2822 HYDKOGRAPHIC MANUAL PaGE 166 



Small spherical buoys, or 55-gallon barrels without superstructure, anchored with 

 the same ground tackle used for survey buoys, are frequently needed for marker buoys 

 in R.A.R. or buoy-control surveys. The 18-inch spherical buoy used in mooring sea- 

 planes or small yachts is convenient and will generally have sufficient buoyancy to hold 

 the weight of the anchor cable without submerging. Such buoys, without superstruc- 

 tures, are difficult to see at a distance and should be painted a bright yellow, or white, 

 to increase their visibility. Suitable rope loops should be rigged on top of them into 

 which a hook may be inserted when they are being lowered or raised over the ship's side. 

 (See also 2835.) 



2822. Small Buoy 



The smaller auxiliary vessels frequently require buoys to control offshore hydro- 

 graphic surveys but the standard survey buoy cannot be handled by their limited 

 equipment. For such use a miniature of the one-barrel buoy (see 2824) may be con- 

 structed. A 10- or 20-gallon barrel is substituted for the 55-gallon barrel and all other 

 parts are made correspondingly light for ease in handling. The design of the small 

 buoy should be similar to that of the standard buoy but lighter lumber should be used 

 and the counterweight should not exceed 35 pounds in weight. The over-all length of 

 the small buoy structure should be about 15 feet, the small barrel being 8 feet above the 

 lower end. A 10-foot staff with target flags is secured to the upper part of the buoy 

 structure to increase the over-all height of the buoy, when afloat, to about 16 feet. The 

 counterweight is shackled to an iron plate which is bolted to the lower end of the wooden 

 structure. 



2823. Shoal-Water Buoy 



Buoy control may be required in extremely shoal areas where the long submerged 

 part of a standard one-barrel buoy might groimd in the shoal water. A special buoy 

 structure, with a short submerged section, is required in such a case. 



The shoal-water buoy is built by enclosing a 55-gallon steel barrel in a short square wooden frame 

 from which a mast extends. Two frames, about 10}^ feet long, made of 2- by 4-inch lumber, are crossed 

 at right angles around the steel barrel, extending 5 feet above the top but only 3 feet below the bottom 

 of the barrel. Each frame is secured to the barrel by two iron rods bolted through the frame, one just 

 below and one just above the barrel to hold it firmly in the structure. One end of one of the upper 

 iron rods is made with a 2-inch eye to which the anchor cable maj^ be attached. 



A 10-foot mast is stepped on the top of the barrel and secured vertically to two pairs of 1- by 4-inch 

 cross braces at right angles to each other at the upper end of the barrel and two similar pairs of cross 

 braces at the top of the framework. Crossed banners of suitable size and material are added to the 

 top of the mast. 



To reduce the draft of the buoy the counterweight is incorporated in the buoy structure. The 

 lower end is built as a box form, which includes the lower 20 inches of the framework, into which suf- 

 ficient concrete is poured to furnish the desired counterbalance. 



2824. One-Barrel Buoy 



The use of the one-barrel buoy has become practically standard in buoy-control 

 surveys. It is simple to construct, economic in cost, and its size and height are suf- 

 ficient to be seen at the required distance. The design has developed from many years 

 of field experience in building buoys on shipboard. It can be constructed and stowed 

 in the limited space available and its lightness gives it buoyancy and makes it easy to 

 handle when it is being anchored or weighed. 



