Stool Design Guide: Have a Seat

As a warm up to the upcoming Shop Stool Build-Off, I'm putting together some points to help design an ideal shop stool. After looking at the base, it might make sense to continue up through the structure and arrive at the seat. However, defining the end points illuminates the intervening structure design. Since we have a looked at the connection to ground, now we can look at the connection to your... occupant.

A seat is as unique as the person connecting. Still, it's good to consider options prior to finalizing a personalized design. A few choices to be made:

Functionality

While a stool seat obviously is a place to store your keister, some might also stand or step up on theirs (guilty) or use them as an out feed table, deadman, carry handle, cup holder or bottle opener. These ancillary functions deserve your consideration. 

Bum Interface Materials

Think a bit about what material you want to actually sit on. For many it will be straight wood, but others might prefer leather, cushioning, or webbing. These materials provide some "give" which can add to the comfort of the chair. Still there is nothing wrong with a wood surface especially if like me you have recently installed additional padding to the other side of the interface...

NINNA suspended seat
By Adentro (French)

Risom Stool 
by Knoll

Brian Bogg's 
Webbed Stool

Ergonomics

This is highly subjective, I am not an ergonomics expert, but I do have lots of experience from sitting around...</rimshot>  Based on my own issues sitting at a desk for years and learning from passionate people, I've found some good ideas along the way, though my bad habits are hard to unlearn. (Two TED talks from Niels Diffrient and Esther Gokhale come to mind.)

Playing the angles

It's Brown & Sticky
(and sort of a saddle)

One angle to consider is what angle you can sit on the stool (yaw). Some may want to be able to just set down without thinking. This is convenient, but limits the seat shape to circular and flat/concave/convex. Convex may work (especially around the rim), but concave and flat often have a tactile "edge" along the thigh that I'm not fond of.
If you are willing to go from omnidirectional to directional, you may gain a more comfortable seating position(s). For instance, the Schwarz Roubo stool offers 3 (identical) seating angles. Another option is to have 2 different seating positions like the cock-fighting chairs Mary May recently featured on her blog (I'm not sure if adding a backrest automatically turns the stool into a chair or not, but I like this concept).

Plank (Italian design company)  Miura Stool (sort of saddled)

Rolling Divided Saddle Chair from Salli

Another angle  that keeps coming up from ergonomics folks is the angle of your hips to torso (pitch). Opening up from <90 degrees (hunched over in a flat stool) to something more open ~120 degrees, allows for you to breathe easier, naturally straighten your back, and sit longer without the "hunching begets hunching" spiral. The problem with this waterfall angle effect is that there is a tendency to slide forward, so you might need a stop. "Kneeling" stools are one solution (shins prevent sliding) as are saddle chairs (feet prevent sliding). The later also opens up your hips and may allow you to get closer to your subject, since your knees are less likely to be in the way.

Kneeling Chair

Biker's Saddle Stool

In the end, it boils down to what you want to sit on for long periods of time.

I hope that you've found this useful. Next I'll address the structure of the stool, and then wrap up by sharing the design that is taking shape for my build.