I squeeze those rivets, though, and that is to spray some krylon primer into the inspar area because there are a fair amount of scratches in the akzo from the bucking of all those rivets. This won't take any time, though. In all likelihood, I'll be done with the horizontal stabilizer tomorrow!

9 Feb 2010
When I got home from work, I drilled out the one rivet that Bob and I missed last night and replaced it with a minute of bucking help from Mike. Inspecting the inside surfaces of the horizontal stabilizer before closing up the aft end for good, I decided that there was just too much damage to the Akzo coating from the bucking bar. Some parts were really scratched up. Here is a particularly bad example:

Bucking Bar Scratches in Primer

I took a can of Krylon grey primer spray paint and hit all of the rivet lines on the inside of the stabilizer just to be sure everything had some anti-corrosion coating. Having done that, there was nothing left to do but to rivet on the rear spar. I cleco'd it into place:

Rear Spar Cleco'd In Place

Then I set about riveting all of the spar web rivets (the 1/8" holes on the aft face). Unfortunately, my kit seems to be five short on the LP4-3 blind rivets, so I wasn't able to quite finish. I left five clecos in and spread them out so that each rib had at least one rivet in it. Then I went ahead and squeezed all 252 flange rivets that connect the rear spar to the skins. A total of 289 rivets on the day, but they were all squeezable so they went quickly and required no assistance. Here you can see the result, with the five clecos still sticking out of the aft spar:

Horizontal Spar Done... Almost

I went ahead and stuck the more-or-less completed horizontal stabilizer on some shelf brackets I had hung just for this purpose, with the rear spar facing outward. This will allow me to pop in those last five rivets when I get some more without having to take the stabilizer down.

Convenient Storage

Though it's technically not "done," there's only about a minute of work left on it. Onward to the tail cone!

23 Aug 2010
With the empennage attach activities out of the way and the elevator fairings in place, I am now ready to do the initial fitting of the horizontal stabilizer fairings.

Horizontal Stabilizer Tip Fairing Flange Cut and Drilled

First step was to cut back about an inch from the aft ends of the flange. This allows the fairing to fit in front of the forward spar of the horizontal stabilizer. With those cuts made, I held the fairing in place while match-drilling the skin holes into the fiberglass, starting from the front and working back—clecoing as I went. The piece initially wouldn't seat all the way down despite having the called-for 0.5" of flange. After filing the flange down ever-so-slightly, it fits nicely, though there are some irregularities in the curvature of the nose of the stabilizer skin that don't sit perfectly flat on the fiberglass flange. This'll be fixed during the blending phase.

With the tip fairing in place, I lowered the elevator counterbalance arm into place and drew a line showing where I needed to cut the fairing in order for the counterweight to be clear for its entire travel. This line is shown, above. I made this cut with the dremel cut-off wheel, reattached, found some spots that weren't cut far enough, and repeated. Three times. Now, I have a great-looking space between the tip fairing and the elevator arm:

Horizontal Stabilizer Tip Fairing Initial Cuts/Drills Complete

The only problem here is that the tip fairing sticks out about 1/8" farther than the elevator fairing. Not a lot I can do about that that would be worth the effort. I've only done one side; the other will proceed just like this one. It only takes about an hour to get this far with one. Now the real fun can begin: building up the aft face of the tip fairing with a raw fiberglass layup. I don't have the supplies or tools for that, yet, so that's probably a way off still.

9 Sep 2010
The left-side tip fairing of the horizontal stabilizer still hadn't been trimmed or matched drilled, so I took care of that tonight.

Left Horizontal Stabilizer Tip Fairing Trimmed

It's pretty much like the other one, with the same 1/8" overshoot in width. Also, the aft-most rivet hole on the bottom side turns out to be too close to the aft trim edge of the flange, so it's more or less useless. I'll probably put a big dollup of flox in there before I attach it. For now, the horizontal stabilizer tips are as far as I am going to take them. So soon I'll probably dettach the elevatrors from the stabilizer and store all three. This will free up the work benches for wing work come mid-November.