Baby steps toward the Big Cut

Cutting the canopy isn’t something to rush. I read and re-read Vans’ instructions, and researched other builders’ websites, to get a good idea of how to trim the canopy without damaging it. A replacement canopy is more than $1000, so cracks are something to be avoided.

I started this part of the project a few weeks later than I wanted to…my hope was to get the canopy cut and installed in August while the temperatures are still warm enough to not keep the hangar heat turned up. Fortunately, September has been fairly warm so not too much hangar heating has been required.

Prepping the OR for surgery

I set up everything needed to start trimming.  Per the instructions, I first cut off the portions the canopy where it was clamped in place for molding.  The back of the canopy was the first to go…

The first canopy cut

…and trimming turned out to be a little easier than I thought, but some care is required to get close to the cut line marked by the tape.

Plexiglass snow

The cutoff wheel creates a lot of plexiglass “snow” particles as it works, except that this snow can be uncomfortably hot when it hits your skin. I didn’t want any of that crap in my eyes or up my nose, so I wore safety glasses and a respirator…

Even two pairs of glasses weren't enough to protect my eyes I continued the process around the sides and front.  It was a little difficult to tell where the cut lines should be, especially on the sides.

Prepping to cut the front of the canopy

With the clamp marks trimmed off, I marked a centerline on the canopy per Vans’ instructions. This is a little tough to do as it’s hard to accurately place a tape measure around the canopy.  I wound up using a piece of string pulled tight from side to side…mark  the string where it lies on the edges, then double it back on itself and you have the centerline – sort of. I don’t think it was very precise, but it also seems to be close enough.

The canopy on the fuse for the first time

There are a couple of tabs on the front canopy frame that overlap the side rails. The instructions require that the tabs and side rails be adjusted to match the curve of the canopy’s front edge, then drilled and riveted. There’s not a lot of guidance here, and it’s hard to see through the protective plastic sheeting on the canopy to tell how the curve should lie. So…I took my best shot.

Adjusting the canopy rail bends - holes countersunk And then riveted the tabs…

Canopy rail fitted and riveted on the right side

…and everything looks good for now.

Canopy marked for cutting

I’m reasonably happy with the canopy fit, so I started marking the line across the rollbar where the canopy will be cut into forward and rear sections. This process is not-really-affectionately known to builders as making The Big Cut.

Canopy forward edge

I worked on the front edges a bit to get them to lay down a little more accurately on the front canopy skin, but from what I’ve seen on other builders’ websites, you can do all the work on this area you want but once the canopy is drilled in place, some gaps will open up.  So I’m going to get it close and not worry about it.

Canopy in place for cutting

I hoisted the canopy onto the sawhorses and plywood, and used some long 2x4s to move it off the work surface They also gave me something to clamp some smaller pieces of 2x4s as side supports that keep the canopy from spreading as I cut it.

As other builders have also done, I laid several pieces of masking tape along each side of the cut line to help guide the cutoff wheel. I was skeptical that this would work, but it did and very well too.

I took a few deep breaths, and started cutting…

Starting the Big Cut

…and the process went very well. I used tongue depressors to keep the canopy separated  as I worked my way along the cut line.

The Big Cut is complete

And here’s the completed cut…what a relief to have this done.

Forward half of canopy on the frame

It’s a lot easier to move the canopy on and off the fuselage. I’ll be doing a lot of that as I finish fitting it to the frame and then drilling the attach holes.

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