Hi
I had stacked a set of spars up in the rafters, properly I would have thought.  They were supported in three places in the eleven or so feet of span, they were vertical, and they were sitting on the square bottom cap in both cases rather than on the top caps which are beveled.  Over time, maybe a year and a half, they have bowed, not in the vertical, but rather the other way, I would say two or three inches.  To try and straighten them, I have placed them on my workbench with the ends elevated and weights in the middles to force it into a bow the opposite way, in the hopes that they would go back to an unbowed condition.  A couple of weeks has had little to no progress.  Water/moisture is what comes to mind, have not done that yet.  I believe it would be correct to moisten the side you want to expand thus pushing the bow out of the spars.  Anyone have experience in this realm?
Kim Brown
New Hampshire

Perhaps that has already happened. A couple of it heat lamps, gently warming the convex side might dry it out and, over a week make a measurable difference. Were they untreated? If so, they may have set permanently.

Either way, don't hurry.

Will the compression ribs and drag braces push or pull them straight? And the ply D box will permanently fix them that way.  If they straighten easily with a little weight as you described I wouldn't worry about it.

I think it falls in the category of "assembly will straighten it out", I will continue to leave the weight sitting on it for another week or so and then move ahead.  Thank you.
Kim Brown
New Hampshire