Dave Plowman (News) wrote:
In article ,
Derek Geldard wrote:
To my horror I found that these wooden parts which are about 200 cm
x 3 cm x 2cm have been fabricated out of short lengths of rubber wood
around 20 x 3 x 2 which have been joined together by being machined on
the ends into a male and female tapered comb, and then glued to form a
single piece of material which can be used as virgin timber.

With decent glue that makes a joint as strong as continuous timber.

Not quite.

In bending the composite puts the glue line under tension. Plus any
variations in modulus of the two pieces of wood leads to a stress
concentration at the glue join.

Glue is not good in tension: Largely its fine in compression and
especially good in shear, but fails under tension. The correct way to
reinforce any joint like this is with something that IS good in tension
overlapping the joint. A nice strip of carbon fibre soaked in epoxy, for
example.