Page images
PDF
EPUB

ure 12 shows in the small views sticker storage between piles or loosely strewn in the rear alley, and also a shed at one mill yard for their orderly storage.

WIDTH AND SPACING OF LUMBER PILES

A lumberyard in any case offers considerable impediment to the passage of breezes, and therefore faster drying (and perhaps additional degrade from checking) occurs in the top of any piles built higher than the general level of pile tops. Circulation of prevailing breezes through the piles will depend largely on the air spaces. The main alleys are usually made of adequate width to serve for the passage of lumber loads. The rear alleys, or spacing between rear of piles, should not be stinted, 8 feet or more being usual allowance.

[graphic]

A shorter

FIGURE 11. Short hemlock piled two lengths to pile and end-lapped. lap than here shown would permit better drying at that point. Photograph courtesy of Forest Products Laboratory

The side spacing between the sides of piles along the alley varies greatly; it should be remembered that whatever air gets into the piles must mostly come in from the sides, which would seem to indicate a side spacing of at least an equal amount of seasoned lumber from a like piling space; by this is meant that the wider spacing takes more ground for the pile but promotes drying to finished condition in enough shorter time to compensate.

The season of the year has a direct bearing on this matter. During the season of fast drying closer rather than open piling may reduce the amount of seasoning degrade, especially from checking; and this consideration may involve spacing between piles as well as sticker spacing and spacing between boards in the layers. During slow-seasoning periods of the year piling may be made open to facilitate more rapid seasoning, which probably will not be fast enough to

cause additional degrade and may reduce possibility of damage from decay.

There are some classes of stock in which discoloration of boards by light at the sides of the pile is undesirable, and which closer side spacing might in a measure avoid. Sometimes such stock is protected by piling lower-grade lumber in the two outside tiers at the sides.

[graphic]

FIGURE 12.-Three methods of caring for stickers. Putting between piles interferes with ventilation in the bottom of the piles. The storage shed is much like some seen for sticker storage in factory yards, except that they were usually built of some more durable material than corrugated iron. Photograph courtesy of Forest Products Laboratory

In the air-seasoning study in the California pine and redwood region by C. B. Green, of the United States Forest Service, the following was said about effect of foundation height:

In a particular study unit two redwood piles were erected-one with a foundation height 32 inches in front and 20 inches in the rear, the other 20 and 12 inches, respectively, all other conditions being the same. On razing the piles the former showed an average moisture content of 18 per cent, while the latter was 23 per cent. A more striking benefit of the higher foundation

may be seen from the fact that on it lumber dried to 23 per cent moisture content in 128 days, while on the lower foundation it required 191 days to reach the same moisture content.

Replies to the questionnaires showed that half the manufacturers used foundation 14 inches high, or less, at the low end, while the other half used foundations having a height of 15 inches or more. Subdividing further, 11.3 per cent reported foundations under 10 inches, scattered through all species except redwood, cypress, and Douglas fir; 38.7 per cent reported heights ranging from 10 to 14 inches, in all species except northern pine; 21 per cent reported foundation heights of 15 to 19 inches, the largest proportion being in the California pines and in southern pine; 22.6 per cent reported foundation heights of 20 to 29 inches, southern hardwoods and southern pine leading in this division; and 6.4 per cent reported foundation 30 to 39 inches high, all in North Carolina pine and southern pine. This would seem to indicate that lumber manufacturers generally have appreciated the value of piling lumber well off the ground for air-drying.

EXPERIMENTAL TESTS ON FOUNDATIONS

It is easy for the lumber manufacturer to test in his own yard the effect of improvement in foundations. If they are built of timbers laid on the ground, some of them may have decayed sufficiently to need replacement; a row of foundations elevated on posts sufficiently to let air under the piles from all directions will permit comparative tests between such piles and other piles, and particularly on relative seasoning rate between the lower third of the pile and the upper portion; this will require moisture tests by use of a scale and oven, and it is better for the manufacturer to make actual tests himself rather than depend upon tests reported from other points. Reducing the lag at the bottom of the pile is very desirable. Tests at certain stages of seasoning may show 5 per cent of moisture or more in the pile bottom in excess of that at the top, which means either that lumber in the bottom will not be adequately dry when the pile is torn down or the pile must be carried a longer period in order to secure the desired seasoning in the slower portion. This lag in seasoning can perhaps be reduced to 2 or 3 per cent by lifting the piles above the ground and by using more open piling in the bottom, and these expedients also reduce the time required for adequate average air-drying. Big foundations are most useful in slow-drying seasons of the year.

PILE WIDTHS AND HEIGHTS

Where lumber being piled is also used for the pile crossers the piles are necessarily square, as wide as the length of the lumber, and this requires provision for the various widths of such piles in the arrangement of pile foundations. Where special stickers are used it is possible to adopt a standard length for stickers and standard width for piles, and it facilitates the arrangement of piles in straight lines or tiers both ways, lining up the spaces between the piles into straight openings for the sweep of the wind.

All southern hardwood lumber is usually piled in rather narrow piles, sometimes 6 feet wide and sometimes 8; in the North piles are usually 12 and 14 feet wide, sometimes 10. In softwood yards wider piling is usually seen, 10 or 12 feet or more. Some species of softwood seem to dry evenly throughout in these wide piles; and as more of the lumber is in the interior of the pile it dries bright, with less seasoning defect than is usually found in the outside boards. In the various air-seasoning studies there seems to have been little study of the effect of pile width upon seasoning. In the study made in the California pine and redwood region it is stated that the pine yards are mostly laid out for 16-foot pile widths, but that in redwood continuous foundations are largely used which will accommodate piles of any width and thus permit narrower piling if desired. The report goes on to say:

Piles from 8 to 12 feet wide give much more rapid and even drying without increased degrade, as is shown by the data obtained on this variable. Where pine mills have sufficient quantities of short stock they might well pile it so as to have, for example, on one foundation two narrow piles-stock parallel with alley.

In drying clear and select sinker redwood the stock seasoned in piles of 16-foot width reached a moisture content of only 36 per cent in 136 days, while similar, stock, piled at the same time and under exactly the same conditions except that the piles were 8 feet wide, reached the much lower moisture content of 19 per cent in the same drying period.

The manufacturer can readily experiment on pile width by providing a limited supply of stickers of the required length. He may find that narrower piles show improved results chiefly in the slowerdrying seasons, but varying pile width by season is hardly practical, as it would require a supply of stickers in both lengths. Even with 16-foot stickers it is, however, practical to pile in two 6-foot piles with 4 feet of space between, letting the stickers run across both piles and the middle spacing. Just what the degrade would be on the crosser boards if self-stuck lumber were so piled would require a test to develop. The easiest change to make in piling for slowseasoning periods is to pile more openly, especially in the bottom of the pile, by allowing more space between boards, more chimney spacing, and occasional doubled sticker courses, using a doubled thickness of stickers. Improvement does not usually come from continuing to do things in the way suggested by previous habit or the custom followed by others.

In the questionnaire replies 31.1 per cent of the mills used a pile width of 16 feet, and 10.6 per cent use combinations of 6 and 16 feet, 8 and 16 feet, and 12 to 20 feet. The second favorite width was 6 feet and was used by 19.1 per cent of the mills in southern hardwood, North Carolina pine, cypress, and southern pine; 8.5 per cent used combinations of 4 to 6 feet or 6 to 8 feet. The third most frequent width was 8 feet, used by 12.7 per cent of the mills in redwood, southern hardwoods, and southern pine. A pile width of 12 feet is used by 8.5 per cent of the mills, southern hardwoods and southern pine being the species included. The following widths were each represented in 2.1 per cent of the reports: 5, 7, and 10 feet.

Pile heights of 12 to 16 feet were shown in 54.4 per cent of the replies, the upper grades usually being piled lower. Heights of 18

29055°-29-3

to 20 feet were reported by 21 per cent of the mills, probably representing the higher hand piling that can be conveniently done from elevated trams. Pile heights under 12 feet were shown from 12.3 per cent of the mills reporting, all in cypress and southern pine; and heights of 22 to 28 feet were reported by 12.3 per cent of the mills,

[blocks in formation]

most strongly in California pines and redwood, southern pine, Douglas fir, and western pine being also represented. This high piling can be more economically done by power pilers or elevators, as shown in Figure 13, or by cranes, locomotive cranes, or overhead monorails. The reports showed the use of lumber pilers at 9 plants, locomotive cranes at 2 plants, other types of cranes at 2 plants, and of monorails at 3 plants, though it is not certain that all the monorails served the yards and were used for placing lumber in pile.

Figure 14 shows the "air-line piling" yard of a large western manufacturer, where stock better suited to air-drying than kiln-drying is piled under an overhead monorail. This is a unit-package handling device, as also is the locomotive crane shown in Figure 10; and Figure 15 shows one of a pair of in forming unit packages, portable horses often used though at the sorting chain heavier frames are usually provided with ends for butting the package either

[graphic]

square or at the desired slant for yard piles, and also with channels for the ends of the stickers in order to guide their alignment. Figure 16 shows a simple type of sling used for lifting unit packages by cable with either a crane or derrick. A similar sling is seen in use in Figure 10, which is somewhat more elaborate, having a rectangular framework above the package from which the holding ropes depend. Figure 17 illustrates a straddle carrier used in the large wholesale yard of the H. P. Dutton Corporation, Providence, R. I., and at

« PreviousContinue »