Q. When looking at the strength of a leg, what factors are important?
A. A quick summary. Obviously, the size (especially the smallest diameter) and the species are important. In general, the denser species are stronger. But even within a single species, the density can vary substantially; you need to avoid pieces that are much lighter weight than normal. Another factor is the grain angle. If the grain (as determined by splitting a piece, as a split lengthwise follows the grain) is not parallel to the sides, the strength drops quickly.
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Grain slope Degrees from parallel Ultimate strength (MOR)
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percent
Straight, parallel 0 100
1 in 25 2 96
1 in 20 3 93
1 in 15 4 89
1 in 10 6 81
1 in 5 11 55
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Gene Wengert, “The Wood Doctor” has been training people in efficient use of wood for 35 years. He is extension specialist emeritus at the University of Wisconsin-Madison.
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