The modulus of rupture for green sticks of clear wood is indicated in Table 2, which gives the average results of tests upon pieces 2 inches square, with a span of 28 inches. It will be noted that the strength of these woods varies much the same as the weights given in Table 1 (page 15). There is a very general rule that light wood is weak and heavy wood strong, or that strength is proportional to weight. There are individual exceptions to this rule, but it holds true for most woods.
The softwoods are not generally so strong as the hardwoods; but some hardwoods are weaker than some softwoods; and some softwoods, notably longleaf pine, are stronger than many hardwoods. The ratio of bending strength to weight is about the same for hardwoods and softwoods. Dividing the modulus of rupture by the specific gravity (ciphers being dropped) gives the results shown in Table 3.
It appears that, among the hardwoods, black locust is the strongest in proportion to its weight, and willow the weakest. Redwood is the strongest softwood in proportion to its weight. In fact, redwood. appears to be the strongest in: proportion to weight of any wood yet tested at the Forest Service Laboratory, with the exception of black locust.
Table 3 Ratio of Bending Strength to Weight of Various Woods (Modulus of Rupture Divided by Specific Gravity) Softwoods Redwood 200 Douglas Fir 151 Hemlock, Western 174 Spruce, Red 150 Fir, Amabilis 173 Pine, White 147 Fir, White 171 Pine, Norway 146 Cedar, Incense 168 Tamarack 146 Cedar, Western Red.... 164 Pine, Sugar 146 Spruce, White 163 Cedar, Northern White.. 146 Pine, Longleaf 163 Pine, Table Mountain ... 146 Hemlock, Eastern 362 Fir, Alpine 143 Pine, Shortleaf 161 Hemlock, Black 143 Fir, Grand 160 Pine, Lodgepole 139 Cypress 158 Pine, Western Yellow... 137 Larch, Western Spruce, Englemann 135 Average Ratio of Bending Strength to Weight.. 155 Hardwoods Locust, Black 204 Ash, Pumpkin 155 Oak, Tanbark 191 Tupelo 154 Ash, Green 189 Oak, Swamp White 154 Ash, Blue 182 Gum, Red 150 Osage Orange 180 Butternut 149 Ash, White 179 Witch Hazel 148 Hickory, Pignut 179 Buckeye, Yellow 146 Hickory, Mockernut 178 Oak, Yellow 145 Locust, Honey 177 Birch, Sweet 145 Hickory, Shagbark 173 Basswood 143 Cherry, Black 171 Cherry, Red 140 Hickory, Water 170 Sycamore 140 Cucumber 169 Oak, Red 140 Hickory, Big Shellbark.. 167 Dogwood 137 Aspen, Largetooth 167 Laurel, Mountain 136 Hickory, Bitternut 166 Oak, White 136 Elm, Slippery 164 Maple, Silver 132 Elm, White 162 Sumac 130 Hickory, Nutmeg 162 Hackberry 129 Maple, Hard 162 Ash, Black 128 Elm, Rock 162 Oak, Post 125 Maple, Red 161 Oak, Bur 124 Beech 156 Willow, Black 101 Birch, Yellow 156 Average Ratio of Bending Strength to Weight.. 156
Table 4 Crushing Strength of Various Woods (Pounds per Square Inch; Pressure Applied Parallel to Grain) Softwoods Spruce, White 1,940 Fir, Grand 3,030 Spruce, Englemann .. 1,980 Cedar, Incense 3,030 Cedar, Northern White 1,990 Fir, Amabilis 3,040 Fir, Alpine 2,060 Pine, Table Mountain. 3,070 Pine, Western Yellow 2,400 Pine, Norway 3,080 Pine, Lodgepole 2,460 Hemlock, Eastern .... 3,270 Pine, Sugar 2,600 Hemlock, Western .. . 3,390 Cedar, Western Red 2,630 Tamarack 3,480 Pine, White 2,720 Pine, Shortleaf 3,570 Spruce, Red 2,760 Larch, Western 3,700 Fir, White 2,800 Cypress 3,960 Hemlock, Black 2,890 Redwood 3,990 Douglas Fir 2,920 Pine, Longleaf 4,280 Average Crushing Strength 2,960 Hardwoods Willow, Black 1,320 Oak, White 3,510 Buckeye, Yellow 2,050 Cherry, Black 3,540 Basswood 2,140 Tupelo 3,550 Cherry, Red 2,170 Birch, Sweet 3,560 Ash, Black 2,300 Dogwood 3,640 Butternut 2,410 Elm, Rock 3,740 Maple, Silver 2,490 Maple, Hard 3,850 Hackberry 2,520 Hickory, Big Shellbark 3,890 Sumac 2,680 Hickory, Nutmeg 3,980 Gum, Red 2,690 Ash, Blue 4,180 Aspen, Largetooth 2,720 Ash, White 4,300 Sycamore 2,790 Laurel, Mountain .. .. 4,310 Elm, White 2,810 Oak, Swamp White... 4,360 Cucumber 3,140 Ash, Green 4,360 Elm, Slippery 3,180 Hickory, Bitternut . .. 4,570 Beech 3,280 Hickory, Shagbark . . . 4,600 Oak, Bur 3,280 Hickory, Water 4,660 Oak, Post 3,330 Hickory, Mockernut . .. 4,720 Ash, Pumpkin 3,360 Hickory, Pignut 4,820 Oak, Red 3,370 Oak, Tanbark 4,840 Oak, Yellow 3,390 Locust, Honey 4,970 Maple, Red 3,390 Osage Orange 5,810 Witch Hazel 3,400 Locust, Black 6,800 Birch, Yellow 3,460 Average Crushing Strength 3,580 As with the other tables in this chapter, these results are to be taken only in a broad sense.