The Natural Philosopher wrote:

The only thimng they worry about is acceptable deflection, and there are
tables of spans/weights/sizes somewhere about that are 'to spec' fo the
sort of cardboard-on-steroids that is called structural timber at the BM's.

The usual guide is:

max deflection = 0.003 * Length

(IIRC there is a cutoff limit of 14mm max deflection as well)

I find this book is stuffed full of handy data that can often give you a
clue as to an appropriate starting point:

http://www.amazon.co.uk/exec/obidos/...ternodeltdcomp



--
Cheers,

John.

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