A decade ago, I severely and permanently injured the joints at the base of my second toes on a grueling 425 mile, one week bicycle ride in the mountains due to misadjustment of the clipless pedal attachments to my shoes. Stupidity. I have learned to be very picky about shoes, but my feet ache badly at night if I am on them all day. As a result, I need a stool at my workbench but, for reasons that will become clear, no stool I have ever seen works for me.
I found Chris Schwarz's folding campaign stool very intriguing. Here's some good pics. It looks odd at first. The seat is triangular and concave; you sit in it with one of the points between your legs. The best backpacker stools are similar. I think this general design evolved to best meet the needs for an "active stool," one in which your legs are required to be used for stability and the seat is secure and comfortable.
I think the ideal woodworker's stool keeps you in a nearly standing position with your knees only slightly bent. That keeps you at a good height above the bench and allows you to use the power in your lower body when necessary. This is a very natural and athletic position; look at a player on defense in basketball or a predator about to pounce.
Then it hit me. This is exactly the position your lower body is in on a bicycle when the pedal is straight down. I have often struggled to help people adjust their seats because having the seat so high that your knee is only slightly bent when fully extended feels unnatural and even dangerous at first but most soon find that it works the best. Also, and this is key for me, long distance riders are very sensitive about their seat, pun intended. A good touring saddle costs over $100 and is very carefully shaped for movement and comfort. The shape is surprisingly similar to the campaign stool: triangular and concave. I'd argue that bicyclists pay more attention to active seating than anybody else and I think the lessons learned may be applicable to woodworking. That's what I am going to try.
My rule when designing a prototype is to only use material I have on hand. It's just what I like to do, in part because I am unable to create a plan when I am designing something; I have to see how it looks, works and, in this case, feels. That means I sometimes run into dead ends and have to start over.
I thought about buying a good bicycle seat and seatpost and mounting it on a stool base, which would be a very good but costly option I think, but I decided to have some fun instead: I would replicate the shape of my touring seat in wood! Hey, don't laugh: here in Portland some bikes are made from wood. So I decided to make the stool from baltic birch plywood and some 1 1/4" dowel pieces I have.
I laminated three pieces of baltic birch plywood together to give room for shaping and a secure attachment of the seat to the base of the stool. Then I traced out the shape of my touring seat in three dimensions and cut it out on my power bowsaw. :) To get the contour you have to cut from the top and the side, like you do for a cabriole leg. After some work with rasps and files, the result was better than I expected. It is quite comfortable and a reasonably good match. Appearance is a matter of taste, but I think the plies create an interesting look; they also provide reference lines for shaping. Since this seat isn't adjustable like they are on bicycles, I carefully matched the orientation on the seat dowel to match what is comfortable for me on my bikes. I was surprised to find that the seats on my bikes were all exactly parallel to the ground even though I had adjusted them entirely by feel. If you sit on that seat for 6 hours, it has to be just right.
Making this caused me to think about why a bicycle seat is designed the way it is. I think it allows your legs to move freely while holding you steady in a fixed, centered position on the seat and being comfortable. It's basically the same with the campaign stool. I rarely pay attention to how sophisticated the designs of common objects are, though it is interesting when I do. In many well-made things you can see the accumulated experience of many people over many years.
So, I have the seat. I suspect that most of you will think I am absolutely crazy, but having sat on a bicycle seat for thousands of miles, I know that this will be comfortable, although I don't know if it is suited to woodworking; the only way for me to find out is to try it. Now I have to decide what is between the seat and the floor.