Sunday, September 4, 2011

Drill, Baby, Drill!

There are events during the building of an RV-12 that have a such a bad reputation for being difficult and/or having the potential for the destruction of expensive parts that builders will go to extreme lengths to postpone, delay, and avoid having to do them. The drilling of the canopy is one of them. Having run out of excuses and having read every forum posting or blog entry on the topic that I could find, there were no more potential procrastination possibilities pursuant to preventing the performance of this particular plexiglass(tm) penetrating project to be found. In other words, today was the day that we would drill the canopy.

My perspicacious preliminary perusal of pertinent personal logs on the subject had provided me with a shopping list of items to procure. That list included two plexiglass(tm) bits (9/64" to fill the demand for a #27, and 1/8" to stand in for a #30), a zero-flute countersink bit, and a hand drill.

The recommendations for these items were gleaned from the dozens of horror stories and how-to postings that I read through. They all came down to one thing: drilling the canopy plexiglass(tm) without causing any cracks. I can't say with any degree of certainty whether or not all of the preparatory angst was unwarranted, or whether all of the breathless descriptions of the monsters that lie embedded within the very fibers of the plexiglass(tm) were fabrications, but I do know this: the first hole was drilled with zero drama and zero damage:

As were every single one of the remaining holes:

The days and weeks of stress and worry were for naught. Although, I must add that this gratifying result could in fact be completely because of the stress and worry that drove me to spend all that time researching hints and tips. It's kind of like all those jobs that were "created or saved" with government stimulus dollars: it cannot be proven, nor can it be disproven. All that matters in the end is that we are where we are, and where we are is done with drilling the canopy! Hurrah!!!

After a brief celebration, Painfully Pragmatic Pete pointed out that there was plenty more work to be done. (Well, not really, but I'm having a hard time breaking this irritating alliteration habit.) The holes that had been drilled were in the front and back of the canopy, but the sides remained to be done. The canopy sides are match-drilled through the holes of the aluminum side skirts. The plans describe the correct placement of the skirts:

Which is all well and good, except for the fact that there is no such thing as an F-1277B, as can be seen in the parts inventory:

I just assumed that the not-quite-as-famous-as-E=MC2 Einsteinian equation F-1277-L + F-1277-R = F-1277B was in play. In other words, the drawing in the plans looked like the skirt should be placed flush against the front edge of the turtledeck skins, so that's what I did.

The first set of match-drilled holes was through the skirt and into the canopy frame:

You'll note that the front of the skirt is curled to better fit against the side of the fuselage. This was one of those vanishingly rare occasions where Van's did not do the bending/curving for us. We did it through the somewhat simple expedient of just bending it around a paint can:

One thing that I noticed when I was clecoing the skirts into place was that they weren't sitting flat against the sides of the canopy frame. It didn't take much by way of Sherlockian deduction to find the cause:

I decided to do something about it. That "something" involved one of the wickedest-looking Dremel attachments I've ever seen outside of a dentist's office:

I didn't grind it all the way down flush to the canopy frame, but the amount that I did remove had a very beneficial affect on the way the skirts looked:

There will apparently be some fasteners in the skirts that need to be flush because the plans then had me dimple five of the holes in each skirt and add a matching series of countersunk holes in the frame.

The next step was written by the unemployed stand-up comic that Van's brings in as contract labor now and then:

Always the first to detect an opportunity to relax while pretending to work, Pete quickly volunteered to perform the role of "non-claustrophobic friend/spouse/child":

The N-C F/S/C is in there to hold a block of wood against the thin aluminum braces while the HBWS (hot, bothered working stiff) match-drills through the canopy skirts, the canopy itself, and the braces. To be fair, it's a pretty important job and it was only due to the cold front that passed through last night that it was even remotely comfortable locked into the enclosed cockpit. As recently as yesterday it would have been unbearable in there. I'm not sure how I would have been able to tolerate it after Pete quickly volunteered to be the HBWS...

After the drilling was done, I decided that I had to try sitting in there myself. This would be the first time I'd get to sit in the plane with the canopy down - it was perfect for pretending that I was flying a fog-blanketed approach to minimums after a complete loss of my radio and transponder:

All that was left to do was final-drill the (approx.) #30 holes in the canopy to their final (approx.) #27 size. I think the additional diameter is added to allow for expansion and contraction of the canopy. In any event, this is a step that came with dire warnings from many of the postings that I read. I more than once came across stern admonitions against the very idea of ever enlarging a hole drilled into plexiglass(tm). Somewhere in my meanderings, though, I came across a suggestion to use a hand drill for this. The slow turning speed and the better tactile feel of the hand drill would allow the enlargement of the holes with a vastly reduced risk of causing cracks.

I was true. I could feel the bit beginning to bite into the plexiglass(tm) as I carefully turned the crank handle. Slow and steady won the race: all of the holes were enlarged with no damage.

Once that was done, it was a simple matter to use the zero-flute countersink bit to deburr the holes in the plexiglass(tm) and countersink the holes across the front edge of the canopy for the flush rivets that will soon be installed through them.


Carl said...

Nice Dynon Skyview :)

Anonymous said...

At a later point in the plans (don't have them handy) you will have used small screws and nuts to attach the plexi to the side skirts, and in a row below them, the side skirts will be riveted to the canopy frame. Before you do those rivets, check the clearance with the fuselage side skins with the canopy in place. I wound up drilling those rivets out and installing individual washers as spacers and slightly longer rivets. It would have been easier to prepare a long aluminum spacer for each side. The plans don't mention a spacer or a clearance distance, if I remember right. Bill H.

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