hardwood strength
1    6.3
1.5 11.1
2   20.0
3   24.0
4   26.1
4.5 30.0
5   33.8
5.5 34.0
6   38.1
6.5 39.9
7   42.0
8   46.1
9   53.1
10  52.0
11  52.5
12  48.0
13  42.8
14  27.8
15  21.9