Replies

1. 
   EdHarrow | Jul 31, 2009 05:52am | #1

   You recall correctly, but I don't recall why.  If nobody answers I'll look it up and let you know.

2. 
   SgianDubh | Jul 31, 2009 10:57am | #2

   Here is a short extract from a text I've written that goes some way to providing answers. Slainte.

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   It’s well known that steam bending is easiest to accomplish with freshly felled green wood. Freshly felled green wood is, at the time of introducing steam to it, more pliable and flexible than it will ever be again. The next most compliant wood for steam bending is air dried material (between 18%-25% MC) and, least easily steam bent, is wood that has been dried to 6% or 7% MC; this is because wood kilned to 7% MC, the north American standard, is made stiffer as a result of the drying and, due to a form of hysteresis, it is quite difficult to make wood soft and pliable again once it has reached this level of dryness and stiffness. This applies even if the wood is brought back up to moisture content levels similar to those found at the time of felling the tree. Probably the best choice for steam bending is air dried wood at about 18-23%MC. This is because if very wet wood is bent, i.e., wood well above FSP with significant quantities of liquid in the cell cavities, the bending can cause bursting of the cell walls as any fully charged cells compress and disrupt. Such disruption leads to unnecessary loss of strength in the wood, which is undesirable. There’s less cell wall damage caused during the bending process if there’s ‘wiggle’ room inside the cell itself due to it being empty—the condition that air dried wood is in.

   Not only that, but compared to green wood, air dried wood has had chance to reveal some of the distortion, checking, splitting and other faults that can occur during the drying process. Selecting air dried parts for bending that are in good shape at that stage means they are likely to go through the heating, steaming and wetting process; the subsequent re-drying and cooling after bending with less risk of such faults showing up in the finished bend.

   richardjonesfurniture.com

1. 
   oldusty | Jul 31, 2009 05:15pm | #3

     Richard , thanks that was very informative and interesting to know .

              regards   from Oregon         dusty

3. 
   bob_barnett | Aug 01, 2009 03:33am | #4

   http://www.woodenboatstore.com/prodinfo.asp?number=325-111 

   Greg's book has a good section on bending wood.  He recommends using green or air dried wood.

   The book is a fun book to read if you have any interest in wooden boats.  Greg's character comes through and he can be very entertaining along with informative. 

   Bob