38-23, 24 & 26 Drilling and Countersinking the Canopy

The next couple of days were due to be very warm here for the time of year, so there weren’t any excuses left … I had to start drilling the canopy! Deep breath …!

I’ve mentioned earlier how nervous I’ve been about this … but to give everyone building a 14 reading this confidence, as long as you take it carefully and adopt what has worked for you on the Rear Window, all will be well.

Actually, I nearly enjoyed it! Well, now it’s over, it’s easy to say that, isn’t it? : )


Drilling

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The manual suggests you postion a helper inside the canopy to hold a wooden block against the Side Rails whilst match drilling.

I didn’t think Coral would fancy a few hours locked in the cockpit, so I came up with this arrangement …


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… a simple wooden frame positioned loosely at the front, providing enough support to prevent the sides at the front flexing during drilling.

My plan for the rear holes was to reach round with a wooden block through the Rear Window cavity.

But this frame provided so much rigidity, and because I opened up the holes with a reamer, as it turned out I didn’t bother with the blocks for those holes anyway.


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The weights on the canopy were replaced and the everything positioned back on the marks, with the C-01419-L & -R Canopy Side Skins clecoed in place.

The C-01423 Canopy Shims were a bit awkward, since you need to position them accurately between the canopy and side rails, but at the beginning they have no holes of course.

I used some sticky dots (pinched from Coral’s craft store!) to keep them in place.


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I decided to do this stage with the Rear Window in place, so I could use my 0.032″ shims to accurately position the canopy.


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Once again the holes are first match drilled #40, in a specified order, starting at the top.

As per the process I used for the Rear Window, I match drilled the Plexiglass with a #40 Plexiglass Drill Bit, then a normal #40 on through the aluminium, then reamed #36, #30 & finally #27 to open up the holes for minimum risk of cracking.

The temperature in the workshop for this was 21ºC (70ºF)


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Clecos are inserted as the drilling progresses, and I used an airline to blow any swarf away under the Plexiglass.

I’d placed the carpet to protect the canopy as I worked along the top.


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Marking the holes on the perpendicular to avoid parallax again worked well to help position the point on the #40 plexibit.


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And I used the magic potion again.

In hindsight I’m not totally convinced about the Baking Soda/Isopropanol mix. The baking soda is supposed to provide body for the Isopropanol to stick on the drill bit, but it does leave a residue which needs to be cleaned off. I tried dipping a brush into pure Isopropanol and “painting” the end of the drill bit, and this seemed to work fine as long as you drilled immediately so the Isopropanol had not evaporated.


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This was the stage I was most concerned about.

All the other holes had a little hole in the aluminium underneath for the point of the Plexibit to enter, but the side rails do not.

So I was concerned that when changing to a normal #40 drill bit for the aluminium, the Plexiglass bit would not have cut completely through the Plexiglass due to its sharp point.

But I need not have worried … I used the plexibit carefully, and felt it touch the aluminium. Then I swapped to a normal #40, turned it slowly as it entered the hole, and it worked just fine.


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Once all the holes had been match drilled to a #40 size, I went round with #36, #30 and finally #27 reamers.

No dramas : )


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All done and clecoed in place.

Time for a break … countersinking the next day.


Countersinking

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The manual gets you to do various other little jobs prior to countersinking the holes, but I had these two days of nice warm weather and I wanted to get it done.

It was 24ºC (75ºF).

I had planned to take the canopy off to do this job, and I’d got Coral into the workshop to help lift it off the plane.

And she said “Why don’t you countersink the holes with it on the plane?”

Sometimes you are so close to a job you miss the obvious! You have to countersink the Rear Window aft holes with it off the plane, so I guess I was still in this mindset.

This was a top idea! Shame I hadn’t thought of it.


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This had several advantages … it meant the canopy could stay accurately positioned for those little jobs in the manual mentioned earlier, and most importantly, it was nice & stable.

I placed tape to protect the canopy, and used the cage.

This took a long time, since the depth had to be continually adjusted due to the glass curvature.


But eventually it was done.

This picture was taken later on, after the front fairing had been marked out, hence the tape on the front.

I fine tuned the countersink depth on the Aft Canopy Frame holes by hand to ensure the screw heads were perfectly flush.

Anyway, canopy holes all done, with no cracks! Phew!

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