When to clamp rear spar on wing fixture

[alpinelakespilot2000]

I'm currently building my wings, to the stage of match drilling the wings skins.

When does the rear spar NEED to be clamped to the wing fixture? Van's drawings show it being clamped, but at what stage does it need to be? So far, I've let the wings skeleton hang on its own (with no twist-checked with a plumb bob to within 1/64-1/32") and now have the top wing skins on with clecoes (and still no discernable twist). I have not yet clamped them, but is there a critical point at which I NEED to clamp them?

Steve

[ptrotter]

Steve,

I would clamp them now. They really should be clamped when you cleco the skins and drill out the holes to endure that any pressure you put on the wing does not introduce twist.