Proper Angles for Staked Three Leg Stool

[onocoffee]

I'm starting a little side project to understand stakes better. I've taken a bunch of 33mm x 75mm cutoffs and glued them up into a roughly 12"x12" square.

The plan is to bore three round mortises to fit the legs. I'm thinking 20mm holes and I think they're supposed to be at 15 degree angles - does this sound correct?

Not too long ago, I sat in a stool made by a very experienced craftsman and I loved it. The seat angle forced me to sit properly with good posture. The maker told me he put a ten degree angle on the seat. I would like to recreate this seating position.

If I'm boring 15 degree holes and legs, what is a good way to achieve the ten degree angle (slope?) for the seat? Is it just a matter of increasing the rear-ish legs? Or do the bore angles need to change as well?

Thanks!

 

[Packard]

I Googled “plans for 3-legged stool”.  Lots of information. (And lots of junk as “3-legged stool” is an American English idiom for something that is intrinsically stable.”

Here’s a sampling and my search:
https://www.google.com/search?clien...767d&sxsrf=AHTn8zrYAjcBbM8nAY5eSnhwwhWwOY3gxg:1741446982422&q=historic+plans+for+3+legged+stool&udm=2&fbs=ABzOT_CWdhQLP1FcmU5B0fn3xuWpA-dk4wpBWOGsoR7DG5zJBsxayPSIAqObp_AgjkUGqengxVrJ7hrmYmz7X2OZp_NI91rBH-UXYxTUYaXid-i80rCOFR4ctwEq6XHNFxJDubc12g_V53LOJMleY05mly8yOaToK8jHFz_RVjDQOckXObZarLqIPwvDKgym_MwXF-88dJVFgKg1K7aTJklry2Z7s8A9sg&sa=X&ved=2ahUKEwjC36DG4_qLAxWhMlkFHeE8BroQtKgLegQIFRAB&biw=1024&bih=645&dpr=2#vhid=3V-la3ywQMtFTM&vssid=mosaic

 

[onocoffee]

Thanks [member=74278]Packard[/member]!

 

[smorgasbord]

Get yourself one of those $20-$30 digital inclinometers and take a visit to a couple of furniture stores, maybe even an Ikea, find a chair that's comfortable, and take angle measurements.

In general, seat bottoms are sloped only slightly towards the back (front a hit higher), maybe 5º-10º, and then seat backs are about 10º reclined from that. The more you recline the seat the less you recline the back though.

 

[Packard]

I would note that there can be a huge comfort differential between a flat, hard-surfaced seat and a well-contoured hard-surfaced seat.

I am particularly aware of this differential because of my problems with my hip and back.

Some hard surface seats are comfortable for a could of hours, others generate pain in 10 minutes or less. It seems to be a product of the carved seat bottom and the seating angles.

I am less troubled by padded seats, but again, some are far more comfortable over a longer duration of time than others.

There must be some scholarly treatise some where that defines what makes a chair comfortable.  If you could find one, it could prove invaluable.

 

[Packard]

Herman Miller, a company that knows a thing or two about chairs, published a study on the “art and science of pressure distribution” for seating. 

It is notable for identifying what questions need to be asked, and very little on the answers.  But a starting point in any event (and just 2 pages long). 

Short of building a couple dozen different stools, I don’t see how the final design can be drawn on paper.  I think the drawing needs to be derived from the samples produce, and not the more efficient drawing-first-sample-next method.

I was hoping for answers; instead I got the questions.
https://www.hermanmiller.com/resear...the-art-and-science-of-pressure-distribution/

This was my Google search: “Engineering behind chair design”

https://www.google.com/search?q=eng...design&ie=utf-8&oe=utf-8&client=firefox-b-1-m

 

[ChuckM]

When I made my set of Tage Frid-inspired three-legged stools, I followed his instructions to the dot: 94* for the two front legs and 72* for the back leg. But his design includes a chair back.

 

[Dongar]

Free download of Chris Shwarz book The Anarchist's Design Book. He covers several designs for stake stools.
Don        https://blog.lostartpress.com/2024/02/13/free-download-now-forever-the-anarchists-design-book/