I have a long-term project on the go and the next step requires that I make a "strongback" roughly 12 feet long, with a width between 1-1/2" to just under 2" and height from 3-1/2" to just under 4". I can deal with some imperfections over the length, say maybe 1/8" deviation over the length, but my main concern is stability.
The obvious answer is to go and buy a 12' long 2x4 at the local building centre. Although this may be the right choice, I have reservations because the wood I've purchased in the past is practically still growing and often does all sorts of funky things after a few weeks of drying out at home. If I were to find a really good straight piece, can the stability be ensured by painting or otherwise sealing it?
My second thought was to build a "box beam". I can use inherently stable wood like plywood, but with a small table saw how do you ensure all your cuts are straight enough, let alone the assembly? Working with large panels on my Ryobi BT3000 table saw (no infeed/outfeed table or extension) is very unwieldy.
The third and final option I've considered was a piece of 2 x 4 steel tubing. Stable? Hell yes. Overkill? totally! Not to mention difficult to mount other things to it that are made of wood, which I will need to do.
So, my question is what's the best (or even a really good) way to move forward? This seems to have blocked my progress - ie: paralysis through over analysis.