Q: What is a strongback?
A: A strong back is a workbench that you trust to be straight, plumb, and
true. It is the base on top of which you build your supCAT.
Strongbacks come in multiple flavors.
When I first started, my shop was on a single concrete slab. So putting the strongback on legs and rollers was an easy first version that served me well in that shop version. And then...
I added a raised floor and a center column. On top of that column is a twelve-inch 'lazy susan' turn table. On top of that, I laid down two ten foot long pieces of angle iron, two inches on a side, and strong enough to remain true and straight under the load that a supCAT would create.
Which one is best? It depends on your space. Mounting the strongback on casters gives you freedom to move the strongback in any direction as needed, e.g. when you want to get behind it. A center mounted lazy susan and a spinning deck are nice, too, if you have a high ceiling and a raised floor.
Remember - Murphy's Law applies to DIY projects!
As soon as you build something in one place, you will need something behind it that will require moving the immovable object. Put your strongback on casters. Everything in my shop is on casters, even the drill press. Yet my battle with Murphy and his highly accurate ‘Law’ rages on......
For the most part, I prefer to stand up while working (just like my paddling preference). There are times when you need to sit and I have a stool, along with multiple canoes, for that, but most of the time I'm standing. Make the strongback height such that the top of your upside down supCAT with be at chest level.
Although the picture shows the deck resting on the strongback, a plywood ‘floor’ could be added to the top of the strongback. The main thing is that the strongback is straight and flat, because the supCAT will take the shape of what supports it. Be sure and check the floor, most garage floors are built with a pitch toward the door such that water brought in by a car will drain to the door. Shop floors may be built on the level. Bottom line is check the floor for level. You may not need to do anything with that bit of knowledge, but strange problems you encounter during the build just might be solved by paying attention to weird things like the pitch of the floor. Possibly, I learned this hard way.......
