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Drilling the $$ canopy

W

whd721

Well Known Member
I am ready to start drilling the canopy to the frame on a RV9A tip-up. I need opinions on the following:

Should I drill the frame first and then drill the canopy, or drill through the canopy then the frame?
Should I drill all the way through the canopy, or drill part way through the canopy then remove the canopy to the work bench and finish the holes.
I have the plastic drill bits. Should I drill the hole then enlarge the hole with a unibit or with a larger plastic drill?
After drilling a hole, do you use normal clecos to hold things together? Can clecos cause cracking?
My garage is cold. Has anyone had success with a plastic drop sheet tent and a heater? Summer is a long time away.
Any other good tips, hints or practices I should be aware of?

I have tried the forum archives, but with little luck.
 
Mine is a Slider....if that makes a difference or not.

I will tell you here what I did, but in no way will I guaranty it is the correct way or that you won't crack your canopy! I am convinced some crack, some don't regardless of technique or procedure. You just have to do your best and take appropriate precautions. Shaking the bloody stub of a chicken leg over it and doing a a chant wont hurt....

I drilled my canopy in assembly to the frame with a #40 standard split point. The plexi bits will not drill through the steel. I went carefully and slowly with the drill. I used cleco's to hold things together. I finish sized the holes in the canopy and frame separately. I used the plexi drills to enlarge the holes in the canopy to plans. I used a unibit for the handle hole. This, at the time, was the recommended procedure.

I did this when I was in Hillsboro about this time of year and similar temps as we are having now. I supported the canopy with saw horses and covered the canopy with a sheet of plastic and used a space heater under it.

To date, six years, 450 hours, no cracks, but....
 
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Simple answer......

Do not approach that canopy with a drill :eek:

Check all other threads and glue it on with Sikaflex.

Check my details - send me an email address and I will forward our snaps of us gluing on.

Mike
 
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JonJay said:
There have been several recent reports of canopy cracks on Sikaflex installs.
http://www.vansairforce.com/community/showthread.php?t=79420&highlight=sikaflex
More troubling to me is the potential long term unkowns.
Click to expand...

If by "several" you mean two or three, then yeah, I guess so.

On the other hand, it seems to me that a substantial percentage of riveted canopies crack through the holes on assembly. And as the acrylic ages and get brittle the percentage goes all asymptotic on unity and all.
 
And from the other side of the coin.......

There are literally thousands of RV canopies that were "drilled" and installed with pulled rivets many years ago and still flying around without cracks.
People without cracks don't generally post.
 
Bob Kuykendall said:
If by "several" you mean two or three, then yeah, I guess so.

On the other hand, it seems to me that a substantial percentage of riveted canopies crack through the holes on assembly. And as the acrylic ages and get brittle the percentage goes all asymptotic on unity and all.
Click to expand...

Not arguing one way or another....I am not really sure what I would do if I was doing it again today.
There are not enough Sika canopies in the fleet with enough age on them to know how they may fair in time, but you sure won't crack one while building it I guess.
Anyway, the original post asked about how to drill his canopy, so I did my best to answer that. My response to the Sika suggestion was just to make sure everyone has the facts, or at least, some of the past discussions..
 
William,

Are you a member of chapter 105? Do you go to any of the meetings? The January meeting is here at my home next Thurs. Jan 12th. You should plan on coming. My canopy is at the same stage, and I'm not drilling any holes in mine. I'm going to use Sikaflex. Come on over and let's talk. We're also going to be demonstrating Len Kaufman's canopy cracking escape tool on my original cracked canopy. It's a demonstration you don't want to miss.
 
Read the thread a while ago.

I think what came out was the fact that the Sikaflex is an adhesive sealant, not a straight adhesive.

It is designed to flex and if you look at the Sikaflex product catalogue which is available for download from their site, it gives loads of info regarding bead size and shape.

I think the main thing with any canopy is to get the fit as perfect as you can before you even think about attaching it to structure.

Ours sat on the frame without gaps - yep, it took a while !

But when we attached it with Sika, it took a couple of very light ratchet straps and nothing else. The rear window used 1/8th ply bowed out with carpet to stop scratching.

Very little pressure was used, the canopy 'sat' on the bead.

I still think it is the future as all plastic aeroplanes get their windshields glued on - a Lancair guy wouldn't dream of drilling would he ?
 
Warm

I did my 9 canopy in a room heated to 80f....... no problems with drilling at all.

On my 4 I used sikaflex.............. but then got worried it might come off so then drilled through the sikaflex and put in rivets as well. So I guess on the 4 its a bit of belt and braces!!! Again I heated the workshop to 70 plus.


The tailwind is completely drilled again in a heated shop.

Best of luck
 
I'll take a shot at addressing a few of the specific questions you asked ... this worked for me.
1. Practice on scrap before you start drilling the actual canopy, to get a feel for the drill speed and amount of pressure to use.
2. Make sure the hole is backed up, either with the frame or a piece of scrap material, when you are drilling.
3. I drilled through the plexi with the plexi bit and stopped after getting just a small dimple in the steel. I then switched to a #40 HSS bit to drill the rest of the way into the frame.
4. Enlarging the hole using a Unibit works great. Using a large size plexi bit is much more difficult.
5. Enlarge the holes enough to give yourself plenty of clearance around the fastener (rivet or screw) ... you're just trying to hold the place while also giving the plastic room to expand and contract.
6. Don't pre-load the plexi with stress - if a hole doesn't line up exactly right after you dis-assembly/re-assembly --- don't force it. Enlarge the hole in the plexi a little more...keep the pre-load to a minimum.
7. Cleo's work fine.
8. Find a way to heat your work space. I did mine in Texas in the summer, it was over 100 F every day.
 
Relax

Rick_A said:
I'll take a shot at addressing a few of the specific questions you asked ... this worked for me.
1. Practice on scrap before you start drilling the actual canopy, to get a feel for the drill speed and amount of pressure to use.
2. Make sure the hole is backed up, either with the frame or a piece of scrap material, when you are drilling.
3. I drilled through the plexi with the plexi bit and stopped after getting just a small dimple in the steel. I then switched to a #40 HSS bit to drill the rest of the way into the frame.
4. Enlarging the hole using a Unibit works great. Using a large size plexi bit is much more difficult.
5. Enlarge the holes enough to give yourself plenty of clearance around the fastener (rivet or screw) ... you're just trying to hold the place while also giving the plastic room to expand and contract.
6. Don't pre-load the plexi with stress - if a hole doesn't line up exactly right after you dis-assembly/re-assembly --- don't force it. Enlarge the hole in the plexi a little more...keep the pre-load to a minimum.
7. Cleo's work fine.
8. Find a way to heat your work space. I did mine in Texas in the summer, it was over 100 F every day.
Click to expand...
Every basic thing you need to know was outlined by Rick_ A. Pay particular attention to point #5.

Our techniques may differ but the essentials are pretty much the same. The only thing I do differently is I have no problem drilling the initial pilot holes using a #40 drill bit, often drilling straight through into the steel structure so I can cleco that hole before moving on to the next hole. Pressing the 'glas to the structure usually reveals a faint line that is dead center on the steel tube, the intended target of your drill bit. After that, nothing touches those piloted holes that isn't a plexiglas bit or a unibit. To eliminate any chance of causing a crack when countersinking (which happens to too many builders), avoid using a piloted countersink. An unintended momentary side load on that pilot is all it takes to crack the glass. You can avoid that unnecessary risk completely. For countersinking Plexiglas, a no flute countersink bit is far safer.

14t8qr8.jpg


Drilling Plexiglas has gotten some bad press that gained traction because it plays into our natural fear. After all, that canopy is a major expense and for a lot of people, perception IS reality. To help get over the anxiety many builders never seem to overcome, simply take a scrap piece and drill holes through it with wild abandon. Experiment away. Cool a piece in the fridge and then drill through it with a variety of drill bits. See what happens. The stuff is tougher than you think. Your fear will soon dissippate and when reasonable care is exercised, the chances are excellent you will go on to produce a crack free canopy that the overwhelming number of builders have managed to successfully do without cracking it. That proven method of blind rivet attachment has served experimental aviation very well. Given the recent spate of reports regarding Sikaflex failures, the jury is still out when it comes to the long term viability of that more exotic method of attachment.
 
I drilled mine last summer on a 65 degree day here in Seattle. No problems, in fact I was worried at the begining, but after many practice tests and a few initial holes I had no concerns about cracking.

I used a plexi bit, and didn't predrill. Just used the undersized holes already drilled in the frame as targets and drilled through the plexi with the full sized 5/32nds bit. Drilled through to touch the frame, then backed the drill out.. Threw in a silver cleco and moved on. No problem as long as you aren't stressing anything.

My thinking about not predrilling was that sometimes when you drill into a smaller hole, the bit grabs and pulls through violently.. I figured this could easily crack the canopy. So drilling full size from the start, worked just fine.

Do some test holes full size and see for yourself.

I would do it again the same way, didn't take long at all.

You can see the details in my blog:

http://www.704ch.com/2011_08_01_archive.html
 
aerhed said:
Rick, those cracks in the picture don't help your post much.
Click to expand...

I don't think those are cracks - I think that is the protective plastic coating. You leave that on until the absolute last minute while handling to avoid scratches.
 
Drilling Plexiglass

All the advice above is true and good. One approach I have had success with is drilling the hole in the plexi with the ball end burr that comes in your Dremel kit. It won't pull in at all, even if you have pilot drilled with a #40.
 
Rick, is that really the film on that bottom cleco? Sure looks like an "Oh f$%k" in the photo! Anyway the suggestion about the burr/dremel is good too. For walking holes over etc, a burr or stone is the safest for cracking. As long as it doesn't get away from you and run all over your plexi.
 
There are a number of good ideas in this post, I like Rick's ideas and others, however, the best idea is to go to the meeting with Bruce and learn what you can about the tip-up canopy and the drilling process. You will need heat! Electric heater on the inside of the canopy and 70 plus on the outside.:)


Good luck.

Jim
 
Thanks to all,

I will attend the EAA 105 meeting next week. Then ------
I will check out the Sikaflex.

Bill
 
Rick6a said:
To help get over the anxiety many builders never seem to overcome, simply take a scrap piece and drill holes through it with wild abandon. Experiment away. Cool a piece in the fridge and then drill through it with a variety of drill bits. See what happens. The stuff is tougher than you think.
Click to expand...

This experiment is completely bogus. The scrap is under no stress from being held in place. The canopy, OTOH, has been strapped and eventually cleco'd all over the place during the drilling process. It is these varying surface tensions that contribute to the risk of cracks spreading when drilling.

More two cents:
- People have successfully drilled at all times of the year, but unless you can get even heat in your shop up into the 80's, wait it out. The canopy is a good bit more flexible (melty) at 85+F than 75F. Using space heaters is also another risk for damaging the canopy.
- Throw away the plexi bits. Take a regular bit and drill it into cement for a minute to get it very dull. Drill by "melting" through the plexi with the dull bit.
- Better yet - do sikaflex. The use of sikaflex as the alternative to drilling goes back to at least 2004 when Sport Aviation wrote this up and RV'ers started talking about their experiences more after that. I found one reference which suggests this goes back before 2000.

Most importantly - good luck!
 
Make sure the canopy is supported where you are drilling - if you put too much pressure on, when the (perspex) frill goes through, the canopy will spring back and crack...
 
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