Splitting involves transverse tension, but only a portion of the fibres are under stress at a time. A wood of little stiffness and strong cohesion across the grain is difficult to split, while one with great stiffness, such as longleaf pine, is easily split. The form of the grain and the presence of knots greatly affect this quality. |---------------------------------------------| | TABLE XIII | |---------------------------------------------| | CLEAVAGE STRENGTH OF SMALL CLEAR PIECES OF | | 32 WOODS IN GREEN CONDITION | | (Forest Service Cir. 213) | |---------------------------------------------| | | When | When | | COMMON NAME | surface of | surface of | | OF SPECIES | failure is | failure is | | | radial | tangential | |-------------------+------------+------------| | | Lbs. per | Lbs. per | | | sq. inch | sq. inch | | | | | | Hardwoods | | | | | | | | Ash, black | 275 | 260 | | white | 333 | 346 | | Bashwood | 130 | 168 | | Beech | 339 | 527 | | Birch, yellow | 294 | 287 | | Elm, slippery | 401 | 424 | | white | 210 | 270 | | Hackberry | 422 | 436 | | Locust, honey | 552 | 610 | | Maple, red | 297 | 330 | | sugar | 376 | 513 | | Oak, post | 354 | 487 | | red | 380 | 470 | | swamp white | 428 | 536 | | white | 382 | 457 | | yellow | 379 | 470 | | Sycamore | 265 | 425 | | Tupelo | 277 | 380 | | | | | | Conifers | | | | | | | | Arborvitæ | 148 | 139 | | Cypress, bald | 167 | 154 | | Fir, alpine | 130 | 133 | | Douglas | 139 | 127 | | white | 145 | 187 | | Hemlock | 168 | 151 | | Pine, lodgepole | 142 | 140 | | longleaf | 187 | 180 | | red | 161 | 154 | | sugar | 168 | 189 | | western yellow | 162 | 187 | | white | 144 | 160 | | Spruce, Engelmann | 110 | 135 | | Tamarack | 167 | 159 | |---------------------------------------------| PART II FACTORS AFFECTING THE MECHANICAL PROPERTIES OF WOOD INTRODUCTION