For the last few weeks, we’ve been working on drilling the perspex canopy and preparing for attaching it permanently to the fuselage structure.

Drilling perspex is scary, especially as there are so many horror stories online about it going wrong. We were really worried about cracking the window, not least because it’d be ridiculously expensive to ship a new one, but actually if you take things slowly, take precautions and use the right tools, the process is fine.

One of the ‘precautions’ is to ensure the perspex is warm when you want to manipulate or drill it. Unfortunately, this meant cranking the heating up to 30C on one of the hottest days of the year, an uncharacteristically warm one for Scotland. It wasn’t pleasant, but the perspex is definitely softened and made more flexible by the heat and this should reduce the risk of cracking it during alignment and drilling. We haven’t cracked it, so I can only assume it works!

There is some fiddling required to fit the canopy, ensuring it’s aligned and limiting any bulges at the front, whilst also having a decent position at the back. We found the fit remarkably good – minimal tweaking and chamfering was required but it was amazing how quickly it was sorted. We added some weight to the front and used the ratchet straps from our kayaks to hold it in alignment whilst we drilled the holes.

For the drilling, we wanted to improve control of the drill and reduce the risk of damaging the holes on exit by having a block of wood on the inside. Unfortunately, whilst access will be easy once the canopy is installed in its final location, when it’s not attached you can’t flip the canopy frame open and the only way to access the seat area is by climbing between the roll bar and the seat back. This meant one of us (me, as J couldn’t fit) had to crawl/limbo inside the thing and sit there cooking – don’t forget the room was at 30C – in a tiny greenhouse while we drilled about 100 holes…not the most fun I’ve had in my life!!

We had read quite a bit earlier in the build process that buying special perspex drills was advisable to prevent cracking and chipping, and we’re glad we did – they bite into the material really well and produce nice clean holes.

Once drilled, all of the holes need to be countersunk for the screws which hold the perspex in place, so we lifted the canopy off and worked our way around these as well.

About three of our holes had minor damage from either drilling or countersinking, which was fixed using a soldering iron after reading a useful tip online – this was just to round off the sharp edges and reduce the risk of future cracking.

Starting to drill holes in the perspex
Help!

Once the canopy was fully drilled, we turned our attention to the catch-up jobs required before permanently attaching it and working on the fibreglass faring.

We masked off, primed and painted the dashboard area black, as it will be hard to reach with the canopy attached. For this we just used barbecue paint from our local hardware store and it came out with a nice matte finish (important to reduce reflections on the canopy when flying), although annoyingly there’s one location where it has since cracked up – presumably as the primer didn’t take so well. Just a cosmetic issue but a shame as it otherwise looks quite uniform and professional.

Painted dashboard

We then worked on drilling the holes and adding attachment brackets for the GPS antennae and the angle of attack indicator that will sit on the dashboard once it’s finished – simply doing those things now whilst access is easier rather than kicking ourselves later on when we can’t get our hands into the gap! For the same reason we have run some wiring around the canopy frame to facilitate later connections. We also installed the cooling fans, which look quite smart.

GPS anntena and fans in final position
Angle of attack indicator and mounting bracket

Once the dashboard work was complete, we screwed the canopy into position (loosely for now, to allow some movement) and riveted the cover plates along the sides. Just as with the drilling, the screws need to be tightened in a very specific order.

It was pretty terrifying to be using a hydraulic hammer (rivet gun) so close to our fragile perspex dome! The riveting had to be done, but it felt a bit counter-intuitive to bash something that we’ve been tiptoeing around for months. Thankfully no cracks or dents, but I’ve never been so focused on controlling the bucking bar and gun. Again I had to contort myself to get inside the thing to work on the rivets and tighten the screws – can’t wait until the canopy can be tipped up so we can climb in and out using a space that’s designed for people to fit through! We decided to back rivet the plates on as they are very visible and we also thought that having the gun inside would hopefully allow me to be more precise and reduce the risk of hitting the perspex accidentally. I’m glad we did it, as it’s resulted in a really nice finish on the outside.

Ready for fibreglass!

The canopy then needs to be marked out, masked off and sanded down in places in order to get it ready for the fibreglass farings. The perspex ‘mates’ with the canopy skin more effectively in certain areas than others, so there are places that need to be sanded down to make the slope more even and ensure the faring is a more sensible shape.

There are also a series of small canopy clips that need to be drilled, dimpled and pop-riveted into place. The instructions are – out of necessity – uncharacteristically vague, as Van’s can’t be completely sure where the areas of best and worst fit between the perspex and aluminium will be on each specific aircraft as they will vary individually. The instructions call for at least three clips – one in the middle and two at the sides. Once I installed these three, I could see that a further two would make for an even better fit, so I went ahead and added these too.

Annoyingly, the canopy clips are extremely fiddly and small, so working with them and in particular match-drilling them onto a curved and slippery canopy skin, is really difficult! The drill kept wanting to wander and I ended up drilling a much smaller hole to anchor it first and then drilling it out to size. The instructions also call for dimpling the canopy clips followed by ‘match drilling’ to number 30, but the holes in my clips were quite a bt smaller than number 40 so I couldn’t dimple them at all before drilling and came to the conclusion that I’d need to drill them out to number 30 and dimple, then drill the corresponding hole in the canopy skin afterwards. I’m not sure if this is what Van’s intended but it worked OK.

Finally, some dubious sorting (either on our part or Van’s) meant we had a mix of LP 4-3 (domed head) pop-rivets and CS 4-4 (countersunk) pop-rivets in the same bag, although it was only supposed to contain the CS 4-4 type, according to the instructions. I didn’t realise, and the result is that a domed-head rivet has snuck in on my central clip and it’s sitting slightly proud of the edge of the perspex (whilst the others are nicely inconspicuous), it will still be well below the level that would make a difference to the fibreglass faring. I was way too scared to drill it out that close to the perspex as I thought the result of getting that wrong didn’t bear thinking about, so it’s better left as the strength won’t be affected in the slightest!

We’ve come a long way from freaking out about tiny things, and we now have a much more intuitive sense of what does and doesn’t matter.

Masked off and scuffed faring area, including canopy clips

There is some fairly complex measuring and marking to be done to establish the location of the forward and aft faring lines, which took me most of an afternoon, but I was reassured that it looks like the pictures in the manual and the examples I’ve seen on the LAA/EAA instruction videos.

We have also made a ‘skirt’ for the canopy out of some plastic sheeting and masking tape, as we’ve chosen to leave the canopy on the fuselage for the fibreglass (the alternative is to clamp it to a bench).

We thoroughly scuffed the aluminium and perspex and washed it with alcohol to prep the surfaces for the fibreglass work.

Whilst J mixed and applied the ‘void filler’ to the cap between the perspex edge and the canopy skin, I began the mammoth task of cutting all of the lengths of glass cloth and peel ply that will be needed for the work on the faring.

The process of making the faring itself will take several hours and we need to leave at least half a day clear to do that, so we probably won’t manage it until the weekend, but we wanted to have everything sitting ready to give us more chance of getting it done when we do have a time window.

The Van’s instructions call for a seemingly precise set of pieces to be cut from the glass cloth in progressive lengths and widths, which I dutifully followed, although I’ve since read that the accuracy of these pieces is not critical. I used a rotary cutter for the glass cloth, which worked well once I got the hang of it, but I found it didn’t really work on the peel ply so I used scissors for that.

Like a number of people (judging by the forums), we did not receive the paper templates with our finishing kit and instructions and we didn’t notice its absence until we were well into the process. We were able to request the PDF from Van’s and have it printed locally to save the time and cost of shipping. The templates are cut out and used as a guide for masking off the faring area and also for cutting out the glass cloth and peel ply. They have to be printed to scale (24 x 36 inches) so I had to send it to a print shop rather than just relying on my tired and temperamental home printer.

The pieces have to be rolled up to prevent them from going out of shape, so I’ve now got a random assortment of little parcels sitting waiting for me in the workshop and reminding me of the fibreglass fun that awaits…!

Pre-cut glass cloth and peel ply strips and shapes, ready for constructing the fibreglass faring
RV-14 build: Completing the canopy

Post navigation


Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.