Canopy Drilling

rv8gibbo · #1 03-16-2019, 01:00 AM

Hi Guys, I've just about got the canopy where it needs to be and Its time for the bit cut! My question and excuse my ignorance, is what is the best way of drilling? on or off the fuse? in a prefabbed frame?

Many thanks
Gibbo

https://photos.app.goo.gl/FQ17B44ot6Bmsjcx5

rv8ch · #2 03-16-2019, 01:48 AM

The way I did it was to not drill at all, but use a windscreen glue like Sikaflex. If you do a google search like this you will find lots of hints about how to do it.

https://www.google.com/search?q=rv8+canopy+sikaflex

If you have decided that you will drill, I'm sure that someone will chime in with some tips.

mike newall · #3 03-16-2019, 05:54 AM

Sikaflex !

Much, much easier and less fraught !

That is how your windshield is attached to your car

Blain · #4 03-16-2019, 09:15 PM

+1 Sika. Holes equal cracks.

Carlos151 · #5 03-17-2019, 06:59 AM

+1 for Sikaflex.
Drill = cracks = repair

rv8gibbo · #6 03-18-2019, 02:32 AM

Thanks everyone, I'm going with Danny Kings Grommet idea, my engineer mate advised that I shouldn't use sika as it uses an acid cure and that it will accelerate any cracking, my question was more about wether or not it's recommended drilling and fasterning with frame off the fuse.

rkbrown819 · #7 03-24-2019, 08:40 AM

Can you provide a link to this or share the information.
Sounds interesting, but I don't see this as part of this thread.
Thanks!

Tankerpilot75 · #8 03-24-2019, 12:28 PM

Check the EAA website ?Hints for Homebuilders.? If my memory serves me correct, their recommendation for drilling into plastics like the canopy was to use a ?dulled bit? in that the heat generated will keep a crack from occurring. But please don?t follow this advice without first reviewing the video. My memory has been known to be a little suspect at times.

Carl Froehlich · #9 03-24-2019, 01:33 PM

Addressing the orginal question, this process has worked well on several RV-8/8A over the last 15 years:
- Trim the glass do it fits as desired while clamped.
- Take the glass off and put a line of 1/2? wide or so masking tape on the frame - use just enough pressure so the tape does not fall off.
- Put the glass back on and clamp. You will see the tape now shows a perfect line where the glass is exactly tangent to the frame. This is where you want the rivets so you don?t stress the glass with side a side load. Remove the glass.
- Take your sharpie and draw in the line on the tape. Now space out your hole pattern.
- Drill #40 the holes in the frame without the glass installed.
- Remove the tape, replace the glass and clamp.
- Drill through the glass into the holes, cleko as you go.
- Once the glass is done, drill the skirt.
- Remonve the glass. Drill the holes in the frame out to #30.
- With the glass off, drill the #40 holes to #30 using a plexiglass bit. After that use a Unibit to open the holes to 3/16?.
- On the roll bar counter sink the glass to accept a #6 screw tinnerman. The rivet will go through the tinnerman - the tinnerman spreading out the force and teh rivet does not touch the glass.
- The fairing goes on per the instructions.

Carl

Breezy · #10 03-24-2019, 02:02 PM

Gibbo,

I have installed canopies both new and replacement. All have been drilled and pop riveted or machine screw. I have never experienced a crack while installing. There are some simple precautions that will help with avoiding cracks.

Keep the plastic warm, about 80 deg.F works well. Warmer is not better, the material expands and contracts quite a bit in the normal temperature range. Fastening while too warm will cause stress after cooling.

I have used both plexiglass drill bits and dulled HSS bits. Either one works. Dull a HSS bit by running it in concrete for a few seconds. While drilling don't push very hard and have a hardwood block supporting to prevent pushing through.

If drilling over the steel canopy frame keep the bit aligned to the contact point of the tube and plastic. This will prevent glancing as the bit comes in contact with the frame. Use a bit that is slightly larger than the fastener, pop rivets expand while pulled and will cause pressure in the hole. Drill the frame with the correct size bit for the fastener.

An easy way to find the contact point of the frame to the plexiglass is lightly wet with water or window cleaner. Hand squeezing the two together will reveal a line at the contact point.

As I was typing, I recall mistakenly using steel mandrel pop rivets on one install. That aircraft has been flying for years with no cracks.

Take your time.

Also, I am not against SikaFlex. It looks like a good system, just never had the opportunity to use it.

Cheers!