Bending the Rules

Back to the woodworking.   I'm reheating a spindle here to straighten in out.  You can see below how it dried with a kink in it, and to spokeshave it, I had to straighten it.  I learned this little trick from Curtis Buchanan.  I would have thought that once a piece, riven or not, was steamed and then dried, that was it, game over as far as bending was concerned.  But Curtis showed me that heat bends wood, not heat and moisture. The steam is just a convenient way to get the heat to the wood, but the moisture had nothing to do with it, other than to prevent the piece from drying out.

 
So, by heating the spindle and putting some pressure on it, once the wood hits the right temperature, the wood will give and bend, pretty cool.  Then just over bend a little bit, wait for it to cool a little bit, and then bingo, straight.

This shows what I do on the arms of a sack back or any chair with flat arms.  Notice how flat the ends of the arms are relative to each other.  I do this the same way, basically.  I clamp the whole arm rail, hands up, in a shoulder vise and heat midway up the arm.  I use a big adjustable wrench to hold the arm, again placing pressure on the hand, and you will feel arm give.  Keep an eye on the hand, over bend a little, and keep flat relative to the other one.  Or tipping slightly in, but not tipping out, and definitely not both tipping both the same way, that looks bad.  It's nice to know that if the steam bending and drying leaves the hands a little funky, you can tweak them back in to shape.

 

www.leevalley.com has a great article on steam bending, look under the steam bending section of their catalog, and poke around til you find it.  You can download it as a free PDF.  One thing they say is that wood will compress a lot, but it will not stretch at all.  And that's the whole idea behind straps.  By using straps with a sturdy, definite end block, and cutting the pieces to closely fit between those two points, you compress the whole piece.  

If you bend a piece of wood over your knee, say a branch, you'll notice that the half towards your knee bends fine.  And roughly halfway out, the fibers tear apart, because they aren't able to stretch.  So, by using the strap, you shift the midpoint to the outside, and thus all the bend becomes compression, which wood will do.  I use straps to bend, all except the continuous arm.  I think it's cheap insurance.  I spend a fair bit of time prepping the piece, and I don't really find the strap a pain, so I use one.  Check out the Lee Valley PDF, it really is informative.

Here's a coat rack I made awhile back, these bends were fun, except the ring, that was not fun,  but overall I was happy the way this piece came out. 

On the syrup front,  the sap hasn't been running very well, maybe tomorrow the weather will be better.  Fingers crossed.