38-03 Drilling the Rear Window

Tools & Strategy

There are lots of posts on the various forums about drilling plexiglass. Reading them make me very nervous!

After lots of thought and trying to filter out the best advice, this is what I came up with. It has worked well for the Rear Window, but at this point I still have to drill the canopy.

For the first #40 holes I used a Plexi Drill, giving the best chance to avoid chips as the drill bit exits the material.

This is easy on the skin holes, but the Roll Bar match drilling is a bit harder. This is because you have to match drill through the Plexi into the aluminium. I decided to use the Plexiglas drill until it just touched the little hole in the Roll Bar, and then swap drill bits to a normal #40 and carefully drill on through the aluminium.

Then I used #36 & #27 Reamers to open up the holes. Since reamers scrape there is less chance of chipping.

Temperature … I waited for a warm couple of days, but in the UK at this time of year, that’s not that warm : ) It was about 16ºC (61ºF) in my workshop.

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Lastly, I’d also read that some kind of lubricant and cooling fluid helps.

I’m not sure why this combination works, but an internet search revealed Isopropanol mixed with Bicarbonate of Soda.

It seemed to work, especially during the tapping.

I mixed in enough soda to give the Isopropanol some “body” to stay on the drills/tap.

Skin Holes

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There is a specific order in which to drill the holes, but the first to get done are 5 holes at the top through the skins.

As the manual suggests, a helper with a wooden block helps to reduce the chance of chipping, also keeping the Plexiglas firmly against the skin.

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Phew! First 5 match drilled and clecoed : )

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As the drilling progressed, if a refelction wasn’t visible to judge a perpendicular, I used a set square.

Roll Bar

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The first Roll Bar holes are an easy start, since they aren’t flush against the F-01431D shims.

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Because of this, I shimmed the gap to prevent flexing.

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Lots of swarf in the gap …

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… easily removed with compressed air.

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One of the challenges with this stage is making sure you drill exactly into the little holes in the F-01431D shims.

I marked each hole whilst viewing perpendicularly to avoid parallax.

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Then it was an easy job to begin drilling with the point of the Plexiglas bit exactly on the mark.

I used the reflection to judge the drill angle … but be careful on the curves … it’s easy to get it wrong!

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As each set of holes are drilled & clecoed, you have to keep pushing the bottom of the window back to ensure a snug fit.

I found that clamping as suggested in the manual diagram worked well, with virtually no movement.

Eventually all the holes get done!

Next job is to ream and tap the Roll Bar.

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3 Comments on "38-03 Drilling the Rear Window"

  1. Steve, good to see you flying along with the build.
    Finishing kit finally arrived, 6 months after ordering and still have items on back order. 😕
    Your write ups are great. Where did you get your #40 plexiglass drill bits and reamers from?

  2. Lew MacKechnie | June 30, 2020 at 4:17 am | Reply

    Hi Steve…
    I’m just getting to the point in Section 38 where I’m wrapping up the canopy frame construction and I’m about to start on the dreaded plexiglass drilling. I’ve postponed working on the rear window for as long as possible and can delay no longer. I’m hoping that drilling the rear window plexiglass will make me comfortable with the process before tackling the main canopy drilling. Your posts have become required reading as I plan the next days activities. Thanks again for your thorough documentation. It’s proving to be enormously helpful..
    Have fun with your build and keep up the good work!!
    Lew MacKechnie

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