: When I built I found it difficult to make a plywood box spine that was
: straight. I've got cabinet making and carpentry experience so I was a bit
: annoyed. I finally clamped my plywood box (baltic birch 1/2"cut true
: on a very good tablesaw) to a 4" x 4" square steel tube I had
: and then screwed it together. Unclamped it stayed pretty straight. Much
: improved but what's the obvious next step?????

: Your aluminum strong-back looks great,especially the way you handle the ends.
: A thin walled rectangular steel tube would be a bit heavier, but a lot
: cheaper--less than $100USD. And they come in lengths up to 20'
: If it did sag, you could support it in the middle while you reinforced it
: with plywood along the sides, or bolt on another or smaller length of
: tubing along the top to stiffen it. Once straight it would never warp.
: I'll never use a wooden spine again. They work, but the worry factor is
: eliminated with strong straight stiff metal.

My current and fairly long term strongback is from Tom Yost's site, just a bunch of 2x4's bolted together topped with a 1x6 that's drywall screwed to the top. All comes apart for storage if need be. Is it perfectly straight? nope, doesn't need to be. I just use a string stretched from end to end as a straight reference and that "is" always straight. Base the building on the stretched string and not on the strongback. Works for me.

Bill H.