On Mon, 25 Jun 2007 07:36:45 -0700, Todd wrote:

A piece of 1" red oak can be bent to radius of 1" if supported by a
metal strap and 11.5" unsupported according to "wood Bending Handbook"
published by Woodcraft Supply. That sounds about right to me as long
as the strap is fixed at both ends so that the neutral axis is pushed
to the outer radius. Also, remember that it is primarily the heat that
plasticizes wood and that you do not gain any additional softening by
heating the wood beyond the boiling point of water. Luthiers use dry
heat as did barrel makers. I have never had very good results from
simply getting the work piece wet, it must get hot.

If you need to do further testing for your application before building
a steam box you can try boiling the piece of wood or wrapping the
section that you need to bend in rags and pour lots and lots of
boiling water over the rags.

Leverage helps but does not prevent breaking or crushing the grain on
the inner radius. Bending over matched male and female forms with
plenty of clamps does help.


Back when I lived on the coast of Maine I helped with the rebuilding
of a 40 ft. dragger under the supervision of an 80 years old boat
builder. We were replacing 4 X 4 inch ribs.

The ribs were made from green oak or at least not seasoned for years
and years. They were sliced down the middle for all but the butt where
they mortised into the keel timbers. Then they were boiled. A long
piece of large pipe sat at an angle with one end in a fire. The pipe
held three or four ribs and was full of soapy water (I have no idea
why soapy water was better). We boiled them for a while and then bent
them into the forms. If they didn't seem limber enough we took them
out and boiled them some more.

It was all new to me but the 80 year old boat builder didn't seem to
think it was anything out of the ordinary.




Bruce in Bangkok
(brucepaigeatgmaildotcom)

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