Aligning the Wings
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- Written by Kevin Horton
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I was home all week, but didn't get as much done as I hoped. Tuesday evening I unpacked a big crate that arrived with my engine cowling, exhaust system, and a whole bunch of odds and ends. Wednesday I was in Montreal for the day, and didn't get home til late. Thursday I started aligning the wings in preparation for drilling the rear spar. Friday night we had our first restaurant meal outside this year - it was a beautiful evening - spring is finally here!
Getting the wings aligned is a long, iterative process. You need to hang two plumb bobs from the leading edge of each wing, one at the wing tip, and one at the root. You know the wings are on the same line when the four plumb bobs are lined up. Van suggests using a chalk line on the floor to check that the plumb bobs are all on the same line, but that seemed cumbersome. I stretched a piece of dental floss from side to side about 14 inches off the floor, so it cleared the wheels. I had to put the dental floss a half inch back from the plumb bob strings to ensure that it didn't hit the landing gear legs, but it was easy to measure from the floss to the plumb bobs to confirm they were all in the same plane.
After getting the wings aligned with each other, you measure from each wing tip back to the tail end of the fuselage - you need to have the same distance on each side. Once you get those measurements sorted out, then you use a level and a spacer to set the incidence angle. Of course, I had to adjust the height of the rear spar where it attaches to the fuselage, and that screwed up the fore and aft alignment of the wing tip. I eventually got the rear spars clamped to the fuselage with all the measurements perfect, and then drilled the rear spar bolt holes. The trick now is to never check those measurements again, because you can no longer change them :-)
There is a piece of fuselage skin that overlaps the wing on the lower surface to close the gap - I drilled and clecoed it to the wing. Then I started mounting the ailerons so I can adjust the lengths of the pushrods.
Mounting the wings
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- Written by Kevin Horton
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I was on the road for four of the last five weeks, but I finally got the last bit of scheduled flight testing done on Thursday. I got home about 2:30 AM on Friday. I was too bagged to do any work on Friday, Saturday I spent 6 hours fighting a plumbing leak (it was a classic fiasco with three trips to the hardware store - at least I didn't have to call a plumber), and Sunday was spent trying to figure out how the squirrels are getting above the soffits at the edge of the roof in my house (no success).
Today I had a couple of friends come by to help me fit the wings. I had a near brush with disaster though as one of the jack posts that help up the wings came loose and fell over. Fortunately Jim (one of my helpers) sacrificed his body to save the wing. A bit of blood was shed but bodies heal. Bent aluminum is dead for good. Thanks Jim!
It only took 45 minutes including the time to haul the wings up from the basement. It took a bit of messing about to get the bolt holes at the front spar lined up, but the fit was perfect in the end. I was worried about the distance between the front and rear spars, but the fuselage and wings mated up exactly.
Aileron Pushrods, etc
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I was on the road for much of the last two weeks, so I didn't make a lot of progress. I did measure the width of my garage and discovered that I have more than enough room to temporarily attach the wings. I had forgotten how much shorter the wings are when the fibreglas wingtips aren't attached. I had expected that I would have to fit the wings after moving the aircraft to a hangar.
So, this weekend I fabricated, riveted and primed the various aileron pushrods. I've got a few more odds and ends to do, then I'll fit the wings, adjust the aileron and flap pushrods, fabricate the fuel lines from tank to fuselage, fit the intersection fairings between wing and fuselage, etc. I'll start the engine installation after I remove the wings.
On the Gear!
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Two big milestones today - my engine arrived, and I got the aircraft sitting on its gear for the first time. The engine is a 200 hp Lycoming IO-360-A1B6 overhauled by Aero Sport Power. I wasn't expecting it for another couple of days, but the trucking company called today to say it had arrived. It is sealed in plastic, with several large bags of desiccant inside. I'll leave it in the plastic up for awhile until I am ready to hang it on the firewall.
I had finished fitting the wheel pants last night, so I asked the guys who had come buy to help unload the engine to help me lift the aircraft off the stands and put it on its gear for the first time. Thanks Jim, Bruce and Rob. This thing is looking more like an aircraft all the time. Wow!
Wheel Pant Update
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I finished fitting the wheel pants today, and got all the holes pilot drilled. I just have to drill them out to the final size, enlarge the hole at the bottom to provide more clearance to the tire, and install the anchor nuts, etc. But, all that stuff can happen with the aircraft on its gear, so I can take it down off the stands as soon as I install the tail wheel.
Wheel Pant Update
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I was on the road for three days last week, so progress was slow again. I got the gear leg fairings trimmed and drilled and riveted the piece of hinge that closes the trailing edge. The shims I was waiting for arrived, so I permanently installed the axles and rechecked the alignment. One side is perfect, and the other is toed out 1/4 degree. Good enough.
Fitting the wheel pants is a bit tedious. You've got six degrees of freedom to work with (three positional axis, and three rotational axis), so it takes a lot of messing around. Van provides a bunch of measurements, and location cues, but it still takes longer than you would expect. I got both wheel pants drilled to the mount on the outboard side on the weekend, which leaves you with just three degrees of freedom left to worry about. The inboard side will be the real trick, because that will fix the alignment in all six axis.
You can see two pieces of paper taped to the floor, one under each end of the left wheel pant. I dropped plumb bobs from the centre of the firewall, and the tailwheel mount to establish a centreline on the floor. I measured over 3 ft laterally, and marked a line under each end of each wheel pant. Then I dropped plumb bobs from each end of the wheel pant and made sure they fell an equal distance from my line to check the alignment with the longitudinal axis of the aircraft. They came out really close, and I'll be happy as long as I never measure it again ;-)