Quick-Build Kit – Delivery and Unloading

After nearly two months from the day she left the factory, my Sling 2 quick-build kit has found its way to my shop.

We were on the clock to get everything unloaded and to restore the container to a completely empty and clean condition. Heartfelt thanks to my good friend Charlie, my wife Mary Ann and our nephew Brandon for their indispensable assistance. We extracted the contents of the container with great care and had no issues of any kind. It all went perfectly. Nevertheless, the process certainly called for a good bit of thought and anticipation of the challenges – there are some, to be sure.

Everyone pitched in, including the truck driver. He was very intrigued by the whole affair and happily offered to help. He had no idea what was in the container and his eyes were almost bigger than mine when the seal was broken and the doors opened to reveal an airplane inside! Wow! How cool is that?!

The fuselage, two wing panels and four wooden crates were sequenced out of the container. Initially, the three biggest crates had to go in to the garage. The wings fit perfectly on my handy EAA stands. The fuselage is still perched (and bolted) on the shipping structure, just as it was inside the container. I did loosen the bolts holding the rear [wooden] shipping structure, just prior to extraction from the container. This was to allow some play between the framework and the empennage mounting points on the fuselage, where it had been tightly bolted during shipping. I didn’t want anything on the airframe to get stressed or bent as we moved the unwieldy payload from the container to the shop.

It’s all very exciting. The next steps are to complete parts inventory and build inspections.

Quick-Build Kit – Sea Container Shipping

I’ve been tracking the progress of my shipping container since it left the factory at Tedderfield Airpark, near Johannesburg, South Africa on December 19 – just hours before the factory closed for a 3 week holiday.

The container found its way aboard the Xin Ri Zhao and sailed from Durban on December 24, bound for Singapore. Upon arrival on January 6, the container transferred to the YM Upsurgence and departed on January 13. The Upsurgence made several port calls in Thailand, Vietnam and China. Finally, on January 26 YM Upsurgence departed Yantian, China. Next stop – Tacoma, Washington USA!

The last position update I was able to find for the ship, before it was out of touch from the free online tracking service was January 30 – abeam South Korea, west of Japan.

During the Pacific crossing – Yang Ming route PN1, I was able to determine – the ship’s ETA in Tacoma was being updated. It looked like it would enter the Strait of Juan de Fuca during daylight hours on February 10. I live just a mile or so from shore and was hopeful I’d be able to see YM Upsurgence sail past.

Up early on the Monday morning of the 10th, I checked my tracker and it was updating the ship’s position again. Just as I’d hoped to see, the ship was reportedly churning along just a few miles west of where I live. We drove ourselves to the near by Ediz Hook in Port Angles, WA and had a perfect view of the strait. There she was – the YM Upsurgence was just where the telemetry said she was.

It was a beautiful morning, sunshine poking through the clouds. The ship passed very close to us and it was exciting to see.

It’s been quite a long journey, but my Sling 2 quick-build should be in my shop very soon. I’m waiting for a call to learn the day.

Closing Up the Horizontal Stabilizer

Completing the horizontal stabilizer went smoothly and turned out beautifully – ultimately. The fine folks at TAF, now Sling Aircraft, were super-supportive. Without going into great detail, I’d found that the leading edge bends of both HS skins were not on centerline – root to tip. They just wouldn’t fit properly – imposing significant stress and twisting of the structure. Sling Aircraft stepped up to quickly provide replacement HS skins and that saved the day.

I’ve been impressed with how precisely the holes in the skins match with the assembled structure. I’ve made a very conscious effort to take advantage of the kit precision. I try to get the skins initially positioned with very few clecos. I want to be able to move the skin slightly, until I can see that nearly all of the holes in the skin and structure are concentrically aligned. Starting the fitment process with fewer clecos makes that easier – possible. In practice, I’ve found that good overall initial skin position, relative to the underlying structure, allows the great majority of rivets to drop in – effortlessly. Once I’ve got the skin in place, I can further anchor things down with alternate clecos and hand-inserted rivets for the entire HS assembly.

I used a vertical HS working orientation that allowed me to evaluate skin fitment on top and bottom surfaces at the same time. Once the skin was in place, very few rivet holes needed attention – and then, only the slightest dressing with a chucking reamer in my lithium battery-powered drill. With a relaxed final fit of skin, rivets and structure – I’ve seen that when the rivets are pulled, nothing really moves. The permanently fastened skins are remarkably free of surface deviations. I’m quite pleased and anticipating that the contours of the final painted surfaces will be excellent.

HS Structure Assembly

The horizontal stabilizer assembly started by fitting together 2 sections of rear spar channel with the center section sandwiched by doubler plates – front and back. The result is over 8ft long. Appropriately sized cleco fasteners temporarily hold the parts together. A laser level helps to confirm that the channel is true – straight and free of twist.

The rear channel components were permanently fastened with a combination of 4.0 x 10mm and 3.2 x 8mm pulled rivets. Assembly continued with ribs joining with the front spar channel and clecos hold the front components as they are fitted and fastened in a similar fashion as the rear.

I’ve found that when 2 or 3 parts are sandwiched together with many rivets, it can be a little tricky to get a relaxed fit. Many overlapping holes must align precisely, in order for the rivet shanks to fit through all of the layers easily. I try to take whatever time is necessary to get the best concentric alignment of as many holes as possible, so that little or no reaming is necessary. The kit parts are punched very precisely and overlapping holes will likely line up, given the chance.

My assembly process starts with just a few clecos, while test fitting rivet shanks in many or most of the holes. Then I loosen and reset those few clecos until there is good natural alignment of as many holes as can reasonably be achieved. Eventually, a majority of the holes will line up perfectly, leaving only a very few that may need a little reaming to easily accept a rivet. Straight-shank chucking reamers seem to do a great job. Use the exactly right sizes. #30 and #20 are common.

The HS structure, without skins, is somewhat delicate. I’ve used a couple of stiffeners, from a Vans Aircraft workshop (skills practice) kit, clamped to the innermost HS ribs to provide support while the entire structure is riveted.

The HS structure is symmetrical. At some point, a decision must be made as to which side will be the top and the other side, therefore, the bottom. For my HS, continuity of how the rib flanges relate to the spar channels has turned out to be somewhat better on one side than the other. The side with the best potential for smooth skin support was chosen to be the top. I used a black permanent marker to make indications inside the front spar channel, where they can be seen during the various assembly phases.

With the HS top chosen, left and right HS panels become apparent. 2 Heyco 0.375in snap-bushings have been placed in the rear forming holes of the 2 innermost left-side ribs and anchored with some dabs of gray RTV. The nylon snap bushings are intended to protect the pitch trim servo wire (cable) as it passes through the ribs. I’ve elected to use nylon snap bushings instead of the rubber grommets supplied with the kit.

EAA Wing Stand – Construction

It was time to get an EAA wing stand built. The container with my quick-build kit is on a ship, heading my way. It’s going to be sailing in to Tacoma, WA on or about February 5. A few days after that, I’ll have a shop full of Sling 2 airplane sections – wings, fuel tanks and fuselage. I’ve got to have a place to store both wing panels.

My good friend Charlie used a rainy day to help me. He’s been working hard, building his new home. I enjoy that he lets me help him sometimes. It was nice to have his craftsman expertise and company for my project.

The new portable propane heater can be seen in a couple of the photos.

Horizontal Stabilizer – Prep and Prime

I’ve temporarily set aside the rudder and moved on to preparing the parts for the horizontal stabilizer (HS), after finding a poorly formed rudder hinge bracket, about a week before TAF folks returned from holiday break on January 13. Once they were back and after a few emails and phone calls – TAF (USA) has a new part on the way to me.

The preparation processes for the HS are the same as I’ve detailed for the rudder (RD). Several days of indoor and outdoor work have all the parts ready for assembly.

We got some snow and for a couple of days, it got too cold in the shop for painting. Inside the shop temperature dropped to 42 degrees F – overnight. I really needed more than my electric 1500W ceramic and 1200W infrared heaters.

I made a good deal a small portable propane heater and was able to continue with priming all of the HS parts. In the morning, I can bring the shop up to 60 degrees F in just a few minutes.

Rudder – Prep and Prime

Preparing the rudder parts during the last few days of December and on into the first week of January 2020, involved increasingly familiar processes.

Inside the shop, deburring of all edges and holes was done with my Avery Speed Deburr tool and Scotch-Brite C/P 7A wheel. Light scuffing with a fine (red) Scotch-Brite pad seems to help make subsequent chemical treatments more effective. Initial parts degreasing was done by wiping with a splash of acetone on a paper towel.

Outside the shop, degreasing continued with Extreme Simple Green Aircraft Cleaner, using a soft clean rag, followed by a water rinse from the garden hose. It’s winter on the Olympic Peninsula and my well water is very – VERY – cold. My hands, wearing only thin nitrile gloves, are almost frozen. A few minutes in the shop to dry the parts and then it’s back outside to apply Alumiprep 33 with a silicone basting brush and freezing hands, while hovering over a black plastic mortar tub. Rinse, dry and repeat – this time with Alodine 1201.

It’s cold and it takes until the afternoon to get the shop inside air temperature above 50 degrees F. It’s something of a hassle to run my paint booth vent fan, as there are some gaps that let cold air in. Without the venting, I quickly and lightly spray just a few parts per day – often only one side. Then I have to abandon the shop until the next morning. It took several days to prime all of the rudder parts.

For me, degreasing and chemical treatments take hours and hours – most of it outdoors. I’m trying to use absolutely minimal amounts of material, not make a mess, and get satisfactory results. I just can’t afford to make or deal with dipping tanks. I tried to save time by not etching with Alumiprep. Unfortunately, I’ve found that even with thorough degreasing, there were places where the Alodine instantly sheeted off un-etched aluminum surface. Those parts got re-scuffed, etched and then re-treated with Alodine. I’ve tried not scuffing and short-cutting other steps – only to find that results tend to reflect the level effort that I put in.

The parts quality of the TAF Sling 2 kit is frankly remarkable – excellent in IMO. I could probably get away with little to no deburring – certainly much less than I’ve been doing. Priming is truly in the realm of optional effort. I’m taking it slow and having fun doing it all.

Somewhere on the TAF website there is a recommendation to start your building journey by ordering only the empennage kit and putting it together over a weekend – just to see what you’re in for. Maybe someone could take the parts out of the box – rivet them together over a couple of days – and end up with serviceable tail feathers. I suppose it’s mechanically possible, but highly unlikely, even for an experienced kit builder – if they haven’t previously built the empennage for some model of a Sling aircraft.

I believe a significant limiting factor of how fast you can go – is missing information detail. There are certainly a few pitfalls that only careful consideration will allow you to avoid. It takes time to understand. Achieving correct part orientation, relaxed fit and knowing exactly where and where not to rivet – is very important. If you get ahead of yourself, it’s going to take considerably more time, effort and cost for rework. Be careful. Strive to get things right on the first go.

Closing Up the Vertical Stabilizer

Final preparation, fitting and riveting of the skin to the VS structure was done today. Everything went together beautifully. I’d done extensive research, detailed review and careful pre-fitting to be certain that I had confidence in a process that would – and did – produce my intended result.

First EAA Tech Counselor Visit

I was privileged to have a visit from a fellow EAA Chapter 430 member and Technical Counselor – Harry Cook. Together we reviewed my build environment and progress. I was pleased to receive positive feedback relative to my understanding of what I’m doing and workmanship involving the vertical stabilizer to the point immediately prior to covering.

VS Structure, Antenna and Cables

Over a couple of sessions, I’ve installed additional m4 rivnuts, permanently riveted together the VS structure and mounted the VOR antenna base to Rib 004 – previously reinforced with its doubler.

Edge grommets have been applied to lightening holes of the rear channel and rib 003. I’ve elected to replace the factory-supplied rubber grommets with Heyco 0.375in nylon snap-bushings – to protect the coax and strobe light wiring where it passes through the VS structure. I enlarged the forming holes to 9.5mm, as directed. The forming holes at the front of ribs 002 and 003 were similarly enlarged to accommodate the bushings for my (optional, build-specific) VOR antenna coax cable. Routing the coax near the front of the structure is intended to keep the cable clear of the ‘works’ for the elevator.

After a bit of experimentation with my newly acquired rotary coax stripper, I installed the Amphenol BNC male connector to the RG-400 coax cable. As mentioned in a earlier post, I’ve decided to use M27500-20TG4T14 for the strobe – rather than the factory-supplied PVC jacketed wire. Some heat shrink tubing bulks up the cables as they pass through the bushings and the edge grommets. A few dollops of aluminum-compatable gasket-forming RTV locks down the bushings and the cables to the structure. I don’t want any movement from vibration.