Thread: reducing stress in hardwood logs.

It was some time ago that I did the visual stress grading course and I recall the key strength attributes that resulted in the appropriate F grade. Origin of the timber was not one of them. The F grades are applied Australia wide based on the visual defects, heart, knots, bow, sloping grain, want, wane, sap, species, seasoned/unseasoned and a few other things that I don't recall. I don't think a piece of timber will not get a higher grade if it comes from Queensland.

To open another can of worms... tension in logs was once said to come from the "pull of the sap" hence when a log lies around for a while and the sap rots off it has less tension. I think this is incorrect. I think the tension in a log comes from the wide growth rings at the heart. This is why the twin edger saw has been so successful in sawing small logs (takes of both sides at once leaving a straight centre billet). Also an older log, especially one with a pipe will have less tension as the heart has rotted out.
A very free log will pop and crack on its own while waiting to be sawn. So if you leave it long enough it should eventually stop popping but the boards will still curl around and look at you to some degree. I prefer to cut them up while they are still green - no sun cracks, no sand in those cracks, no stain, less bugs, still soft etc.

cheers
steve