Well, I keep chugging along on this right wing skeleton.
Except by “chugging,” I really mean “don’t seem to be making any progress.”
First thing, I wanted to free up one of my clamps, so I drilled and bolted the outboard rib’s special angle to the support of my wing stands.
Here’s my first mistake. I was really careful to line everything up the first time so I wouldn’t have to notch the support angle to accomodate the skins (which overhang the spar end). I didn’t remember this on this go around, so now that they are bolted in, I’m going to have to notch the supports.
No big deal, but just annoying that I forgot.
Unlike everyone’s very pretty lower outboard support, I made an ugly one.
After getting it clamped to the rear spar, I used my air drill and a 3/8″ bit to drill a hole for a 3/8″ bolt.
Here’s the inboard rear spar support.
And the outboard rear spar support.
Then I spent some time leveling the spar to 0.0°. After that, I dropped some plumb bob’s and carefully measured from the plumb bob string to the top of the rear spar. The outboard side showed 2 1/4″, and the inboard side showed 2 3/4″. A half inch of twist doesn’t sound like a lot, but of course I wanted this to be perfect.
I chose to split the difference. I pulled the outboard edge of the rear spar down (aircraft axes) and clamped, then pushed the inboard side up and clamped.
Here’s my problem. It seemed like I really had to push the spar to get it exactly where I wanted it, and there was plenty of (what I’ll call) springback force.
After clamping the rear spar in place, I remeasured the spar, and it was now no longer square. (Of course, moving the spar edges moves the ribs, which twists the main spar.)
I releveled the main spar and really tightened up the clamps. I’m now level with the main spar and within 1/32″ on the rear spar.
I’m sure I can get it even closer, but I’m worried about how much force I’m holding with the clamps.
To see if I was close with the skins, I clecoed them on. They fit great.
Anyone have any thoughts? Have any other builders seen a lot of force required to straighten the wings?
Jan 31st update:
Oh man, I love the forums. bkthomps had the following to say:
did you put skins on yet? you’re on the prepunched kit like i am, the twist thing is a null issue- once you cleco both sets of skins on, it will be dead on, other than the slant of your stands/garage floor.
I followed jamie painter’s blog and decided not to spend countless hours with the lasers/bobs/etc that I had and I just built the wings doing only the basic level checks and a string down the spar length to get rid of the droop, after finishing them, they are dead level in every dimension, if that helps w/ encouragement.
1.5 frustrating hours. (After talking with bkthomps, I am much happier. I’ll push on now and verify straightness after clecoing both sets of skins on. Wuhoo!)