The three-legged form of backstool is ideal for uneven or dirt floors, though it looks wrong at first to modern eyes, like a Zap Xebra three-wheeled car. Though we all know in our heads that a three-legged stool is stable, adding a backrest to it throws our eyes off.
Even Victor Chinnery, the dean of English furniture, wrote the following warning in “Oak Furniture: The British Tradition” (Antique Collectors Club).
“Three feet will stand with greater stability on an irregular surface, but it nevertheless takes a certain amount of skill to sit comfortably in such a chair, since it is easily overbalanced.”
Judging from the number of extant three-legged backstools, that statement seemed like it was written with the eyes, not the buttocks. But the only way to test the statement was to build a three-legged critter and sit in it after a few beers. So I did.
As I designed this backstool, I followed the geometry I found in other three-legged backstools and chairs – usually the back leg rakes backward significantly. So I was careful to replicate that feature when I made models of three-legged stools before building one.
As my backstool came together I sat on it at every stage in construction. At first I expected to be tossed to the floor. That didn’t happen. And when I had my first formal sit-down in the completed backstool, here’s what I felt: stable.
My front legs were planted over the front legs of the backstool. My tailbone was on top of the back leg. I leaned back and my head hovered over the footprint of the rear leg. I cautiously creeped my buttocks left. Then right. I reached for my fourth beer.
How does the backstool get its reputation as tippy as a drunken uncle? Part of the instability is an optical illusion, but part of it is real. It just has nothing to do with sitting on the chair.
We use chairs and stools for more than sitting. If you stand or kneel on this seat and the pressure is outside the triangle created by the feet, you’ll get a rude surprise. Or stand behind the chair and lean on the crest rail. If you lean on its center then nothing happens. But if you lean on one end of the crest rail, you might just bite the floor.
If you aren’t sold on the idea of a three-legged chair, that’s OK. It’s simple work to make this backstool with four legs instead of three. But consider this: If you do have the guts to make the three-legged version you’ll never have to yell at your kids for tipping backward in their backstool.
— Christopher Schwarz