GeoffsWoodwork     

for Students of Woodwork                                                          

 

The strongest direction is A. the Longitudal direction i.e. towards the end grain. It is unlikely to use this except for columns, pit props, etc.
For all construction purposes no difference is placed on the tangential or radial faces when calculated strength and deflection of timber.
However more attention should be placed on knots, sloping grain, shakes and other timber defects which have more affect on the strength of a board.
Therefore the difference between the force directions shown at B and C are negligible in square section timber.







If using boards, of any type it is much stronger when placed in the direction shown at Ref 4.
This is more related to forces on the cross section rather that the wood but tangential boards are marginally stronger than radial boards in this direction.






Sloping grain does weaken boards and the more slope, the weaker the effect. And to labour the point, straight grain is stronger.
Be especially aware of cutting shaped struts and avoid what is called short grain where the curvature cuts across from long grain to cross grain. This considerably weakens the strut at this point.
The remedy, applied by medieval carpenters was to select the 'crook' of a tree for this member.
This provided a natural curved and hence strong strut for beams and ships timbers.

Last uploaded 10th June 2008