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Canopy Plexiglass Attachment

J

JohnF

Well Known Member
I have the plexi canopy in place and everything seems to fit well. I have not yet started any drilling because I am going really slow here, but one point leaves me a bit confused: The instructions have you mark and drill the front tube of the canopy frame with a #40 bit, then later you are to drill through the plexi with a #30 plexi bit through the plexi AND into the tubing.

Does that make sense? Will be plexi bit cut the #40 hole in the tube out to #30 with no problem? I am at a bit of a loss as to why the small hole to start with then enlarging the tube's hole while drilling the plexi? Am I missing something?
 
Hi John,

You may find that when you have drilled the #40 holes through both the Plexiglas and the frame that you can then separate the parts and use the Plexiglas drill to enlarge the holes in the Plexiglas and a regular steel drill to enlarge the holes in the frame.

Have a good day.

Best regards,
Vern




JohnF said:
I have the plexi canopy in place and everything seems to fit well. I have not yet started any drilling because I am going really slow here, but one point leaves me a bit confused: The instructions have you mark and drill the front tube of the canopy frame with a #40 bit, then later you are to drill through the plexi with a #30 plexi bit through the plexi AND into the tubing.

Does that make sense? Will be plexi bit cut the #40 hole in the tube out to #30 with no problem? I am at a bit of a loss as to why the small hole to start with then enlarging the tube's hole while drilling the plexi? Am I missing something?
Click to expand...
 
JohnF said:
I have the plexi canopy in place and everything seems to fit well. I have not yet started any drilling because I am going really slow here, but one point leaves me a bit confused: The instructions have you mark and drill the front tube of the canopy frame with a #40 bit, then later you are to drill through the plexi with a #30 plexi bit through the plexi AND into the tubing.

Does that make sense? Will be plexi bit cut the #40 hole in the tube out to #30 with no problem? I am at a bit of a loss as to why the small hole to start with then enlarging the tube's hole while drilling the plexi? Am I missing something?
Click to expand...

The original intent was to drill with a #40 plexi bit. This would allow for some adjustemnt when upsizing the hole in case you missed hitting some of the holes on center.
It turns out that until more recently, their wasn't a good source for plexi bits in teh #40 size so the plans were changed to use a #30 (which does drill into the aluminum frame quite well). If you have or want to acquire, a #40 plexi drill you can start with that and work your way up to the final size.
 
Plexi/canopy

My concern centers on the instructions FIRST having you drill ONLY the frame's forward tube with a #40 regular bit. No plexiglass involved. That's easy.

Now the instructions have you put on the plexiglass canopy and use a plexi #30 bit to drill through the plexi, hopeing to hit the hole you previously drilled separately in the underlying aluminum tube.

If you don't hit that underlying hole exactly (quite probable) you are going to put lateral forces on the hole you are drilling in the plexi, seemingly risking a crack in the plexi because the bit will be in the plexi hole as its tip enters the (perhaps) misaligned underlying hole previously drilled in the tube.

If you escape that, then you can later enlarge the plexi hole to #27 and still later countersink the plexi hole that you have enlarged.

Since you are going to use pop rivets to secure the plexi to the metal tube on the front of the frame, the allowance for plexi thermal movement seems somehow lost since the rivets will not allow movement anyhow.

This is the way I read the instructions (over and over) and it really makes me wonder if there isn't a better (and much safer) way to do this.
 
John, while your analysis is correct, you are over thinking it. I don't remember any issues here at all. Common sense and high speed and I sailed through the canopy attachment. This area is covered with fiberglass BTW.

Good luck!
 
I'll add this

If you need/want to over-size a hole in plexi, do it with a uni-bit. They will not break the plexi. Lots has been written about this subject.

John Bender
 
Jim F

I used Sikaflex on the windshield of my 9A and avoided the whole issue of drilling the plexi. Would this work on the 12? Perhaps. The adhesive was a quick and secure way of attaching the plexi to the metal bow and the foredeck.
 
Sikaflelx probably would work, Jim, but the ELSA it has to be made exactly as the SLSA (Van's prototype) or you cannot get an airworthiness certificate. No options, no choices. So Sikaflex would probably not be accepted by a DAR that knows his/her business.

I got the frame tube marked and drilled out to #40 today but need to screw up my courage a lot to go much further. I ordered the SkyGeek Permagrit countersink today, and have Starlite Industries tapered countersinks coming for the rest of the holes.

We cowards really do die a thousand deaths!
 
Just did this on a 7

I am not a fan of the Permagrit countersink. It does the job but I found a standard caged countersink in a slow drill worked great and left a better surface.
What I would suggest is that you possibly enlarge the hole a bit over a #30 in the plex before countersinking.Both the Permagrit and standard #30 countersink were quite tight in the plex and IMHO makes it easy to crack with any side pressure. I reamed the hole up one size before using the piloted countersinks and had no problems.
Regardless make sure you test on scrap first!
 
Plexi Attachment

Thanks for all your suggestions...I now have the plexi drilled on the front and aft parts of the canopy frame. That went well in spite of my fears. The overall fit is really quite good..all uniform and per instructions, except the bottom of the sides of the plexi..the instructions call for 1/8-inch to a max of 1/4-inch between the bottom of the plexi sides and the frame. I have some points that touch, and gradually increase to about 3/32....I don't want to cut the bottom edges, but wondered if it would be best to use #60 or #80 sand paper and remove enough to provide the called-for clearances. What's your take on the best way to proceed?

I emailed Van's technical folks, but because of the holiday it might be several days before they are able to respond, so I am turning to the expertise on the VansAirforce group.
 
JohnF said:
Thanks for all your suggestions...I now have the plexi drilled on the front and aft parts of the canopy frame. That went well in spite of my fears. The overall fit is really quite good..all uniform and per instructions, except the bottom of the sides of the plexi..the instructions call for 1/8-inch to a max of 1/4-inch between the bottom of the plexi sides and the frame. I have some points that touch, and gradually increase to about 3/32....I don't want to cut the bottom edges, but wondered if it would be best to use #60 or #80 sand paper and remove enough to provide the called-for clearances. What's your take on the best way to proceed?

I emailed Van's technical folks, but because of the holiday it might be several days before they are able to respond, so I am turning to the expertise on the VansAirforce group.
Click to expand...

A sanding block with 80 grit will work fine (I thought the construction manual mentions that....). just be sure to finish the edges through 220 grit when you are done. Even as little as 1/16 " gap from the frame would be acceptable.
 
A sanding block is very controlable, but slow. I used a 90 degree angle die grinder with a 2" sanding pad and those quick change discs avialble from 3M or Harbor Freight. It does require a "gental touch", but you can remove material much faster. I used the sanding block for final shaping of the edge, and smoothing.

Good luck!
 
Geico266 said:
John, while your analysis is correct, you are over thinking it. I don't remember any issues here at all. Common sense and high speed and I sailed through the canopy attachment. This area is covered with fiberglass BTW.Good luck!
Click to expand...

Larry - I am probably also overthinking this, but all these posts about cracked canopys are enough to scare you to death! When you "sailed through" this operation, did you have all the specified plexi drill bits, including the #30? Avery did not supply a #30 with the tool kit, and I don't even see one listed in their catalog. Second question - What did you use for the countersinking?
 
Geico266 said:
A sanding block is very controlable, but slow. I used a 90 degree angle die grinder with a 2" sanding pad and those quick change discs avialble from 3M or Harbor Freight. It does require a "gental touch", but you can remove material much faster. I used the sanding block for final shaping of the edge, and smoothing.

Good luck!
Click to expand...

BE CAREFUL HERE!!! I took the EXACT opposite approach. Low speed. In fact, used a manual hand drill to open up the holes (the front bow where rivets are used). Used the Unibit at very low speed to open up other holes. (the sides and aft bow).

When drilling at high speeds, the bit can grab and pull the plexi up the bit. When it penetrates, the plexi will snap back before you know it. A crack will result nine times out of ten.

Maybe overkill but it worked very well for me. See my blog.
 
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