To Launch a Light Sport

Proceeding apace, despite some setbacks.

Looking like some sort of white beetle, the fuselage is ready for easy installation of the gear legs. It’s a bit heavier, so turning it over is no longer a one-man job.

I was interviewing another builder recently, John Deneke, who’s hanging a Rotec radial on the front of a B cker Jungmeister. He made an almost casual comment that we’d spend more time under the airplane than in it. His meaning was clear: You’re unlikely to fly as many hours as you spend building. It caused me to consider the project in light of that ratio; that is, if we spend so much time anyway, why not spend a little more to do it right?

That brings me to the Jabiru. Jabiru distributor Jim McCormick made a comment whose truth I didn’t appreciate at the time: “Anybody can build one of these, but it takes a lot of work to build an exceptional one.” The Jabiru factory owner, Rod Stiff, concurred. “We leave the appearance up to the owner,” he said. From what I’ve seen, I have no reason to doubt it. More to my point, though, rather than be discouraged by the poor quality of some of the fiberglass, I’d have to recalibrate and see it as an opportunity to spend more time, more effort to make this Jabiru exceptional.

I can’t let that comment on the quality of the fiberglass stand without making it clear that some of the work is first class, and some appeared to be done by someone in his first class. I’ll reveal the good and the bad as this project progresses—and share some of my and McCormick’s solutions. But the point is this: On my Jabiru kit, the consistency of the fiberglass just isn’t there.

I’ll go on a tangent for a moment and say that to achieve quality, you need to first define it. Quality is supplying exactly what the customer expects. I expect to finish the plane, not repair the manufacturing goofs. The second step in achieving quality is to be consistent, even if it’s wrong. Once the process is repeatable, it’s fixable. Without consistency you spend your time chasing down one-time problems.

Sip, Sand, Repeat

Off we go to the shop, coffee in hand, and with the realization that I now move on to installing the landing gear. Wow, this is going fast! The fuselage is so light I can flip it over by myself and work on the gear upside down.

Speaking of things rubber, the screeching of tires usually precedes the sound of a crash, and in working on the brakes I’m hearing that awful sound. I ordered the brake upgrade kit on McCormick’s advice. It seems that the stock setup works fine at first, but then degrades in performance due to a design flaw: The inner caliper does not move to compensate for wear. The result is that you have to bend the rotors to actuate the brakes.

But there are no instructions or drawings showing the assembly of these upgraded brakes. A phone call fixed that, and the sound of tearing rubber was avoided. The directions said nothing about the fact that there is, or should be, a left and a right to the brake rotors. The two rotors are interchangeable and reversible so that each can be installed with the webs in tension or compression. It probably doesn’t matter because the webs are short, but I prefer to not give away any advantage.

This is one of those tricks that really sharp manufacturing companies do to keep costs down. They realized that it’s cheaper to build it right than to repair it. Upstream, it’s cheaper to design it so that it can go together only one way than to rely on a tired assembler late on a Friday afternoon. When done, it came out looking really nice. I just wish they’d keep the instructions up to the speed of the revisions of the components. This wish kept coming up.

The gear legs are easy to install with the holes in the fuselage already drilled. The wheels and brakes went on readily through match-drilled holes. This is fun! Oddly, the nosegear is not on it and the instructions say to turn it over, wheels down. Well, that’s simple! This plastic tadpole almost rolls over as it is.

Put a brace under the nose, and it looks pretty good. Put a brace under the tail while you’re at it, though. Some knucklehead is sure to climb in that big back area and get a surprise…No, I am not that knucklehead.

That’s weird. The gear legs are curved too much. The last time I saw something that bowlegged under an airplane it was a bomb rack! The addition of a 5/8-inch spacer under the centerline mount point spread them a bit, but it was insufficient to put the tires perpendicular to the hangar floor. Perhaps they’ll spread with the addition of the engine, wings, systems and the pilot. We’ll see.

The sound of screaming rubber returned when I got to installing the aileron trim cable. If you read Part 1 of this series, you’ll recollect that the slot on the bottom of the tail was undersized. The judicious use of a round file mounted on a 30-inch shaft fixed that issue, and I felt that all was well. Had I read or thought far enough ahead, I would have asked myself: “What does this do? Will it do it?” and been a much happier camper.

As it was, that large bracket that was bonded precisely over the marks was supposed to be displaced to the right, not to the left. The drawing shows it correctly, but the marks were not where the drawing said they should be. I would have to sort that out later. The worst-case scenario seemed to be routing the cable with an extra jog in it, or so I had hoped. The latest version of the manual would have made the marking error instantly apparent, and a lot of rework would have been avoided.

Learning from that, I went on to the next almost-gotcha in the positioning of the master cylinder for the brakes. This aircraft has a steerable nosewheel, but not independently actuated brakes. You work the rudder pedals for direction and pull back on the brake lever to slow down. My neighbor has a Chinese Nan Chang with the same setup, and it works fine.

Before I get into the nitty-gritty of the fabrication/installation, I have to point out that the newest version of the manual shows the master cylinder located on the outside of the center console. This appears to be a far better solution, but it’s neither how my kit was configured, nor how the instructions described it, so I can’t assess the process.

Back to the actuality. The brake lever is on the right side of the console, but using the factory holes would have the cylinder targeting a non-existent lever on the left. I re-drilled the holes to cant the master cylinder in alignment with the pushrod, and all seems fine.

The frustration meter went up again when I started to hook up the brake lines. All worked well until I got to the master cylinder. One cylinder splits to feed two brakes, so a “T” is needed and supplied. However, the threads are not the same. The T isn’t a T either, but a beautiful bit of machining that points the lines not at 3 and 9 o’clock, but at 4 and 8 o’clock. This is nice in that the space is a bit restricted, so it helps in routing the lines—except it has the wrong threads: They’re straight instead of being a pipe thread. There’s no provision for an O-ring either, so pretty it may be, but useless it is. The good news is that the cylinder is an off-the-shelf item, so a trip to the local auto parts store put me back in business.

Not so fast. In Section 12, item 4, the instructions read “note–trim cable has been pre-fitted.” This was odd. That was the second time, or the third, that this cable has been my nemesis. I don’t recall reading that it should have been installed, so I went back to check. Nope, no directive to do so. This is especially distressing because now that the master cylinder is pop-riveted in place, it’s almost impossible to feed that cable through a grommeted and tight hole in the master cylinder bracket. Perhaps this is one reason for the relocation and reconfiguration of the system on the newest version.

The Surprises Continue

Next I found it surprising to read that painting the interior occurs early in the process. Do I hear a voice saying, “Yeah, too early”? A read-ahead (I’m getting better at this) reveals an interesting sequence of procedures. In Section 13 it says to “bond” the elevator trim stop in place after all the cables and elevator have been installed. OK, but that won’t happen until Section 55, and Section 14 has me painting the interior. That means I’ll have to sand off the paint, bond the elevator trim stop into place and then re-paint the interior after the instrument panel is installed per Section 45.

And that does not answer the question of what bond means. In previous chapters the directions for attaching two fiberglass parts specified the use of either an epoxy/flox or a two-part adhesive called Araldite. In this instance, the word bond is not qualified. The list of materials on the page includes Araldite, but with the track record of the documentation so far, it’s best to think for yourself. Let’s see, epoxy/micro is for filing holes and smoothing out discontinuities. It’s made of little glass balls. Glass breaks rather easily and this is a load-bearing part, so that’s not a solution. Epoxy/flox is a whole lot stronger and will fill a gap, but it’s messy. Araldite has almost no gap-filling ability, but there’s no gap and the part is only under compression. Araldite it is.

In the recent movie remake of The Mummy there’s a scene where the monster’s followers are slavishly intoning his name: “Im-ho-tep. Im-ho-tep.” I’ll try to substitute a mantra of “Read-a-head” in any prospective builder’s brain by pointing out that not only will it allow you to dodge a bullet, but it can actually speed up the building process.

Read ahead and plan on waiting for epoxy to dry. Example. Section 20 starts off with bonding the mount for the flap handle into place and “let dry for 24 hours” followed by the installation of the aluminum flap position plate. That would limit you to about an hour of work and then waiting 24.

Having read ahead when you were on step 18, “Install rudder pedals and cable,” you would jump to that epoxy operation of step 20, and while it was setting, you could do the drilling-and-bolting operation of the rudder pedals. No point in watching epoxy set (grass grow). I suspect that this is one of those points of experience that causes the factory to say that the average builder takes 600 hours to build this airplane when they (Aussies) do it in 300. (As I write this I just passed the 600-hour mark. Although the plane is flyable, fine-tuning and preparation for painting will take at least another 200 hours.)

Back to the Build

Once again, there are detailed instructions for installing the rudder, trim and elevator cables when the trim and elevator cables had been installed in an earlier step. “We make airplane kits, not books” may be the mindset in the industry, but rather than being business as usual, it ought to be an opportunity to jump ahead of the competition. The builders themselves are partly to blame. Feedback takes an effort, and many may think, “Hey, I want to build/fly this airplane, not write it up.”

There is another not as well recognized factor akin to the attitude taken by the victorious general who returns from the battle claiming victory over a worthy adversary. “It was an easy win” is not something likely to warrant a promotion, and so it is with builders. “It was an easy build” is not likely to garner great respect and awe, so I think that we builders fail to demand instructions that are simple to follow.

Why should we? Joe Experienced wants the respect and doesn’t heavily rely on the instructions for his second build. Jane Newcomer can’t evaluate the instructions until she’s actually completed the work. When she’s done building, what proves to be important isn’t sending complaints to the manufacturer, it is, understandably, “I’m now a member of the club, and let’s go fly.”

The point is that those of you who are just starting out with the new instructions and have the newer kit now have the responsibility to write in and augment my experience. Jabiru is evidently shaking things up, and the nature of what the company delivers is changing. Experience is what we call our mistakes; wisdom is what we call it when we don’t relive the experience.

One year and 640 hours into the building of the J250. In the year spent building, the factory has changed a lot of the manual. Indeed, I’ve received three significantly different versions of it from Jabiru. The second was marginally better than the inadequate first version; the third appears to be a significant improvement over the first two. In an effort to give an up-to-date evaluation of what you are likely to receive, in future articles I will be describing my actual experience, but I’ll try to assess how it might have been different had I been working from the current documentation.

For more information on the Jabiru J250 visit http://www.jabiru/

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Bob Fritz
KITPLANES readers will remember Bob Fritz (1947-2011) for his acclaimed Home Machinist series, but his accomplishments go well beyond that long-running feature. Following a stint in the U.S. Navy, Bob put his degree in mechanical engineering to use and was a tireless advocate for effective and consistent quality control. He brought that discipline to his work for KITPLANES. An avid diver and motorcyclist, Bob's love of flying was a surprise to no one.


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