. Concepts for drilling and excavating in and below the ocean bottom. Underwater drilling; Ocean bottom. A less costly concept for employing wood in buoyancy shapes is illustrated in Figure 44. Typically the compressive strength of timber per- pendicular to the grain is many times less than that parallel to the grain. For coast-type Douglas fir at 12% moisture content, for instance, the relative values are 870 to 7,430 psi, respectively, a ratio of over 1 to 8 (USDA, 1955). This suggests the fabrication configuration shown in Figure 44, in which the fibers are selectively oriented to take adva
. Concepts for drilling and excavating in and below the ocean bottom. Underwater drilling; Ocean bottom. A less costly concept for employing wood in buoyancy shapes is illustrated in Figure 44. Typically the compressive strength of timber per- pendicular to the grain is many times less than that parallel to the grain. For coast-type Douglas fir at 12% moisture content, for instance, the relative values are 870 to 7,430 psi, respectively, a ratio of over 1 to 8 (USDA, 1955). This suggests the fabrication configuration shown in Figure 44, in which the fibers are selectively oriented to take advantage of the anisotropy. This relatively inexpensive wood with minimum water- proofing of sheathing should be useful at least 12,000 feet in the ocean. Other even more advantageous arrangements could probably be developed. For one thing, it appears that some collective reinforcement should be pos- sible with suitable preferred fiber orientations, so that the measured stiffness in the complex structures would be greater than calculations based on indi- vidual components. This phenomenon is referred to as "; A recent development in buoyancy, not yet fully tested in a pressure environment, is described by Madden (1970). Figure 45 from that source shows closely packed spheres formed from brazed hemispheres in a possible replacement for the well-established honeycomb core material developed for industrial and aerospace applications. The material offers promise both as a buoyancy and a structural material. end grain. Figure 44. Composite wood buoyancy shape, with end grain exposed on all faces for greater strength. 56. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Naval Civil Engineering Laboratory (Port Hueneme, Calif. ). Port Hueneme, Calif. : Naval Civil Engineering Laboratory
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