After my last session of priming the canopy skirt, it finally became time to look towards cutting and fitting the canopy. This post encompasses the work of several sessions in the shop over the course of the past week. The canopy skirt looks great – I am really proud of how its turned out.

The first step in cutting the canopy was to gather my tools, plan the cut, and make measurements. After some research I decided to use a 506CU cutting wheel on a dremel. Any cutting disc WITHOUT teeth should work fairly well.

Keys to a good cut: 1) Make sure its a warm day. Anything over 70 should be fine, but the warmer the better. 2) Use the proper tool – don’t use a saw or any blade with teeth. 3) Take your time. 4) Measure at least 4 times.

There are essentially two initial cuts that need to be made. The cut along the red line at the base of the canopy, and the rear cut for intersection with the fastback turtledeck. The first cut, in terms of difficulty is rather trivial. This is the cut along the base of the canopy. The second cut, at the rear of the canopy, requires careful measurement.

Measurement. Showplanes instructs you to measure a line 77 inches from the front center of the canopy (on the pre-marked red line) and 72 inches along the side. The canopy itself isn’t necessarily perfectly true, and the extra material is certainly anything from square or equally spaced, so determining the exact center of the canopy can be a challenge. I measured in both directions around the side and used my eyeball to mark the center. This ultimately resulted in about 1/2 inch disparity between the left and right marks at the base. My friend Jack and I debated what to do about this. Certainly you could move the center mark 1/4 inch and level it out, but again, with things not perfectly true you’re still not guaranteed to be right on. In the end we decided to cut an inch less (moving the cut rearward). We could then put the canopy on the skirt and see the true fit.

Ultimately this was unnecessary. The 77 and 72 inch measurements were conservative. Had we made the cut at that point, we would still ultimately have had to trim at least another inch if not two. After we trimmed the both the base and the rear of the canopy we placed it on the canopy skirt and both on the plane. After reviewing the fit, I was delighted to find that I had not made the un-repairable error of trimming too much. Quite the opposite in fact – we had plexi to spare in every dimension. The question was then, which area to trim and fit first? I settled on the front of the canopy. The front will require shaping to match the curve and to be far enough aft to intersect the existing fairings.

My thought was that the front of the canopy, by virtue of its angle coming to a point was relatively set in stone. It must touch the skirt at the intersection points which thus dictates the forward/aft positioning of the canopy. Without shaping this gives you the distance, but further shaping could slightly affect the rear angle. So, in short – shape and fit the front first. This will provide the proper distance to trim the rear of the canopy. After you trim the rear, the canopy should be seated in the proper up and down position allowing trimming the sides. Trimming and shaping the front was a slow and iterative process. I took my time and got it right.

Trimming the sides is, perhaps, the most iterative portion of the trimming. The canopy is a circle that cannot lay flat while it isn’t fully trimmed. As you trim the canopy, the radius slightly reduces and thus your trimming dimensions reduce.

My technique here was to position the front and rear of the canopy in their final locations and centered, and then tape them in place. I then taped the canopy as tightly in place as possible and used tape to mark the trim of both the left and right. I only trimmed the left side. After trimming the left side, I again put the canopy back on the skirt and this time I was able to tape the canopy in position on the front, left, and right. As predicted, this reduced the radius and resulted in the trim line on the right moving about 1/2 to 1 inch! Had I trimmed both, I would have still had to trim the right again.

So, now I trimmed the right. And, again, placed it back on the skirt. You’d think it’d be a perfect fit, but again, a small change meant I still needed to trim a little more.

Unfortunately, I’m still off by about 1/8 to 1/4 inch when the canopy is squeezed into its final position. I will evaluate options in my next trip to the shop.

No photos today – there isn’t much to show. I used some epoxy, and epoxy with microballons to address some of the faults in the fiberglass last night. Today, I retrieved the skirt, sanded the applications from yesterday and then applied a new coat of filler primer. I plan to cut the canopy this weekend.

Yesterday I skim coated the entire canopy skirt with epoxy. The idea is to fill as many pin holes and deviations as possible before moving to the priming step. The first thing I did today at the airport was to sand the skim coat to make sure everything was even and smooth as best I could.

Then I brought the canopy skirt home to allow me to prime with out folks at the airport complaining. Here is the canopy skirt ready for its first coat of primer.

And here it is after the first coat of primer. I have to say I’m really happy with how it turned out, and a bit surprised. Areas that I thought would look horrible are actually pretty darn good, and other areas that I thought were good still require some significant attention.

This left side of the cross brace is one of the worst parts – in the areas that will be very visible. There are some pinholes, a few imperfect applications of the carbon fiber, and in general it still looks a bit gnarly. However, its not far off.

Its hard to tell how good or not things are even from these photos. The light and shadow combined with the varying thicknesses of primer (I went pretty light with the first coat) can be deceiving, however the intersection of the lower stiffener and the rear bulkhead are fantastic.

The outside of the canopy is nearly flawless – granted this needed the least work out of the box, but I’ve paid special attention to making this smooth as it will eventually have a shiny clear coat application like the rest of the aircraft. The interior of the canopy skirt will have a some what more matte to reduce glare.

Again the lower stiffener to canopy skirt fillet is flawless.

The corner here has a little flaw – I’m pretty confident I can get rid of these.

After the primer had time to dry, I went back and sanded with 120 grit sandpaper. This area, as one of the high visibility areas that was worse than other areas got lots of attention.

A few pinholes – but again – very happy with how this looks at this stage. This is, after all, my first significant foray into fiberglass work beyond the empennage tips – which are child’s play next to this!

I didn’t prime the top one inch of the skirt – this area will still need to be bonded to the canopy, so there isn’t much point to putting primer there – quite the opposite in fact. I’d think primer would only serve to weaken the canopy bond.

I will not be able to get this 100% primed and ready for painting prior to the canopy installation. The canopy itself will need to be bonded and faired. Then I will make final adjustments to fit and finish. My goal at this stage is to use the filler primer to identify flaws and fix the flaws. There is no avoiding more priming and paint once the canopy is on, but I can minimize the amount of sanding and adjustment post canopy bonding.