Month: January 2022

Avionics / Magnetometer / Misc

Avionics rack and wiring harness install

Got started on fitting the rack today. Doubler panel. The latest offering (Jan 2022) from MWPB splits the harness into two. One for the airframe and one for the equipment rack behind the dash. It is quite overwhelming figuring out where the tentacles of these wiring harnesses go at first. Unlike the rest of the Sling kits where you have many diagrams and the parts down to every last rivet and grommet. The MWPB panel and harness no install instructions or layout diagrams other than Facebook videos. You are also on your own sourcing any extra clams and tie wraps. Two things were needed to get started. Where do the ground and power busses mount, and which wires need to go through the firewall (so that I can get that done and fix the top skin). Once I got my bearings, it become s easier. The rack behind the dash has a sub-rack that is designed to mount an audio panel transponder and second com radio. It’s white heavy (820 g) and made from 2mm aluminium. I also was concerned about accessibility to service the audio [panel after the windscreen is fitted. I could not see how it could be removed. (Whereas the transponder can be removed with screws from below). I decided to remove the sub-rack to save weight and improve serviceability.

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Avionics

Fitting the panel to dashboard

Lots of work with the Dremmel was required on my dash to open up the fibreglass/leather. Slow messy job. There is very little space below the main switches on the left. Fitted rivnuts with epoxy glue. Used pilot countersink to get an accurate position. All line up nicely. Had to remove the leather at the end to make a good fit without warping the panel.

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Misc

Seat belts

Test fitted the seat belts to see if I have all the right bits. KAI is not clear. Emailed with factory, updated the rivets to 4.8 mm on the front seat belt brackets. Torqued the belt clamp AN4 bolts to 7 Nm. Will fit the belts later when nearer completion. At least I know how they all go for now.

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Canopy / Doors

Canopy and Doors

I have QB with canopy factory installed. However, there is still some tricky work to do on the door composites, so I removed them to work on. The main door latch mechanism has a complex shape composite fibreglass cover over it. This needs to be cut and machined to fit the door lever and latches. It’s a firm snap-on fit plus two M4 rivnuts. It took quite a bit of work (2 hours per door) with the Dremmel and filing the mouldings to get a nice fit. Worth spending some time on. It’s very visible and used every flight. I also adjusted the latch mechanism to run smoothly and then added some medium strength Loctite to the connecting rod and latch pivot nut. The KAI shows an optional adjustment hole for the two main pivot points (to enable tightening them up if they become loose). Having seen how tricky it is to get this moulding on and off, I don’t want to have to reopen it after it’s painted, for sure it will get very scratched. So I added the adjustment holes. Following info in case, I need to remove the mouldings in future. Here’s the way I did it. Remove 2 x M4 button head screws, then. Bent the strike plates per instructions. Not clear why they are labelled right and left they seem identical. KAI says shiny side inwards, but my plates were identical on both sides.

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Avionics / Misc

Static Ports

The factory has moved the static ports to 25 mm in front of the Nacca duct. (Used to be in the rear fuselage). The ports now require a shield to be riveted around them. A kit is on its way to me. Although not essential, I wanted to get the ports installed before the top skin is fixed as it’s easier. Unfortunately the rear of the static port clashes with the Nacca duct, so I machined a little of the Nacca duct away and filed the static port to fit.

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Canopy / Top skin

Installing the top skin

Using Evan Byne video guidance affixed the top skin. The composite seemed to need twisting a little to get it to fit evenly on both sides. Using the hole finder tool, the trick is to align the firewall flanges to be flush with the front of the top skin. Then drill the composite. Made a test fit of the dashboard. Not a bad fit but some gaps on top left side. Sourcing a suitable 120-degree pilot/countersink tool for the top skin (and empennage) composite proved tricky in the UK. I found one from a company on the south coast (BSA Regal Cutting Tools) that made one up to the size I needed. 1/8 inch pilot with 5/16 head (3.2 mm x 7.9 mm) that should suit the 3.2 and 4mm countersunk rivets. KAI calls for painting the composite black.

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Misc

Getting ready for closing front composite

The arrival of my avionics panel is imminent and I will need to fit the LRU rack. To do so ideally the front composite needs to be in place to secure the avionics first rib. With the front composite and LRU in place, access to the heater, fuel pipes and rudder pedals will be difficult. So finished off the rudder pedal riveting to the floor and pedal rivet, ensuring free movement in the plastic bushes (I had earlier filed the lock plates and bushes for a smooth movement). Rudder pedal assembly install is quite difficult in a QB, as you have poor access. Attached the rudder cables and steering pushrods. Torqued nyloc nuts AN3 to 3 Nm and AN4 to 8 Nm and marked. Fitted booster pump. Assembled so that it can be removed with its attached hoses and check valve as one. Likely the SAE R9 fuel hose will need replacement when needed on condition in 5 to 10 years time. Fitted heater temperature control wire. (removed 200 mm from the 1m Bowden tube). Per Evans video. Fitted heating hose, ensured hose clamps well seated. Would be fiddly to fix later. I am using the large ‘Rotax’ firewall hole for all electrical connections. Because the large Rotax connectors have to pass through, there’s a large hole to be filled. I remade the kit ‘horse shoe’ plates to a smaller diameter (34 mm to close up the hole. The remaining gaps to be filled with high temp RTV.

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Empennage / Horizontal Stabiliser

Horizontal Stabiliser

Extra countersinking in the forward spar is needed in my case, to accommodate the 8 extra dimples I made in the skin (top surface only). Many do not rivet locations. I needed to take great care to rivet. Awaiting for my main spar so paused for the moment. 5 Feb 2022 missing empennage parts arrived so I could finish the skeleton with Andrew’s assistance. Wed 9th Feb 2022 Spent a lot of time with laser level getting the HS absolutely straight (no twist). Level the table to start with. Various advice from other builders. partially cleco one side, level, then cleco the other side. Add more clecoes, check, turn, check, check again. Rivet from the centre outwards along the main spars, check, check, check all the way. Seems to be very hard to do accurately without a laser level. (9 hrs to do the HS alignment and skinning, but I am very happy with the result.

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Elevator / Empennage

Elevator

Started elevator, the instructions and Evans video are very clear. Note the 2 stainless steel rivets. Different rivet size on end ribs. 10 Feb 2022 Having got the HS absolutely straight proceeded with the elevator skins. Important notes. There are two floating ribs that need to be inserted the right way around. There are small pieces to strengthen the trim tab hinge. Smaller 6mm rivets are needed just on the right side at the thinnest point. The elevator composite tip on the right needed to be worked up with extra fibreglass. Add the trim servo inspection hatch mounting ring inside the elevator before skinning! Test fit to HS to check hinge alignment and elevator deflection. One hinge is is a bit stiff. Hard to attach on the bench. This will be hard with unsupported HS and Elevator. Deflection seems to be good and within specification in the POH (+30 Degrees). Earlier builders report having to remove some of the HS skin to achieve the required deflection.

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Empennage / Vertical Stabiliser

Vertical Stabiliser

The vertical stabiliser has some points to watch. Important to open up the M4 holes in the lower part of the vertical spar. Use some bolts to be sure they freely fit later on. I opened them up to 5 mm. The rivnuts are by design I think held behind the vertical channels. Looks a bit strange, but all holes do align and it seems that Evans Sling official build video advocates this assembly. (Rather than drilling clearance holes for the rivnut flange heads. (This may weaken the effectiveness of the rivnut). I set aside for the moment as I am missing rib 1. 26 Jan 2022 Avionics package arrived from the USA, did a fit of the RAMI 525 VOR antenna, carefully filing out the holes per KAI. With the grommets in place, it’s a tight fit. A bit of a bulge, let’s see how it goes with the skins. Note that the pins on the top of the antenna are connected to the antenna elements and could easily short over time with the doubler plate. I filed them flush and added some Teflon tape. 8 Feb 2022 LAA inspector signed off the empennage skeletons, so started skin riveting with the vertical stabiliser.

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Rudder

Rudder

Assembled the rudder today. Pretty straightforward. Printed KAI has the wrong rivet size of 3.2 mm rather than 4 mm in one place. The latest dropbox KAI is correct. Took some time and care to get the composite rudder top to fit nicely. Did a dry fit of the skin, aligns perfectly. Will await inspection before riveting up. Glued some aluminium M3 washers to the inside of the composite rudder cap. Checked alignment and hinges on VS. Plenty of deflection 20 degrees required almost 40 available before clashing with VOR antenna.

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Empennage / Priming

Priming

Did my first real priming today. My earlier test on the internal panels didn’t turn out too well. Streaky and poor coverage. Too cold and me never used an air spray gun before! Anyway, after a bit of learning on YouTube and an understanding of gun adjustments. I did some tests on the packing crate wood, I started on the real parts. Rudder and vertical stabiliser. It’s December and the outside temperature is 4 C, Aerowave 2001 the two-part primer I am using requires at least 15C and less than 80% humidity.  I heated up the booth to 15C and carefully started. Took about an hour and 300 ml of Aerowave to do the first parts. Used a small HVLP gun at 29 PSI with a 1 mm nozzle and works quite well once I got the hang of the adjustments. For the second run of priming, I used 400 mL of Aerowave for the larger parts of the HS and elevator including skins internal surfaces only.

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Empennage

Let the dimpling begin

The empennage kit finally arrived (rudder, vertical stabiliser, horizontal stabiliser and elevator). Although some major parts missing, like the main spar! Anyway started by unpacking and removing plastic coverings. A good tip is to use a heat gun on the larger skin areas. It’s quite hard to remove the plastics in a cold workshop in December. Sort parts to main subunits – rudder, vertical stabiliser, horizontal stabiliser and elevator. Then to deburring mostly with a large drill bit or a small cordless drill with a countersink bit, a steel rule and a deburring tool for the larger holes.  Purple Scotchbrite to finish off deburring. 2 days prep and deburring all parts of the empennage. Then my first dimpling. Having never done dimpling before, I read up around the topic. Philip Rueker’s blog has some good info. Important to note that Sling uses 120-degree dimple dies (not more standard 100 degrees). Two sizes of dimple dies are included in the kit. (Although since the materials are quite thin, the same size die is used for both skin and rib). The introduction KAI instructs that the holes to be dimpled are smaller (2.8 mm) and match drilled to 3.1 mm before a countersunk rivet is used. (I placed the Sling dies in my hand dimple tool). Andy kindly lent me his DRDT2. As my project is a quick build, I think I only have the empennage skins and possibly the aileron skins to dimple with the DRDT2. The rest of the ribs can be done with a hand dimple tool. The next step is to purple Scotchbright all internal surfaces, degrease and spray with Aerowave.

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Priming

Paint booth and PPE

There’s a lot of debate about corrosion protection. As I have a quick build kit many of the parts are already treated with Alodine at the factory. However, for the empennage flaps and ailerons, I am on my own. After a lot of studies, I decided since I live on a rainy island in the Atlantic, that I needed to do something. Elected to use Aerowave 2001 primer.  It’s not intended for general public use, so spent a lot of time studying the safety sheet and also learning about respirator types and specifications. I needed some decent personal protective equipment. The main one being a good full-face respirator with the correct filters.  That is both a vapour filter (for the VOC’s) and a very fine dust filter for paint droplets. So an A2 for VOC’s plus a P3 filter, also known as (EN149) FFP3 or N99 in USA. (Note P2 or FFP2 (Europe) or N95 (USA) or KN95 (China) are lower specification and not suitable). I used a full face respirator to give sufficient Assigned Protection Factor. Went with a 3M 6000 series respirator. Not wanting to risk my exposure to chromates to a fake mask or filters. Also used a full paper suit and a good (Vevor 200 mm) extractor fan with 10m of hose to poke out of the window.

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