28 HYDROGRAPHIC MANUAL PaGE 162 



that will remain in good condition for one season. It will usually be recoverable the 

 following year but ought to be re-whitewashed if it is to be used to any appreciable 

 extent. The shapes and sizes should be varied to make the signals distinguishable and 

 easy to identify. 



28. SURVEY BUOYS 



"Wliere buoy stations are required to control hydrograpbic surveys beyond the 

 visibility of shore signals, they must be marked with a suitable buoy structure. A 

 design for a buoy structure for use in a particular area depends largely on the character 

 of the area and the visibility required. Shallow water at the station will limit the length 

 of the underwater portion of the buoy structure. The strength of current, the prevalent 

 weather conditions, and the depth of water are factors which influence the amount of 

 buoyancy required in a buoy. The weight of the anchor and the weight and size of the 

 buoy structure are limited by the ability of the ship's equipment to handle them when 

 they are behig anchored and weighed. The conditions influencing the size and design 

 of buoys are likely to vary with different survey projects and the descriptions and 

 specifications in this section should be considered general, subject to modification to 

 suit the particular conditions encountered. 



The general designs of buoy structures are influenced by a number of elements. 

 Buoys are generally constructed on board ship by the ship's personnel and a simple 

 design that may be made from readily acquired materials and with ordinary tools is 

 necessary. The design must be such that the buoys may be built in the space available 

 on board ship. They should be built of light but strong material — light for buoyancy 

 and ease in handling, yet strong enough to withstand the strains and stresses to which 

 they are subjected while being handled and during stormy periods while anchored. 

 The design shoidd allow for partial disassembly so that they may be easily handled 

 and stored compactly on board ship. They should also be constructed of inexpensive 

 materials that are commercially available and should not require parts of special design. 



Buoys of various designs, embodying many unique ideas, have been constructed 

 to meet the conditions encountered in various areas, but these designs have recently 

 become more or less standardized. The buoy structures in most common use at present 

 are described herein in some detail; others that are seldom used are included, but in 

 less detail, for possible use in unusual circumstances. 



Experiments with streamlined buoys have given promising results and their use 

 is probably indicated where there are strong currents (see 2843). 



281. Buoys in General 



The essential parts of a survey buoy structure are: One or more drums (or barrels) 

 for buoyancy, which support a centerpole or light framework forming the body of the 

 structure, on whose upper end is a target or flag to increase the visibdity, and on whose 

 lower end is a counterweight to hold the structure upright, and suitable ground tackle 

 for anchoring. Each of these parts varies with the type of buoy and its intended use, 

 and also with the material available for its construction. Only materials of good 

 quality should be used to build buoy structures. It is poor economy to use cheap 

 materials of doubtful quality that are likely to fail and result in the loss of a buoy 

 after it has been placed on station and its position has been determined. The value 

 of the ship time lost in replacing a single essential buoy is equivalent to the cost of the 

 material for several buoy structures. 



