Radial and Tangential Shrinkage
Don Stephan
I've always been curious - is there a characteristic of different woods that suggests how much radial shrinkage and tangential shrinkage will occur? Something like ring porus, diffuse porus, and so on?
Radial and Tangential Shrinkage
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Re: Radial and Tangential Shrinkage
#2Re: Radial and Tangential Shrinkage
Bill Tindall, E.Tn.
Shrinkage observed has to do with the structure of the cells. The cell structure depends on species, variables within the species and growth early in the tree's life compared to later. Not sufficiently appreciated is the fact that the shrinkage tables, which I find of limited value, are averages. The range, as I recall, is about 30%. When trees are young and shooting up to reach light they make a cell that shrinks more than the cells in mature wood. For this reason the center of trees usually will be stressed upon drying, and usually shatters. In cherry, the sapwood shrinks greatly more than heart wood. A board with sap on one side and heartwood on the other will dry unrestrained into a trough.
Re: Radial and Tangential Shrinkage
#3Re: Radial and Tangential Shrinkage
Robin Corell in Atascadero
As Bill has already written, the tables are an average, and at that they are a generalization. Another example of this is that most tables make no distinction between old growth and second growth and in woods such as redwood, douglas fir, or western hemlock, the difference between old growth and new growth can be like two different species.
For me one of the most useful generalizations about shrinkage is that for the most part the lower the ratio of tangential to radial shrinkage, the more stable the wood is. This usually translates to a wood with fewer drying defects when going from green to dry as well as fewer problems when making properly designed projects. Again this is a huge generalization and there are as always exceptions.