Tuesday, October 11, 2011

Happy Anniversary!

October 9th was the second anniversary of my RV-12 build and I celebrated by starting the fiberglass of the forward canopy arms. This is one of those jobs that takes days of effort - the first day is spent thinking about ways to avoid doing it, the second through fifth days are spent doing the things dreamed up on the first day and, as it turns out, there are a few more days of preparation work to do as well. Sunday dawned temperate and clear, and promised temperatures suitably warm for the efficacious curing of the epoxy. It was on!

The days of preparation are all a blur now so I can't put a firm timeline on the process that I will be detailing below; suffice it to say that the time period is roughly a week of on again, off again effort.

The point of all of this is to create a smooth, attractive, and aerodynamic blending from the stark, angular facets of the metal canopy frame into the canopy bubble and fuselage. Just between you and me, I'll settle for two out of those three, and I don't particularly care which two it is. The plain truth is that I do not like working with fiberglass.

That having been said, here we go with the narrative.

The first step is to provide a support for the fiberglass. You could almost call it a mold, I suppose. It starts out as a pair of foam blocks, one for each side of the airplane. Those were trimmed and glued into place as detailed in this post.

Pete happens to own a very nice sanding block and was kind enough to bring it down to the hangar. In turn, I was kind enough to let him use it to trim the blocks. I'm generous that way - known for it, in fact.

Van's supplies a pair of paper templates that serve the dual purpose of acting as aids to masking off the appropriate areas of the fuselage and for the eventual cutting to shape of fiberglass cloth. I had stored them in a safe place where I wouldn't lose them; I found them after only three days of searching.

A strip of high quality electrical tape is used as to protect the canopy and provide a guide line for the fiberglass strips that will fill in the area between the forward fuselage and the canopy bubble.

I finally found a use for all of the paper that the kit parts come wrapped in.

There are ten fiberglass cloth shapes to be cut out, five for each side. One of the template paper sheets is used as a sacrificial cutting template whereby it is cut smaller for each size of cloth "part." I bought a very sharp rotary cutter to use for the somewhat complex curves required.

A perplexing problem quickly manifested itself. No matter how carefully I would trace the cutter around the template, the resulting sheet wouldn't come out shaped anything at all like the template.

As you can imagine, this problem created quite a bit of back and forth discussion between Pete and myself with suggestions and theories flying fast and furious. We eventually reached a consensus: the loose weave of the cloth combined with the shear forces being applied by the cutter were distorting the shape of the cloth as it was being cut. The solution? I would mark the outline of the template with a Sharpie(tm) marker and cut the cloth without the template paper blocking the view.

That worked somewhat better, but it was still hit or miss. It seemed that the large piece of cloth that I was cutting from might be part of the problem; various areas of it tended to get stuck to the work table and cause strange bends and transformations to occur. We finally hit upon the brilliant idea of cutting out a piece of cloth only slight larger than the finished part would be. It was much easier to get the smaller piece to sit straight on the table than it was when dealing with the huge sheet.

That problem solved, we finalized the masking job by covering the instrument panel and seeking out any sneaky little holes that might allow epoxy to drip into inconvenient places.

The Van's plans rely on a temporary forbearance of gravity to keep the wetted fiberglass from sinking into the areas

Pete had done some research and found a pretty good suggestion on another RV-12 builder's blog. He suggested using the left over scraps of foam to fill in those areas in order to provide support for the cloth.

There wasn't enough foam remaining, so I took a somewhat less satisfying path: I used some weather stripping that I had bought for the RV-6 canopy (which turned out to be a real fiasco, but that's a story that I'd prefer to just forget about).

The piece of foam that Van's specifies gets fiber glass permanently glued to it, but we didn't want that to happen with our extracurricular foam. We covered it with packing tape and waxed it with paste wax to keep the epoxy from sticking to it.

The next step was somewhat painful. The parts of the pristine canopy and the aluminum side skirt that get covered with the fiberglass have to be scuffed up to provide a bite for the epoxy to grab ahold of.

Everything was finally ready to cover with the fiber glass.

So I went flying. I thought it might be instructive to go take a look at a finished RV-12 to see what this fairing was supposed to look like when it was done. While I've said that I'd settle for two out of three of the goals, here's what a three-out-of-three exhibit looks like:

It was a pretty nice day to fly, as it turns out.

The Fall colors are proudly showing the way to a dismal winter.

Back in the hangar, it was time to wet and place cloth.

Three and a half hours of grueling and tedious work later, the peel ply was on.

Things happen fast when you'r working against the ticking time bomb of mixed epoxy and things get pretty messy:

The peel ply came off a couple of days later to reveal a nice, solid build-up of fiberglass. Naturally, the number one rule of airplane building (what has been done will soon be undone) will soon be in play: most of this will get sanded off.


Jeff said...

Dave don't think that the " loss of the Miata " is going un noticed.

Leon said...

ditto what jeff said.
is blogger working for you? i don't see any pictures but pictures in blogger are not working for me today so it is hard to say.

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