Wings are ready for move to the hangar. Cleaned up/fastened some wiring, perma-mounted the flaps, switched the shop back into fuselage mode.
Wing skins are done! I reinstalled the flaps and got a strip of UHMW tape along the back of one, and I’ll do the other tomorrow. The other thing I have to do is find or refabricate the flap hinge pin fasteners. After that, I just have some minor wire tidying to do and the wings are done, done, done.
Yesterday, my friend Derek came by for a few hours and helped me rivet the bottom wing skins on. Derek is peripherally responsible for me being where I am today with regard to aviation: Flying leads to skydiving, skydiving leads back to flying and flying lessons, rental airplanes lead to homebuilts. Before he arrived, I did some pondering about the best way to rivet the wing skins on, and the first two things that needed to happen were the removal of the aileron push tubes and the flaps, so I did that.
Riveting the skins on the wings would have been really tough without help, especially the inboard rows near the bellcrank. As it was, I really had to stretch to get the bucking bar up in there far enough to reach the rivets closest to the aft wing spar. But it gets easier as you move outboard, and we finished off the left wing yesterday afternoon. Derek had to leave at around 3-ish: newborns really don’t care all that much about Daddy’s friends’ projects, but I kept going.
Before he left, Derek helped me get the double row of rivets on the right wing, then I got going on the rest. To say that riveting those big bastards by yourself is awkward would be like saying Stephen King sells a lot of books. Fortunately, the skins do bend quite a bit, and I wish I had a photo to show you how I did it, but the general gist of it this:
With the double row riveted, cleco the spar side and leading edge side holes together. Then climb in between the skin and the ribs, which will allow you to get a hand and a bucking bar in through the lightening holes to just about anywhere you need to go. And it should go without saying, remove the blue stuff from the inside of the skin before it gets riveted on, or you’re going to have a lot of fun later. Good thing I remembered this before we got too far along, but if you’re reading this, I hope it reminds you before you buy yourself a long night of failure-drinking.
I thought the autopilot servo was going to cause a lot of problems, but with the push tubes out of the way, it was really a non-issue. By myself, I got another row done, up to the access panel for the bellcrank, then quit for the day. I was sore and tired. Even with help, riveting wing skins on is like yoga for gearheads.
Left to do: the remaining skin rivets, and some minor wiring cleanup, since I replaced the puny 14-ga wire intended for the landing lights with a much beefier 10-ga flavor.
I managed to get home for an hour yesterday from work (yes, still working the occasional weekend) and Dave came over to help me finish riveting the top skin. We got that done, and today, I think I blew my back out trying to get the canopy back on. It wouldn’t slide into the blocks, no matter what, and I couldn’t figure out why. That’s when I had one of those dark moments and issued forth curses and bile.
This is the MGL IO eXtender. It is placed on the subpanel between the instrument panel and the firewall. It is also directly in the path of the canopy frame. In retrospect, I probably should have marked out the 1 3/4″ zone in which nothing should be placed. But I didn’t. At this point, I’m like, whatever. I can move that. I think. Actually, not really. Not too many other places I can put that thing without some rewiring and I wanted the canopy on TODAY. So I came up with this:
Originally, I had a backing plate on the IOX because of the way the mounting tabs worked. Since this thing weighs basically nothing, I’m pretty confident that the arrangement here will be just fine. Now the canopy frame clears.
All that aside, I will be paying dearly for the amount of crouching and wrestling I had to do to get the canopy back on the aircraft. It’s not terribly heavy, but it’s awkward, and fragile, and it took quite a bit of work to get it into place with the hinge pin holes lined up. But it’s now on. When I get back from Seattle, I’ll put the struts back on, and then it’s hurry up and wait for some hangar space.
And yes, it’s a shout out to Neal Asher, whose writing has gotten me through a tough couple of months. When you’re having horrible-seeming things happen to you, reading about truly horrible things happening to somebody else and the truly horrible people who cause them getting their comeuppance is very therapeutic.
As far as this aircraft project goes, yesterday was not horrible. I actually might have the temerity to call the firewall-forward process almost done. The only two things missing from the equation is a 2″ hose clamp for the cabin heat SCAT tubing (which is actually missing, I can’t find it right now) and the manifold pressure sensor fitting and tubing, both on order from McMaster-Carr. I can look at the engine installation and say with fairly high confidence, yes, this engine will turn the propeller repeatedly. Today I’ll go through my periodic shop purge/clean ritual and see if the clamp turns up.
I also took a long look at all the stuff just behind the firewall and ahead of the subpanel, to make damned sure there was nothing else I needed to put there, because as I’ve mentioned before, once you rivet that top skin on, you can’t get to anything below it without a flashlight, a mirror, and possibly tentacles. Satisfied to the limits of my ability with such things, I began riveting the top deck skin on. This is hard. This is hard because you have to have a rivet gun on one side and a bucking bar on the other, separated by a 3-foot sheet of metal and ‘awkward’ only begins to describe the process. There are two holes in the subpanel support capable of taking my hand holding a bucking bar through them, and it’s a little like the reverse of a monkey trap. There is much maneuvering into position, then there is riveting, whilst holding the bucking bar perpendicular to the rivet without being able to see it. This process enabled me to do the center row of rivets, and the canopy hinge support bracket, but failed on the outboard subpanel support rivets because to get my hand into the right position, I had to bend the skin away from the surface it was being riveted to, causing a gap. I couldn’t get the leverage I needed and the skin ‘pillowed’ on the support rib. Bah. Curses. Foiled. I’ll need to enlist a helper for this step, but as soon as it’s done, I can put the canopy back on and officially list the project as ‘more parts assembled than not.’
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.
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.