Saturday, December 27, 2008

Close only counts in horsehoes

The wing is connected to the fuselage by two brackets that bolt the spars to the fuselage. It also has two struts that attach from down by the landing gear and bolt into the wing almost halfway out, forming a triangle. These struts are reinforced and spaced by a jury strut, which bolts from about two-thirds of the way up struts into the wing, forming another smaller triangle inside the first one. In addition to critical reinforcement, it also provides a handy place to put your gun case and snowshoes.

But the holes in the wooden spars were drilled an eighth of an inch too high on the front spar and an eighth of an inch too low on the rear spar to attach the bracket. (Guess who didn't find this out until it was the last piece of hardware standing between her and a completely trammeled wing?)

Well, when dealing with a wooden wing, the answer is emphatically NOT making a larger hole in the wood. You want to keep the wooden spars as pristine, free of damage or holes, as possible. So, first I tried the bracket on the old spars. Nope, fit fine there. Then I tried the other bracket, hoping maybe that one had been repaired oddly over the years. No luck. So, what to do?

The answer is: take tape and make an inverted T around the holes, on both sides of the spars. With the help of a square and a level, draw lines exactly through the centerline, horizontal and vertical, of the hole on the spar. Then, re-attach the bracket, and put tape over the tab with the bolthole, while clamping it down with a C-clamp. Using the same square and level, complete the lines across the tape on the bracket, so you have the centerline drawn as crosshairs where the hole now needs to be on the bracket.

If I was in the field, I might just drill the hole a little longer, then weld a washer on top in order to reposition the hole. If I was a better welder, I'd weld an extended tab on the bracket, or fill the current hole, and drill a new one. As it's been six years since I was good at welding, I'm being smarter.

Monday, I'm going down to F Atlee Dodge, and having the welders there do it. See? Smarter cookie than I first appear. And because I'm such a smart cookie, I checked the bracket on the other wing so I don't have to repeat this when I get there on the other wing. But guess what? That one's fine - no, I don't get it either.

Progress continues.

Unrelated notes: Thirty Second's To Mars video for their song "From Yesterday" is extremely pretty - possibly too pretty for the song.

And Jenny? I adore your .22 rifle. I hope you don't mind I put a cheap little scope on it - but it's let me see far enough away that I'm now consistently pegging dime-sized targets at 25 meters. I know this because a certain lanky gent disappeared from the lane next to me, and reappeared with a roll of small orange dot stickers - so I had to put them on and promptly peg them!

Friday, December 19, 2008

Trammeled Not Trampled

I've now reached one of those highly important celebratory steps - trammeling the wings. This is again something that would take an accomplished A&P fifteen minutes to do, and has taken me three days. The first part is to draw a reference line on the top of the spar that marks the middle of the compression strut, and a crossing line at the halfway point. The easy way to do this is to take a square (which is actually a triangle-shaped piece of steel used for making things square), and lining up the top and bottom bolt holding the compression strut in, follow the line up and mark it.. You'll use these lines to measure whether or not your bays - the distance between compression struts - are square, and tighten or loosen the drag & anti-drag wires in order to pull the spar into a square shape.

Except, well, the holes aren't always - or even usually - straight up and down. There's a very slight angle that puts the line well off to one side. To make matters worse, the ribs and brackets get in the way and don't allow the square to easily lie there or line up. Also, your eyes are not in the center of your head - so if you look at something when standing directly over it with your left eye closed, your line will be way off to one side, or way off to the other if your right eye is closed.

Finally my IA disclosed some of the great truths in life:

1. Use a sharp pencil for a fine line.
2. You don't have to be absolutely precise or absolutely accurate - but you must be consistent. If the reference line is off by 1/4 inch, he said, that's fine - as long as it's off by 1/4 on every strut. So mark it as well as you can, and do it the same way, every time.
3. Loosen all your wires before you start, so the wing can be easily adjusted. Then start from the wing root and trammel out to the tip.
4. A piece of inner tube rubber cleaned with brake-kleen is slightly sticky and great for holding the drag wire.
5. If you have a 1/2 inch to square, only tighten the drag wire halfway (for 1/4 inch in this case) - the tension on the spars & other drag wire will pull it the rest of the way. It's geometry, Watson.

It went a lot faster after that!

But wait, there's more - after getting it all square, I have to go back, tighten all the bolts, and re-trammel after all the hardware is tight. This is slightly stymied by the two AN5-16 bolts called for actually need to be shorter than AN5-11. I don't have shorter bolts than that - parts run tomorrow!

I count today as four steps forward with only one small step back - measurable progress!

In other news, Lost Prophet's "Rooftops" is a good song, and I'd really like to hear it live, as it sounds like it'd be a lot better in person than car stereo.

Wednesday, December 3, 2008

winter grey, summer green

An overcast arctic winter day is a study in a hundred thousand shades of gray. Most everyone drives with headlights on, as it's not much lighter outside the buildings in daylight than it is inside. (Even the camera wants to take a midday picture with flash). Somewhere beyond the clouds the sun comes up in the south, reaches the apogee of its arc less than a handspan above the horizon, and sinks down a few hours after it first showed: each day, we're still losing 5-8 minutes of daylight more.

Between the layers of clouds, recent snow, sanded snow, old snow with a layer of windborn sand and glacial silt, and freshly disturbed snow, a thousand shades of grey show - and the windsock swinging gently in the breeze seems almost unreal, almost glows with its safety orange brilliance. Staring at it as I drive by, it is too colorful - seems almost like a photoshopped object, misplaced bright splash of color on the right of the road. On the left, the stars and stripes glows red and blue as it ripples in the wind above the POW-MIA flag similarly cut from another world where colors exists, too vivid to be real.

I remember summer like a fever dream now, when these mountains are green...

Flying a PA-12 with tundra tires and flaps, supercub landing gear and every spare ounce stripped, we made our way through mountains with no roads out. We'd followed the right fork of the glacier up the valley it had carved out of the mountain, and past its gleaming blue-white swaths found the small U-shaped bowl in the mountains mostly free of snow. It was the height of summer in the arctic, and the sun rarely set - but it was low enough that it was on the other side of the mountain, making the world seem a rare dim twilight below blue-white skies.
We came around a massive rock, past a chunk of glacier not yet melted, stranded, and found the faint lighter strip of earth ahead, beside a winding creek fed by hanging waterfalls tumbling hundreds of feet down sheer drops to the valley floor. It seemed like a mere scratch in the earth from our height, as though a bear had raked a paw there - but that slightly crooked bare patch of earth was where we needed to land. A slight nudge of the throttle lever pulled back the power as we glided down low, swooping over it to take a look at the bare earth. It was rutted with tracks where prior planes had landed when it was muddy, but it was light, the color of dry dirt now. All around, low scrub willow and dwarf fireweed grew, flourishing in the short, intense arctic growing season above the treeline and setting swaths of pink-purple against a hundred shades of green.
The creek was a light blue-gray of glacial silt, a jewel set in wide green swaths of reeds, and we scanned for smaller, still pools or ripples in the reeds that might show the direction of the wind. Finally, one showed the light breeze was headed down the valley by a wide band of clear, calm water toward the up-valley side, and a patch of wind-stirred water to the down-valley side. In the absence of movement by the larger air mass, the cool air on the snow-capped mountains was sinking and tumbling down, like the meltwater from those snowcaps, gathering and spilling down to rush out as a strong breeze above the new-born river at the base of the glacier.
Coming back around, we paced the plane as though the scratch in the earth were a normal, if smaller-scale, version of a runway (at least three hundred feet if it was an inch - lots of room, but crooked, narrow). Pre-landing checks, going very slow but engine set up to growl and claw out of there if it wasn't going well, we came down with a flaps out and nose high like an eagle scooping air to nearly hover before landing. Only here, we straightened out and bled off a little more speed to gently touch her mains down, then drop the tail solidly and controlled, and roll to the end of the strip. It was rougher than I'd expected, with the ruts, and we had to add power to make it to the widest spot near the end. Only then did we apply brakes and lift the tail up and around by the force of the wind coming off the propeller alone, so she was parked off to the side. Whenwe left, we'd taxi down the strip, shut down and drag her tail back in the weeds for maximum distance.
Shutting down, we climbed out, and listened, looking around. The waterfalls made a distant background rushing noise, and the breeze blew gently in our ears, tugging our jackets and hair. A few birds chirped somewhere, unseen in the low willow scrub, and on the creekbank were the tracks from a single pair of moose. Otherwise, it was completely silent. If not for the friend next to me, I would be the only human in miles. If not for the ruts under our feet, our plane could have been the only sign of humanity had ever set foot here.