« Posts tagged empennage

More odds and ends

4 hours.

A few things here and there. I installed the MAP tubing and put a couple of heat shields on the pipes to protect the throttle and mixture cables. I also installed the canopy seal, which is going to need some assistance from some RTV or proseal. I do think firewall forward is just about done, though. The cabin heat SCAT tube rubs on the engine mount a little, but some UHMW tape should fix that. The two things I did that were of major importance were the autopilot test and getting that ridiculous piece of lead off the flange of the left elevator counterweight rib.

A while back, I’d balanced out my elevators, or so I thought. You’re supposed to put the elevator tips on, then drill holes in the lead weight until the elevator balances. Well, guess what? You’re not supposed to have the elevators connected when you do this. I discovered this, freaked out, then riveted a flat piece of lead (cut from an extra counterweight) to the outboard rib.

When I put that away, thinking I was just about the smartest cat in the whole barn, I started imagining the kind of beating a control surface takes in flight. So what happens to a little piece of lead riveted to this structure with a couple of Cherry countersunk blind rivets? The piece of lead comes off and somehow jams the elevator in the dive position and I go screaming downward like a holed Stuka, straight into a busload of orphans on the 405. This has bothered me for months, but I could never find a good opportunity to fix it until Saturday. I drilled out the rivets and put the lead back in a drawer. I also read about a neat trick you can do when balancing your elevators: Pour some lead shot into the tip through the tooling hole in the rib until th elevator balances out, then stick it in place with epoxy resin. Even if it’s not perfect, bias it a little heavy, because paint will change the balance.

I also mounted the MGL GPS antenna on the top side of the glare shield. It works; I get an intermittent GPS position while still inside the guest house.

Oh and one other thing: I dragged the wing cradle over to the shop and tested out the bank servo of the autopilot. Since I actually followed a wiring plan and wired the fuselage-side and the wing side according to it, I was able to test out both servos simultaneously. I do need to make a new ground connection though. The ground from the servo bracket sucks and I was only able to get a good ground by cleco-clamping the ground terminal to a wing rib.

Wiring and fiberglass.

12 hours.

This is for yesterday and today. I finished up the elevator and HS fiberglass tips. You’ve heard me piss and moan about fiberglass before, so I’ll spare you that this time, but yesterday’s experience was not great. I got the HS off the futon in the other room and set it up on the bench so I could mount and balance the elevators. When I last left the HS, I’d done the fiberglass tips, but I hadn’t done much else with them, and they needed a good amount of shaping before the elevators could swing freely. One side was fine after some filing and sandpaper, the other had the foam too close to the edge so I sanded all the way through the filler and started taking out foam.. This isn’t good. Raw foam isn’t helpful, so I had to mix up some flox, both to fill in the elevator tips after balancing and reinforce the left HS tip. I had this cool thing set up where a thin piece of sheet was curved round the elevator tip, making a form for the flox that would guarantee the free motion of the elevator through its travel.

Would have worked too if the tape hadn’t popped loose, leaving me with a distorted lump of flox on the front of one elevator. I had to file/sand that back into shape, then glop in a load of micro filler to get the final shape.

So there it is curing away.

I busied myself with antenna mounts while the epoxy was setting up. First was the transponder antenna. I’ve decided to put this on the floor behind the baggage bulkhead. All antennae need doublers, even the stubby transponder antenna. The skin of the aircraft isn’t thick enough to provide structure on its own, so I had to take a piece of .063 and make a plate that the antenna can grip onto.

Today I did the final shaping and priming of the HS and elevator tips. While I was waiting for paint to dry, I worked on the doubler for the Garmin GPS antenna.

Installing these doublers aft of the baggage bulkhead is interesting. First thing you do is drill the holes in the plate at four corners, then one in che center. Then you go inside the ship, down the Jeffries Tube, and position the plate where you want it for proper antenna location. Don’t forget to bring your drill. Use the plate as a guide, and drill the skin using the center hole in the plate as a guide. Then measure to square the plate up with surrounding stuff, then drill the corners of the plate. Now it gets fun. You have to dimple all four holes in the skin that match the corners of the plate. You need to use your 3/32″ pop-rivet dimpler for this, but you do it by crawling into the ship, placing the dimpler, getting back out, making the dimple, then repeating 3 more times. In the case of the GPS antenna, there are also screw holes to deal with, which means platenuts. Oh, don’t forget to countersink the skin side of the plate.

Since I was in the tailcone a lot today, I figured I’d do some nagging things I was going to have to do anyway, like the restraint cable clevises and removing the ELT antenna cable. Yeah, can’t run the ELT cable through bulkheads. If you crash, the airframe might fold and sever the ELT antenna cable where it passes through a piece of sharp metal. I decided to run the trim servo wire down that run in its place. Then I ran the transponder antenna wire alongside the two GPS wires on the left side and did the BNC connector.

I don’t want to spend a lot more time down there. It’s cramped, hot, and dusty in there. If I can get enough servo wire slack so I can work on the connector outside the ship, that will make me extremely happy.

Foam arrived, finally.

1.5 hours.

Cut and glassed in the emp tip foam inserts. This damned foam took nearly a month for Aircraft Spruce to get it to my house. It was backordered, then backordered again, and I finally got it today. They sent me a 2×4′ sheet of it too, and I’m pretty sure I ordered a lot less of it. Oh well.

This was easy enough, cut out some foam bits that fill the shape of the fiberglass tips, closing them off to outside elements. Mostly. I applied fiberglass and foam with the tips clecoed on so when the resin dries, I can pull them off and the tips will stay the shape they where when clecoed on. A couple of layups on the inside of the foam block and some micro filler frosting on the outside and those will be done. Then I don’t have to see the empennage again for a while.

Since I had some resin in the pot, I used up all the rest of my cut scraps to glass in the Archer VOR antenna in the wingtip, something I’d been planning to do for a long time but never got around to it. I did two layups on that, which should be enough to hold it in place, it’s not structural, just something to keep the antenna from flopping around in the wingtip. Another thing done.


4 hours.

Got the emp fairing done, or at least as done as it needs to be, for now. It needs paint, and maybe another round of micro, but it looks OK as far as I can tell. I had to install the elevators to figure out the control horn cutout, but smart-monkey was in charge instead of impulsive dumb-monkey and I got them perfect on the first try. I got the fairing countersunk, then got the platenuts installed on the VS and HS. Oh, and packing tape sucks. The packing tape I had on the aluminum to protect it from epoxy sticking there did its usual trick and ripped apart when I tried to take it off. A little bit of cajoling with the heat gun and making sure to stop and pull it all off evenly helped. Then I took the tail pieces off, but of course, I forgot to do the lower emp fairings, which I currently can’t find. Next time.


3 hours.

Aircraft Spruce, for some reason, has twice screwed up getting me my foam that I need to do the empennage tips. OK, fine, plenty of other stuff to do. Like the empennage fairing. This is a fiberglass piece that fits over the place where the tail section is bolted to the fuselage. In theory, you have to pop this on there, drill the holes you need to drill, and fill in whatever gaps are left with flox or some other structural filler. The problem arises when the fit sucks so bad the part looks like it belongs on a different airplane. The only recourse at this point is to start hacking up the fairing and making it fit. Fortunately, fiberglass lends itself very well to this. I had to excise a whole section where the curve of the fairing conflicted with the vertical stabilizer and threw the fit of the whole thing into the toilet. The other thing that had to be done was the part had to be split into two pieces at the front vertical curve. Now it fits. Oh, also, there’s a scribe line around the edges of this part that’s a guide for trimming away the excess. Wish I’d seen that before I started butchering the fairing. With the excess cut away, the fit might have been good enough to just fill the gaps along the edges. I’m tempted to order another fairing and start over. Either that or I’ve bought myself a good 10 extra hours of fumbling around with multiple layups and a crapload of sanding.

But I have to go out of town for five days on business, to rainy, possibly snowy Vancouver BC, so the next chance I get to mess with this thing will be next Monday.


I need five uninterrupted hours to do the glassing. I’m not going to get that.

A piece from here, a piece from there…

1 hours.

Last night was one of those “what’s there to do in an hour” nights. Enough time to get something done, not enough time to make a big ol’ mess.

I got some 2″ hose clamps a couple of days ago, so I decided to finalize the cabin vent tubing. OK, as final as anything is on this project. The 2″ black tubing connects the NACA vents on the side to the SteinAir eyeballs at the panel. You twist them one way, air blows out. Twist them the other way, nothing. Just like the ones in airliners. I tested them, they both work and they dont’ seem to leak, but I need to check that. Cold drafts (draughts?) at altitude are bad, because they’re an annoyance that can make a flight suck for a non-rugged-individualist passenger.

After that, I trimmed and drilled the fiberglass tip for the vertical stabilizer. These need to be closed at the back end with some kind of filler, but I didn’t want to make a fiberglass/epoxy mess at 9pm on a weeknight. The crap part is, the filler needs to be put in place while the tip is in place, because there’s no other way to ensure the proper shape due to the tip’s flexing when not pinned down. The VS might have to come off for this, but before it does, I’ll drill the hole necessary for the tail and strobe wires.

Emp Tips.

.5 hours.

I’m trying to get back into the rhythm of doing something, anything, once a day. On my list of odds and ends has been the fiberglass empennage tips, and I’ve been avoiding it because I hate fiberglass and there was always something more important to do. This morning, I did the easiest of the 6 empennage fiberglass parts, the rudder tip:

Easy enough. Cut off the excess with a Dremel, drill, countersink for CS4-4 pop rivets, rivet on. There may or may not be later stages of filler, but at this point, it’s done, it’s on, and it won’t come off. The other tips will need a bit more work, since there’s trimming, and a need to reinforce them. The elevator tips need to be covered up and filled once the counterweights are drilled for balance. But then that’s DONE, and then it’s all about wiring and firewall forward.

Halloween Horror.

8 hours.

My parts arrived from Van’s last week. A couple of ribs and a HS-710 angle that I had ordered because I was tired of that nagging feeling of something not right in the structure of the horizontal stabilizer. Yesterday, I finally got to drilling the offending part off, with the intention of making a new one that satisfied all the edge distance requirements. This is the old HS-710:

You can see how beat up this thing is, and that’s from me sucking at riveting a long time ago. Not only that, see the holes along the flat part, near where the angle starts? Those holes are too close to the edge of the part. The general rule is that the center of a hole should be 1.5x the hole’s diameter from the edge of the part or another hole. This isn’t even close.

This part is one of four structural elements holding the tail onto the airplane, so it’s kind of important and it has to be perfect. No ovaled holes, plenty of edge distance, good rivets, deburred holes and edges. This part connects the inboard ribs and both spars as well, so it’s all got to fit together in such a way that all those requirements are satisfied. The plans for this section suck, and the design could be better too. This is one of the first things you have to do as a builder, and a fit this important could do with a little more explaining of the whys, and some clarification on the steps. It’s almost as if it’s deliberately designed to get your nose off the paper and understand the structural priorities for yourself, and the lessons are taught in mangled metal and UPS shipments from Aurora, Oregon. The main lesson here is that you have to trim off just enough of the nose rib flange to let it fit between the HS-710 and HS-714 angles, and that it’s better to be closer to the edge on the aft rib than on the angle.

So, armed with 4 years of aircraft construction savvy between then and now, I set about replacing the HS-710 angle and the inboard ribs.

This is the shiny new HS-710, ready to install. The tapered ends didn’t get as much of a taper this time, leaving more metal on the edges. All good, right? Wrong.

Another important lesson: Get rid of all annoyances and irritants before you do anything critical. Find your neutral space. My jeans were falling down (belt not tight enough, getting less fat, good news really), the drill charger fan was running, the psytrance station started playing something screechy, tweaky, and annoying, and the shop vac hose and air lines were completely underfoot. I drilled the new HS-710 in exactly the same place as the old HS-710, through the spar in the old hole. I needed a whole new class of profanity to accurately describe the situation at that point. I didn’t have one. So I threw stuff. Nothing heavy or expensive, but even watching my hearing protectors explode in a bright flash of red plastic and skip across the concrete didn’t satisfy the frustration and disappointment. Even the time I drilled a hole in my finger wasn’t this maddening.

At this point, I wasn’t much into taking photographs. I spent the next few minutes contemplating selling the whole mess and buying a Cessna. Slower, but for the money, hauls more cases of wine back from Napa. But then the ‘F— You’ took over. F— You happens at the darkest hour, when you just say F— You, this is not stopping me. F— You, you are just soft metal. F— You, I will get this done. Today. So I made a new HS-710 from some angle stock. That’s right. Made one. And I can make more. I’ve got plenty of angle stock. We can do this all weekend, so settle in, princess. This time, there was way more measuring than there was drilling, and I now have a fully functional, structurally sound, properly installed HS-710. Here are all 3 HS-710’s, old, new, and new new.

Getting that little bastard on was only the first of the fun things to do. This setup is designed to be assembled before the skins are on, and getting it all together requires some basket weaving and the use of the double-offset rivet set, which is a deep, dire pain in the ass. The procedure is: Stick the aft ribs in, drill them through the spar, then use those holes to match drill the forward rib making sure the edge distance is good. Before you drill that, make sure the skin-to-rib flange lineup is good. Get this part locked down, then do the skin holes. But riveting the flanges to the spar is a bitch. The double-offset set likes to walk around, and you really need to secure the assembly and keep the set seated or you’ll mangle the rivets and that will mean drilling out and possibly enlarging the holes. Trust me you do NOT want to go up to an AD5 rivet in there. The rivet gun just barely makes it in there to get a good lock on the rivet heads. Like I said, it was designed to be done without the skins in place.

If you get it right, you end up with something like this:

See how there’s plenty of room between the center of the rivet and the edges of the metal?

Squeezing the skin rivets is easy. I even remembered not to rivet the holes for the empennage fairing this time.

Assembled and resting. The next horizontal stabilizer I build better be on the next airplane.

The Telltale Heart is no longer beating.

4 hours.

Today I started the fix on something I should have done a long time ago. When I first started building this thing in late 2005, I knew FA about how airplane parts go together. I also had pretty weak skills in precision metal cutting. I didn’t know how big the saw kerf was, I didn’t know how much metal would come off from the grinding wheel, and several other things that are pretty much muscle memory now. When I was building the horizontal stabilizer in 2006, I still didn’t quite have the knack of it,

This is what I’m talking about:

This is the forward reinforcing angle that spans the forward spar of the horizontal stabilizer. This part is structural. I probably shaved off too much metal from the bottom when making the angled tab, so that’s what killed me on the edge distance. Then I further beat the crap out of the two inboard ribs during the process of sticking it all together. I sent photos to Van’s of the whole sad-looking assembly and they told me it was ugly but not a problem structurally. Maybe it is OK, but it’s been bugging me for nearly four years. So today I ripped out the ribs and the HS-710 angle. New parts are on their way from the mothership.

It’s going to be rock solid this time, and I know that because I now know HOW those parts are all supposed to fit together, so I’ll have a drilling and riveting strategy that insures everything has the proper edge distance. I also have a tungsten bucking bar that I didn’t have before, and I have a decent array of skills built up over the last 4+ years so I think I can rivet the new pieces together without giving them that hand-hammered bronze-age look.