Sunday, August 28, 2011

A game of fractions

As our April in August continues apace, I vacillate between a visceral, slow-burning anger that I am still mowing the vast grounds of my palatial estate and the joy that I find in having some decent flying weather for what seems like the first time this year. Tempering the desire to go flying at whim, however, is the extraordinary cost of gas this year. In a nutshell, I am digging deep to find even the remotest excuse to fly in order to avoid being burdened by the guilt arising from the conspicuous consumption of carbon-based combustibles coincident to clearly casual usage.

Fortunately, I was able to scare up the semblance of a mission yesterday. Some of my long-time readers will remember that one of the project ideas that I kicked around during those empty, meaningless years before I embarked on the current RV-12 journey was to find an older RV-4 that would make a good platform for updating/upgrading. A soundly built, minimally equipped RV-4 with a medium time engine is selling in the mid to upper $30s these days, so the acquisition cost is reasonable. I would never undertake to actually build an RV-4 due to the order of magnitude more difficult nature of the build process as compared to the RV-12 (which is quite challenging enough, as we've often seen), but I would enjoy re-wiring and updating the electronics/avionics quite a bit. That's fun work!

Through the miracle of the internet, I learned of a guy that is doing exactly this, and he lives right here in town. I begged a visit to his work site in order to get a feel for the nature of the work involved.

Cadillac Pete and I flew up to Delaware Co. (KDLZ) airport early yesterday morning. As you will be able to see from the following photos, the job is nearly (and neatly!) done:

While the wiring and avionics work was interesting, I found the air-locs used to replace the frustrating cowl hinge pins absolutely fascinating. This is something that I wish I had done on the RV-6 and will almost certainly do on the RV-12 at some point.

Back at the Schmetterling shop, Pete and I laid the canopy in place for its first trial fit.

We immediately found a problem. The pre-drilled hole for the canopy latch handle didn't line up. This caused a notable degree of angst in the sensitive belly of your's truly - the idea of elongating that hole simply did not appeal to me for any number of reasons, and I frankly couldn't fathom how Van's could have misplaced the location of that hole so egregiously.

"No Panic" Pete, provider of prescriptive and prophylactic advice pertinent to any particular problem providentially perceived the providence of the problem: when I had moved the wooden spacer blocks and the clamps holding them to the bottom of the roll bar, I had allowed the blocks to settle to the lower portion of the roll bar, thus allowing upper portion of the roll bar to angle too close to the rear window. I moved the wooden spacers such that they provided support for the entire back edge of the roll bar.

Problem solved! As I said at the time, "I wish they could all be California girls, but I'll settle for all problems being solved this easily."

Working under the assumption that having the pivot tube for the canopy latch handle now centered into the pre-drilled hole in the canopy strongly indicated (I hesitate to say "proved" - I'm done with alliterative 'P' words) that we could move on to performing (drat!) the measurements provided (argh!) in the plans (I give up). One such measurement is the requirement for a 1/8" gap between the lower edges of the canopy sides and the edge of the canopy frame. I was at a loss as to how we could ensure that gap, but a search of the scrap bin came up with a 9" length of 1/8" angle aluminum. I cut it into 12 little segments to use as spacers.

We started taping down the sides of the canopy with the spacers in place.

Then we ran into a problem. The 1/8" gap on the left side of the canopy was mostly uniform for the entire length of the canopy, but the ride side had an area where the gap was far larger than 1/8". We tracked this asymmetry down to a difference in the two sides of the canopy: one had a 14" length from the back of the canopy to the spot where the edge changes direction, while the other had only a 13 3/4" length.

That difference throws everything out of whack. Looking ahead in the plans, it appears that the gap will be covered by a skirt piece made of aluminum, but I'm reluctant to accept this discrepancy as allowable without doing a little bit of research first. It's these little fractions of an inch that end up being bigger problems further down the road.

As it turns out, a closer reading of the plans shows that 1/8" is the nominal gap, but up to 1/4" is allowable. No harm, no foul as they say. We are clear to proceed.

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