2832 HYDROGRAPHIC MANUAL PaGE 172 



There are two general types of railroad car couplers, one incorporating a heavy- 

 steel spring used on passenger cars, and another without spring used on ordinary 

 freight cars. The latter are shorter, stow better on deck, and are recommended when 

 a choice is available. 



Junked car couplers are frequently available only at ports with extensive railroad 

 yards. At other ports other material will have to be substituted. A suitable anchor 

 may be made from condemned anchor cable. A 750-pound anchor may be made from 

 7^2 fathoms of 1 }^-inch chain, faked in lengths of about 4 feet and securely wired together 

 to form a solid mass. This forms an anchor that is easily handled and, because of its 

 many irregularities, has good holding qualities. 



An anchor or counterweight may also be cast fiom concrete, but a mixture of 

 cement, sand, and gravel only has too light a specific gravity. A mixture of one part 

 cement and two parts sand should be used as a binder to hold together solid pieces of 

 scrap iron to furnish the desired weight. A concrete anchor is usually cast in a square- 

 shaped block in which an inverted U-shaped rod is embedded to which the anchor cable 

 may be attached. A 12- by 12- by 26-inch form filled with 300 pounds of scrap or pig 

 iron cast in concrete in this manner will weigh 450 pounds. This size is suitable for 

 the counterweight of the two-barrel buoy. Two grommets of 4-inch Manila line should 

 be spliced tightly around the block to serve as skids when the block is moved around 

 the deck. 

 / Danforth anchors have recently been used successfully to anchor survey buoys. 



The Danforth anchor is a patent anchor of new design intended principally for use in 

 anchoring yachts and motorboats. It is "claimed to have a much superior holding 

 power for its weight than other anchors of conventional design. The manufacturer 

 claims a holding power of 200 or more pounds per pound of anchor weight. The 

 anchors are made of cast alloy steel or nickel-chrome steel in sizes from 15 pounds up. 

 The manufacturer is R. S. Danforth, Berkeley, California; other manufacturers make 

 anchors of similar design. 



The design makes the anchor self -burying in mud or sand bottom, where its use 

 would seem to be most advantageous. One survey party substituted 30-pound Dan- 

 forth anchors for 750-pound car-coupler anchors on two survey buoys and reported that 

 they held through 50-mile gales. That survey party enthusiastically recommends 

 their use. 



2832. Wire Rope and Chain 



The anchor cable with which a buoy is anchored is generally a combination of wire 

 rope and chain, but variations in the types and sizes of these are necessary in various 

 depths of water. In general, a larger diameter cable may be used for buoys anchored 

 in shoal or moderate depths because they do not have to support such a long length of it. 



Chain should be used for that portion of the anchor cable adjacent to the anchor, 

 which will chafe on the bottom. It is generally also used to join a relieving buoy 

 to the buoy structure, if the former is used. Satisfactory results have been obtained 

 with %-inch galvanized boat chain and its use has become almost standard for this 

 purpose. 



In order to keep the weight of the anchor cable at a minimum, galvanized wire rope 

 is used extensively. The two sizes in general use are %-inch and }2-inch diameter, 

 both of 6 strands of 37 wires each of extra strong cast steel. 



In general, the anchor cables of buoys, anchored in depths of 20 fathoms or less, 

 may consist of %-inch chain exclusively. In moderate depths, to 50 or 60 fathoms, the 



