Drilling canopy frame mounting holes

[GVilleFlyer]

I'm ready to mount the plexiglass canopy on the canopy frame, but it sure seems a lot easier and more accurate to drill through the plexi and into the frame in one step, rather than marking, drilling, then trying to match drill the canopy holes. Seems like every time I take off the canopy and put it back on, it goes back on in an ever so slightly different position. Has anyone else done this?

 

[dbhill916]

My canapy went on 10+ years ago, and thus I have no clear recollection of how i did it, but I think your observation and logic are excellent. I would make sure you have two drill bits -- a dull one for the plexiglass and a sharp one for the aluminum bow. Figure out the best you can to keep everything in place, then choose one side and drill thru the plexi, change bits and drill the bow. Cleco them together. Go to the other side & repeat. With two widely spaced locations clecoed together, that should minimize the relative motion of the canaopy on the bow. Go back to the first side and do the next hole, then the other side, etc. That should give you the most rigidity as quickly as possible. It's going to be a royal pain to drill plexi with the dull bit, then change to the sharp bit for the bow, then back to the dull bit, etc.. If you have two drills, that would be great. Again, my memory is suspect, but I recall that the plexi bit should also be slightly larger than the metal bit so there is room for thermal expansion and vibration to occur w/o excessive stress on the plexi.

 

[ravenstar]

I just finished drilling my canopy yesterday. I chose to do it pretty close to the KAI: I used tape to establish the contact line, removed the canopy, used a Sharpie to mark the contact line, and predrilled #40 pilot holes every 2" on the contact line. However, before doing all that, I had a lengthy session of sanding the canopy edges down to fit the dimensions shown in the drawings. I don't know if it was intentional, but my canopy was larger in every direction and needed fairly extensive sanding, including removing over 1/4" from some places on the aft edge. Because that involved installing and removing the canopy many times, I put tape on the canopy near the center of the front and rear edges and tape on the adjacent fuselage surfaces then drew index lines across both pieces so I could reposition the canopy exactly the same way each time. When I was done with the sanding, I replaced the tape on the front bow with a fresh piece to establish the contact line.

I had no trouble drilling through the canopy into the pilot holes. When you think about it, you've got many more holes to match drill in the same manner on the rear bow. The real trick is establishing the contact line. My results were not perfect in that I didn't quite hit the center of the contact line with every pilot hole, but I don't think I could have done better drilling directly through the plexiglass into the bow. I found it very difficult to see whether the bit was aligned over the holes as it was. I don't think I could have reliably hit the contact point between the plexiglass and bow without a clear target. I'd also worry about the drill bit going through the plexiglass then trying to walk on the curved surface of the bow and putting strain on the plexiglass. My concern may be overblown, but it worked well enough the way I did it I think.

 

[mcgaughy]

I'm ready to mount the plexiglass canopy on the canopy frame, but it sure seems a lot easier and more accurate to drill through the plexi and into the frame in one step, rather than marking, drilling, then trying to match drill the canopy holes. Seems like every time I take off the canopy and put it back on, it goes back on in an ever so slightly different position. Has anyone else done this?

All I'll say is the tip up on my 7a was more frustrating than any other part of the build. I'm thinking the canopy alone constitutes 51%. I sika flexed my canopy to the frame so it was a one step process to attach it. I would think if you did screw's that you'd start at the top and work your way down but idk. Regardless, follow instructions to avoid cracks. The fiberglass transition at the front and skirts on the side will cover imperfections. I left the rear edge too sharp thinking it will help me get a more perfect gap for the rear canopy and subsequently got a cracked corner. Luckily a targa strip covered the crack.

 

[trib]

Just drilled the holes in the front bow a couple of weeks ago. I didn't like the method of trying to determine the location by sticking a piece of tape to the bow and then have the canopy press into the bow to locate the place to drill. It wanted to stick prematurely in the wrong place. Instead I put blue tape directly on the canopy then painted the tape with a thin layer of latex wall paint. Place the canopy into position on the frame and press the canopy along the bow to leave a painted line where it makes contact. Remove the canopy, give the paint 10 minutes to dry and drill holes every 2" as specified. The paint easily scrapes off in second with your fingernail. Then remove the tape from the canopy.