Matt's RV-7 Project » Empennage

Empennage fairing fitting

Matt — Mon, 25 Aug 2008 02:21:00 +0000

This morning I woke up early and flew a rental spamcan up to Falls City in Nebraska, taking advantage of the unseasonably cool (for August) morning to get a little daylight between me and the ground. Falls City has always held a certain special fascination for me; the first airplane I owned came with a Falls City Aero Service keychain, and though I never got around to making the short flight, I always wondered just what sort of a place it was. Turns out it's exactly like you'd think: a medium-sized runway, some old tin hangars, and a flock of agplanes. Nice morning though.

Later on, I got out the empennage fairing and spent some time cleaning it up. I used heat and pressure to reshape the areas that didn't fit so great – by clamping down a small section of fiberglass with wood blocks and duct tape, heating up the surrounding area with my heat gun, then letting it cool down, I iteratively got it to fit pretty well. Then I trimmed back the edges, countersunk the holes for tinnerman washers, and installed it with #6 screws to see how it looked.

Not bad really. I may have some additional shaping to do along the top edge, but that's all cosmetic. Overall, I'm pretty happy with how it turned out. There are some gaps of a 32nd or two here and there, but at Oshkosh this year I saw some that looked like they'd been put on with a hammer… quarter inch gaps, even. So, I think mine looks pretty good.

Since I was already sweaty and gross from cutting and sanding fiberglass, I decided to make it a trifecta by mowing the lawn and then going for a nine mile bike ride. Now it is, as they say in the old country, die Miller-Zeit.

Installed empennage for good

Matt — Sat, 26 Jan 2008 17:00:31 +0000

The tailwheel mount shares several bolts with the vertical stabilizer spar, so before you can put any substantial weight on the back wheel you have to install the vertical fin first. I've had the tail propped up on a pile of styrofoam insulation for a long time, but now it's time to get this thing standing on its own feet, or wheels as the case may be.

To provide the proper amount of vertical stabilizer offset, there is a single AN960-10 washer between the spar and the up-elevator stop, on the left side bolt only. This photo confirms that I did remember to install that pesky washer:

I torqued and marked all the bolts that attach the horizontal and vertical stabilizers:

I couldn't get a socket onto some of these, so I just tightened them using a wrench and German torque.

More bolts:

I couldn't get enough access to the nuts on these bolts to apply the orange torque seal goop, so I just marked the bolt heads to remind myself that I did actually torque the bolts.

The horizontal and vertical stabilizers are now mounted permanently, and the tailwheel is capable of supporting real weight. You can't really tell from this photo, but the tail is now resting on the tailwheel instead of sitting on a pile of foam.

Extended elevator stop

Matt — Sat, 14 Apr 2007 22:00:01 +0000

I wrote to Van's to ask their opinion of my elevator travel situation, and their reply was:

Matt,

You can either make a new elevator up stop or add a piece to the existing stop. The horns hitting the aft bulkhead is not a bad thing, but that will not happen when you fix the up stop.

Bruce Reynolds

Okay, I can do that. Since the existing elevator stop is already drilled for the bolts that attach the vertical stabilizer, I decided to leave it alone to avoid causing further problems. Instead, I created this little elevator stop extension out of some 1/8" angle:

It's riveted to the underside of the existing stop, using the existing three rivet holes through the stop and aft deck. It effectively moves the face of the stop forward about 3/32".

I also added three flush rivets to attach the other leg of the stop extension to the aft bulkhead. Probably overkill, but it makes me feel good.

Now to test the new elevator travel. Here's neutral:

Here's the new up position:

I now have 29.4 degrees of up elevator travel, which puts me in the allowable range of 25-30 degrees. I probably could have made my stop extension even a little bit longer, but as long as the elevator travel is within the okay zone I'm happy.

Canopy work aborted

Matt — Sun, 01 Apr 2007 00:11:51 +0000

After putting some protective tape over the end of the slider frame latch tube, I flipped the canopy over and laid the frame inside.

The goal is to get the frame aligned on the previously marked centerline, in the fore-aft location that results in the best fit along the center spine tube. Then you mark the location of the latch tube and drill a 5/8" hole. I got as far as marking the hole location, but the temperature didn't get up nearly as high as I thought it would, so I had to give up on drilling/trimming the canopy for another day. Bah.

In an effort to find something else to do, I dug up the subpanel pieces, dimpled the top rib flanges, and clecoed the whole works into the fuselage.

Then I deburred the forward top skin, which I hadn't yet bothered to do. I dimpled where I could reach along the edges, leaving the holes along the firewall undimpled for now – the cowling attach hinges still need to be match-drilled there, much further down the road. Then I packed up the skin and drove over to John's to use my DRDT to dimple the rest of the skin. Not a very efficient use of building time, but it felt like a good day to spend a couple hours driving.

Somewhere in there I did some more filler work on the left horizontal stabilizer tip fairing. I've had this clamp for at least ten years and I'm pretty sure this is the first time I've ever used it.

Also, I stopped at Lowe's and tried to buy a new belt sander, but they were out. Bah.

Misc stuff

Matt — Mon, 26 Mar 2007 01:33:54 +0000

I spent the whole day in the garage but didn't take many pictures. I guess I didn't actually get all that much accomplished – mostly I puttered and cleaned up the garage. It was great to be outside in the nice weather though.

One of the pre-tail-mounting chores I've been meaning to do is drilling the holes for the strobe and nav light wires that will go through the vertical stabilizer spar into the rudder. I picked the same location as Dan for much the same reasons – with the taildragger there aren't many other good choices for where to run these wires. I drilled a 5/16" hole for the strobe cable and a 3/16" hole for the nav light wires. Both holes are a little oversized so I can use a few layers of shrink tubing and some RTV to protect the wires from chafing.

Another day, another round of filling and sanding empennage fairings. I'm just doing a little bit every work session, fitting the glass work in between other tasks that are more fun.

I rearranged the garage a bit, and made a little table out of a sheet of plywood and a couple sawhorses. This is where the canopy is going to sit while I work on it. Yes, I've decided to work on the canopy some more before I put the airplane on the gear and mount the engine. Matthew convinced me that it'll be easier to get to it while it's down low and not high up on the wheels. Plus it seems to be warm enough these days to start thinking about working with plexiglass again.

I got out the canopy frame to make sure it still fits – yep:

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.

Finished rudder cable fairings

Matt — Wed, 21 Mar 2007 01:33:34 +0000

I installed the other rudder cable fairing, same as the first. Ignore the black lines, those are sharpie marks I was using to help tweak the part to lay down properly against the fuselage skin.

Same type of nut ring too. Matthew says my airplane will have ten pounds of nutplates in it. Oh well, I won't be carrying an angle valve engine around under the cowl, so I have a few pounds in the weight budget to play with. And hey, check out the dead moth that lives inside my fuselage.

It's nice to be able to check something off my to-do list. Also, I got a perfect score on the commercial written exam, which was nice.

Rudder cable fairings

Matt — Mon, 19 Mar 2007 01:48:11 +0000

On Saturday I tripped going down the stairs with a big basket of laundry and wrenched my ankle rather smartly, so between icing down my swollen ankle and studying for the commercial written exam I didn't get a lot accomplished on the airplane this weekend.

I did however manage to get one little task mostly done, which was fabricating and installing the rudder cable exit fairings. The plans just have you punch the rudder cable fairings straight through the fuselage side, and there's probably nothing wrong with that, but it does seem like a small set of fairings would help to aerodynamically clean up that area. You can get pre-made fairings, but I wanted to do it the hard way and make them myself. So, first I drew a whole bunch of lines on a piece of 0.020" alclad scrap, using the dimensions given by Sam Buchanan as a starting point.

Then the two pieces were cut out:

A little work with the hand seamer, and I had a nice looking pair of fairings. All for the low low price of free.

I laid out holes along the flanges and drilled the fairings to the fuselage. They are aligned with the main longerons, which are level in cruise flight. Notice there are three holes on top and only two on the bottom – that's because the lower fuselage stiffener is in the way of where I would have put the third lower hole. Actually I did drill a hole in that location, which you can see in one of the other photos below, but it's too close to the stiffener to dimple so I just covered it up with the undrilled fairing.

I had several choices for how to attach the fairings to the fuselage. In order of increasing difficulty, they were: A) round-head pop rivets; B) flush pop rivets; C) flush screws and nutplates. If you've been reading this site for long you've already guessed that I picked option C. However, it wasn't just as simple as riveting nutplates to the fuselage skin, because it was too tight inside the already-riveted tailcone to have any kind of decent bucking access. So, after some head scratching and trial and error, I made a nut ring to support the nutplates on the back side of the skin. The odd shape lets it clear the cable slot and the various other structural elements back there.

The same screw that attaches the adel clamp to the fuselage side also holds the nut ring in position. The fairing and fuselage skin are dimpled, and the nut ring is countersunk to accept the skin dimples.

On the exterior side, flush stainless 4-40 screws hold the fairing to the skin. Since it's removable I was able to iteratively shape the edges with my hand seamer until the whole thing laid down tight against the skin with no gaps anywhere. Now I have custom, scratch-built rudder cable fairings that continue the cool attached-with-screws motif that I have going on with the other empennage parts. Hopefully at least one person at a fly-in somewhere will look under the stabilizer and go "woah, how'd he do that?". Plus if I ever need to replace the rudder cables I won't have to drill out any rivets and mess up my paint.

I still need to finish installing the other fairing, but now that I have a template to make the nut ring it should be no sweat.

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.

Yet another trim tab

Matt — Mon, 26 Feb 2007 03:32:09 +0000

So here's the deal.. I decided to build a new trim tab today. The reasons were many:

1. I was fed up with fiberglass and wanted to make something out of metal.
2. I had the left elevator out already.
3. I was already in posession of the necessary parts, having ordered them a while ago (see #4).
4. John brought his trim tab to work to show it off, and it was so much better than the other one I'd previously made that I was shamed into building a replacement in order to redeem myself.

Absolutely the first thing I did was cut off the little flaps on each end of the skin. This trim tab ain't gonna have no bent flaps, it'll have ribs like a real aircraft control surface.

To make the inboard rib, I simply took an extra E-709 rib I'd bought from Van's and cut off the back end.

Here the inboard rib after being shaped to fit and clecoed in place. I decided to make the flanges point outboard, even though it made riveting harder – having the flanges point inboard would have put the web in a position to interfere with the rivets holding the control horns to the skin.

The inboard rib has a couple of strategic divots to clear some of those previously mentioned control horn rivets.

To make the outboard rib, I first cut a block of wood to the correct shape. I then took a piece of 0.025" alclad, started the bends with my hand seamer, and clecoed it to the form block.

Using a flush set and with my rivet gun turned down low, I finished the bends by hammering the aluminum down onto the form block. This is, of course, the same technique that the plans have you use to fold the tabs on the end of the trim tab skin, but doing it this way is a lot easier and more precise. Plus, if you screw up you just throw it away and grab another piece of alclad.

Here's the outboard rib after being fitted and clecoed in place. Notice I staggered the rivet holes at the aft end for clearance.

I fitted the hinge to the elevator in the usual way:

Then, after deburring but before dimpling, I formed the bend in the lower skin. The plans have you do this after the entire trim tab is riveted together, but if you do it before the spar is in the way you can make a slightly nicer bend. However this gives you less clearance for riveting the hinge, so you have to think carefully about the order in which you rivet the various things together.

I put a nutplate on the trim tab spar to capture the hinge pin, the same way I did last time around.

Here's the finished product, all riveted together and ready to go:

And, installed in its home on the elevator:

The gap between the trim tab and elevator is nice and uniform. You can see that I had to use one blind rivet at the aft end of the smaller outboard rib – this is the only pop rivet on the (more visible) top surface of the new trim tab.

Here's the underside of the outboard rib – I used one pop rivet at the aft end here too.

On the inboard side, I was able to use all solid rivets on top.

On the bottom, I used all solid rivets except for along the spar – there I was forced to use a row MK-319's to close everything up. I think if I had to do it over again (oh no!) I could probably find a way to turn the inboard rib the other way 'round and build the whole trim tab using only two pop rivets, but oh well. Come to think of it, that could be a good game show: "I can build that trim tab with two pop rivets!" – I'd watch. Anyway, lots of builders use blind rivets on the bottom just like I did, and it's approved by Van's. Good enough.

And finally – celebration.

Empennage fairings part V

Matt — Sun, 25 Feb 2007 02:00:34 +0000

I decided on a new plan of attack for the elevator caps – I'll attach them permanently, but I'll make them look like they can come off. Then at least all the fairings on the tail of the airplane will have a consistent look, which is important if you're obsessive like me. First I rounded off the forward edges of the lead counterweight with a file, then I match drilled the untouched elevator cap and installed nutplates and reinforcement strips:

The two nutplates at the aft end are very close together. If I hadn't been forced to use the prepunched holes I would have staggered these a bit to avoid interference, as I did with the aftmost rivets holding the aluminum strips to the fairing. As it is I had to cut down some screws to keep one screw from trying to push the other one out.

Here's another thing that I'll do differently on my next airplane – when you dimple the attachment holes for the elevator caps, the rib flange gets between the dimple die and the skin and all your dimples end up with this little crease on the inboard side. You won't be able to see this once it's all painted, but if I'd known this I would have at least match drilled the fairings and dimpled these holes before riveting the elevators together.

Here's a test fit to make sure all the nutplates and holes are lined up:

I riveted a #10 nutplate to the outboard side of the counterbalance arm, using the 3/16" tooling hole that was already there. The reason for putting a nutplate here is that I can use it to bolt on a wide-area washer or two if it turns out that my elevator needs a little bit more weight up front… call it balancing insurance. Also, this photo is proof that I checked the torque on the outboard counterweight bolt on the right elevator – it will be inaccessable once the fairing is on for good.

Okay, I wasn't able to take pictures of how I performed the next series of steps, but I'll describe it and show the result. I mixed up a slurry of epoxy and flox, and applied a thick layer between the lead counterweight and the inside face of the tip fairing. This should glue the fairing to the lead and also fill in the gaps between them. Then I put in all the screws, and covered the edge of the skin with a layer of electrical tape. Next I mixed up a big batch of epoxy and micro, and used it to fill the gap between the skin and fairing on both sides of the elevator. I also applied a generous helping of filler to cover over the forward face of the counterweight, and the corners with the fairing and the counterweight come together. Most of it will get sanded off later, but this should hopefully provide the basis for a nice looking fairing closeout.

After all of the above was finished, I figured the right elevator would be out of commission for the rest of the day before the goo was cured, so I started thinking about the left elevator. It turns out that a replacement elevator cap is thirty bucks from Van's, so instead of throwing away the one I'd previously tried to put glass on, I spend some time sanding off my mistakes and restoring it to nearly-new condition.

Then I performed the same series of steps – match drilling, installing nutplates, and so forth. This photo is proof that I installed the spare nutplate and checked the torque on the inaccessable bolt on the left elevator

After all that (a couple hours of work) the left elevator cap got the same filler treatment:

Once both elevators are dry I'll start sanding them down. For now, though, I'm sick of composites.

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.

Started removing the tail

Matt — Mon, 12 Feb 2007 01:52:07 +0000

I decided that I'd better get the tail permanently mounted before the engine arrives, since without the weight of tail back there the engine will tip the airplane over. But before I can put it on for good, I need to take it off once more in order to finish up a few chores. Tonight I got as far as removing the vertical stabilizer.

I squeezed the remaining rivets on the rudder stops that were previously blocked by the VS spar. I also smoothed out a few scratches in the aft bulkhead that were a result of the initial stabilizer fitting. Looks like the primer dripped – doh.

I attached the nutplates for the fairing to the vertical stabilizer:

…and one to the fuselage just in front of the tail:

Working on empennage fairing

Matt — Sun, 10 Dec 2006 02:00:06 +0000

I got the empennage fairing out again and continued playing around with it. Here it's clecoed to the tail using the holes I'd previously made:

There's a ton of extra material to be trimmed off where the fairing wraps around the leading edge of the horizontal stabilizer. Then the gap underneath the stabilizer is closed by aluminum cover plates. You're sort of left to your own devices to figure out exactly how to make the front part of this come out looking nice.

I had to trim a fair amount off of the F-794 cover plates to make them fit. Maybe I can sell the scraps as aluminum curly fries.

The kit comes with some rubber weather strip type of stuff, which you have to trim down.

Here's one of the cover plates with the rubber strip on it. It's clecoed to the fuselage through some rivet holes in the longeron and bulkhead that I had to drill out. I wish the quickbuilders had left those holes open, because it's somewhat difficult to get under there and drill them out with the stabilizer attached, but oh well. It's hard to get the rubber strip to go completely around the curved are in the front, so I sized the cover plate piece to almost touch the stabilizer in that area instead.

Here I've trimmed and sanded away the excess fiberglass of the fairing at the forward corners (ignore the sharpie lines, I was using them to test various ideas). As you can see, there's only a very small area that's not covered by fiberglass, aluminum, or rubber. It's on the bottom of the airplane so you'll never see it. Good enough.

I also finished the cutout for the elevator horns, and sanded the aft edges of the fairing to be even with the edges of the vertical and horizontal stabilizer skins.

Because the front part of the vertical stabilizer is offset to the left (i.e. right rudder) the center of the fairing doesn't sit on the centerline of the fuselage. I eyeballed this spot for a screw and nutplate on the forward lip.

Interestingly, in the spots where the fairing attach screws go into the fuselage longerons, the plans call for you to just tap the hole in the longeron instead of installing nutplates. I used to have problems with the screws backing out in this area on my old RV, so I'm wondering if it would be worth the extra trouble to use nutplates back here (because nutplates have a self-locking feature to secure the screws). May need to call Van's to make sure the extra rivet holes in the longeron wouldn't be a strength problem. At first glance it looks like there would be plenty of room between the nutplate rivets and the next rivets over.

Worked on pitch controls

Matt — Mon, 04 Sep 2006 23:22:56 +0000

Not much got done on the airplane today because I was tired. However, I did figure out what was wrong with the F-789 forward elevator pushrod… it's not that it was too short to allow sufficient down elevator travel, it's that the control column was hitting on the seat ribs. I dremeled out some small bites from the F-716 seat ribs, just enough to allow full forward stick plus about 1/16" extra for clearance.

Another photo of the other side. The duct tape is to protect the finish on the control column.

I likewise had to trim the removable parts of the two center seat ribs:

Once I had full stick travel, I put in the pilot's stick and seat in order to adjust the neutral stick position. Man, these seats are comfortable as heck.

Here's me doing ergonomics testing. I was in and out of the fuselage a half dozen times before I got it the neutral point adjusted where it fell easily to hand. The pushrod has a little more than the minimum required thread engagement, which is good. If you're reading this and you haven't fabricated your F-789 yet, do yourself a favor and make it about 1/4" longer than what the plans call for.

Yes, I made airplane noises:

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!