Iterate and Repeat

It’s important to keep making progress and not get bogged down on any one thing – like wingtips. Oh those wingtips! Will they ever be done?

Parachute, flaps, ailerons, seats, control sticks were all calling for attention. It was well worth spending time on to those things. Circle back to composite work later.

Much of the work is pretty straightforward. Other items require a bit of faith and commitment – like finalizing the riveting of ailerons and flaps closed, for example. Getting the control surfaces locked down with rivets and while maintaining alignment with the wing, is both science and art. I think maybe there’s a good bit of luck involved too.

Chopping off the control sticks is somewhat a leap of faith. The KAI doesn’t say to do that, but the Tosten CS-8 grips need to be in the right spot. They’re different than the push-on type that is typical for Sling 2s. You just gotta do what you gotta do.

Figuring out what to do with the parachute cables has been an exercise. There is almost no guidance from the factory. I asked them directly and they admitted that the factory rarely installs parachutes in Sling 2s they build there, and haven’t for a long time. There’s an old video. I’ve watched it repeatedly.

The one actual attempted in-flight deployment of a parachute-equipped Sling 2, ended in failure – loss of the aircraft. Fortunately, that was during factory testing and the pilots had their own parachutes – which they needed. That sad outcome reportedly resulted in consultation with the Stratos 07 parachute company. Changes were made and presumably incorporated in my kit. It is, nevertheless, clear to me that a builder could easily insure a complete tangle of the parachute and cables during a deployment. I’ve studied photos of several other Sling 2 parachute installations and identified things I thought could be problematic. I’ve tried dress and secure the cables to allow the best fighting chance for the parachute canopy, shrouds and airframe-cables to deploy without hindrance or entanglement. My guess is probably as good as anybody’s. Maybe better.

The weather is getting rather nice. Competing interests punctuate my days.

Some of This and Some of That

There’s lots of composite work to start and finish – and no shortage of details that need attention in the center and forward fuselage. It’s time to fit wheel fairings and prepare the compartment for the whole-aircraft ballistic parachute. The wingtips are getting closer. What a job those have been.

Under the Cowl – Work Goes On

With a bit of study and suitable periods of procrastination, I was able to rework the newer of the cabin heat shroud parts to fit the muffler. Knowledge and experience gleaned from my work with the heat valve duct was transferred to the outlet duct for the muffler shroud.

I got a start on the oil hoses and fittings. I’ve elected not to use any of the hose and a number of the fittings supplied with the FFW kit for the oil system. Rather than struggle with a vice to clamp fittings and attempting to push the hose onto the barbs – by hand – I picked up a Koul Tool. Not cheap, but it works ever so nicely – if, that is, your 90 and 45 degree fittings have a shoulder. Some of the FFW kit fittings don’t have a shoulder. I’ve replaced those with Aeroquip AQP AN8 fittings. I’ve also gone with matching high temp Aeroquip oil hose. All very nice stuff. Each hose I’m making has swivel fittings at both ends to make an entire system of modular components. Admittedly, I’ve deviated slightly from the plans and supplied parts here, but in a good way. I’m building as experimental in the USA, so I can tweak some things without a big hassle.

Now seemed like a good time to get the radiator and oil cooler secured to the lower cowl with the factory-supplied Sling 2-specific brackets. I’m using Camlocs instead of the kit-supplied Dzus fittings. They’re just better.

Cowl fitting continues, this time with a minimal cutout to clear the exhaust pipe. Eventually, I’ll be bonding reflective fiberglass heat shield to the inside of the cowling where needed.

Windscreen Bonding

Bonding the windscreen is a critical milestone. It isn’t nearly as glamorous as mounting the engine or powering up the avionics, but it means a great deal to the overall aircraft structure and final outcome of the project. It’s a make or break moment.

Surface preparation of the bonding surfaces is very important. Various special primers promote adhesion. Accurately locating the about-to-be-bonded windscreen while things are battered with jet-black SikaFlex polyurethane marine adhesive, onto the frame and fuselage, is aided by reference holes and locating pins. Masking and protecting areas where adhesive does not belong, makes it just possible to get the assembly together without too much of a mess. Gentle, even clamping keeps the windscreen in place while the adhesive cures.

Minimum working temperature for the adhesive is 50ºF. At that temperature it will take up to 12 days to cure and it will be all I can do to keep my workshop warm enough though the winter days, here in Pacific Northwest Washington. Time will tell.

All in all, it seems like I’ve pulled it off! Looks like a good fit, no Plexiglass cracks and plenty of nice adhesive in the right places. Now I just hold my breath for a couple of weeks. Whew! Glad to have this step in my rearview mirror. What a relief.

Windscreen – Trim to Fit

Having put this off as long as I could, I’ve summoned the courage to trim the windscreen until it fits. I absolutely do not want to crack it and I cannot afford to over-trim. It has to be done, just so. If ever there was a time to apply, measure twice, cut once – this is it!

Along the way, I take comfort in and from small stress-reducing distractions. Testing out my fancy new lithium battery charger yields a few moments to gather myself. The charger has a feature that can supply up to 10A of current to power the avionics and allow for extended sessions of testing, configuration and familiarization – ok, play! There’s a lot to learn and it’s going to take quite a bit of play time.

Canopy Latch and Exhaust System

The canopy latch is inset within an oval area that must be carved out of the top front of the canopy plexiglass and underlying composite frame and held in place with blind M5 rivnuts and screws. Let’s just say that this is a challenging and nerve racking set of tasks. And – that’s a major understatement. But, with patience and a good bit of careful work with my trusty Dremel tool, I was able to achieve what I deem, at this point anyway, a satisfactory result.

The latch mechanism is an over-center affair with a hook engaging a latch pin that mounts to the top underside of windscreen support arch. Four 3,2 x 10mm CSK rivets attach the pin and it’s mounting plate to the arch, along with whatever additional security is afforded by a dollop of JB Weld epoxy. Where exactly to position the pin is an exercise left entirely to the discretion of the builder. Good luck with that.

I think by the time I get the weather seal in place, the latch will pull the canopy closed – firmly and without gaps. We’ll see. All of this latch fitment has happened before having the windscreen and support arch bonded in their forever positions. I’ve got my fingers crossed. Time will tell.

The exhaust system has been languishing in a box and it seemed a good time to see how well (if) it fits with the engine and airframe. It looks… maybe not so bad. Good!

There’s going to be some work needed to get the cabin heat muffler shroud assembled, because I don’t have a part that actually fits. So far, I’ve gotten 2 different parts (and part numbers) from the factory, but neither part matches the mounting rings on muffler. Argh. I’ll have to adapt and/or fabricate something. But, at least it seems the exhaust pipes and muffler do fit. Hooray for that.

Windscreen and Canopy – Initial Fit

Rivets, wires and avionics are friendly territory for me, compared to where I’m headed now. Fitting the windscreen and getting it bonded in position are tasks I’ve been apprehensive about – extremely apprehensive.

Manipulating clear acrylic sheet – Plexiglass and Perspex are brand names – that’s been molded into compound curves of unusual size, is just asking for trouble. I don’t like trouble. Dealing with this stuff is tricky, all by itself. Don’t even get me started about cutting or drilling holes in it. Eventually, I’m going to add sticky gooey pitch black marine adhesive caulk to the mix. That could easily lead to – yes, you guessed it – super trouble!

The time has come. I can’t avoid it any longer.

Because I opted for a factory quick-build kit, it came with the main canopy already trimmed and bonded to its painted composite frame. That’s fortunate because it may well have spared my frazzled nerves just enough to be able to deal with the windscreen.

The initial canopy placement seemed easy enough. Screw holes in the frame aligned with the ones in the slide assemblies. Countersinking of the frame will be needed to correspond with the short M8 stainless steel CSK mounting screws.

The arched windscreen support frame was fitted and match-drilled to align with M5 rivnuts that were installed at the factory. I made cardboard templates for left and right sides because they’re different. (They shouldn’t be – but that’s how the factory built it.)

The trial fit reveals that the rear edge of the windscreen will have to be cut back by at least 4 or 5 cm to align with the arched support frame. The lower rear edges (corners) of the plexiglass will just barely be under the fuselage top skin when it’s riveted in place. Precise positioning of the windscreen is going to be extremely important to avoid any unsightly gaps between the aluminum skin and the plexiglass.

A latch mechanism has to be fitted into the canopy. I inventoried the latch parts when I received them, but I could not have detected that the supplied spring was not correctly formed. I checked with the factory and confirmed the situation. They’re going to send me a replacement spring.

Windscreen cutting, drilling and bonding comes next.

Glareshield/Dash and Instrument Panel

I’ve been working hard to finalize work behind the instrument panel before I permanently close up the area and bond the windscreen in place. Once that happens, any work behind the panel will have to be done though the openings where the GDU 460 displays go. I could possibly remove the whole panel from the dash, but it’s really and truly so nestled into place that I don’t want to disturb it. Disconnecting it, reconnecting it, pulling it out and fitting it back seems more challenging than I want to contemplate — or actually deal with. Get everything right before it all gets locked down – that’s the plan.

Instrument Panel Powered Up with Engine Information System (EIS) Displayed

The fuselage top-skin on my factory QB came partially riveted in place. I removed it. I also dimpled the skin and the rib to accept 3,2 x 10mm countersunk rivets. The parachute compartment cover skins will eventually go over the countersunk rivets, to be held in place by just a few domed rivets and slotted “fingers” at the edges of the cover skins. I’ve put the top skin back into position with clecos. The dash has been positioned and match drilled with the skin to accept 3,2 x 8 mm domed rivets. The lip of the dash is bonded to the skin with very sticky double-sided tape – supplied with the kit. The next step is to pull the rivets on the lip of the dash.

Once the dash lip is riveted, it’ll be time to fit the windscreen. The windscreen has to transition from outside to inside. The dash does the same thing. The windscreen needs to go between the dash and the skin at the edges. It’s going to be tight. I probably won’t rivet the skin until, or even perhaps after, I do the bonding process for the windscreen with Sikaflex adhesive.

Before bonding, the windscreen and support arch must be fitted with the canopy. The windscreen will almost certainly need to be trimmed along the rear edge of the arch. It’s all going to be very delicate and require great care. If I crack or otherwise damage the plexiglass windscreen it would likely be many months before I could get another one.

At this point, I’ve managed to get the panel and dash positioned and connected to the harness. The wiring looks crazy. Ok, it is crazy. But, it’s pretty much the nature of the beast. This is a custom plug-n-play harness that’s essentially one piece. I laid it into the CF like a sleeping octopus. There’s extra craziness because of how much stuff I’ve got to connect. I think the only way to make it any neater would have required building the harness on the airplane. That just couldn’t happen. As it is, I’ve got all of the various “tentacles” dressed and secured about as naturally and as stress free as they can be. I’m very happy with it, even if it looks rather wild. There’s a lot there.

I’m delighted to report that once again, the panel has life. This time, the Engine Information System (EIS) is active. The sensors seem to be working. There are still things that aren’t connected yet. But for the things that are, it all looks great and my confidence is high.

So far, working the flap control, hearing the actuator run and seeing the indicator change is my favorite thing. The VP-X Pro and the G3X Touch integration seem nice. Working the radio frequencies and the remote audio panel is very cool. Both radios transmit and receive. The headset jacks are working, but I haven’t been able to try the LEMO connectors yet. Navigation, position and strobe lights work. Cabin lighting works. Oh so nice.

I’ve got to say, it’s more than just a little exciting. Build on!