Measurement of Pulpwood - Cord Scaling
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 (Image from Blinn, C.R. and Hendricks, L.T. 1991. Marketing Timber from the Private Woodland. Minnesota Extension Service, Bulletin NR-BU-2723-D.) |
Thus, a pile of wood measuring 8 feet × 100 feet × 20 feet high (average) would contain:
| 8 × 20 × 100 | ||
| = | 125 standard cords | |
| 128 |
There are many variations of this standard. In the Lake States, for example, a cord length of 100 inches is used instead of 8 feet. In this case, the volume of wood in a cord is 4 feet × 4 feet × 8.33 feet = 133.3 cubic feet. In many areas of the South, a unit with a pulpwood bolt length of 63 inches is used, since this is the length that can be loaded double wide on a "V" bottom rail car.
While a cord occupies 128 ft3 of volume, it is important to realize that a cord does not contain 128 ft3 of wood. A significant portion of gross volume is composed of bark and spaces between the pulpwood bolts. Various studies have found the solid wood content of a standard cord to vary from 58 to 94 ft3, with an average of approximately 80 ft3.
The amount of wood contained within a cord increases as bolt diameter increases; larger diameter stems have a lesser percentage of bark, and although the average size of air spaces between individual bolts is larger than if bolts are smaller in diameter, there are far fewer of these air spaces when bolt diameter is large.
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The volume of wood in a cord also varies by length. As pulpwood typically comes from small, often crooked trees, or from tops of trees, it is not uncommon for long bolts to be crooked. Much of this crookedness can be eliminated by cuting bolts into shorter lengths. Therefore, the shorter the bolt length, the greater the volume of wood per cord; volume differences between long, crooked stems and short, straight ones can be as great as 20-30%.
An example of the effects of log diameter, straightness, and surface smoothness on solid volume per cord is provided by the following table. Note that in this case bark volume is included in the solid volume measure.
| Solid Content in Cubic Feet (Including Bark) of Stacked Cords of Unpeeled Softwood | ||||||
|---|---|---|---|---|---|---|
| Mid-diameter in inches, and length of bolts in feet | ||||||
| less than 6" | 6-12" | more than 12" | ||||
| 4' | 8' | 4' | 8' | 4' | 8' | |
| Straight Smooth |
90 | 88 | 95 | 93 | 100 | 98 |
| Slightly rough and knotty | 84 | 80 | 91 | 88 | 96 | 94 |
| Not Straight Slightly crooked and rough |
80 | 76 | 88 | 84 | 93 | 91 |
| Crooked, rough and knotty | 70 | 65 | 79 | 75 | 83 | 80 |
| Source: Dobie, J. and Wright, D. 1975. Conversion factors for the forest products industry in Western Canada. Environment Canada/Forestry Directorate/Western Forest Products Laboratory, Information Report VP-X-97. | ||||||
The 200 ft3 Unit
Wood chips are sometimes measured on a volume basis. In this case, the most commonly used measure is the unit. One unit is a pile of chips occupying 200 ft3 of space. While the volume of wood contained within a unit varies with the size and shape of the chips and packing pressure, as a rule of thumb the wood volume is about 80 cubic feet - or about the same wood volume as in a standard cord.
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