Fabricating the main slide channel

Now I start adding the components that will facilitate the sliding feature. But first, I have to sheet the bottom side of the rear canopy using 1/32" aircraft ply. This thin surface is very hard/durable but very light.

Then I was able to cut a slot in the bottom of the canopy to insert a slider tab into. The tab I made was about one inch wide and sticks a little more than an inch into both the canopy and the fuselage. The tab was made from some leftover laminate that I had made earlier for my custom control horns. It's a piece of aircraft ply sandwiched between two pieces of G-10 composite.

After installing the tab into the canopy with Gorilla Glue, I cut a slide slot into the top of the fuselage. The slot is a little more than 1/4" wide, about 4" long and 1-1/8" deep. The slot needed to be lined with something that would be very hard and durable, yet light. So I took two balsa planks about 1/8" thick and surfaced them on one side with the G-10 composite sheeting. With the G-10 sides facing inward in the slot, I have a hard surface in the slot that will be resilient and allow the tab to slide smoothly.

I also began cutting out another scale hatch that would allow me to hide the locking pin for the slider tab. The idea is that if I have some sort of locking pin (I used a dowel) that would slide through the fuse, into the slide channel and through the slider tab on the canopy... this would lock the rear end of the canopy down when closed and keep it from sliding back as well.

Like on the other hatches I've installed on this plane, I had to permanently glue a thick AC ply "bulkhead" deep inside the hatch hole. This gives me a strong support to slide the locking pin/dowel through.

Installing the slider lock pin

Also like the other hatches on the plane, I install all hardware in a carbon fiber faceplate that is screwed to the ply bulkhead. This allows me to easily remove, change and/or service any hardware in the hatch.

I start by installing the CF faceplate and drilling a hole through it, through the ply bulkhead, through the sliding channel walls, and through the slider tab on the canopy. Obviously I do this step with the full one-piece canopy slid all the way forward in final position.

Now I pull the CF plate back out of the hatch and epoxied a small spring to the front of it. Note that I also folded back a small section at the base of the spring so I could pull it through the hole and glue it to the backside of the CF plate. This will add a lot of strength to the glue joint holding the spring to the CF plate.

I then slid a dowel rod through the back of the CF plate and up into the spring. I secured it by adding a servo screw into the end of the dowel, pinching the end of the spring. With the canopy slid into "closed" position, I was able to then install the entire locking pin assembly inside the hatch. By pulling the end of the dowel out about half an inch, it releases the slider tab and allows the canopy to slide back into the "open" position.

Lastly, I added a small hatch door from scrap fiberglass from the engine cowl. This door, like the others, got a small brass piano hinge. Permanent installation will take place after the plane has been painted.

Alignment pins

While the slider tab does a pretty good job of holding everything in place, additional alignment pins were needed to make the canopy slide straight, and also to lock it down up front where it meets the front windscreen section.

To facilitate this, I first added another slide slot that extends forward from the first slot. This one is narrower and shallower than the first. Also, it does not get surfaced like the first slot did. I then inserted a piece of carbon fiber rod into a small section of dowel rod, then glued the dowel up into the underside of the rear canopy. This pin slides in the narrow slot that was extended forward from the main slide channel. This adds a great deal of torsional stability to the assembly while also helping to keep everything "on track" when sliding back and forth.

Now it's time to go ahead and us a razor knife to cut the front and rear sections of the canopy apart. The scoring from the inside will make this much easier to accomplish. Lastly, I added a couple small carbon fiber pins to the front edge of the rear canopy frame. I also drilled two holes in the rear edge of the front windscreen section. As the canopy slides forward and locks into position, these two pins slide into the holes and lock the front end of the canopy down.

With the big locking dowel inserted at the rear of the canopy, it is held down at the rear, and is also pushed tight up against the windscreen. Then the two alignment pins at the front do the job of holding the front end down onto the fuse. The finished assembly is very secure and has very little slop in it.

Final steps

Once everything was fabricated and/or installed, the last thing to do was to fine tune the sliding and adjust anything as necessary for efficient operation.

The canopy also needed to be blended into the turtledeck. To do this I glued a 1/2" strip of 1/32" balsa sheeting to the turtledeck, butting it up against the trailing edge of the canopy material. This would minimize the need for putty and make it easier to blend the step down from the canopy material into the balsa sheeting.

After sanding the area to blend, I added some balsa putty to further feather it out and sanded again. I also used some balsa putty to better feather the fuselage balsa sheeting into the new 1/32" AC ply sheeting that is surfacing the top side of the fuselage.

Once I glass the plane, all these areas will get further putty and sanding work until it all blends and feathers well and is very smooth and level.