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Drilling and Deburring Canopy

Jwputnam

Well Known Member
My Finish Kit for my RV-9a slider arrives tomorrow. I fear the canopy process, I will admit.

Some basic questions that I don't seem to be able to get clear on:

1. I purchased standard sized plexi bits (1/8, 5/32, 3/16, 1/4) from Cleaveland Tool, but instructions say to pilot drill through the canopy into the frame tubes with a #40 bit. Do they mean a plexi #40? They just say "#40" and that the holes in the canopy will be later enlarged with a 5/32 plexi bit. If so, why am I not worried about cracking with the #40 through the plexi and into the frame? Won't a #40 plexi bit cut into the frame tubes and avoid cracking potential? Why not use one of those then? I am obviously confused here.

2. What tools are used to deburr these holes and freshly cut edges and in what sequence? They mention filling, but files can cause cracking I would guess. The holes are too small for a file anyway it would seem. Perhaps I am to use my deburring bit on the holes (as I would on aluminum) and a super fine file on the edges, followed by 200, then 400 grit paper? Won't my deburring tool be rather risky on plexiglass?

3. Am I to use my deburring tool to counter sink these plexiglass holes as well, or my #40 micro sink (which seems a little scary).

Needless to say, I am scared to death! I would abandon drilling completely and use the SikaFlex process, but I am a disaster with glues. My fuel tanks look like they were in a war.....but they don't leak!

Any advice will be much appreciated.
 
Relax

Once you get to trimming the plexi you have plenty of trimmings to practice with.

1) I took the standard bits and drilled through the plexi to the aluminum frame (tip up). The plexi bit could be used in aluminum but not so sure about steel. It will leave a nice dimple for a standard metal bit.

2) A single flute countersink will make a nice deburring, or countersinking tool. Very smooth cut and no snagging, or chattering during cutting. Cleaveland might have them. Get one larger than 1/4, it is a bit small for a countersink.

Remember reduce your fear with practice on parts of no consequence.
 
Do you use this single flute countersink on a hand tool (like my deburring tool) or a drill.....or even in a micro stop deal?

And what to deburr the edges of the cuts. A fine file?
 
I think you will want to sand and near polish the perimeter of the cut plexi. I use a 100 grit on a palm sander then 220 and 400 grit wet-or-dry sandpaper - you know the black stuff in the auto body section. The 400 leaves it nice and smooth.

After you do the trimming with a die grinder and the Vans recommended cutting wheel, test some of the trimmings, over 70 F is highly recommended and you should have no trouble where you are. I trimmed 1/8" strip off my canopy recently (dremel cutting wheel) and tied it in a knot - about 10" in diameter. It can bend nicely, but will break too, so be respectful.

ATC has the zero flute cutters. I just used one without a pilot. Mine goes in a drill chuck.
 
Don't be afraid of cutting and drilling the plexi, I too was stressed from the horror stories of cracks when drilling. Turned out to be a non event, I purchased the plexi drill bits but never used them. instead using "dull from regular use" bits with light steady pressure on the drill. A zero flute countersink also worked perfectly. The cut edges polish up easily.

The soft pulled rivets called for set easily without undue stress being applied, even a "hard" rivet inadvertently mixed up with the correct ones set without damage despite the really obvious extra effort needed to pop it (that was a worry...) This is on a 3B (slider) so it is considerably smaller than a 9, obviously lots of support needed when you do the cut.

As suggested you can practice everything on the off cuts. The stuff does break but it is remarkably flexible. Do keep it warm, 22-24 deg Celsius.

I considered the all Sika - no rivet approach too but chose to go with the plans, (if you can call the vague RV 3 drawings plans). Its fun, enjoy yourself.
 
SEE! you have lots of practice with the tanks, go for the Sika, I have one hole in my canopy, latch. just tape everywhere the primer goes and look at others build sites on how they did it. This topic is almost as bad a primer, but the deciding factor for me was the different expansion rates of the steel and plexi, there is a 100 degree temp Delta season to season where I live.
 
Just finished my 9 slider with sika. I was worried I would crack it doing it Vans way. One hole where the latch goes through drilled with a step drill. Sika is messy but only sticks on the primer. The stray bits rub off with finger pressure. Plenty of masking and it can be touched up for a neater job. I recommend it but also understand it is just another way to skin that cat. I also did fibreglass rear fairings. A lot of work.
 
Sharp #40

One mistake I made when drilling my 7A slider canopy was not having a sharp #40 bit when I got to the rear, skinny steel tubes. When the drill got through the plexi it slipped around the side of the small steel tube, an gave me an oval hole in the plexi. Switching to a fresh bit solved the problem, and I abandoned the bad hole.
 
All excellent advice. I am going to reconsider the SikaFlex and study up on it again. Bruce Swayze has a good web blog on it.

I also like the zero flute counter sink and will get one. What size should I order? 1/2"? 82 degree? I see them on MSC site
 
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I drilled all holes with a #40 drill bit, then used a uni-bit for increasing the size of the hole to desired. A key is to go slowly on the drilling with the #40. Going slower lets the plexi heat up some, which reduces cracking potential. The big risk when drilling is when the bit goes through the last bit of plexi. You may have seen this when drilling wood. I slowed down quite a bit when I thought my bit was ready to break through the plexi and didn't let the bit pull through.

I used standard countersink bits for countersinking and some deburing. I believe they were double flute. Most deburing I did with the unibit. Each "step" is essentially a single flute countersink.

Larry
 
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