Matt's RV-7 Project » Fuselage

Fastener madness!

Matt — Mon, 29 Nov 2010 01:00:23 +0000

I finally got sick of being embarrassed about a few of the rivets in the F-705 bulkhead – other builders will know exactly which ones I'm talking about – so I drilled them out and replaced the ones that are impossible to properly buck with AN525 structural screws.

View from the aft side. I also drilled out and replaced the rivets whose shop heads are hidden under the canopy decks, because I didn't have a tungsten bucking bar last time I tried to set these and they were kind of ugly. This time they were relatively easy to redo using two pounds of element 74 and a double-offset rivet set.

A quick spritz of paint and you can't even see the screw head unless you know right where to look.

Then it was back to working on the baffles… except wait, it looks like one of the screw holes in the engine case isn't tapped deep enough. Maybe I can just force the screw in there?

Nope! Big mistake. Twisted the head right off, and now there's a broken screw stuck in the engine case. In the very expensive engine case.

What to do? Over the course of half an hour I went through all five stages of grief:

Denial – "That hole can't be very important, and I can still make the baffles work without it, right?" (no)
Anger – "Stupid screw, you suck for not being stronger! Stupid hole, you suck for not having enough threads!"
Barganing – "Maybe I can build some kind of brace to transfer the load to a different hole?" (no)
Depression – "I should just chop this thing into bits and push them out to the curb and let them be hauled to the dump."
Acceptance, starting by very carefully drillling through the center of the bolt:

…then going to the store to buy a bolt extractor:

The screw broke in half and I had to re-drill it and restart the extractor, but I got it all out!

Whew, what a relief:

Then I did what I should have done in the first place, which was to tap it about 1/8" inch deeper so the screw can be fully inserted:

Now it can be threaded in far enough to hold this bracket in place. No lockwasher yet since this screw will be removed and replaced many times before the baffles are done.

Very expensive engine not ruined after all. This whole episode really took the wind out of my sails, but I sure earned this:

I also spent many hours this weekend researching stuff about the baffles, and I think I almost know what to do next. Now that the Great Screw Disaster is resolved, baffle work will resume next time…

Fuel plumbing rework

Matt — Mon, 03 May 2010 02:03:20 +0000

Lately, most of my free time has been taken up by house chores and other pursuits, leaving little time for the airplane. Today I did manage to redo the fuel plumbing that I'd previously discovered was interfering with the center tunnel runs.

I replaced the straight bulkhead fittings with 45-degree ones:

A view of the new plumbing run on the left side:

Right side:

There's sufficient clearance between the wiring and plumbing now:

Here's what it looks like from the aft side, once the fuel pump/valve/filter assembly is removed from the airplane. Lots of intertwined pipes here and not much room to fit them.

After changing the angle of the banjo fittings on the fuel selector valve, I tightened and safety-wired the nuts:

This is a common sight when you're working with rigid tubing. Cut a line too short, or overbent it, or kinked it, or scratched it? Toss it and start over. My recycle bin has plenty of 3003 aluminum in it this week.

VOR antenna

Matt — Mon, 02 Nov 2009 01:00:55 +0000

A forum thread convinced me to buy and install a traditional cat whisker VOR/ILS antenna on the bottom of the fuselage, rather than the hidden wingtip type often seen on these aircraft. I'm happy to give up half a knot for reliable navigation performance.

I decided to mount the VOR antenna just aft of the F-710 bulkhead, which is just barely accessible when the empennage is attached. A doubler ties into the bulkhead and the F-779 bottom tail skin.

The doubler is made out of 0.063" alclad. Here it's drying after having alodine applied, although in retrospect I'm not exactly sure why I bothered to do this – the "puck" part of the antenna is plastic, and the mounting fasteners don't make electrical contact with anything in there. Oh well, at least it won't corrode.

Here it is riveted in place with the antenna attached via nutplates. The brown stain is alodine that ran downhill while it was drying.

It would be pretty easy to use driven rivets here during the initial build of the tailcone, but on a nearly finished fuselage with the empennage installed it's essentially impossible. Cherry Max rivets to the rescue.

Test-fitting the VOR antenna using some random bolts… when I go to install it for good I'll use AN525 screws instead:

When the rudder and elevators are installed, you won't be able to step on the VOR antenna, so no danger of tripping over it while walking around the back of the airplane.

Yeah, it's hanging out in the breeze, but the airflow down there will be pretty disturbed anyway, so it shouldn't cause too much drag (he said, despite having only a journeyman's understanding of aerodynamics). At least the nav radio reception should be pretty good!

Now that all seven of the antennas on the fuselage are mechanically installed, it's time to move on to wiring them… but that will have to wait for a future work session.

GPS antennas

Matt — Sun, 01 Nov 2009 01:00:52 +0000

My airplane needs a bunch of external antennas on top of the fuselage… one WAAS GPS antenna for each 430W, and a combined GPS/XM antenna for the G3X system. I cut up some 0.063" alclad and made a doubler for each antenna:

I chose to put the two WAAS GPS antennas on either side of the canopy track, about halfway between the F-706 and F-707 bulkheads. As long as they're not placed too far forward, the canopy will pass over the top of them as it lifts up and slides aft. I couldn't put them all the way at the aft end of the canopy track, since the upper fuselage stringers taper together and make it too narrow to for the antenna doublers to fit. I used a yardstick as a spacer to make sure I drilled the doublers parallel to the fuselage centerline, and to ensure adequate space for the canopy slider block to pass by.

Lots of big and small holes drilled in the top of the fuselage… no turning back now! The doublers will be riveted to the inside of the skin, of course, but it's way easier to drill them from the outside. I also had to shape them a bit with hand seamers, since a perfectly flat doubler won't quite lay down on the curved fuselage skin.

The third antenna doubler is located just aft of the F-707 bulkhead. There's plenty of room for the canopy slider block to fit between the antenna and the end of the track, so there should be no problem removing/reinstalling the canopy.

I alodined the doublers and fuselage skin for good electrical bonding, and riveted on floating nutplates.

John came over to help buck the rivets, while I crawled back into the tailcone to drive them from the inside.

The actual riveting went pretty quickly:

A shot of the finished rear antenna doubler:

Now the fuselage has sprouted a crop of antennas:

Victory! Thanks to John for the help.

Spar holes and wiring

Matt — Tue, 08 Sep 2009 02:21:35 +0000

How was your labor day weekend? I drilled two big holes through my airplane's wing spar:

Relax, I got approval from the factory first:

Matt,
Yes, you can provide additional holes within reason. Use the same diameter as we have, and also keep in mind the proper edge distance (2D). Also keep clear of other structure such as seat ribs, spar bars, flanges, brackets, etc.
Joe Blank Builder Support Vans Aircraft Inc.

Since doing this incorrectly would basically ruin the airplane (or at least be extremely time-consuming and painful to repair) I spent a lot of time measuring and contemplating various locations. I eventually picked a spot outboard of the F-716 seat ribs and inboard from the F-783 cover support ribs.

Vertically, the new holes are equidistant from the upper and lower spar reinforcing bars, and have more than enough distance from the existing holes I've been running wires through. I had to pull the wire bundles out of the way to drill the new holes, and I had to use an extension to keep the drill chuck from grinding up the ribs, but it all went just fine.

You can bet I deburred the heck out of these holes.

I wasted no time putting the new wiring holes to use… this is the coax for the transponder antenna, which runs down the right side of the forward cabin floor, goes up through one of the new holes, and then turns inboard before running down the right side of the center tunnel.

After passing through the rear spar, the transponder coax jogs outboard again and runs down the F-727 rib before passing through a bushing in the baggage bulkhead.

This is as far as I got before I had to go mow the lawn. Later on I'll figure out a way to secure the coax to the floor, and put on the BNC connector. By the way, this particular piece of coax is actually the same one I had previously cut and run to go to the nav antenna connection in the left wing root. Subsequently, this thread on VAF convinced me that it would be a better idea to instead use a V-shaped dipole antenna under the tail instead, so I ripped that cable back out. By happy coincidence, it was the perfect length to use for the transponder, so nothing is wasted.

I ran a few other wires this weekend too. The tail and each wing got power wires for the nav and strobe lights, plus a wire to synchronize all three strobes. I have decided to go with LED nav/strobe lights, although since I am an inveterate bet-hedger I made sure to size the wires for the strobe lights so they'd each be sufficient to run a single-output power supply for a more traditional certified light head, should I have a change of heart and decide to go that way instead. I also ran a spare wire to the right wing with an eye towards eventually using it to power an APRS tracker (someday).

Many feet of wire are ready to be run back to the tail too, although not everything is in place yet.

New game! Whenever you drill a hole in your spar, you have to take a drink. Tonight's beverage was a summer seasonal from Blue Moon, which was not half bad.

Riveted transponder doubler

Matt — Mon, 10 Aug 2009 02:00:59 +0000

Al Stuber put his CH 750 project on hold long enough to drop by and hold the bucking bar against the belly skin while I crawled inside and backriveted the transponder doubler. Thanks Al.

The brown discoloration in the above photo is alodine, by the way. Don't want any surface corrosion forming here and messing up my antenna ground plane.

Here's a shot of the transponder antenna bolted to the bottom of the fuselage… nothing to it, just a plastic shark fin thingy:

One more thing checked off the to-do list.

Elevator/aileron speed controller

Matt — Mon, 27 Jul 2009 02:00:32 +0000

One of the things that always annoyed me about my last RV was that the electric elevator trim was incredibly sensitive at normal cruise speeds… trying to trim out control pressures would always turn into a game of "how fast can I press and release the trim button so the airplane doesn't get out of trim in the opposite direction". So to improve that situation with this airplane, I bought a Safety-Trim two-speed trim control unit, which gives you the ability to slow down the trim servos when flying faster than a preset airspeed threshold. It also provides some protection against trim runaway due to a stuck switch, which is nice.

To mount it, I made some little standoffs from scrap alclad:

I attached it to one of the ribs under the pilot-side baggage floor. It's a pretty short run forward from there to the control sticks, and the wires to the servos can go fore and aft through the center tunnel. I'll run the wires to it later – right now I'm just trying to get all my boxes mounted where they need to go so I can plan my wire runs.

In the photo above, you can also see that I've riveted a bunch of plastic tie wrap anchors to both sides of the left and right tunnel ribs. They'll get put to use soon when I start running wires through the tunnel

Transponder antenna doubler

Matt — Mon, 27 Jul 2009 01:00:16 +0000

I bent a doubler for the transponder antenna out of 0.050" alclad and drilled a bunch holes for rivets and mounting studs and antenna connectors through it:

Then I crawled into the fuselage and match-drilled the doubler to the belly skin and the F-729 bellcrank rib, about a foot behind the baggage bulkhead. In terms of the length of coax needed to reach this location, I'm right at the limit of what the Garmin install manual allows, but I couldn't find a better place to put it. Not to mention, I hope the transponder-rays won't do anything weird to the pitch servo. Also, I shortened the doubler slightly between these two pictures, since I'm thinking about moving the ELT back here and I wanted to be sure to leave plenty of room.

A view from the outside. I need to deburr, dimple, and alodine the mating surfaces, and then see if I can coax Mary into helping with the riveting duties.

Flap motor wiring

Matt — Mon, 20 Jul 2009 02:00:12 +0000

Since I had one of the required components in hand already, I decided to also work on the flap motor and associated wiring this weekend. Here I've mounted the flap positioning system control box on the new backrest brace:

Here's another view to show how it stands off from the underlying rivets, thanks to a few nylon washers. That dimpled hole in the foreground is for mounting an adel clamp.

As I previously threatened, I cut the wire harness between the control box and position sensor and crimped on some connectors. Now the motor and control box don't have to both come out of the fuselage at the same time.

Since the flap motor is now no longer permanently tethered to anything else, I couldn't think of a reason not to (semi) permanently attach it to the flap actuator channel. This photo is proof that I did put the cotter pin in:

Then I spent several hours running wires to the flap switch and pulling wires back to the flap motor. Properly bundling and securing new wires takes me about ten minutes per linear foot per wire (longer if I have to drill new grommet holes or install new clamps or tie wrap anchors) so consequently this took all afternoon. I left the flap switch hanging from the panel for now, since there's no need to go to the trouble of bolting it in place for an electrical test.

Once I had all the connectors installed, I plugged it in and gave it a floor run… it works! Bump the switch, and the flaps move one notch up or down. Nice. I'll clean up the wires in a future work session.

Made new backrest brace

Matt — Sun, 19 Jul 2009 02:00:14 +0000

At some point in the last year I managed to bend my F-785 backrest brace – that's the vertical piece that goes between the F-705 bulkhead and the baggage floor, and forms the aft end of the flap motor housing. I'm not sure if I accidentally put too much weight on it from above, or inadvertently kicked it while crawling around inside the fuselage, but I definitely buckled one of the flanges. I bought the parts to make a new one many months ago, but only got around to building it this weekend.

Similar to Bob Collins' idea, I decided to reinforce the new backrest brace by riveting some angle-aluminum doublers on the inside:

The finished product, after several hours of fabrication… note how the rivets at the bottom end tie the doublers into the attach angle. Compared to the old one, the new brace is a couple ounces heavier and a heck of a lot stiffer.

Installed in the fuselage for final fitting:

Pneumatic squeezer and beer… you can theoretically build an airplane without either one, but why would you want to?

Comm antennas

Matt — Tue, 31 Mar 2009 02:13:10 +0000

My brother helped me install the belly-mounted comm antennas while he was in town this weekend. In the photo below we're lining up the antennas and drilling the mounting holes… much easier to do it with the antennas inside the fuselage than outside:

My camera was low on batteries so I didn't get a picture, but we made doublers for the antennas out of 0.050" alclad. You can kind of see one in this photo:

Since the antennas are grounded via their mounting screws, ensuring good electrical contact is essential for proper antenna performance. I used an alodine pen to corrosion-proof all the mating surfaces:

Here's a better shot of the fuselage doublers, with the alodine drying. It looks blotchy but that doesn't really matter.

I likewise cleaned, scuffed, and alodined the areas of the fuselage floor destined to be covered by the doublers:

Adam helped me rivet the doublers to the floor:

They're also attached to the seat ribs with blind rivets – plenty strong. Each antenna is attached with four screws that go into floating nutplates, and the BNC connector protrudes through the hole in the middle.

Voila, antennas. This arrangement should make for easy wiring, keep the antennas out of the plume of exhaust gunk, and satisfy the radios' requirement for minimum antenna separation distance.

Fuel flow sensor

Matt — Sun, 04 May 2008 20:25:27 +0000

If you choose to research the topic obsessively, as I have been doing lately, you'll find that there are about three locations where people have been mounting the fuel flow sensor, and everyone thinks the way they installed theirs is best. You can put it on the cabin floor downstream of the electric fuel pump, near the engine between the mechanical fuel pump and fuel injection servo, or in the line between the fuel servo and the fuel distribution spider on top of the crankcase. I accept the argument that your fuel flow readings will be more accurate the farther downstream your sensor is placed, but there are also vibratory and thermal factors to consider when mounting a somewhat delicate sensor in the harsh environment of an engine compartment. After a weekend of head-scratching, I couldn't settle on a location forward of the firewall that I found completely satisfactory, so I gave up and elected to mount my flow sensor on the cabin floor. I can live with the fact that I may get inaccurate readings when the electric fuel pump is turned on, but that will only occur for a few minutes per flight. There is theoretically an increased chance of vapor lock as a result of adding another restriction upstream of the mechanical fuel pump, but I don't know of any evidence of this actually happening in real life (and if it does, I can still turn on the electric pump). There's also the fact that I put the flow sensor on the cabin floor in my last airplane, and it seemed to work fine.

Anyway, end of rationalization section. I pulled all the fuel plumbing out of the fuselage – it's easier than it sounds: you only have to undo three flare nuts and four screws and the whole works lifts right out.

I cut the line that previously went from the electric fuel pump outlet up to the firewall, re-flared it, and installed the fuel flow sensor.

The sensor body is partially tucked under the mounting plate, so it won't hit the fuel pump housing. It's not attached to anything, just sandwiched between the mounting plate and the floor. I stuck some foam weatherstrip material to the bottom, to hopefully isolate it from exhaust vibrations coming up through the floor.

With the flow sensor spliced in, the fuel line runs up to the firewall as before. Notice that this location satisfies the manufacturer's recommendation to give the sensor 5" of straight line on both the inlet and outlet sides, which is much more difficult on the other side of the firewall.

The housing fits without hitting the sensor or any of the plumbing:

Throttle quadrant cable bracket

Matt — Mon, 17 Mar 2008 02:00:40 +0000

To attach the engine control cables underneath the panel, I made this little bracket out of 2"x2"x1/8" aluminum angle. The three small holes are for the cables, and the other holes are just to lighten it a bit.

Because the bracket will be somewhat visible hanging down under the panel (at least when you're standing on the ground behind the wing looking in) I decided to paint it black. The paint was taking forever to dry in the cold garage, so I laid the bracket on top of my little electric radiator, using a piece of scrap alclad as a tray. It cured fully after just a couple hours in the sauna.

Here is the cable bracket clecoed to the throttle quadrant supports. The green cable is from Van's and the clevis ends are from Aircraft Spruce (the clevises that Van's sells won't work).

Another view. I had to have at least one cable on hand so I could know where to mount the bracket, but without mounting the bracket I wouldn't know what length of cables to get. I chose to solve this dilemma by buying one cable in a standard 48" length, and using it both to locate the bracket and to determine how long the real cables actually need to be. Since it's a standard length, I can return it for 90% credit later, and I don't have to waste money trial-fitting with expensive custom cables that can't be returned if I guess the wrong length.

I hooked my test cable up to each of the three engine controls in turn. Here's a view of how the prop cable is routed from the eyeball in the upper-left corner of the firewall, down to the prop governor bracket. With this part adjusted correctly, the portion of the cable inside the fuselage needs to be a few inches longer.

The throttle cable comes through the firewall low and in the middle, and runs up to the bracket I previously bolted to the sump.

Inside the fuselage, the throttle cable is about an inch too short:

I forgot to take a picture of the mixture cable, but you get the idea of how this process went. In the end, I decided I needed cables that were 49", 51", and 52" long. I called Van's to order these and found that they also have standard-length cables in 49.5" and 52.5" lengths… the cable lengths can be varied somewhat, so I decided to order those two standard lengths and one custom 51" cable.

By the way, these cables come with a most interesting label on them:

Not for use on aircraft indeed.

Throttle quadrant

Matt — Sun, 02 Mar 2008 22:41:29 +0000

I've been agonizing for quite a while about how to mount the throttle quadrant that Mary gave me for our anniversary last year. Specifically, I was concerned about the degree to which the throttle quadrant was going to impact the amount of available legroom – I'm somewhat tall and I want to be comfortable sitting in this airplane on long trips. Another perplexing issue was the inconvenient lack of substantial structure behind the panel to which a throttle quadrant could be mounted.

Well, recently I started playing with the standard Cessna-style, plunger-type control cables, and was surprised to find that the bracket required to mount them was going to come uncomfortably close to my right knee. You see, my panel is an inch or so taller than stock, and the bracket that the plunger controls attach to has to be pretty wide because the knobs are arranged side-by-side, with a couple inches of spacing in between adjacent knobs… the combination of those two factors made the bracket intrude on my personal space. So, I started taking a hard look at just how the quadrant might be mounted. I started by mocking up the mounting location using spring clamps and scrap aluminum, then installing the pilot's seat and climbing into the fuselage for an ergonomics check. You can see in this photo that there's at least a couple of inches between the throttle quadrant and my right knee under normal circumstances:

On long solo trips in calm air in my RV-9A, I always used to like slouching sort of sideways across the cabin, stretching my right leg over to the passenger side. That airplane had the short, stock panel, so it was easy to do. With the throttle quadrant here, I can't get my leg all the way across without my knee hitting it, but a decent amount of slouching-ability is still retained. I can deal.

I put the transponder into its rack, just to make sure that my hand won't bump it when the throttle is fully open. With the way I have the quadrant suspended below and aft of the bottom of the panel, there's plenty of clearance. And yes, I did make airplane noises.

This is how the quadrant mounting setup looked about halfway through the process. I sort of made up the design as I went along, using various bits of scrap angle. With the airplane up on the gear, access to the under-panel area is somewhat inconvenient, involving a lot of crawling in and out of the fuselage with the help of a stepladder, so it was tricky to get all these pieces measured and aligned.

To close out the top of the throttle quadrant and make it look nicer, I freehanded this little cosmetic trim piece out of some scrap aluminum. I don't fancy myself much of a metalworking artist, but I'm pleased with how it turned out.

I painted the trim piece flat black to match the quadrant and panel. I also painted the exterior faces of the side mounting rails, since they'll be visible after they're mounted.

Here's the finished product, bolted in place. It's very strong – if I had any strength or agility whatsoever I could probably do handstands on it. The prop lever (i.e. the middle one) is centered laterally on the panel, so the pilot and passenger have an equal amount of legroom. Since the travel-sized Mary will be my main passenger, I thought about biasing the quadrant to the right a bit to give myself more room, but in the end I decided to take a more egalitarian approach so giants like John can ride in comfort.

The fasteners at the aft (panel) end of the mounting structure are primarily loaded in tension, so I used #8 structural screws (AN525's) instead of rivets there.

At the forward end, I drilled out one of the subpanel reinforcement brackets and replaced it with a longer one that ties into the port-side quadrant mounting rail. A couple more little pieces of angle tie into the other mounting rail and give it some additional torsional stiffness. All this aluminum angle is starting to make the under-panel area look like a jungle gym, but it's strong and light and nobody will see it.

The painted trim piece looks pretty sharp:

When the throttle lever is in the idle position, the sticks can get tangled up with it if you use full forward-stick and full aileron deflection. I'll be trimming the sticks to eliminate this potential safety issue – they're overly long as received, so I'd planned to shorten them anyway – but I'll wait until I have the elevators and ailerons hooked up before I do it. I have a feeling that the stick has a wider range of motion when it's not hooked to the rest of the control system, compared to how it will actually move in the finished airplane.

Now that I have the throttle quadrant installed – and I must say, it turned out great – I'm left with the problem of determining what length of cables I'll need to connect it to the engine. Dave Parsons was kind enough to share the cable lengths he used for his quadrant setup, so I'll use those as one data point. To avoid wasting money having custom-length cables made only to find I picked the wrong size, I decided to order from Van's a single 48" cable, which is one of their standard sizes. If that works for one of the three controls then great, I will keep it. If not, I can send it back unused for a credit, and having it on hand should get me close enough to be able to measure how long I need my custom cables to be.

Gearleg nuts

Matt — Wed, 06 Feb 2008 02:01:12 +0000

In this week's Aircraft Spruce shipment I received the proper nuts to go on the bolts that secure the gearlegs to the engine mount, so on they went:

The plans call for regular AN365 nyloc nuts here, but I've already decided to use only all-metal locknuts forward of the firewall, no exceptions. AC43.13 only forbids nylon nuts where temperatures exceed 250°F, but since I'm not in a position to measure peak temperatures in various locations forward of the firewall, I'd rather just outlaw nylocs entirely.

Rolling on the gear

Matt — Sun, 27 Jan 2008 02:00:46 +0000

I reamed the bolt holes in the engine mount's gearleg sockets to 0.311", which is a few thousandths undersize for a 5/16" bolt. The goal is to have a zero-slop press fit for the bolts that go here, to keep them from elongating their holes as the gear absorbs loads during use.

I set up Scott's hoist and attached it to the fuselage, using sections of clear vinyl hose material slipped over the engine mount tubes to keep them from getting crunched up by the chains.

"Not to be used for aircraft purposes" – hmm.

Having one end of the the fuselage suspended several feet in the air and the other end supported by a single little wheel induced a certain degree of nervousness.

I had to grind off some of the excess powder coating on the gearlegs to get them to go all the way into their sockets. I also ground a very slight chamfer at the top to keep the rod from getting hung up inside the socket.

Since Mary had other things to do, I had to call and beg Scott to come help me steady the fuselage while I persuaded the gearlegs into the engine mount. The first one went in relatively easily, but the second one was a real pain, especially the last half-inch or so.

I used a low pressure in the rivet gun and a brass-tipped rivet set to drive the bolts home. This worked very well and seems to have resulted in some nice tight-fitting bolts. I need to pick up some AN363-524 metal locknuts, but in the meantime these bolts aren't in danger of going anywhere.

With both gearlegs installed, I put the wheels on the axles so the plane would have something to sit on when lowered to the ground:

The fuselage is on the gear! Suddenly, the airplane is much taller.

Big milestone today. Also, big thanks to Scott for his assistance and the use of his hoist. Don't tell China that I used it to lift an airplane, or they might come take it away.

How about them packers

Matt — Fri, 25 Jan 2008 03:34:19 +0000

Tonight I packed the wheel bearings with fresh grease, replacing the preservative stuff that they come filled with. Sorry I didn't get any photos; my hands were too messy to handle the camera.

I've repacked many an aircraft wheel bearing in my time, but I've always done it the low-tech way – globbing in new grease by hand. This time I wanted to try out one of those fancy bearing packer tools. I picked up one of these at Sears, but its plastic housing broke almost immediately. Then I bought one like this, which worked better. It's pretty crudely constructed, but at least it's made of metal. It didn't eliminate the sticky-fingers problem, but using it was somewhat easier than packing bearings by hand. It probably does a more thorough job of getting grease into the bearing, too.

The old-timers' approach is to use Aeroshell #5 for wheel bearings, and #6 for everything else (pivot bushings, etc.). I'm too lazy to keep two different kinds of grease around, so I've always used Aeroshell #22 for everything. (specifications here) It costs a couple bucks more, but one tube is enough to do a half-dozen annuals.

Wheels and tires

Matt — Mon, 21 Jan 2008 00:47:42 +0000

Well, I figured out how the landing gear axle, brake mounting flange, brake mounting plate, and U-810 bracket are all supposed to fit together. You're also supposed to make little 13/32" aluminum spacers to maintain clearance between U-810 (to which the wheel fairing mounts) and the brake disc, but I just used stacks of washers instead. When I had my RV-9A, I accidentally squashed a couple of the aluminum spacers while tightening up some loose bolts – no chance of that happening here.

Seven AN960-416 washers stacked up gives you the required 1/16" clearance between the bracket and the brake disc. By the way, my U-810's are actually aftermarket replacement jobbies, made from stainless steel. I'm not sure this is really necessary, but I've had them laying around for a couple years (impulse purchase, again) so I decided to use them. They're heavier than the stock aluminum brackets, but I guess they ought to be pretty much indestructible.

Here are both gearlegs with all the bracketry mounted:

I installed the elbow fittings in the brakes, although I haven't gotten around to mounting the brakes for good just yet. I gooped Bakerseal (teflon paste) on the threads before installing.

Then I dug the tires and tubes out of storage so I could assemble the wheels. The red dot is opposite the heavy side of the tire, so you line up the valve stem with the dot. One trick I learned somewhere is to put a couple psi of air into the tube after you get it into the tire, before you try to mount the tire on the wheel. When it's just slightly puffed up, it's much harder to accidentally pinch the tube between the wheel halves and ruin it.

One other thing I want to mention about tires… the tradition is to put talcum powder inside the tire, to keep the tube from sticking to the tire at high temperatures – this is supposed to make it easier to remove the tube later on. I'm not sure if I believe this is really a problem, but when changing tires on my airplanes I've always done it anyway. This time, I decided to go looking for unscented talcum powder so my wheels wouldn't smell like baby. I went to three or four different places looking for it, and here's the thing: What is up with hot babes obviously checking me out when I'm shopping in the baby aisle? This never, ever happens during a normal day, but I swear it happened at least twice while I was looking for airplane supplies between the diapers and those little jars of strained carrots. I mean, attention women of North America: Doesn't it seem logical that if a guy is standing next to the Pampers, he's probably less likely to ask you for your phone number?! Women.

Not to mention, in the end I could only find the baby-fresh kind so that's what I bought. Anyway, I torqued the bolts holding the wheels together to 90 inch-pounds, which is higher than normal but that's what it says on the sticker. I also had to enlarge the hole in the rubber grommet to get the valve stem through without resorting to pounding on it.

To drill the axles for the cotter pins that keep the nuts in place, I ignored the plans and followed the Tony Spicer method. Basically, it goes like this:

Install the wheel and tighten the nut to where you want it.
Use a 12" #30 drill bit to mark the location of the first hole with a small dimple.
Remove the nut and wheel.
Grind away the threads on the axle in an area about 1/8" in radius, centered on the dimple you made. I used a small hemispherical stone in my Dremel.
Replace the wheel and tighten the nut back to where it was.
Use the 12" #30 bit again to re-mark the dimple for drilling.
Remove the nut and wheel.
Use a sharp #30 bit to drill the first hole through the axle, using the dimple as your guide.
Replace the wheel and nut.
Put a drill bit through the hole you just made, to keep the nut from rotating.
Repeat steps 2-9 for the second hole.
Use the 12" #30 bit to clean out the two holes so a cotter pin will go all the way through.

You end up with nice-looking holes and you don't have to worry about splitting the threads and getting the nut jammed on the axle, which can happen if you use a center punch like the plans tell you.

I installed the wheels and nuts but didn't bend the cotter pins yet, since I'll need to remove the wheels again to pack the bearings.

Here's two gearlegs with wheels installed (but no brakes yet) ready to go on the airplane.

Scott was nice enough to loan me his engine hoist, which I will use to lift up the fuselage for fitting the gearlegs (not to mention for hoisting the engine). I just need to get a few things in order and then it will be gear-attaching time.

Gearlegs & misc

Matt — Mon, 14 Jan 2008 03:19:48 +0000

The first thing I did on the airplane this weekend was to finish riveting the tricky rivets that I hadn't been able to finish last time I worked on the subpanel/firewall area. While setting the bottom-most rivet on the starboard side, I screwed up the shop head bigtime and had to drill it out (which I didn't do a great job of either, sigh). I discovered that I also managed to crack the very edge of the dimple – from whacking it with the bucking bar, maybe – and decided to drill out the hole to get rid of the crack and use a bolt instead. So now I have this mystery bolt on my firewall:

I fished the gearlegs out of storage and got to work getting them ready to go on the airplane. These things are about the size of golf clubs, but are made out of solid steel and weigh something like ten pounds each.

Here are the Cleveland wheels and brakes. This stuff is all made of magnesium… light but expensive!

I swapped the pressure and bleed ports on one of the brakes so I'd have one left and one right.

These are the U-403 brake mounting flanges, bolted to the gearlegs. It took forever to get these on here, since I had to grind away all the excess powder coating and then polish the outside of the axles with emery cloth to get the flanges to slide into place. Then I needed to ream the pre-drilled but undersized bolt holes up to 1/4". I'm glad the holes in the gearlegs were already there, or else I'd be taking these things to a machine shop… I looked up the properties of 6150 steel, and it doesn't sound like drilling through an inch of the stuff with hand tools would be a lot of fun.

I swear that two hours elapsed between the last photo and this next one. See, the plans for the wheel/brake installation aren't exactly clear. It took me a couple hours of fiddling, head-scratching, and web-searching to realize that if you follow the instructions as they're written and bolt the U-403 flange to the gearleg first, it's impossible to get the brake mounting plate installed because the bolt is in the way. Of course, it wasn't obvious to me which way around things were supposed to go, so I wasted a lot of time trying to get things to fit the wrong way. An exploded view would have saved me a lot of time here, but oh well.

I can't believe that's all I got done on the airplane all weekend. Blah.

Oh yeah, somebody told me I need to take more big-picture pictures so the casual reader might be able to have half a clue what I'm rambling about, so here you go, a photo of the fuselage… soon to be converted from a metal canoe to a real live honest to goodness airplane fuselage on wheels. I hope.

Upgraded tailwheel

Matt — Sun, 13 Jan 2008 02:00:41 +0000

I finally received the Doug Bell tailwheel fork that I ordered a couple years(!) ago. I was one of the first RV builders to place an order for one of these upgraded forks, but since the one-man production shop's output is limited, I kept giving up my delivery slot to people who were closer to flying than I was. But now that I actually need to get the airplane up on its wheels for good, I told him to go ahead and ship it to me.

Much has been said about the Bell tailwheel before, so I won't repeat it. Suffice to say that it is well made, easy to install, and way ahead of the stock Van's tailwheel when it comes to ground clearance. Not to mention that Doug has a payment policy of "I'll ship it to you so you can try it out, and you can either send it back or send me a check." You don't see that very often.