Thread: Wood movement

The answer to your query is not quite as simple as the question first appears.

Timber never really 'stops' moving, it will tend to react to any changes to humidity in it's environment. The older it becomes, the less it moves around (much like me ) but you should never rely on it actually stopping.

Quarter-sawn is desirable, as it's the most dimensionally stable... it tends to move in equal proportions in all directions whereas flat-sawn will want to move in one dimension more than t'others.

Warp and twist can (and will) affect both cuts, depending on how even the grain distribution is. A denser grain on one side of a board, or a knot, can lead to significant bowing with changes in humidity. If we assume that you've carefully selected your stock to have nice, visually even grain all over then the odds of such warpage are greatly reduced.

So... what does all this mean?

Given careful design to allow for future movement, a controlled environment for the clock to be displayed in and a modicum of luck, you could get away with using flat sawn.

(By a controlled environment I mean the same temp/humidity all year 'round. 6 months of heater blasting followed by six months of of A/C is asking for trouble!)

It's still better practise to use quarter-sawn where possible, especially in any size critical components such as frames, and use the flat sawn elsewhere, where movement can be accommodated. eg. floating panels.

Thanks Skew, much as I thought. I’ve been out in shed and arranged timber as best I can to get as near quarter as I can.

BTW good luck with your 200% humidity, thankfully some it is heading our way and filling the tanks.

Hmmm... correct me if I'm wrong, but you're making the entire face from 8 triangular panels joined into an octagon?

Alternating the panels 'ring up'/'ring down' (similar to the practice of alternating the ring direction in boards when building into slabs) should work alright with flatsawn.

The theory being that each panels' movement would counteract it's neighbours movement, keeping the overall face flat to a degree. Probably best to use a spline or liberal dowels in each joint for strength.

O' course, I could be well off base here... if so, just ignore me.

Yep the clock face is as you describe and your suggestion is a valid one ( I hope ) which I intend to try, Thanks
I was thinking of using biscuits, the segments are about 3” wide
you can see the clock here, just 921CA387-9428-4502-A880-67D8FFE0F954.jpg

My first thought was that you were making the face of the clock, a complete disc of wood using eight segments. That size can be a problem. It now seems to me that you are making a ring of eight segments with a separate clock face. If this is the case you should have no problem with flat sawn timber. As Skew said, quarter sawn timber would be better to use if possible. The use of biscuits will make the job that much stronger.

Jim