Hello ,I was just wondering if anyone know if the seasonal expansion/contraction of wooden planks occurs along the length or across the plank.
which way do planks expand?
- Thread starter adburn
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It must get longer, else why leave an expansion gap. My guess its a % of dimension based on original water content & a thousand & one other parameters. Come on where is the formula
Edit... found this.at http://www.auf.asn.au/scratchbuilder/timber.html
Remember from the preceding section concerning moisture content and density that movement is insignificant longitudinally but generally quite significant in the tangential dimension [along the rings] – that often being more than twice the movement in the radial dimension, so it is important to align the cross-section grain of a structural member so that the extra tangential movement causes the least stress. The green rectangle in the image shows expansion due to moisture intake, though greatly exaggerated. If it is desirable that minimum all round movement should occur then the longest dimension of a rectangular section member should be aligned in the radial direction. Howwever the tangential movement in hoop pine is much less than the norm for aircraft softwoods and only about 40% more than the radial movement, thus the overall dimensional movement in a quarter sawn hoop pine board will be quite small.
Edit... found this.at http://www.auf.asn.au/scratchbuilder/timber.html
Remember from the preceding section concerning moisture content and density that movement is insignificant longitudinally but generally quite significant in the tangential dimension [along the rings] – that often being more than twice the movement in the radial dimension, so it is important to align the cross-section grain of a structural member so that the extra tangential movement causes the least stress. The green rectangle in the image shows expansion due to moisture intake, though greatly exaggerated. If it is desirable that minimum all round movement should occur then the longest dimension of a rectangular section member should be aligned in the radial direction. Howwever the tangential movement in hoop pine is much less than the norm for aircraft softwoods and only about 40% more than the radial movement, thus the overall dimensional movement in a quarter sawn hoop pine board will be quite small.
It does a bit. Not as much as in the width, but still. Hence the expansion gaps all around.JohnD said:
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real wood as in grain in one direction will expand virtualy nill along its grain and in comparison quite a lot across the grain
plywood and blockboard is held full in check except the edges where it will expand slightly"out the edges" but not a lot [perhaps 1 or 2mm max]
allround expansion comes when its reformed wood and the grain goes randomly in all directions [mdf chipboard ect]
so it all depends on what "wood" you are talking about
plywood and blockboard is held full in check except the edges where it will expand slightly"out the edges" but not a lot [perhaps 1 or 2mm max]
allround expansion comes when its reformed wood and the grain goes randomly in all directions [mdf chipboard ect]
so it all depends on what "wood" you are talking about
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