Tag Archives: rivet

QB Fuselage Rework – Part 2

Sometimes you have to go backward to go forward. Drilling out rivets is one of those things you have to do sometimes when building and airplane. Fortunately, I’ve had to do very little reverse-assembly. But, there are a couple of parts I needed to add and I’ve opted for an upgrade to the cowling fasteners that calls for replacement of narrow, factory-mounted parts, with wider aftermarket replacements. Drill baby drill!

There’s a reinforcement plate, near where the ballistic parachute rocket canister mounts. The plate rivets to the RIB that forms the back wall of the parachute compartment. Several rivets had to be drilled out and removed so that the plate could be positioned and riveted. Done.

There was also a missing attachment angle for the top right edge of the parachute compartment. It should have been installed at the factory. It’s going on now, but a few rivets had to be removed before the angle was riveted using those same holes.

To go along with the other rework, I’ve opted for an upgrade to the factory-supplied cowl fasteners. I want to use Camloc fasteners rather than the Dzus fasteners that come with the kit. The Camloc parts are more user-friendly when it comes to unfastening and re-fastening of the cowling. For best results, getting the fasteners a little farther away from the edges of the fiberglass cowl is a good thing to do. That involves replacing the factory cowl fastener strips with wider parts that I ordered from Midwest Sky Sports. They make these wider strips and use them for the planes they build and they seem like a good idea to me.

The rivets holding the factory-strips needed to be drilled out. I did it. Now I don’t have that to contemplate anymore. I did a quick fit of the new cowling fastener strips. They look like they fit pretty well. That’s a relief after removing the factory parts.

Rudder Pedals – Trial Fit

The sight of rudder pedals in their proper home makes the whole project seem like it’s on track to be a finished airplane. That’s important for me to realize, now and again, and helps to reinforce the idea that finishing the airplane is possibly doable.

My Sling-branded rudder pedals are an option that I knew about, liked, and deliberately ordered with the quick-build kit. When my QB kit was delivered, the pedal parts I ordered were not there. Most of the related parts I got were for toe-brakes. It took more than 6 months to get things sorted out with the factory and finally get all of the parts for the pedals I ordered — all good now.

The typical braking configuration for Sling airplanes is a simple, single hydraulic master cylinder, lever-operated mechanism that evenly applies the Matco disc brakes for both main wheels. Toe-brakes are a necessity for Sling tail-draggers, but are available as an option for us lowly nose-dragger pilots. Space is pretty tight for 4 independent toe-brake master cylinders with all of the plumbing. From what I’ve been able to determine, Sling pilots find they like the hand-brake, even if they’re used to toe-brakes. I’m going for simplicity. My Piper Warrior has toe-brakes. They’re fine, until they leak all over your pedals and carpet and demand maintenance. I’ve been there, done that and got the T-shirt – thank you very much. Simplicity is a virtue. I’m going through the simple-is-better phase of my life now. You can have toe-brakes in your Sling.

I had hoped that I’d be done with this pedal mounting business – the final assembly. But, it’s turned into a trial attempt. The pedal tubes, bushings and brackets fit nicely, but I did find some clearance issues with the pedal stops that I’ll need to address. That means the whole pedal assembly has to come out again, except for the permanently riveted floor brackets. As I moved the pedals I heard squealing. It’s a little hard to explain, but the edges of the lower hands of the stops can (and do) occasionally touch the edges of the control arms where the nose-wheel pushrods and rudder cables attach. I have to do something. Exactly what, I don’t quite know. Something will come to mind. That’s where procrastination comes in.

Fortunately, I’ve elected to retain the top bushing brackets with M4 x 12mm SS cap screws, washers and elastic stop-nuts. That makes for straightforward disassembly. (I may eventually be forced to use 4mm pulled rivets, if the retainers show any signs of movement, but for now the M4 screws seem reasonable. Space is very tight and riveting would be a challenge – explanation below.)

Typically, the rudder pedal floor brackets, tubes and stops are fitted and mounted much earlier during fuselage assembly, with just the CF floor sitting ever so conveniently on the workbench. For my factory-assembled QB project, this didn’t happen and I’m doing the fitting and assembly work inside the completed CF structure. It’s certainly more challenging to do this work while kneeling and reaching into the cockpit foot wells.

LH Aileron – Finishing Up

The LH aileron had been languishing under the bed in my guest bedroom with the skin cleco’ed in place. It just needed the outboard rib with the reworked hinge brackets.

Riveting the skin on the bottom went well. Now it’s back under the bed again, with and in the same state as its buddies. Final riveting of ailerons and flaps will wait until I’m in the mood to fit them on the wing assemblies. That might even wait until I have the wings joined to the fuselage. We’ll see. I think that decision depends on what I decide to do about painting. Fly first or paint first? Yes – another excellent opportunity for inspirational procrastination.

Ailerons – Fab, Rework and Pre-Assembly

Aileron assembly has been delayed by ignorance and procrastination. It’s amazing how long it took me to decide to lever $20 out of my pocket for a tool. There’s an anchor nut that gets attached to a rib with a couple of stainless steel rivets that have a 120 degree countersink. I was reluctant to spring for a 120 degree, #40 pilot cutter. This left me pondering various alternative ways I might proceed to attach the anchor nuts. The door was left open because the construction manual doesn’t say anything about it. But, I did have reference examples – other builder’s and identical anchor nuts mounted in my quick-build fuselage. I finally ended up getting the stupid pilot cutter and then mounted the anchor nuts as I knew they should be from the very beginning.

Another self-inflicted setback has been in play. Sometime earlier, I’d riveted one of the aileron hinge bracket and rib sub-assemblies together. Unfortunately, something I’d noticed, but dismissed during initial fitting, had to be corrected. The bolt holes on the inner and outer aileron hinge brackets were not in alignment. To compound the problem, I reasoned that it would probably be ok to ream the bolt holes a little – make them oblong – and somehow that work out ok. Wrong! The result was better alignment, but at the cost of precision (proper) fit.

Sloppy fit for the outer aileron hinge just isn’t going to cut it. What could I do? Eventually, I did what I I should have done in the first place – ask the factory for guidance. I sent an email and got an overnight response directly from Mike Blyth – designer of all Sling Aircraft models. The outer bracket just needs to be bent a bit more. So simple! That absolutely did not occur to me. Sadly, I’d ruined (by reaming) the inner and outer brackets for one aileron and needed new ones. TAF USA rushed me replacements. Fantastic service!

With new brackets in hand, I slightly increased the bends on the outer brackets for both ailerons, removed the old brackets from one of the ribs and riveted all of the sub-assemblies together. Beautiful! I can sleep again. No more worries thinking about how I would try to rationalize wobbly ailerons to myself, the DAR, my technical counselors and everyone else.

RH Flap – Ribs and Skin Assembly

With a now ample supply of 4,8mm rivets in both 15 and 10 mm lengths, finishing the lefthand flap could proceed. I did, however, have to make a decision about how to address hole misalignment involving the short ribs of the hing-rib subassemblies. The solution I chose was hole enlargement and larger 4mm rivets.

I’ve learned that perfect factory bends are required in order to get relaxed fit and freedom from structure twists and wags on the trailing edges of control surface skins. Knowing what to look for during inspection is essential. It had been months since I’d received the quick-build wing kit components and done my inspections. I was reasonably confident the skins were good, yet there was a huge sense of relief to see them actually fitting very nicely.

For the flaps and ailerons, it is common practice to initially rivet only the bottom surface of the skins to the ribs and brackets. The top surface and the row of rivets at the leading edge of the control surface remain free until they are fitted to and the trailing edges are perfectly aligned with the each other and the wing.

Seat Assembly

Assembly of the adjustable seats has been straightforward. They’re made up of 2 hinged panels that have a simple channel structure, sandwiched with identical skins – top and bottom. Inside the seat base is spring-loaded lever and cable mechanism for the slide locking pins. I opted to adapt some clevis pins instead of using the kit-supplied (large) solid rivets to assemble the linkages. The rivets proved difficult to deal with. It took a few days of pondering, but I eventually realized that custom fabrication of clevis pins were the way for me to go.

The only metal preparation I did was deburring and scuffing with a Scotch-Brite pad. I may or may not paint the seats as they’ll be almost entirely covered by the upholstery. The structures and panels fit perfectly and went together quickly. Sling 2 seat design has apparently changed over the years. The recently manufactured parts I had didn’t exactly match the construction manual, but understanding and dealing the differences was not difficult.

There are now at least 2 ways that the piano hinge can be mounted between the seat base and back, so that it can folded forward to access the luggage compartment area. The deciding factor seems to be how far beyond perpendicular to the seat base the seat back will naturally recline. The construction manual shows the hinge on the surfaces, riveted across step transitions where the side channels overlap the skins. The hinge, mounted to the back and bottom edges of the seat panels just seems more appropriate and allows for about 21 degrees backward and no restriction (until the panels meet) in the forward folding direction. That’s perfect. Seat recline angle is set by side-straps anchored to brackets at the edges of the seat panels.

The seats slide on rails mounted to the center fuselage. Clearances are pretty close, but appear to be perfectly aligned. Finding that helps to confirm that the center fuselage is built straight and square. Oh let me tell you that’s good news!

LH Flap – Prep and Assembly

As I near the end of dealing with fitting skins to structure, my confidence was pretty high that this would go well for the flaps (and eventually the ailerons). I’ve learned important lessons about how to inspect skins for proper fabrication – especially bends.

As I discovered from the building the empennage, lengthwise bends (folds) of the skins must be very close to perfect or else entire structure will be pulled out of true alignment when preparing or attempting to close up the final assembly.

There has proven to be considerable lead time in the process of securing replacement parts and the earlier a problem is discovered, the better. Almost immediately after the main QB kit was delivered in February, I looked over the flap and aileron skins – very carefully – and determined that they’d likely be acceptable.

Outdoors metal preparation with Alumiprep 33, Alodine 1201 and then rattle-can primer is much more convenient and pleasant with the warm summer weather. I opted to use NAPA 7220 gray self-etching primer, as none of the surfaces would be exposed. I had the stuff on-hand, but find that I don’t like it as well as the Rust-Oleum product, if for no other reason than the performance of the spray can. The any-angle can from Rust-Oleum is superior, even though I paid considerably more for the 7220 primer. (As I’ve mentioned before, if I do another build, I may well forgo alodine and primer altogether. With my budget and facilities it has been a huge time sink and perhaps not worth the effort. Even at my tender young age, I’ll be pushing up daisies before corrosion would be an issue with an untreated airframe.)

Due to a shortcoming with the listed shipping quantity in the wing kit packing list (KPL), I received only enough 4.8 x 15mm rivets to assemble one flap. I also found that one-size-fits-all — didn’t. It turns out that the overall thickness of one parts stack-up was very slightly less than the recommended grip length of the 15mm rivets. Even though there was no mention of this issue in the assembly instructions, it became obvious that a 10mm length would be better.

I ordered more rivets – both 15mm and 10mm lengths – twice. Once from TAF USA and then from a supplier of Gesipa rivets in UK. TAF sent a big batch of 10 and 15mm rivets to me overnight. Bravo! Great support effort! Thank you!! But, the rivets were not to my liking. They are some alternate brand, different design, slightly larger diameter (didn’t fit) and not nearly as well finished as the Gesipa product. I ordered the real deal, but it took 2 weeks to get them in-hand.

Rudder – Composite Tip and Beacon

Never underestimate the amount of procrastination required to get something done.

As usual, parts preparation takes most of the time. The fiberglass tip, as supplied in the kit, was a bit rough. There were quite a few voids and other imperfections in the layup. The trailing edge was too fat to fit nicely with the skin. Cutting and re-gluing with a bit of glass cloth and West 105 epoxy resolved that. The contour of the tip leading edge needed building up and shaping – requiring several passes. Epoxy takes hours to cure, so each step takes a day. Epoxy filler and wet-sandable primer attends similar time-sinking characteristics. Along the way, test fitting and match drilling of the mounting (rivet) holes was accomplished.

I didn’t really like the way the construction manual prescribed M4 rivnuts for the aluminum doubler that serves as the mounting base for the strobe. My concern is that rivnut installation might crush the fiberglass. I opted instead to make a new part that uses MK1000-06 anchor nuts and is riveted in place with AN426-3 solid flush rivets. Having the patience to eventually arrive at the decision to do this and then actually fabricating the mounting plate demanded all of the procrastination I could muster.

Copious foot-dragging precipitated the decisions about wiring and method of tip attachment. For some reason, I just didn’t want to shorten the (rather stiff) wire bundle of the Aveo Mini Max LED beacon. At the same time, I didn’t want the splice to be at or near the point where the wire exits through the bushing in the rib. A loop seemed the answer. And so it was. Final fitting of the tip to the rudder and pulling of the 3,2 x 8 mm rivets went well. I’d long struggled with the temptation of making the tip removable, à la Pascal Latten, by installing dozens of anchor plates, flush rivets and #4-40 screws, but my steadfast procrastination eventually paid off and the scales tipped in favor of just pulling rivets and being done with it.

Rivet Shortening – Apparently, Someone’s Got to Do It

There are several points in the build where short rivets are required. Sling Aircraft (TAF) has chosen to leave this task as an exercise for the builder, to adapt some from the ordinary ones supplied with the kit. Here I’m shortening 3,2 x 8mm rivets to about 5mm. These will be used to fasten the piano hinge and control horn to the elevator trim tab.

For some steps, I use a small box end wrench and a socket to provide support around the entire head of the rivet, as I drive the mandrel out or back in using a hammer. I use a cutoff-wheel in the Dremel Tool to trim the rivet body.

Closing Up The Rudder

With a good rudder skin, I was able to prepare, fit and secure the skin to the structure. Using techniques that I’ve learned from building similar components, the rudder went together smoothly. It’s a fine result.

There are still several tasks remaining to complete the rudder – fit the skin for the aero counter-balance, mount the internal counter-balance weight, run the strobe wire, fit the strobe to the rudder tip, and then finally, finishing the fiberglass and mounting of the rudder tip.

The great people at TAF USA worked hard to support me and promptly get me a rudder skin that I was satisfied with. The one that came with my empennage kit wasn’t bent properly on the trailing edge. It simply did not fit happily on the structure. A second skin was unfortunately damaged from moving about inside the crate during shipping. The third one was the charm.

It is crucial that the skins are fabricated perfectly. This plays a huge part in the resulting components being true. Precise fabrication is a critical element of the pre-punched and bent parts that allows them to assemble into a component that is uniform and free of twists, even without the use of jigs. The design of Sling aircraft absolutely depends upon the accurate fabrication of the parts. If yours aren’t right, work with TAF to get ones that are. Don’t mess around.