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.
A couple of 1/4" bolts will do just fine here.
Unlike everyone’s very pretty lower outboard support, I made an ugly one.
See? More ugly. (Functional, though).
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.
I'm not sure why I took this picture.
Here’s the inboard rear spar support.
Inboard rear spar support.
And the outboard rear spar support.
I'm using the clever clamping trick that many builders before me have used.
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.
Here's a picture of just the skeleton, squared up within 1/32" (I want to improve this).
To see if I was close with the skins, I clecoed them on. They fit great.
Another picture with the skins clecoed on.
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.
and
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!)
Andrew's RV-7 Build Log 