2826 HYDROGRAPHIC MANUAL PaGE 170 



described for the one-barrel buoy. The additional buoyancy provided by the two barrels will permit 

 the use of a heavier counterweight. One weighing 450 or 500 pounds will provide adequate stability 

 and with it the buoy will float with about one-half of the upper barrel above the surface of the water. 

 Two methods of attaching two barrels to a single-pole buoy structure are shown in B and C, 

 ^figure 46. Iron bands, laent to fit around the barrels, are used to hold the barrels to the centerpole. 

 The centerpoles for these structures are made of rough 2- by 4-inch lumber spiked together to form 

 a 4- by 4-inch cross section, except for the uppermost 8 feet. In the scheme represented in B, figure 46, 

 the barrels are held more firmly in place by wooden lugs made to fit over the chimes of the barrels 

 at top and bottom. One bolt through the centerpole is used to hold each pair of lugs in place. The 

 construction represented in C, figure 46, requires two wooden blocks, one to fit on each side of the 

 centerpole. These blocks are cut from 2-inch lumber approximately 6 inches wide with their opposite 

 sides shaped to fit the curve of the barrels and are secured to the centerpole by wood screws or through 

 bolts. 



(A) ADDITIONAL MATERIALS FOR TWO-BARREL BUOY 



(Arrangement A in fig. 46) 



Number 

 Description Size required 



Lumber 2" by 4" by 12' 1 each. 



Barrel, G. I 56 gallon 1 each. 



Rod, tie, both ends threaded H" by 32" 1 each. 



Nuts, hexagonal-- W 2 each. 



Washers IW by Yie" i^Ae" hole).-. 2each. 



Strap, drilled for H" bolts as shown W by 2" by 6' 2 each. 



Bolts, with nuts and washer H" by 5" - 7 each. 



Counterweight of car couplers or scrap iron 450 pounds total. 



2826. Three-Barrel Buoy 



Three-barrel buoys have been used in the past. Their use is not recommended 

 under ordinary circumstances because their larger, more cumbersome size makes them 

 more difficult to build and to handle on board ship. The three-barrel buoy does carry 

 larger banners which result in somewhat better visibility, but a heavier counterweight, 

 heavier anchor, and stronger anchoring gear are required. 



Three 55-gallon barrels and a 4-inch square centerpole, 23 feet long, are used to construct the 

 buoy. Two of the barrels are laid side by side on their bilges and temporarily secured. The center- 

 pole is placed on top and parallel with the barrels, with two of its sides tangent to their bilges and 8 

 feet of its length projecting above the tops of the barrels. The centerpole is then trimmed slightly 

 so that, when the third barrel is placed on top and parallel to the lower two, it rests on them and the 

 trimmed pole simultaneously. The three barrels are tightly bound together at each end with several 

 turns of J^-inch galvanized wire cross lashed in the three spaces between barrels and made tight with 

 Spanish windlasses. 



Wooden wedges are driven between the barrels and the centerpole to prevent movement of the 

 barrels along the centerpole. Four pieces of 2- by 4-inch lumber, long enough to extend 6 inches 

 beyond the edges of the barrels, are notched to fit the chimes of the barrels. Two of these, crossed 

 at right angles, are nailed to the centerpole just above the barrels, and two just below, and the project- 

 ing ends are tightly lashed with wire from top to bottom. 



A 2- by 4-inch mast, 13)^ feet long, on one end of which are crossed wire-screen banners, is spiked 

 to the centerpole with an overlap so that the top of the banner is 16 feet above the top of the barrels. 



The centerpole is braced by four pieces of 2- by 4-inch lumber extending diagonally from its upper 

 end to the outer ends of the cross braces at the tops of the barrels. The mast is also braced by four 

 pairs of galvanized guy wires, each tightened by a Spanish windlass, extending from about the middle 

 of the crossed banner to the outer ends of the cross braces. The centerpole below the barrels is 

 braced by four 2- by 4-inch by 6-foot diagonals to the lower cross braces. 



Crossed banners as large as 6 by 8 feet in size may be used, but then a counterweight of at least 

 700 pounds is required even for ordinary conditions of wind and current. The counterweight should 

 be attached by suitable fittings to the lower end of the centerpole, so that it is readily detachable. 



