Canopy Latches

Little by little, I'm tidying up loose ends.  I measured the mixture and throttle control cable routing about 500 times so I can get cables ordered.  I'm hoping I don't have to have cables custom made, but I haven't found any that match what I need, given my "non-standard" engine and routing.

I think my wire runs up to the panel are finished, so I drilled a hole in the vertical firewall brace on each side of the firewall recess and clamped the wire bundles in place.

I bolted the glare shield fans in place and tested them.  They actually move a decent amount of air, so I think they'll do a good job of both clearing a fogged canopy as well as keeping the avionics cool.  I will wrap the wires and heat shrink the connections once I'm sure the canopy doesn't need to come off again.

I designed and 3D printed fan grills (a new version - my first version a month or two ago was too thin and warped under the screws), just because I can.  I used a high temp PLA filament that's good to about 300 degrees, so hopefully they last. If the heat on the glare shield is too much, I'll either reprint in even a higher temp filament, or I'll send the design off to get cut out of aluminum.

Back to the canopy!  The next step is getting the latching lugs mounted.  These are the fingers that drop down through the canopy deck on the fuselage and get captured by hooks to secure the canopy.  Since there's no way to actually clamp the lugs in place to get them fitted, this seemingly simple task turned into an all day affair.  I wish Van's would make the top portion of the latch a little wider to allow for some side to side cheating after the bolt holes are drilled.  As is, they don't have much wiggle room since the nuts barely fit.  So I bolted them in place aligned as close as I could get to the holes they have to drop through.  Unfortunately, close was not close at all.  The canopy has a tremendous amount of flex when it's lifted and closed (since you lift from one side, so it's not symmetrical force), and the lugs were off by more than 1/8", so they wouldn't cleanly drop through the holes.  I used the dremel and iteratively ground away at the holes until the lugs finally fit.

Even when the lugs would drop cleanly through the holes when I held the canopy from the center (vs the side, as would normally be the case) the issue of the canopy flexing still caused problems.  This is a common issue, and one of the most common fixes is to make some guides for the lugs to hit as the canopy is closed.  I grabbed some scrap UHMW plastic and made some guides that I screwed through the roll bar.  It sounds simple, but this is all off book, so took most of the afternoon to get the guides made and laid out exactly where they need to be.  I put one guide on the outside of each side of each lug.  As long as I don't let the canopy slam down and I guide it down to the last 3 inches or so, the lugs hit the guides and the canopy slides into place.

I'm happy with how the canopy closes now, although I'm still contemplating making a fiberglass and carbon fiber top strip that goes over the canopy at the roll bar.  I've heard that carbon fiber can really stiffen things up so the canopy doesn't flop around like a wet fish when closing and opening.

The other thing I discovered in my testing - the lugs cleared the front of the hole just fine when I would manually push the canopy into place and wiggle it a bit to get the aft clearances good.  However, after 2 or 3 opening/closing cycles where I just let the canopy do its own thing, the lugs would start hitting the front of the holes and make opening the canopy almost impossible from just one side.  I'd heard that a lot of people run into this, but I was really hoping I'd be one of the few who didn't.  Apparently the issue is that during closing, the geometry of the struts pulls the canopy forward.  You wouldn't think that the setup would allow that much movement, but it does, at least without the forward skin on.  My guess is that the forward skin will stiffen the subpanel (where the canopy hinge pins are) up considerably and keep this forward migration of the canopy to a minimum, but I'm not sure.  A lot of people put adjustable bumpers at the subpanel - basically something for the canopy frame to butt up against to keep it from shifting forward.  I'll leave things as-is for the moment, but I may have to go ahead and add these bumpers before I fit the rear window, otherwise the canopy and rear window gap will be hard to judge.