The bare canopy frame comes with the kit, welded and ready to receive various add-on bits required for attachment of the plexiglass canopy. The frame consists of a "front bow" and a "rear bow" connected by
After the pivot bolts are installed, the rear bow is clamped to the roll bar with spacer blocks between them, assuring the frame is positioned correctly. At this point there should be 1/8th inch between the rectangular tubes and the fuselage rails. Not close. The build manual suggests taping strips of corrugated cardboard, as found in typical cardboard boxes, to the tops of the fuselage rails to provide this gap. The problem was that when the frame was clamped into place, a compressive load was put on the cardboard, causing its thickness to be reduced. The angle between the two welded-together pieces of rectangular tubing needed to be altered.
At this point, I made the lucky discovery that the little wooden paint mixing sticks which you're given when you buy paint at Lowe's or Home Depot are exactly 1/8th inch thick and won't be compressed by the frame. With the pivot bolts installed and a small block of wood positioned under the weld (which can be seen in the pic as a vertical line joining two straight sections of rectangular tubing), I put my weight on the rear bow and bent the tubing at the weld. Got it right the first time! The frame fit like a charm, verified by little pieces of paint stirrer sticks placed all along the interface between the rectangular tubing and the fuselage rails. Now just pop the canopy in and drill baby, drill! Uh, no.
The canopy is supposed to have 1/8th inch clearance between the forward edge and the plane of the instrument panel and 1/8th inch clearance between the bottom edge and the canopy frame. The build manual says to trim the aft edge to produce 1/32nd inch clearance between it and the rear window. This is the only mention of trimming the canopy. Clamping the canopy in place, these dimensions could not be achieved. I wasted countless hours repositioning the canopy and re-clamping. Couldn't be done. I finally decided to trim the bottom edge even though no mention of this is made. Bingo! After many iterations of install-measure-remove-trim, it finally fit. I was worried that having the canopy frame held to shape by the canopy would unnecessarily stress canopy, promoting cracking.
The drilling was uneventful (this time -- see rear window post). After clekoing the now-well-fitting canopy in place, I discovered that the canopy and frame wouldn't pivot open, requiring further trimming of the forward edge (goodbye 1/8th inch clearance!). This doesn't matter at all since it will all be covered with the fiberglass skirt (post to follow).
Also in this section of the manual is the fabrication and installation of the canopy latch. This involves shaping the exterior part of the handle (which I did by eye using a belt sander and Scotch-Brite wheel)
and attaching it to the shaft connected to the interior part of the handle. The parts must be carefully aligned and drilled. I found this difficult even though I fixtured it as best I could on the drill press, ending up with a definite angle between them. The interior handle must be fore-and-aft in order to properly engage the latch, meaning the part out in the 150 mph slipstream (yeah, I'm an optimist) will be at a small angle of attack, causing drag. Being an aero guy, this was unacceptable.
My fix was to carefully elongate the hole in the shaft until alignment was perfect, fill the shaft with a mixture of epoxy and flox, and re-drill with the two parts assembled. The screw holding all this together is tapped into the aft portion of the handle. I coated the portion of the shaft which is inside the handle with wax so the epoxy wouldn't stick. Everything is working well. Opening and closing the canopy requires significant torque on the shaft. If some play develops there over time, I'll remake the part.
