Design Criteria

This page was written in 1998 and titled "Designing the Weeks Rocker."
It lists our design criteria in general and has an example of their application.


Comfort

I wanted to build a rocking chair in which:

  • anyone could sit for hours without feeling an edge, a flat, or an odd angle
  • a parent could rock for hours in the middle of the night and feel as softly enfolded as the infant in arms.

Longevity

Building for generations of use requires:

  • joints appropriate to the load
  • technical specifications for the material
  • craftsmanship of the highest order.

Beauty

  • The lines, curves, contours, and surface quality of the chair must secure it as a work of art.
  • The figure, color, and character of the wood must be carefully composed and revealed within the form.

Efficiency

  • How can the parts be developed from available lumber?
  • Can we build a tool, jig, fixture, or machine to perform this task safer and with more precision?
  • Where can we apply our handwork to the most benefit of our patrons?

Service

I wanted to build handmade rocking chairs:

  • to the highest standards of beauty, construction, fit, and finish
  • sell them for less than such artistry would suggest
  • deliver them on time.

Still do.


Applying the Criteria to the Back Splats

After finding the curve for supporting the lumbar and upper back, I decided to use the lower muscles of the back as user supplied padding — two vertical muscles, therefore, two vertical splats. I tried two splats, each about the width of a lower back muscle, and the two about as far apart as those muscles are. I thought two might do, but a trial showed that more support was needed at the rib cage. We tried six, but there was no functional or visual benefit.

I settled on a 1/2" thickness for the splats, thick enough to be firm and supportive, thin enough to be light. A 2" thick piece of wood of at least 4" in width will make a blank from which splats can be efficiently cut. Selecting flat sawn wood for the blank, the growth rings will be perpendicular to the face of each splat. This is the strongest orientation of grain and displays the most pleasing lines in the overall composition of wood figure in the chair.

The drawings showed that a tangent to the back curve intersected the plane of the seat at 7-1/2 degrees and entered the crest rail (headrest) parallel to its face. To fix the splats at both places, I chose to mortise them deeply into their receiving parts. The splats were clunky looking so I tapered them--making them a quarter inch narrower at the bottom than the top.

I solved every problem similarly: draw, think, draw, try--rethink, redraw, retry, refine. I made a rocking chair. Many people sat. I made minor changes until I thought it was right. I knew it was right when I received a card (still have it) from Elizabeth F. who received number 6 as a gift. She wrote, "The rocking chair is a perfect blend of art and engineering."