Tag Archives: fit

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!

CF – Upholstery, Painting & Wiring

Upholstery work takes a bit of courage and determination – at least for me it does. A big part of the work involves trimming the vinyl leatherette-like covering to fit the center console and then bonding pieces of material to some rather sizable and awkwardly shaped panels – everything is frighteningly sticky with spray adhesive.

I got through it and it all seems to look rather nice. I can’t say I’d do it the same way again, but at the same time, I don’t exactly know what I’d have done differently. You’ve just got to do the best you can.

All of the center upholstery pieces came in a kit, along with fiberglass-backed side panels, seat and seat back cushions, and carpet panels for the floor and luggage compartment. The seats cushions are covered with genuine leather and stitched by professionals. I got to choose the colors. Methinks it’s going to be a rather sporty and plush setup for this little 2-seater. Oh well! What can I say?

Once the rear portion of the center console was covered, it seemed a good time to put it into position. The inside seatbelts pass through, so it was time to assemble those to their anchors. I haven’t riveted the rear console yet – just clecos for now.

The front console panels have 3 sections. The top panel of the LH side is removable for inspections, as are 4 other square panels – 2 of which are covered with the vinyl. The 2 forward most panels are painted, along with 2 panels for the baggage area.

Bonding the covering to the RH side panel was the biggest challenge. The section of material was large enough to be unwieldy. Working conditions inside the CF were awkward. I did, however, manage to lay in the material and get it satisfactorily positioned. I’m happy to have that task in my rearview mirror.

This seemed a good time to complete more of the wire connections to the rear fuselage (RF) section for the tail beacon and electric pitch trim servo. The PVC jacketed wires in the RF were routed and secured as part of the factory quick-build (QB). My custom avionics harness was provided with “pigtail” connectors. I connected the wires of the pigtail to the fuselage wires with Raychem D-436 series butt splice connectors. The connectors are a bit expensive and a special crimp tool is required. I believe the resulting connections are more than satisfactory. As usual, I insulate and protect the connections and secure them from movement.

FFW and CF Tasks

While the engine mount is off, I’m getting firewall forward and center fuselage tasks done that would be more challenging to do later.

I’m not keen about how the factory seems to expect the stiff-wire push-pull cable to go from the instrument panel, through the firewall and then to the heat box on the firewall. As with other firewall penetrations, I’m not content to just stuff the cable through the firewall with a grommet. I’m also not going to settle for having the cable penetrate the firewall at the absurd angle needed to even have a chance of getting to and working the heater box vane. Instead, I’ve designed and fabricated a jack-shaft bellcrank arrangement as an alternative. I’m still going to use the factory-supplied cable assembly – straight through the firewall, a bowden cable clamp and then attaching the wire to a nylon control horn. Another control horn, at the other end of a shaft, translates the push-pull control motion approximately 90 degrees – to be in line with the action needed to work the arm on the heater box vane. I made a couple of brackets out of aluminum angle and mounted the mechanism on the firewall.

Since my QB airframe was built and delivered, the factory has rethought how and where the ELT antenna goes – to just ahead of the vertical stabilizer. It’s too late for me. The structure was changed to accomodate a new mounting bracket and I’m not going to attempt a retrofit. The old location for the ELT antenna was inside the cabin. I’ve designed and fabricated a bracket to mount the antenna inside, just ahead of the rollover structure on the RH side of the fuselage.

Now that I’ve got my hands on the main battery – EarthX ETX 900, 16AH, LiFePo4 – I’ve been able to build and connect 4 AWG cables from the battery terminals to the 12V contactor and to the airframe ground lug. The high current cables are short and tidy.

I’ve had to acquire [standard AN] replacement hardware for re-mounting the engine mount, but this time, along with the front cables for the ballistic parachute. Longer bolts are needed to pass through the heavy cable-attachment tangs. Initially, I didn’t have the tangs. I eventually got those, along with a bunch of other factory parts that should have shipped with the main kit. The cables and the engine mount are on! Good deal.

With the engine mount in place, I’ve mounted the nose gear strut. Some months ago I accomplished fitting of the bushings, retainers and bolts. That made is super easy to just bolt it all together and connect the push-pull rods to the rudder pedals linkage.

I’m still waiting to put the wheels on because the fuselage is that much lower to the ground, making the inside of the center fuselage (CF) somewhat more accessible than it would be with it higher. I’m taking advantage of the easier access while I dress and secure the wiring and prepare parts of the control linkages and autopilot roll servo.

I’m pretty happy with my approach to securing wire harness bundles as they pass through various openings in the CF structure. I found a source for AN743-13 aluminum angle brackets. These brackets are just right for supporting insulated (Adel) clamps around the wire bundles. It was very challenging to drill holes and rivet the brackets at this late stage of the build. I didn’t have the luxury of doing it while the structure was open, sitting on the bench. Nevertheless, the brackets and clamps are in place and they’re pretty nice. I’ve also put some edge grommet in a few places, just for peace of mind.

I’ve previously tested the flap actuator with temporary connections, but now I’ve made the connections permanent with crimped butt-connectors and various layers of insulation and protective armoring. I’ve done checks to insure that the wiring will be clear of moving mechanisms. It all looks very promising and I’m feeling happy about the work.

Another thing I’m pretty happy about was my purchase of a simple jig for drilling nice cross-holes in the control tubes. Beautiful!

IBBS Mounting

The navigation avionics and engine management systems each have a TCW Integrated Battery Backup System (IBBS). The backup systems provide essential power in the event that one or both alternators in the Rotax 912iS engine should fail. There are 2 battery power units that have to be mounted someplace. I’ve found a spot on the fuselage rib, behind the parachute compartment that is within comfortable reach of the associated wiring harness connectors.

I thought that the batteries could use more support than they would get, were they attached directly to the rib. I designed and fabricated doubler plates to reinforce the rib. The batteries are fastened to the doublers.

I’ve had to consider that one day the battery units will have to be replaced. It won’t be easy, but I will be able to get to them from the front, after I remove the pilot side display and the remote LRUs and vertical rack that sit behind it.

LRU Rack Fit and Mounting

Most of the remotely mounted avionics will be behind the instrument panel, on a custom designed and fabricated rack. Each Line Replaceable Unit (LRU) has a specific position on the rack and the harness is custom tailored to precisely reach and connect all of the units together, along with all of the other electrical systems in the aircraft.

I elected to have the harness and panel professionally designed and fabricated by Midwest Panel Builders in Lapeer, Michigan — specifically for my Sling 2 and its extensive Garmin G3X advanced IFR avionics suite. While I might have been able to manage the panel and wiring for a modest VFR setup, there was no way I was going to attempt it for this project.

Even with the custom-made harness, rack and panel there is still plenty of fitting and integration for me to do. This is no paint-by-numbers ELSA project. It’s full-on experimental amateur-built — all the way. I can’t wait to begin training for my IFR rating in this aircraft.

The LRU rack is a replacement for the one I received back in April. The original rack was the first of an all new design and needed several refinements.

The new rack needed to be fitted and the mounting points established. The center portion of the rack needed support. I designed and fabricated a bracket. Everything fits nicely.

Wingtips – More Rework

After a gallant effort on the original RH wingtip, I ordered and received a replacement RH wingtip. The new part still had too much length and thickness at the trailing edge, but the workmanship of the layup was much improved and it had noticeably better overall shape. It has still taken lots of work to get the new RH tip to fit. But, it’s coming along and it’s going to work out well.

The LH tip is proving to be huge headache. Despite extensive rework, it’s now clear that the LH wingtip isn’t close enough to the proper cross section to fit and it would take extraordinary effort to get it in the ballpark.

Just like the RH wingtip, the length of the LH part at trailing edge is too long and the trailing edge profile (taper) is too thick to fit the trailing edge wing skin. But the kicker is the overall height. It’s just too narrow – top to bottom. It’s almost 2 cm short, at the widest point.

Trying to stretch the height of the LH tip requires too much force. The LH wingtip has no imbedded reinforcement strip on the bottom edge. The top reinforcement is out of position. Without proper stiffness, the tendency for waviness between the rivet holes would be profound.

To continue with the original LH wingtip, I’d have to section the part and almost re-manufacture it. I’ve decided that it’s much too much time and effort, although I have seen one other builder go to such lengths and spent over 130 hours on just trying to get his wingtips to fit. I’m at more than 40 hours on wingtips and I’m going to cut my losses and get a better baseline part.

I went ahead and negotiated a new LH wingtip from the factory, as I did for the RH side. They’ve kindly agreed to send me one. Kudos to Sling Aircraft for standing by their product. Stay tuned.

VS – Trial Fit

One things leads to another. A question about the factory-installed rudder cables got me started down the road of test-fitting the vertical stabilizer. I was very pleased to find that it was easy to do and the fit appears to be excellent.

I hadn’t really expected to do this step just now. But, in order to evaluate much about the rudder cables, the entire control mechanism for the rudder and steerable nose-wheel needs to in place and adjusted. I learned this during a customer support exchange with Sling Aircraft’s Jean d’Assonville. I’d called him because I was concerned that the rudder cables may have been installed improperly during factory the quick-build of my fuselage. Jean assured me that it was very unlikely that the cables were wrong.

I was wondering because the KAI talks about one cable being slightly longer than the other. Somehow they seemed to be the other way around. Jean said that the only way to properly evaluate the setup would be to assemble everything. It only takes 15 minutes, he tells me! LOL. But, he really meant it!

It’s going to take me hours and hours, over days and days, to get the entire rudder control mechanism in place. That’s not only because I’m slow and plodding, but also because I’m not ready to install the nose-wheel yet. It’ll all just have to wait until I get the avionics rack, LRU’s and harness in place while the wheels are off and the fuselage is low and as easily accessible as it can be.

So then. I still don’t know for certain that the rudder cables are installed properly. But, I did get inspired to get the VS out from storage in the house and get it fitted on the fuselage. Technically, that’s progress! The nice fit between the fuselage and vertical stabilizer is satisfying too.

Custom Cowl Mounting Strips – Trial Fit

The upgraded cowling strips fit remarkably well. Clecos are in many of the holes at this point and that’s without having to drill anything out. Ultimately, holes will need to be lightly ‘dressed’ with a #30 reamer. This will allow the rivets be positioned and set easily in the 3 and 4 layer stack-up of parts without a fight. The good news is, it’s all a pretty decent situation to begin with.

Earlier I did a little priming of the underside and edges of fastening tabs for the galvanized steel firewall. It’s winter cold outside, and I can’t really do spray painting just now. It was a small hidden area so I brushed on the gray 2-part epoxy primer. It took several days to cure fully. I’ll probably paint the entire firewall, mostly for aesthetics, when the weather warms a bit.

Care will be needed to address some gaps between layers of the parts stack-up. I believe that by removing most (or all) of the clecos across the top edge of the firewall and then riveting around the corner, fitting and pulling one rivet at a time while the pieces are free to move and pull together will allow the gap to close where the rivet is pulled.

I’m planning to install the ballistic parachute and that means I’ll be needing to accomplish some dimpling for most of the holes across the top of CF-RIB-003 and actual countersinking with a 120 deg pilot-cutter, along the top edge reinforcing pieces of the firewall, to accept 3,2 x 8 mm countersunk rivets. More on that in a future installment.

We’ll see how it all goes. Warmer days are ahead.

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.