Canopy & Glare Shield

Over the last few days I've continued to chip away at canopy tasks.  I'm getting very close to the point of attaching the canopy to the frame, so need to have all of the miscellaneous build items done that will be more difficult to do once access is limited by the bubble.  I'm undecided on whether or not I'll just leave the glare shield bare or fit some sort of material to it, but regardless of that, I figured having it painted black would cover all bases just in case.  The picture is deceiving - once the paint dries it'll actually be a flat black (to minimize reflections on the canopy).

Once the paint was dry, the next thing on the punch list was to drill holes in the aft edge of the glare shield for the edge trim.  I'm not going to attach the trim until the rest of the interior goes in, but the mounting holes need to be in place.  The trim from Classic Aero came with a template, which made life easy.  I threw down some tape, put the template on top of it and marked the hole locations.

The last thing I need to decide on is whether or not to drill a couple of large holes in the glare shield for defrost fans.  It's common to put a couple of small computer fans in to pull air from behind the panel.  I'm not convinced it'd be all the effective though, especially given that the space to fit the fans is so small - probably 2" or so (which means the fans are even smaller after accounting for space for their housings).  The main reason people put these in is to help with defogging during taxiing (there's no way they would actually "defrost), but I think the more compelling argument is using them to help cool all of the panel electronics.  I'll have to mull it over a bit more.

I didn't bother taking the time to get the glare shield paint edged perfectly in line with the canopy since it'll actually be scuffed back a ways for the Sika primer anyway.  This whole front skin looks like a nightmare right now with all of the primer, paint and markings.  I'm having a hard time not tackling it right away to clean it up, but I know that would just be wasted effort since the entire thing will be covered in fiberglass down the road.

The canopy will get sandwiched between the frame side rails and the side skins.  I trimmed the skins down to match the side rail height, then match drilled it all.

Once match drilled, the skins were dimpled and the side rails were countersunk.  I should have drilled the aft two holes in the front skin (where it meets up with the side skins) back before I riveted the front skin on, but since I didn't, dimpling and countersinking wouldn't work.  I decided to just countersink through the skin and into the frame.  This approach is used in a few other areas of the airframe.  The downside is that it doesn't leave a lot of meat on the skin itself for the rivet to grab, but this area isn't under much stress, and like everything else, will be covered in a few layers of fiberglass down the road.

For the 100th time, I trimmed various edges of the canopy.  I think I'm close enough to the final shape that it's time to polish the edges.  That's for another day though.

Pitot Regulator Wiring

I needed a break from trimming the canopy, so I went back to working on the pitot heat regulator mount.  I went back and forth on where to mount it, from just attaching it to the nearby access cover, to building a bracket for it that would run between two ribs.  I want it to be out of the way enough that I can get my hand through the large hole in the rib for pitot access without having to remove the regulator.  The easiest solution is to simply bolt it to a rib web, but in the future when the skin is on and the only opening is the access cutout, getting two hands in to hold bolts and nuts would be almost impossible.  I ended up drilling 4 mounting holes in the rib web just outboard of the aileron bellcrank (the rib between the bellcrank and the pitot mount itself), then went back to the scrap pile and made some nutplate mounts for the back side of the rib.  Nutplates are at least a bit easier than nuts to deal with in tight spaces since once you get them started, you only need one hand.  To simplify things down the road, I riveted the two nutplates together so as soon as one is on, the other is in the right position.  I obviously could have just made it out of a single piece of aluminum, but didn't have anything quite big enough in the thickness I wanted to use.

Since the ribs have the raised edges around the lightening holes, the controller can't just set flat on the rib web.  I had a few inches of leftover aluminum tubing from who knows what, so I cut down 4 pieces to make some standoffs.  

The routing of the wiring to the pitot itself and the pitot and AOA tubing through this rib is still to be determined.

In the meantime, I went ahead and cut wires to length, pulled them through the conduit and spliced them together with the existing regulator wiring.  I put heat shrink on the exposed wiring and ran some RTV around the hole in the conduit to keep the wiggle factor down.  I didn't keep much of a "service loop" on this end of the wiring.  The other end will have some extra length should I ever need to pull things apart.

Canopy Handle & Side Skins

Even though the canopy primarily latches using the hooks at the bottom of the roll bar, there is a handle that rotates underneath the roll bar at the top as well.  This handle doesn't really have any kind of positive locking mechanism - it just acts as a failsafe in case the hooks don't latch (or you forget to latch them).  I match drilled holes from the channel into the plastic block that the handle sets in.  The plans say to use a washer and cotter pin to hold the handle in place, but I'm thinking about adding a spring underneath the washer as well.  As-is, the handle could relatively easily swing underneath the roll bar when you lower the canopy.  If you're not inside at the time, you are now locked out of the plane!  A spring won't make it foolproof, but it would hold the handle up against the block and trap it against the channel.  In order to rotate it underneath the roll bar you'd have to pull down first.

The canopy bubble will set outside of the side rail, but inside skins that are attached to the side rail (the side rail has a jog in it to allow for the canopy width).  I put the blank skins in place and marked all of the cut lines to match the front skin, the rear skin and the top line of the side rail.

I trimmed and sanded the sides, then started laying out the rivet locations.

Once I realized that the rivet locations were going to be slightly different for the top line of rivets vs the bottom line, I lost interest in laying it all out by hand.  Amazon to the rescue, and within hours I had a new rivet fan!  I should have bought this a long time ago!  Just mark the first and last rivet location, then decide how many rivets you want between those.  The fan does the rest.  So my head scratching of how to best lay out the slightly different spacing of the top and bottom became a dead simple task.

Once again I put the canopy back on the frame, this time to see how much more I needed to trim off of the side following my last trimming.  I had to pull back the tape in order to see the side rail to try to mark off where to trim.  Each side needs at least 1/8-3/16", as well as more material taken off at the curve from the front to the sides.  The good news is that for the crack I found the other day, cutting another 3/16" off in that location will leave so little of the crack remaining that it'll probably make sense to just sand away the material vs just stop drill.  I'll just have to play that by ear.

Canopy Trimming (2)

The canopy went on and off the plane a number of times today. The primary edge that needs to be fitted first is the front windscreen edge.  In its initial shape, it had a tendency to gap on both sides (about 1/3 of the way between the long edge and center). After 4 or 5 trimmings to cut the corner further and further up, it finally fit well enough to duplicate on the other side.  I took a bunch of measurements using my grid paper and transferred those over.  It's not worth trying to get the fit perfect at this point, since the canopy won't set down on the roll bar until it's cut in half.

I had already drawn a line down the center of the roll bar, so with the canopy sides pulled in and taped to the skins, I transferred that line to the canopy.  I then ran a piece of tape down each side of the line to give me a cutting guide.

The cut to separate the two pieces was relatively painless.  I taped the parts together after every foot or so of cutting, just to keep them from collapsing and cracking as the cut neared the end.

Once I had the big cut done, I put the canopy back on the frame, pulled the sides in tight to the canopy rails and marked where the long sides needed to be cut in order for them to set at the right level on the rails.  Then the canopy came back off and I trimmed the long sides.  For the most part, everything seemed to work out just fine, but as I was sanding down the edges I noticed that there was the tiniest of chips in one edge.  Pulling back the tape revealed that the chip had created a hairline crack.  It goes about 1/4" into the material (it looks a lot worse in the picture than it really is).  Luckily, as long as I can get the crack stopped, it should be completely hidden by the canopy side rails and skin.  It will also be encased in the Sika adhesive, which should help matters a little bit.  I don't have a plexi drill bit, so I'm going to have to wait a few days to get one.  Fingers crossed the crack doesn't grow any between now and then!

Canopy Trimming

The first thing I needed to do to get ready for trimming the canopy was mark the center of the front and back.  This is to make sure I consistently place the canopy in the same place every time I put it on the frame.  There are two black marks that the manufacturer puts on the canopy that appear to be on the center(ish).  That's what I'm going with anyway, since otherwise there is no way to actually find the center (measuring from the edge of the material very obviously does not find the center - it doesn't seem they care about centering the raw material on the form they use).

Rose helped me pull the canopy off again.  I pulled the plastic back on the front edge and taped a cut line.  I initially put a space heater under the canopy, but I found that the infrared heater did a much better job of warming things up.  I actually had to turn it off part way through the cutting because of how warm it was getting.

Instead of using a cutoff wheel in my die grinder, I decided to use my oscillating multi tool.  It's a little slower than a cutoff wheel, but it's much easier to control.  The blade I'm using has very small teeth and vibrates/melts its way through the material really nicely.  The big bonus is that while the cutoff wheel throws dust absolutely everywhere, the multi tool just creates some big, melted chunks and virtually no dust.  Every foot or so I duct taped the pieces together for support.  Most cracks I've read about happen when the cutoff piece falls away from the canopy because it's not supported before the cut is complete.  After the cut was done, I put the sanding attachment on the tool and hit the edge with 80, then 120 grit to smooth it out.  Once I have all cutting completely done I'll polish the edges, but for now all I need to do is smooth them out so there's no sharp edges.  I'm going to have a lot of back and forth cutting before I reach the point of polishing.

Even though the instructions recommend cutting the canopy with it setting upright on its edges and held from spreading with 2x4s attached to the bench top, once I got to the long edges I realized that wasn't going to be a great approach.  As soon as I started cutting, the heavy weight of the canopy made it push out and away from the cut (the cut piece being held in place by the 2x4s clamped to the bench).  Ripe for a crack!  I flipped the canopy on its back instead.  This was much better since the only weight I had to deal with was the couple of inches of the cut piece.  That was easy to control with duct tape.

All the edges were trimmed to the form mold lines with no casualties!  Just for fun I bent the scrap pieces to see what it takes to actually break them.  The material is far more flexible than I thought it would be.  I had to bend the narrow pieces in half and then step on the bend to get it to break.  When it breaks, it breaks in spectacular fashion though.

And now, back on the plane for the first iteration of shaping.  It's kind of hard to figure out where to cut at this point.  There are absolutely no measurements provided.  I know the front windscreen needs to be cut at the curve of the material, where it comes down and then gradually flattens out. The flat part needs to be completely cut off.  The problem is it's extremely hard to tell where that point actually is on such a clear canopy.  I put tape down, then got down on my knees and marked as close to the curve as possible.  For now I'm erring on the side of leaving it too long.  I'll continue to chop it back little by little.  The same is true for the curve from the front to the side.  I've marked a gentle curve, but I know it's forward of where it ultimately has to be.  I also taped off a little more on the aft end of the canopy - just chopping off the corners and creating a little more of a curve that matches the skin.  I'm not bothering with this end all that much for now.  Once I'm done with the front and it's been cut away from the rear window portion, then I'll figure out the right cuts for the back.  The picture below is before I started the extra taping.  Rose helped me pull the canopy back off.  I think the first step tomorrow will be to pull the plastic back a little more on the inside and put tape in its place - easier to keep the canopy clean without cut junk working its way under the plastic that isn't perfectly adhered.

Wheels & Canopy Prep

The proseal is almost dry enough to start messing with the canopy, but I want to give it another day to set up so it doesn't attract dust and shavings from the process of fitting the canopy.  I've been told that it's best not to let the tire tubes stay folded up for too long, so I decided to assemble the main wheels for a change of pace.  The wheels are made up of two halves with the brake rotor bolted to one side.  The bolts holding the halves together are set super close to the wall of the rotor, and I couldn't get a socket or wrench on them.  I ended up grinding down the wall of an old socket until it was super thin.  The bolts are only torqued to 100 in/lbs, so the socket doesn't have to be all that beefy to do its job.

I covered the inside of the tire with talc to help the tube slip in and keep it from catching and creasing during the assembly process.  Then I put one half of the wheel in place (it has a notch cut out for the valve stem, and the valve stem has a nut on it to center it in the notch).

The other wheel half went on next with the brake rotor set on/in it.  The bolts go through the rotor and both wheel halves and were torqued to 100 in/lbs.  I inflated and deflated the tire a number of times to help the tube settle into place.  The first tire took a while to figure out since there are zero instructions about how to do it other than a short blurb that came from the manufacturer (Matco).  The second tire was done in a matter of minutes. I won't add the brakes or anything until the plane is up on the gear.

I'm slowly checking off all of the random things I can do while I'm psyching myself up for the canopy fitting!  There is a never ending list of course, but I'm ready to get going with the canopy.  Once done with that, then the departure from the Van's instructions begins (electrical and firewall forward).  There's just not much guidance from Van's once you get beyond the basic structure.  I'm definitely thankful for all of the information online these days!

I set the canopy frame back on the plane and pinned the hinges.  In order to make sure everything is in its final position, I had to put the front fuselage skin back on as well.  This skin is still an excruciatingly tight fit though, so I decided to leave the outside most holes unclecoed and just strap it down for now.  If I cleco those longeron holes too many more times, they will start to elongate from having to pull them into place.

The canopy doesn't come with any layout on it that would aid cutting it symmetrically at the front (it starts with a somewhat straight center line then curves around to the canopy rails).  I'm not sure if it'll end up helping or not,  but I printed out some grid paper and taped it to the glare shield.  The lines don't come together perfectly, especially at the aft edge since the glare shield isn't flat, but I think it'll still help me get in the ballpark of symmetry from side to side.

And here it is!  There is a lot of material to trim from the front and back.  The first step will be to trim all of the excess material off that is there to help in the forming process.  Once the basic shape is set, then it's iterative trimming of the front to get that shape correct, following by splitting the front canopy from the rear window material.  Only after you've done that will the front canopy set down on the roll bar enough to trim it to final size.