The Economics of Bowbending: A study in hand-tool processes for the data driven.

A little splitting, but plenty serviceable.

Psst.  Here's the secret.  The title of this post may be the longest one in the whole MODA blog, but it's intended as a gate keeper of sorts, to keep out all but the most nerdy.

Congrats, by the way.  C'mon in and join the nerdy fun.

When we bend bows for a class at Tillers, they get bent as square stock.  Since they take a while to set in the form after steam bending, the class is often using the bows bent at the previous class.  Students get a pair of "square" bows and then set about rounding them.  Most of this is pretty straightforward work with a spokeshave.  Except the inside of the curve.

Particularly on smaller (5" and 6" bows) the inside of the curve is a bear to round out.  Compounding this is the usual rules for reading the grain the students have been learning while carving the beam no longer apply.  Since the bow started life as a stick, the grain runs whichever way it runs, regardless of the direction of the bend.  In short, it's frustrating.  I love working spokeshaves and it's still frustrating.

Maybe we need an economist to set us straight.

A chair in need of a new crest rail.

I spent yesterday getting the steambox going to make a new crest rail for a chair I just finished.  Since
the box pumps the same amount of moisture into the shop whether it is mostly empty or mostly full, I decided to bend several things.  Chair rails, hay rake bows, and a set of 5 inch bows.

The bows gave a chance to experiment with a streamlined process.

Starting with square stock, I marked each bow blank with my "octaganizer."  From there, I used my trusty No. 5 Stanley plane to make the squares into octagons.   This is simple work as long as you grind a nice 8" to 10" radius on the plane iron.  Plane down to the lines and stop when you get close.  (I've taught high school students to make tapered octagonal chair legs this way and they can do it with zero hand tool experience.  See Christopher Schwarz for more on the subject.)

Then, I use one of my beloved spokeshaves to round out the middle 12 inches or so of the blank, particularly the side that will form the inside of the curve.  Here's why:

1.  Once that stick is a bow, the inside of the curve is hard to round out, but as a stick it's child's play.

2.  By taking off a little more material on the inside, the bending is easier.  For instance, I was able to bend these 5" bows just by hand pressure.  For the last one, I didn't even clamp the form down the the workbench.

So why not make the entire stick round?  Economics.

The "Octagonizer"

The whole process of marking, octagoning (yeah, it's a new verb) and shaping the center took me seven and a half minutes.

I bent three bows.  Two were fine and one split.  That's about average.  So I had 22 minutes and 30 seconds in the shaping and two bows to show for it.  That means that each bow cost me 11 extra minutes and change before it was bent.  I know I will save more time than that after the bending takes place.  If I was to fully round each one, the time / effort equation would more than likely get out of balance.

Plus, the stick work is fun.  The bow work isn't fun.  So I trade a few minutes of fun work for more minutes of drudgery.  Makes sense to me.

Hay rake bows as well.  Easy Peasy.

Economics.