Matt's RV-7 Project » Rudder

Empennage fairings part IV

Matt — Thu, 22 Feb 2007 03:19:14 +0000

One more application of filler to the rudder cap – hopefully the last one, save for the inevitable pinhole filling. I'm really happy with the way the rudder cap has turned out.

I'm much less happy with the elevator tip I did the other day. I will probably throw this away and start over with a new one from Van's. The stupid counterweight is totally in the way, and it's looking less likely with every try that I'll be able to have removable tips on the elevators. Darn.

Here's the other, mostly untouched tip fairing, just to illustrate the situation.

Once again, I'm really glad the whole airplane isn't made of this crap.

Empennage fairings part III

Matt — Tue, 20 Feb 2007 03:07:00 +0000

Okay, so the first try at closing up the elevator tip fairing didn't turn out so well. I forgot to take a picture, but basically the fiberglass had nothing to adhere to (the lead was coated with tape to prevent sticking) so it was very wavy and uneven. Also, since I only used three plies of 1 oz cloth it was very flimsy.

One of the nice things about fiberglass is that if you screw up you can usually grind off your mistake and try again. This time I'm going to try using a piece of aluminum to provide the structural strength, and the fiberglass will just be there to hold it all together. I made a forward bulkhead out of some scrap alclad (0.040" I think), scuffed it up so the epoxy would stick, and temporarily attached it to the counterweight with double-sided tape.

Then I laid up three layers of 5 oz cloth, with a single layer of 1 oz cloth over the top to help fill in the weave. We'll see how this turns out.

I must say, the new style of elevator counterweight is a real pain. The old arrangement seems like it would allow you to spend a lot less time messing around with fiberglass to get the tip fairing to come out just right. But what do I know…

Back to the rudder, I mixed up another batch of micro and applied it here and there. This photo is kind of hard to interpret, but what you're looking at is a glob of micro applied to the front face of the rudder cap, with a piece of scrap alclad (covered with duct tape to make it non-stick) taped in place to make it cure with a nice smooth, even surface.

My cat wanted to help write this entry:

More empennage fairings

Matt — Mon, 19 Feb 2007 01:30:41 +0000

Today was an all-fiberglass day. Sorry, no action shots – hard to hold a camera with sticky fingers.

I sanded most of last night's primer off of the top rudder fairing, then put another glob of filler on the front where it still needs to be built up. My favorite tool for this kind of sanding is a 3" red scotchbrite disc in a die grinder turned down to low pressure. I also use a 60 grit sanding block where necessary, but power tools make the job go faster.

While the rudder fairing was curing, I got out one of the elevator tip fairings and started playing with it. The lead counterweight at the front is going to throw some sand in the gears of my plan to make removable empennage tips. It is tempting to permanently attach the elevator tips and just glass over the counterweights, but I'm still going to try to make them removable because I love a challenge. (Mary would probably say that I'm just plain stubborn)

I laid up three layers of lightweight cloth, sufficient to cover over the open end of the fairing where the counterweight lives. It's not much to look at right now because the peel ply is blocking the view. Underneath is a layer of electrical tape to prevent the fiberglass from sticking to the lead. With any luck this will form the starting point for a closed-end fairing that will cover the counterweight but will still be removable – we'll see tomorrow.

Hours later, the second coat of filler on the rudder was dry, so I proceeded to sand away at it. The shape is almost there now – just needs one or two more layers.

After shooting a coat of primer to help me check the finish, I put more filler on a few spots to fix some of the more egregious pinholes. My goal is just to get the basic contour correct – I'll leave the detailed surface finish work to the painter.

In the middle of all this, I bought and put together this particle board file cabinet for Mary. I found myself thinking how awesome it would be if airplanes were put together with quarter-turn fasteners. I'd already be flying!

Working on top rudder fairing

Matt — Sun, 18 Feb 2007 02:34:37 +0000

I decided that I should work on the empennage tips next, because it will be a lot easier to mess with them while I have the tail removed from the fuselage. Once the engine goes on I'll have to keep the tail attached to prevent the fuselage from tipping over on its face, so I'm trying to get as much done on the empennage while I have the opportunity.

For no particular reason I decided to start with the top rudder fairing. I trimmed the flanges enough to get the part to fit onto the rudder, and match drilled #30 holes through the skin into the fiberglass.

It isn't a terrible fit, although it is quite a bit shorter than it needs to be. I'll have to build up the forward face with filler.

The plans have you attach the fairing to the rudder skin with flush pop rivets. A lot of people use filler to make their fairings match the contour of the empennage surface, then use a layer of fiberglass to hide the joint between the aluminum skin and the composite fairing. Me, I really like the look of a well-fitted fairing with a perfect, visible seam between the two parts, so I decided to steal Randy Pflanzer's method. He made his fairings removable by using 4-40 screws and nutplates instead of blind rivets, which lets you take the fairing off to clean up the join line.

I riveted nutplates to the fairing, using a thin strip of alclad as a backing strip to keep the rivets from pulling through the fiberglass. On the first side I did (facing down in this photo) I used the same rivets to attach the nutplates to both the aluminum and the fiberglass. That turned out to be a pain to do properly, so on the other side I first riveted the nutplates to the aluminum strip, then riveted the strip to the fairing with one rivet between each pair of screw holes. That way turned out a lot better, since I could do the tricky riveting of those tiny little nutplates out in the open where I had better access.

By the way, the gaps in the alclad strips in the photo above are there because I made the them out of scrap and I didn't have anything long enough to span the full length of the fairing.

Here's an initial view of how the fairing looks when screwed in place. A #4 flush screw fits in the same dimple as a 1/8" rivet, and I really like the look of the visible fasteners. There is about a 1/16" gap along the join line, which will need filling.

I protected the rudder skin with a layer of electrical tape (very thin but rugged enough to resist sanding) and some duct tape too for good measure. Then I used some 60 grit to knock down the high spots in the fairing. The very tail end was the worst spot, as the fairing was quite a bit thicker than the rest of the rudder back there.

Then I mixed up a batch of epoxy and microballoons that was about the consistency of peanut butter, and slathered it all along the join line, making a special effort to try and force it down into the gap. I also tried to build up a big glob of filler on the forward face where the fairing is too short, but I expect I'll have to revisit it a couple more times in order to get enough material where it needs to be.

I'll let the whole mess dry overnight, then sand off all the excess and see where it leaves me.

Oh yeah, while I was doing stuff in the airplane workshop I installed the eye bolts through the firewall, to which the rudder pedal return springs will attach.

Made rudder stops

Matt — Mon, 04 Sep 2006 04:30:21 +0000

If I worked at a real airplane factory, I'd get fired for taking like eight hours of work over two days to make these stupid little rudder stops. Of course it doesn't help that the design requires each set of stops to be tailor-made to the individual aircraft. I spent a huge amount of time measuring, making and discarding test pieces, and fiddling around with templates. Out of absentmindedness or frustration I forgot to take any photos of this process, so here's a shot of the first rudder stop I was able to produce that actually fit:

You can see that I've temporarily installed the rudder cables to make sure that the rudder stops and cables don't get tangled up at any point along the full swing of the rudder.

Here's an overexposed overhead view showing the angle the rudder horn is at when it hits the stop. Lots of cutting and filing to get to this point.

It means nothing unless it has that swing – when the rudder hits the stop and the elevators are neutral, it's just a shade over an inch from the rudder to the inboard corner of the elevator trailing edge. Plenty of clearance to keep the tail surfaces from banging together, and slightly more travel than is called for in the plans. Extra rudder travel is good, it means extra rudder authority. I've heard of some people making this dimension more like 1/2", but that seems like cutting it bit fine to me.

After I was finally satisfied with the fit, I rounded off all the corners and made the stops look pretty, and countersunk the rivet holes. These two I was able to do with the countersink cage; for the two that are closer to the flange, I used this setup to make the countersinks freehand.

I primed the stops and the skin underneath, then riveted them halfway on. The plans call for CS4-4 blind rivets in the front two holes. I used CherryMax CR3212-4-4's instead since I have a whole drawerful; the literature says they are something like 3x stronger in shear. The aft two holes will have to wait for now, since I can't squeeze those rivets until I remove the vertical stabilizer.

This photo is to remind me that I haven't torqued any of the control surface jam nuts yet – my torque wrench has a 1/4" drive and my crow's foot wrenches take a 3/8". Time to go to Sears!

Hung the rudder

Matt — Mon, 28 Aug 2006 01:54:12 +0000

I didn't work much on the plane today, but I did get the rudder hung on the vertical stabilizer. It swings without any binding at all, which I suppose means that everything is straight. I'm not completely sure that I have the two hinge lines parallel, so I will probably remove and tweak it a few times before I torque the jam nuts.

Holy cow, the tail is getting huge!

Since the rudder stops aren't in place yet, I jammed a couple pieces of foam rubber beteween the rudder and the vertical stabilizer spar, to keep the rudder from swinging too far and getting banged up.

Finished second rudder

Matt — Sun, 27 Aug 2006 03:11:01 +0000

I took my replacement rudder over to John's place in order to make use of the five foot long back rivet plate he made. It made riveting the trailing edge pretty easy. First I set the rivets partway with the back rivet set, then flipped the rudder over and finished them off using the mushroom set.

Here's another one of those photos that shows I really built the airplane. Also that I shill for the Boulevard corporation on laundry day.

I alternated the rivet directions because I'm anal like that.

Then while we had everything set up, Chad and John finished off the trailing edge of John's rudder:

Two rudders completed!

After I brought the rudder home, I set about rolling the leading edge:

Done! I'm happy with the rudder now. Whew. The very long back rivet plate is an excellent way to do it, at a total cost of about $24 worth of steel angle and machine shop work.

Prosealed new rudder trailing edge

Matt — Sat, 08 Jul 2006 03:00:02 +0000

Today I prosealed the trailing edge on the new rudder. I first squirted some blobs of proseal into the trailing edge of each pair of stiffeners, to guard against future cracking.

Then I buttered up the AEX wedge with a very thin layer of sealant…

…and inserted it into the rudder. The clecoes squeezed out a bead of proseal, which I wiped off.

Now to let it cure for a while. Upon reviewing these photos, it appears that the proseal I used here is a little lighter in color than the stuff I used on the fuel tank covers. Maybe I didn't get it mixed quite enough? It will probably take a bit longer to cure, but that's okay as long as it eventually does.

More work on new rudder

Matt — Wed, 05 Jul 2006 01:00:55 +0000

Back from far-flung lands! I deburred and dimpled the rudder skins, including the six holes at the aft end of the top rib that you can only dimple before you rivet on the skins.

Then I countersunk the new AEX wedge to accept the dimples in the skin.

I riveted the counterweight skin on, then bolted on the counterweight. This time around I decided to put some J-B Weld on the nuts, since you can't access them once the top rib is in place. Don't want those guys vibrating loose.

The J-B Weld package cracks me up. Better than bailing wire, indeed.

Next I riveted on the top rib, and riveted the counterbalance skin to the rudder skins.

Then I finished riveting the rudder skins to the ribs and spar.

I got out my old piece of straight angle and clecoed it to the trailing edge to test the fit. Yep, it's straight.

The next step will be to proseal the new rudder trailing edge, when I get some time.

Match drilled new rudder

Matt — Thu, 22 Jun 2006 02:00:29 +0000

All I've had time to do this week is to match drill the new rudder skins to the old skeleton. Deburring, dimpling, and riveting will have to wait a while, since I'm leaving on a trip for the rest of June.

Working on new rudder

Matt — Mon, 19 Jun 2006 02:08:18 +0000

I worked on the new rudder on and off this weekend. On Friday night I match drilled the stiffeners to the skins. (This was a mistake; taking the wife out on Friday night instead of working on the airplane is smarter and causes fewer difficulties.)

On Saturday I deburred and dimpled the skins, which was harder than it sounds because my DRDT c-frame tool was 50 miles away in coworker John's RV-9A workshop. Mary and I threw the skins in the car and made a day out of it, stopping at a couple other places and driving around in the country a bit. We also stopped by briefly to look at RV-7 builder Bill Gill's project – or rather I looked at the airplane, and Mary played with Bill's dogs. Everyone was happy.

After we got back to town, I primed the skins:

On Sunday morning I got up before it was too windy and primed the stiffeners too:

I spent most of the middle of Sunday messing with the air compressor – the "off" position on the switch has never worked since I bought it, and despite my best efforts today it still doesn't work. Then in the evening I back riveted the stiffeners to the skin:

The complete rudder is now clecoed together and looks like a rudder, all right:

The next step is to match drill the skins to the skeleton, deburr, and dimple, but I'm too wiped out from the gym. Plus I'm going on a week long business trip soon so I suppose it's in my best interest to pay attention to the Mrs.

Made new rudder stiffeners

Matt — Fri, 16 Jun 2006 02:00:10 +0000

Made a bunch of rudder stiffeners tonight:

The balloons attached to the second fuel tank have been inflated for about a week now. That's more than ample proof that the tank is not leaking, I think. Hooray for proseal!

Mary came out and helped me wrestle the wing back into the wing stand. Barring something unforseen, the wings should be staying in the rack for quite a while.

Unbuilt the rudder

Matt — Wed, 14 Jun 2006 02:00:00 +0000

Look at this. This is the trailing edge of the rudder. It's so wavy it hurts to look at it.

I know I said I was happy with it, but now that I've really stared at other RV's and seen how it's supposed to look, I hate it.

So, I'm going to re-skin the rudder. I started tonight by drilling out all the rivets holding the top rib in place.

Then I drilled out about 300 more rivets, until the skin was completely detached from the skeleton. The skeleton is in good shape – only a small handful of rivet holes got elongated, and they can be fixed with oops rivets.

So, now all I need to do is make new stiffeners, rivet them to a new pair of skins, and put the new skins on the old skeleton. Luckily I decided I was probably going to do this a few months back, and I have all the materials I need sitting around.

Finished rudder leading edge

Matt — Thu, 22 Sep 2005 02:02:42 +0000

No progress on the RV in a while, as I've been busy at work. I also took some days off to go on a 3000-nm trip with a friend in his Super Decathlon. Awesome.

Getting back to the project, tonight I did some cleaning in the garage/workshop, and rolled and riveted the leading edge of the rudder. It turned out acceptably well. Sorry, no pictures – still having intermittent trouble with the machine that I use to grab photos from the camera.

Riveted rudder trailing edge

Matt — Sat, 20 Aug 2005 22:08:47 +0000

Riveting the trailing edge of the rudder is one of those tasks that I've been dreading – not just because of all the horror stories, but also because you can tell just by looking at the plans that this part sucks. The goal is to get the trailing edge of the rudder to a) come out straight, and b) have as little waviness to it as possible.

The manual lays out a procedure for doing this that involves the back rivet set – other builders have had success with different methods involving the use of the pneumatic squeezer (1, 2). I started out by grinding one of my flat rivet sets to an angle that matches the trailing edge of the rudder:

Then I clamped angle stock to both sides of the trailing edge, just forward of the rivet line. Using two flat sets in the squeezer, I worked from the center out, setting each rivet about halfway.

You can't see it here, but I put each rivet in from the opposite direction as its neighbor. I figured that would help balance out any tendency for the riveting process to want to bow the trailing edge in one direction or the other.

At this point, everything was going great. Then I switched to the special angled squeezer set with the intention of finishing the process of squashing the shop heads of the rivets until they were flush with the skin. It didn't turn out as nice as I'd hoped – not only did the shop heads not get set all the way flush, but the act of clamping down on the trailing edge with the squeezer caused some "pillowing" of the skin between each rivet. After finishing this process, looking the rudder over, and saying some bad words, I got out my back rivet plate and mushroom set, and went over all the rivets again until they were all perfectly flush.

You can't see the details very well in this photo, but here it is:

It turned out to be almost perfectly straight overall (only about a tenth of an inch deviation along its entire length) but it does have some pillowing and a slight amount of waviness between successive rivets. I think it will look okay after it's painted, though, and at least it's aerodynamically acceptable. I now know that setting the rivets partway with the squeezer and then finishing with the rivet gun is probably the best way to go. Oh well, the rudder trailing edge on my next airplane will be perfect. Or, I may re-skin this rudder some day if I have some downtime. I am glad that I put in each rivet in alternating directions, and I'm fairly pleased with the way the shop heads of the double flush rivets turned out. When it's painted you might not even be able to tell which side is the manufactured head and which is the shop head.

Proseal party!

Matt — Wed, 10 Aug 2005 01:41:21 +0000

I think it's safe to say that no manganese dioxide-cured polysulfide sealant has destroyed more marriages than Proseal. Luckily Mary is still speaking to me after I convinced her to help me Proseal the rudder trailing edge tonight. What a mess. I'd forgotten how much I hate that stuff – an enmity I developed while working on the fuel tanks of my previous RV. Having an extra pair of hands around was a huge help, though. Mary is awesome and now I feel compelled to buy her something shiny.

This sucker will cure for a week before I take out the clecoes and put in the rivets. Note that a 48-count box of wooden clothespins from Dillon's yields exactly enough to help clamp down the trailing edge of an RV-7/9 rudder, plus one extra to put on your nose while you mix up the goop. Coincidence?

Rudder riveting

Matt — Sun, 07 Aug 2005 21:44:58 +0000

Since I need to wait for replacement ribs to continue with the elevators, and I got my pneumatic squeezer back from being rebuilt at Clear Air Tools, I switched back to the rudder. Here the skeleton is coming together:

I used solid rivets to attach the rudder brace to the bottom rib, but I wasn't able to get any of my squeezer yokes inside the brace in order to squash the horn-to-brace rivets, so I used the optional LP4-3 blind rivets there. I could probably have used solid rivets if I'd ground down the top corner of my longeron yoke, but who cares.

The rudder counterweight is installed in its home with nuts and screws. I wonder why this weight is pre-drilled but the elevator ones aren't…?

Here the skins have been riveted to the spar.

Next step is the trailing edge, for which I obtained a big piece of ¹/₈" aluminum angle from the aviation department at Ace Hardware. Clamped to the rudder trailing edge, match-drilled, and held with a cleco in every hole, it will serve to keep the trailing edge perfectly straight while I glue it together and then rivet it.

But that will have to wait for another night since Mary wants to take me for walkies in the park.

Primed rudder parts

Matt — Tue, 19 Jul 2005 02:00:06 +0000

Today I countersunk the rudder trailing edge wedge, and prepped and primed the rudder parts. Not very interesting, but here's a shot of them resting after being sprayed:

So much of this project is this type of mindless stuff – deburr, dimple, prep, prime. Which is okay, since I can do a little bit every day after work when I'm brain dead.

Now I have the rudder parts ready to rivet together, but I'm sort of stuck until I get my squeezer back from the rebuild place.

Rudder parts prep

Matt — Mon, 18 Jul 2005 02:00:16 +0000

The rest of this weekend was spent deburring and dimpling the rudder parts. Here's a shot of my solution for how to dimple the aftmost holes in R-903… pop rivet dimple dies with the nail inserted from the outside, and washers to take up the gap:

The lead brick is attached to the counterweight rib with #10 screws. Dimple dies for a screw that big can be expensive, so some builders use their #8 dies and mash the screw in there to expand the dimple. That sounded like an opportunity for a stress riser and an eventual crack to me, so I found some cheap #10 dimple dies on eBay and used them to make the proper dimple. No big deal. The lead then is countersunk to fit the dimple – it's soft enough that I was able to use my deburring tool to do it.

Trimmed replacement rudder brace

Matt — Sun, 17 Jul 2005 02:00:51 +0000

Here are the old and new rudder horn braces. The new one is on the right – notice how much extra edge distance there is if you don't trim along the prepunched guide holes. I used my Dremel tool to make little stress-relieving scallops where the guide holes were.