Shop Stool Build Off - The Conclusion

It is the day after the Shop Stool Build Off (SSBO) and what a great time it was.  So many people working across the world on a single project, a new shop stool.  One would think this would be a fairly simple thing to build.  Many of us used this opportunity to push our talents to the next level.

At the center of my design is a seat that tilts 10 degrees forward to promote a more ergonomical sitting posture.  The three legged design provides a solid base no matter how uneven the surface it sits upon.  I chose contrasting colors for the stool.  The seat is Ash and the legs and stretchers are Cherry.

I started Saturday morning laying out the seat on a piece of 8/4 Ash and then boring the mortises for the legs.  This is where great concentration was required.  The front legs raked (angle as seen from the side) 19 degrees and splayed (angle seen from the front/rear) 17 degrees as legs normally would.  The single back leg is counterintuitive because of its 1 degree rake toward the front of the seat and 0 degree splay.  This is what is needed to give the seat its 10 degree forward tilt.

After boring the mortises I moved onto sculpting the seat.  This was my second workout for the day.  The first was shoveling out the driveway and the pile of snow the plow left behind.  There is a reason that Eastern White Pine (EWP) is used almost exclusively in the making of Windsor Chairs.  Ash is hard!  What was I thinking, there is a reason they make baseball bats out of Ash.

To change things up I moved onto turning the legs and stretchers.  All was going well until the last leg. It was then that a hidden knot revealed itself.  My fix was to fill the cavity with epoxy and continue turning.  The leg came apart on the lathe.  This meant a design change was in order.   The only way to save the project was to shorten the legs resulting in a stool that is now 21 1/2" tall.

At this point it was late and I was hungry and a bit dejected at this unwelcome development.  So I called it a night deciding to start fresh in the morning.

Sunday morning started with me referring back to my trigonometry tables.  I had to determine the correct leg lengths to maintain my required 10 degree forward tilt of the seat.  After I had determined the correct length of the legs I moved onto reaming the mortises to a 6 degree taper.  In my opinion this is one of the most critical steps in the process.  To have the undercarriage symmetrical I had to be spot on with my reaming.  Here you can see the 1 degree forward rake of the rear leg.

 In the picture below it appears there is one leg when in fact there are two.  This indicates that the extra time and care taken during reaming has paid off.

Things at this point are looking symmetrical.

Next was to measure, turn and fit the stretchers.  After that was the somewhat nerve racking glue up.  First step is to glue up the undercarriage.  If everything was done with care and great attention paid to the details the seat should slide on without much effort.

All that was needed was the usual slight pull on the tapered tenon leg tops and into the mortises they slid.  Next was installing the wedges perpendicular to the grain of the seat.

After a couple of hours the glue had dried and the tenons and wedges were trimmed flush to the seat.  I then scrapped and sanded the seat.  All that was left was to apply the finish.  First was a seal coat of dewaxed shellac.  This was followed by two coats of an oil/varnish mix.  After it had dried I rubbed it out with a gray nylon pad and applied one coat of General Finishes Polycrylic to give it the tough protection it will need.

I have to tell you this was a roller coaster of a ride.  But once the stool was completed and sitting there it became evident that it was one heck of a good time.  Like a roller coaster, I will quickly get in line to participate in another Build Off.  Many thanks to Chris Wong of Flair Woodworks for putting on the SSBO.  I hope I will see you at the next one, whatever it may be.
~ Ray Schwanenberger

Sizing A Chair

Recently I have experienced some neural oscillations about sizing chairs based on the users body dimensions.  I recall reading an article, a few years ago, by Jim Tolpin in which he stated; "The human frame can be roughly proportioned in whole-number ratios of eight".  The theory is this; By dividing the distance of ones hand span into eighths (8:8 ratio), you will then be able determine any dimension needed to design furniture to fit the user.  This led me to do a little research on Leonardo Da Vinci's Vitruvian Man and the proportions of the human form.  From this information one can derive that we are as tall as we are wide with outstretched arms.  Which by the way is equal to eight hand spans (64:8).  Our shoulder span is equal to two hand spans (16:8), our forearm (wrist to inside of elbow) is equal to one hand span (8:8), and the length of the lower leg (floor to middle of the knee) is a ratio of 18:8.  I know what you are thinking.  Very few people fall into the Vitruvian Man "ideal" category.  This is true and most of these proportions will not be exact but should be close enough to use in the design of a chair or any furniture for that matter.

Well, I had to put what I had learned to the test.  I got in touch with my good friend Dean and asked him to measure his hand span.  Yeah I didn't really think it through or look at the time before I initiated the conversation!  After a few questions about my activities that evening, he reluctantly took the measurement and advised me that the measurement was 8.75 inches.  I then asked him if the span of his shoulders was 17.5 inches.  This is when he accused me of drinking to excess and politely cut the conversation short.  Knowing Dean as I do, I knew this would eat at him until he would take the measurement to satisfy his curiosity.  I also knew that I would soon hear from Dean.  As suspected, he did take the measurement and confirmed my calculation, and was still of the opinion that I was drunk.

It is my hope that I will be able to use these whole-number proportions and the clients hand span dimension to design a chair that will fit the client for its intended task.  I especially want to employee this method with my guitar chair that is still in the designing/prototype stages.  Over the next several months I will be building and testing some prototypes using only this method.  If this proves to be successful, imagine how easy it would be to custom build a specialized chair for someone on the other side of the country.

I would deduce that the chair below belongs to someone with rather big hands, and you know what "they" say about big hands.  Big Chair?