BULKHEAD . 1. A structure separating land and 

 water areas, primarily designed to resist earth 

 pressure. See also SEAWALL. 



2. Walls or partitions within a ship. 



BULK MODULUS OF ELASTICITY . The ratio of stress 

 to volume changes in materials subjected to axial 



loading. It is calculated: K = Er 



3(1 - 2r) 

 where K = Bulk Modulus of Elasticity, psi 



E = Modulus of Elasticity, psi 



r = Poissons Ratio. 



BULLPUP . A Navy air-to-surface missile. 



BULL ' S EYE ■ 1. The eye or calm central portion 

 of a revolving storm. 



2. A small dark cloud with a reddish 

 center, sometimes seen at sea, often preceding a 

 storm. 



3. A kind of squall on the coast of 

 South Africa. It descends out of a clear sky with 

 great suddenness. Usually called BULL'S EYE SQUALL. 

 (17) 



BULL'S EYE SQUALL . A squall forming in fair 

 weather, characteristic of the ocean off the coast 

 of South Africa. It is named for the peculiar ap- 

 pearance of the small isolated cloud marking the 

 top of the invisible vortex of the storm. (17) 



BUMED . Bureau of Medicine and Surgery. 



BUND . An embankment or embanked thoroughfare 

 along a body of water. The term is used particu- 

 larly for such structures in the far east. (17) 



BUOY . A floating object, other than a lightship, 

 moored or anchored to the bottom as an aid to navi- 

 gation. Buoys may be classified according to shape, 

 as Spar, Cylindrical or Can, Conical Nun, Spherical, 

 Cask, Keg, Dan, or Pillar Buoy. They may also be 

 classified according to the color scheme, as a Red, 

 Black, or Checkered Buoy. A buoy fitted with a 

 characteristic shape at the top to aid in its iden- 

 tification is called a Topmark Buoy. A Sound Buoy 

 is one equipped with a characteristic sound signal, 

 and may be further classified according to the man- 

 ner in which the sound is produced, as a Bell, Gong, 

 Horn, Trumpet, or Whistle Buoy. A Lighted Buoy is 

 one with a light having definite characteristics 

 for detection and identification during darkness. 

 If the light is produced by gas, it may be called 

 a Gas Buoy. A buoy equipped with a marker radio - 

 beacon is called a Radiobeacon Buoy. A buoy with 

 equipment for automatically transmitting a radio 

 signal when triggered by an underwater sound signal 

 is called a Sonobuoy. A Combination Buoy has more 

 than one means of conveying intelligence; it may 

 be called a Lighted Sound Buoy if it is a lighted 

 buoy provided with a sound signal. Buoys may be 

 classified according to location, as Channel, Mid- 

 Channel, Middle Ground, Turning, Fairway, BIFURCA- 

 TION, JUNCTION, SEA or FAREWELL BUOY. A DANGER 

 Buoy is one marking an isolated danger to naviga- 

 tion. A Bar Buoy marks the location of a bar. A 

 buoy marking a hazard to navigation may be classi- 

 fied according to the nature of the hazard, as 

 Obstruction, Wreck, Telegraph, Cable, Fish Net, 

 Dredging, or Spoil-Ground Buoy. Buoys used for 

 particular purposes may be classified according 

 to their use, as Anchor, Anchorage, Quarantine, 

 Mooring, Warping, Swinging, Marker, Station, Watch, 

 or Position Buoy. A lightweight buoy especially 

 designed to withstand strong currents is called a 

 River Buoy. An Ice Buoy is a sturdy one used to 

 replace a more easily damaged buoy during a period 

 when heavy ice is anticipated. (17) 



BUOY ANCHORS . The most common buoy anchor is con- 

 structed of concrete, cast iron or scrap material 



(e.g. railroad wheels). Some buoys have employed 

 either explosive or specially designed anchors. 

 Explosive anchors are useful in hard bottoms but 

 are complex and expensive for general use. Special- 

 ly designed anchors dig into the bottom and provide 

 high drag for their weight . (28) 



BUOY FLOATS . Floats have wide ranges of size, 

 weight, and shape. This is probably a result of 

 the large number of factors that must be considered 

 in float design, including buoyancy, stability, 

 strength, drag, and weight. The relative impor- 

 tance of these factors in any particular experiment 

 determines shape of the buoy float to be used. Sub- 

 surface floats are probably easier to design since 

 only positive buoyancy and strength need to be con- 

 sidered. Surface floats are more complicated than 

 subsurface floats, and surface floats with tele- 

 metering capabilities are probably the most com- 

 plicated. Telemetry demands that antennae be 

 stable and free from immersion. 



The most commonly used float shapes are cylin- 

 drical and toroidal. Cylindrical floats used by 

 the Canadian Air Force, the Navy Electronics Labora- 

 tory, and the Office of Naval Research range in 

 size from a 45-gallon drum to a 0.5- by 30-foot 

 hydrophone buoy. The toroidal buoy devised by WHOI 

 is constructed mainly of styrofoam wrapped in fiber- 

 glass and provides 6,000 pounds of positive buoyancy 

 with a total weight of only 700 pounds. (28) 



BUOY MOORING LINES . The most popular mooring line 

 material is polypropylene. This material is strong 

 (1.5 tons' breaking strength for 1/2 inch diameter), 

 light in weight, buoyant and flexible. It stretches 

 and tends to eliminate kinks under tension. 



Nylon and dacron are also used. Nylon is 

 about one and 1/2 times as strong as polypropylene 

 but it permanently elongates under heavy loading. 



All plastic line, unless braided, tends to un- 

 wrap when twisted against the lay. The use of 

 plastic line is also limited to independent trans- 

 ducer moors since it cannot carry electrical sig- 

 nal. 



Wire rope is also used as a mooring material 

 for buoys. This material tends to kink. 



For telemetering oceanographic variables at 

 depths, the mooring line must contain electrical 

 conductors. Armored electrical cable has the same 

 disadvantage as wire rope -- it kinks. Watertight 

 electrical swivels can be used to reduce kinking 

 of these cables, but swivels are troublesome and 

 short-lived. Rigid rod sections, which screw 

 together to form a solid rod, have been tested by 

 the Navy Sofar Station. However, a rigid moor is 

 more susceptible to fatigue and mechanical shock. 



Most moors are composed of chain near the 

 anchor. Chain is strong, difficult to tangle, and 

 unaffected by chafing. Chain buffers vary in 

 length from 50 to several hundred feet and are 

 generally selected with breaking strengths commen- 

 surate with the rest of the moor. In many cases, 

 the chain is connected to a weak link which is 

 usually a short piece of small-diameter plastic 

 line. The weak link permits only the anchor to be 

 lost when the moor is broken by exceptionally high 

 strain. 



The ratio of moor length to water depth for a 

 particular buoy depends somewhat on the variable 

 to be measured. Naturally, currents are difficult 

 to measure from a very slack moor. On the other 

 hand, the more taut the system, the more difficult 

 it is to anchor. The largest moor length to water 

 depth ratio (1.4/1) of present buoys occurs on 

 the NOMAD. (28) 



BUOY POWER SUPPLIES . Buoy power is almost ex- 

 clusively furnished by wet cells, dry cells, and 

 nickel-cadmium batteries. Batteries are reliable 

 and inexpensive. Their major disadvantages are 

 limited life and excessive weight. Many exotic 

 power supplies, such as fuel cells, solar cells, 

 and wave generators, are being tested. Use of 5- 



18 



