Matt's RV-7 Project » Horizontal Stabilizer

Installed empennage gap fairings and horizontal stabilizer

Matt — Sun, 25 Mar 2007 03:33:33 +0000

The plans call for you to install nutplates along the F-709 bulkhead where the fiberglass empennage fairing and the forward end of the aluminum empennage gap fairings will attach, and then drill and tap holes in the longeron underneath the stabilizer to attach the gap fairings along the rest of their length. I decided to install nutplates everywhere instead of tapping the longeron – a tapped hole has no ability retain a screw and I remembered how one or two of these screws were always backing out on my old airplane.

Installing nutplates here took only a few extra minutes and was no big deal to accomplish. I did check with Van's before I did this, since I was wondering if the extra rivet holes would do anything structurally back there. Here's what they said:

Date: Tue, 12 Dec 2006 07:38:14 -0800
From: Van's
To: Matt
Subject: Re: Nutplates for empennage fairing

It's OK, but why would you want the extra expense and work?

Vans

I think they must have an automated process that sends that reply anytime they receive an email that starts with "Is it okay if I…"

After double checking my todo list to make sure I wasn't forgetting anything, I vacuumed out the tailcone one last time and bolted the horizontal stabilizer on for good.

Here is one of the empennage gap fairings installed. The topmost hole is left open because it's shared with the fiberglass empennage fairing. I used the hand seamer to get the forward edges of these fairings to lay down nicely on the fuselage skin. I'm not sure what to do about the forward end of the rubber channel – maybe I'll trim it at an angle to try and help keep the wind from peeling it up.

Before turning in I reattached one of the horizontal stabilizer tips and put on another coat of filler to help smooth out the forward edge where the fiberglass and alunimum come together.

Empennage fairings part VII

Matt — Sun, 11 Mar 2007 20:40:48 +0000

Still not too much time to work on the project lately. I did have a chance to reinforce the balsa ribs on the horizontal stabilizer tip fairings with a mixture of epoxy and flox, and to fit and install the 4-40 nutplates that will hold the fairings on.

I mixed up the usual batch of micro filler and smoothed out the transition between the tip fairings and the stabilizer, with an extra blob at the nose to allow a perfect fit after it's all sanded down later. I also put a big glob of filler on the outboard corners – a lot of this will get sanded off, but what remains will be the the first step of building up the tip fairings to match the contour of the elevator tips.

Empennage fairings part VI

Matt — Mon, 05 Mar 2007 02:00:19 +0000

I was either in class or studying for half the weekend, but I got a little bit done on the empennage fairings. I ground down the elevator tip fairings until I got the shape pretty much how I wanted it – they turned out not bad at all. I sanded them down to 320 grit once I got the shape right.

This is why I hate working with fiberglass – dust everywhere.

I removed the horizontal stabilizer from the airplane and laid it out on the bench to receive its fairings.

Trimmed the stabilizer tip fairings to fit and drilled and clecoed them in place:

The plans call for a minimum gap of 1/8" between the elevator counterweight and the fairing – mine is more like 3/16" in the neutral position, or slightly less when the elevator moves through its range of travel. Good enough. I did open up the other side a bit so the gap would be even on both sides of the stabilizer.

You can also see where I'll need to build up the outboard part of the stabilizer fairing to match the contour of the elevator.

I made some ribs for the stabilizer tips out of 3/16" balsa sheet. This reminded me a lot of how I used to build model airplanes as a kid. Actually balsa is really nice to work with. Maybe I'll take up model building again someday… nah.

I epoxied the ribs into the fairings and left them to dry overnight.

Since it was fairly nice outside, I decided to mask off the elevator tips and shoot a coat of primer. This will help me find the low spots and imperfections.

Not too bad. I got the look I was going for, and they turned out pretty nice. I will probably come back and do some more filling and sanding in order to work out a few minor imperfections, but overall I'm pleased.

Before I turned in, I managed to get the tail fairing nutplates riveted to the stabilizer.

All this work on fiberglass fairings, and this guy made his out of aluminum. I can't even comprehend the amount of skill that takes.

Mounted the horizontal stabilizer

Matt — Sun, 23 Jul 2006 03:24:37 +0000

I was going to work on the brake lines some more today, but I didn't receive all the parts I ordered earlier this week – one box of AN fittings from Wicks got shipped to the wrong address and subsequently lost. Kudos to the Wicks people, though – they were able to help me figure out what happened and get a replacement order on its way, at no charge – on a Saturday. Everybody go give Wicks some business, they deserve it. Even if you don't need any airplane parts, they're having a sale on toy gliders, and who doesn't like toy gliders? Nobody, that's who. If there are any such people I refuse to accept it.

Anyway, so not enough parts to work on the brakes. The only things left in the fuselage plans are mounting the wings, which I already decided not to do yet, and mounting the tail. Okay, let's mount the horizontal stabilizer today. I dug out the HS and elevators from the storeroom and rigged them on the bench to make sure everything still fits:

Somehow, the bottom of my left elevator has developed this mysterious dent. I'm not sure what caused it. At least it's on the bottom surface – it will probably eventually be joined by more little dents as rocks and stuff hit the bottom of the tail when the tailwheel is on the ground.

I clamped both elevators exactly in trail, to align everything for the drilling of the elevator control horns.

Some people have trouble with their elevator horns not lining up very well. They're welded individually, so it's likely that there will be some misalignment when you bring the two elevators together. Mine were almost exactly identical, though, which is good.

The left horn was just a fraction of an inch forward of the right one, so the left elevator was the one to get the first hole drilled in it. I took the elevator back off the stabilizer to make sure the pilot hole for the pushrod bolt was in the right spot.

With everything back together again, I measured the distance between the two faces of the control horns at the approximate location of the bolt hole…

Then I made a simple drill jig out of a sandwich of 3/16" birch plywood squares glued together, with a hole drilled perpindicular to the face with a drill press. This got clamped between the elevator horns, and then I transferred the pilot hole across to the right elevator horn. You have to do it this way because you don't want the bolt that joins the two elevator horns to the pushrod to be crooked.

I drilled and then reamed the pilot holes up to 3/16", then trial fitted a bolt. Yep, I'd say that's straight all right.

Next I made the F-798 shims, which go between the HS mounting flange and the aft fuselage deck. This photo makes them look like they're not the right shape, but they are – must be the camera angle.

I had to rearrange the garage to let me fit the horizontal stabilizer onto the fuselage – then, I clamped it to the aft fuselage and measured, measured, measured until I got everything lined up and straight. To help make sure the stabilizer was exactly perpindicular to the long axis of the fuselage, I drilled a hole in a tape measure; by clecoing it to one particular rivet hole on either side of the firewall and pulling it tight, I was able to measure the distance from the firewall to the stabilizer tips without anyone around to hold the other end for me (important tip for those of us building mostly solo!).

I tweaked and tweaked until both sides measured exactly the same – 156 3/16" in this case. The hole in the tape measure was right at the 1" mark, by the way.

There are four bolts that hold the forward HS spar to the fuselage. The two outboard ones are a real pain – each of those bolts has to go through five or six layers of stuff, which means you have to do a ton of very careful measuring to make sure that that one hole has adequate edge distance on every part it goes through. Here's a view of the underside of one of these areas, where the bolt has to go through the longeron, a spacer, and an angle (and then the aft deck, the F-798 spacer, and the forward HS mounting flange). Of course, the quickbuilders also seem to have cut the F-710B angle a little bit short on my airplane, reducing the margin for error even further. By the way, you can't actually see any of this stuff inside the fuselage – I had to use an inspection mirror and take lots of photos like this in order to get an idea of how things were going to work out. Thank goodness I have a small camera…

After lots and lots of measuring, I got out the drill and made some pilot holes for the outer forward holes. Hooray, they both came through right where I wanted them. Here's a view of the right side – the left is similar:

I drilled and reamed the holes up to 3/16", then put some nuts and bolts in. You can see the shims in place there – I decided to ignore the part where the plans tell you to drill the stabilizer to the fuselage without the shims in place, and then put the shims in and match drill the holes. It seemed like it would be easier just to clamp the heck out of everything and drill all the parts all at once, which is what I did. Everything looks good here.

Much measuring later, the other pair of bolts are in. To properly locate these, I had to take the stabilizer off and measure, but I'll spare you the boring details.

Here's a view of the nuts on the left side:

After lots more measuring, here are the other four bolts that hold on the rear stabilizer spar. I used a 3/16" drill bit as a spacer between the rear spar and the aft deck, as suggested by the plans. This puts the stabilizer at a 0° angle of incidence with the aft deck and longerons, which I verified through careful measuring. None of the hole locations on this end of the stabilizer are marked for you either, but at least you can see what you're doing a little better.

Careful measuring pays off – the bolts are centered vertically on the stabilizer reinforcement bars, and almost exactly on the centerlines of the stabilizer mounting bars. Acres of edge distance everywhere.

It's kind of starting to look like an airplane!

Not shown in the above photos are the hours I spent getting things lined up, taking the stabilizer off to mark something, measuring another dozen times to line things up again, etc. You only get one chance at this so I wanted to make sure that everything was as precise as I could make it. Fortunately, It all seems to have turned out pretty well.

Finished Horizontal Stabilizer

Matt — Mon, 13 Jun 2005 01:42:24 +0000

Mary came out and helped pound in the remaining rivets on the other side of the stabilizer…

Then I spent the evening with the squeezer and got the spar attached and the remaining rivets put in. The horizontal stabilizer structure is now officially complete!

Left HS Skin Attached

Matt — Sun, 12 Jun 2005 00:47:20 +0000

Most of today was spent helping Mary paint the living room, but we did have a chance to go out to the garage / airplane factory and finish riveting on the left horizontal stabilizer skin. We also got the right-side HS-707 rib riveted to the skin and the HS-702/707/708 junction blind riveted. This thing is starting to get big!

Freeze, Dirtbags!

Matt — Sat, 11 Jun 2005 02:46:49 +0000

We got about half of the rivets set on one side of the first stabilizer skin before it got too late and we decided to quit to avoid annoying the neighbors. I'll post a photo of the whole thing when it's done. Meanwhile, Mary couldn't resist hamming it up with the rivet gun. I swear she's turning into a regular Rosie the Riveter. I better get myself into some of these construction photos or else the FAA will end up assigning the repairman's certificate to her.

HS rib riveting

Matt — Mon, 06 Jun 2005 02:00:02 +0000

Here we are about to do the first rib-to-skin riveting of the project, where the center nose rib (HS-707) attaches to the horizontal stabilizer skin. I took the hint from a subsequent step in the instructions and temporarily clecoed HS-708 in place just behind it to help pull the skin down.

And, here's the result. This photo isn't the greatest, but these rivets turned out great. Mary ran the gun and I bucked, which turned out to be a good arrangement. I'll try to get a photo of that next time for all the guys at work who are trying to convince their wives to let them build an RV too. (you know who you are)

Then the forward spar assembly gets clecoed in place in preparation for riveting:

Here's a goofy photo of me trying to get the fiddly little blind rivets into the holes in HS-702/707/708. I think I eventually let Mary and her little hands do this job.

Both middle ribs get riveted to the forward spar:

Suddenly we're starting to have fewer loose parts laying around, and this big assembly is starting to take shape. Cool! Too bad I ran out of time to work on it. Anyway, extreme kudos to Mary for being so awesome and helping shoot rivets. I am a lucky man slash airplane builder.

Dimples

Matt — Sun, 05 Jun 2005 02:00:43 +0000

Matthew Brandes came over tonight to check out the RV-7 factory. He pointed out that the dimples I'd done with the DRDT weren't deep enough. Dang. I had originally been lazy and not bolted the DRDT to the bench, so I wasn't able to yank on the handle with sufficient force to set the dimples properly. So, I had to laboriously re-dimple the three skins I'd done so far (2 HS and 1 VS) after setting up the DRDT so it can be quickly attached to the bench and then removed, which is so boring that I won't bother to post a photo of it.

Oh what the heck, here's a photo anyway:

Riveted HS front spar

Matt — Sat, 04 Jun 2005 02:00:08 +0000

Here's the front spar after being riveted together:

Here are the HS-405 ribs riveted to the front spar. I couldn't get all the rivets with the squeezer so I had to shoot/buck some. They turned out pretty good.

And now, here's the HS-404 ribs riveted in place as well – these rivets went in with the gun too:

The left side has an extra rivet, as seen here. I hope I don't have to use aileron trim to counteract the weight imbalance. (joke)

Riveted HS rear spar

Matt — Fri, 03 Jun 2005 02:00:03 +0000

Tonight I got the rear horizontal stabilizer spar riveted together. It went pretty well – the pneumatic squeezer is definitely a must-have for this stuff.

Pretty rows of manufactured heads on the exterior side…

…and nice, consistent shop heads on the interior side:

The elevator hinge brakcets get attached, and this sucker is done. The rivet length callouts for middle and outboard hinges seemed a little weird, but I followed the plans anyway. The center hinge bracket gets bolted in place, which means that I got to use the fancy new torque wrench that I sprung for. Any day where you get to use a new tool is a good one.

Son of Spar

Matt — Thu, 02 Jun 2005 02:00:18 +0000

New left-side horizontal stabilizer spar: drilled, deburred, dimpled, primed, done. Whew. Also touched up the primer on HS-710 and HS-714 while I had on the Darth Vader rig.

I'll tell you why

Matt — Tue, 24 May 2005 00:09:06 +0000

In Saturday's post I idly wondered why Van's was having me drill the hole in the front spar for the trim motor wiring so close to a preexisting tooling hole. We'll I'll tell you why it looked weird: because I had accidentally grabbed the rear spar and happily drilled a giant hole through it instead, thus ruining it. Arrgh. That's what I get for not triple-checking the plans and the part numbers. Of course it doesn't help that the instructions don't even mention this particular hole – I guess they're hoping that you'll notice the tiny callout on the plans, but whatever. At least the replacement HS-603PP is only eighteen bucks. I'm going to be out of town for a week anyway, so it's not that much of a setback other than the couple hours it will take me to drill, deburr, dimple, and prime a new spar. Bah.

Primed HS parts

Matt — Mon, 23 May 2005 01:34:03 +0000

Today I got the HS parts all dimpled – used the Cleaveland tank dimple dies (which arrived Saturday) on the ribs and spars, and it does seem to make the skin dimples sit down in there better. Then I went out in the backyard and primed all the ribs, spars, bars, and angles while Mary and her folks hung out inside.

Probably they were discussing my warped priorities.

Who needs Star Wars when you're building an RV?

Luke, I am your father!

Incremental HS progress

Matt — Sun, 22 May 2005 02:00:47 +0000

The in-laws were in town today, but I kept sneaking out to the garage to work on the plane project here and there. Got all the horizontal stabilizer parts deburred, and drilled the trim wiring hole in the left front spar. I wonder why they have you drill this hole right next to a perfectly workable tooling hole – it could just be enlarged and put to use if they'd put it in the right location.

Update: This was a stupid mistake! See here for details.

HS work – runs, hits, errors

Matt — Mon, 16 May 2005 00:29:40 +0000

Okay, check this out. Here the root end of the left horizontal stabilizer. I trimmed the aft flange of the HS-404 nose rib exactly according to the drawings, and double-checked it against the full-scale template in the plans. Look at all the room between the trimmed flange and the HS-710/714 angles! I didn't need to cut off nearly that much. Then, to compound the aggravation, one of the holes (marked with a red arrow below) that you backdrill through from the aft side came out with way not enough edge distance. The marking of the holes on HS-405 involves some amount of guesswork to make it come through the spar with enough ED on the forward side, and I didn't get lucky on that one hole. It would have worked out just fine if they hadn't had me trim so much from HS-404. Oh well. I decided to drill another rivet hole (the yellow arrow) to beef up this area. There's more than the minimum distance between the new hole and the other two holes in HS-404, so everything is okay now.

After match drilling all the rest of the holes in the skin, I proclaimed the left horizontal stabilizer completely drilled.

Here's a gratuitous shot of it being opened back up, just because it looks cool:

Another shot of the skeleton again:

Flash forward several hours, and the right horizontal stabilizer is similarly completed:

The holes in the root ribs came out better on this side, luckily. But once again I have, per the plans, trimmed more than I really needed to from F-404. Oh well, it is still acceptable, and on the next airplane I'll ignore the plans here and just do it right.

Somebody asked for an explanation of the soldering iron trick. I just take a wooden straightedge and affix it to the skin with one silver cleco and one cleco side grip, and run the soldering iron down it to melt through the blue plastic. (be sure to use a soldering iron whose tip you've ground down so it won't scratch!)

Voila, the blue plastic comes off in nice strips. Props to the fabric store where I went with Mary to get some buttons, or something – they were supplying a precision aircraft skin protection material removal tool and they thought they were just giving me a free promotional yardstick.

Doh! I got a little crooked with the squeezer and it bit a chunk out of one of the holes in the trailing edge of the right stabilizer skin – on the top side where you can see it, of course.

I carefully squished the misplaced dimple flat with the squeezer and some flush dies, then redimpled the correct hole, and spent some time with needle files to make sure there aren't any stress risers in the oblong hole that might crack later. Then I drilled the hole out to #30, which ate up the worst of the misplaced hole. I'll put a NAS1097 "oops" rivet in this hole, and put a little bit of filler in whatever little blemish is still visible. No big deal, every airplane has boo-boos like this. I'm probably the only person who'll even know it's there. Oh, and everyone reading this, I guess. Perhaps there is a downside to being honest and documenting my mistakes where everyone can see…

Decided to take the hint and quit for the night. Here are the parts for the right horizontal stabilizer, all deburred and dimpled and ready to be primed and riveted together.

Left stabilizer assembly

Matt — Sun, 15 May 2005 02:00:08 +0000

Here's the obligatory photo of me working on the plane to prove to the feds that I really built it. After getting all the ribs prepared (finally) the left horizontal stabilizer gets clecoed together, skin and all:

Mary couldn't resist putting in some clecoes too:

Along the inboard portion of the front spar (HS-702) and the root ribs (HS-404/405), only the skin is prepunched, so you have to do a bit of layout work to get the rest of the holes drilled. But in the olden days builders had to do this for the whole airplane, so I guess I can handle a couple feet of rivet holes:

Here the root ribs are temporarily clamped in place to mark the approximate rivet locations. The cleco side clamps really lead the way for this part of the project.

Now the root ribs have been removed, fluted, gotten a centerline marked on them, reinstalled, and are being drilled. I got all the holes in the HS-405 rib drilled to the skin and rear spar before I had to put the tools away.

HS deburring

Matt — Sat, 14 May 2005 02:00:30 +0000

Nothing worth phtographing tonight, just deburring of the horizontal stabilizer ribs and cleaning up the notches I cut in the HS-404 ribs – lots of tedious work with Scotchbrite wheel, emery cloth, and needle files. Started to mark out the holes in the HS-405 ribs where the forward flanges will attach to the front spar. Not a lot of extra edge distance in that area – I wonder why Van's doesn't pre-punch at least that area of those pieces?

HS ribs/spars work

Matt — Thu, 12 May 2005 02:21:34 +0000

Hey, where'd this airplane-piece-shaped thing come from? I temporarily clecoed the middle and end ribs and front/rear spars of the horizontal stabilizer together to check the bends in HS-710/714 (front spar reinforcements) and HS-702 (front spar). Everything looked good so I drilled the reinforcements to the spars. Not shown are the steps of trimming the inboard flanges of each half of HS-702 to make room for the reinforcement angles, and deburring/straightening/fluting the ribs.

Actually here is a photo of the rib fluting crew hard at work:

Marked and cut the relief notches in the HS-404 inner nose ribs to make room for the reinforcement angles here as well. Had to stop using the air tools since it was getting late and I didn't want to annoy the neighbors, so these will be deburred tomorrow along with their cousins.

Switched to the horizontal stabilizer

Matt — Sun, 08 May 2005 02:00:42 +0000

Okay, I said I was going to build the vertical stabilizer first, but then I got to those @#$% AD4 rivets in the VS spar. I was resisting the purchase of a pneumatic squeezer, but that only lasted till about the third one of of those suckers. I guess I could hit them with the rivet gun, but I'd just rather squeeze 'em, so pneumatic it is.

So, while I wait on my rebuilt pneumatic squeezer to arrive from the Yard Store, I switched to the horizontal stabilizer. I figure I can get some prep work done there in the meantime. Here I've deburred and polished out the milling marks from the HS rear spar reinforcement bars:

…and match-drilled them to the rear spars:

Drilled the rivet holes for the center elevator bearing:

And, since I must wait on the squeezer to smash those rivets too, it's on to the front HS spar reinforcement angles. Drilled them to the front spars, then marked and cut the tapered sections. Not shown is the half-hour with the hacksaw and vixen file, plus bad language, that it took to get them looking so nice:

Then the ears on the reinforcement angles get bent to exactly 6 degrees to accomodate the sweepback of the front spars. The manual calls for you to clamp the ears in between wood blocks and beat on them with a hammer, but I found the aluminum was soft enough that I could just clamp the parts at the bend line in a padded vise and bend the ears by hand.

Note the aircraft-quality angle bending template.