Page 169 



CONTROL AND SIGNAL BUILDING 



2825 



the frame, preferably at a 4- by 4-inch section, below the bottom of the barrel. The rope sling is 

 placed on the opposite vertical member as previously explained in (A) above. Banners are made of 

 wire screen tacked to 1- by 4-inch lumber, but neither the banners nor the flagstaff are nailed to the 

 mast at this time. They are affixed just before the buoy is anchored to avoid damaging them while 

 the buoy is being handled and to conserve stowage space, ' , 



2825. Two-Barrel Buoy 



Although the standard one-barrel buoy is used almost exclusively for buoy control 

 there are occasions when additional buoyancy is required to counteract strong cur- 

 rents, deep water, or strong prevailing winds. This is attained by the use of an addi- 

 tional steef barrel, the two being utilized in any one of several ways. 



The two barrels can be mounted vertically one over the other within the framework as illustrated 

 in A, figure 46. The over-all length of this buoy structure and the general details of construction 

 are the same as for the one-barrel buoy, the sketch showing only the details that are different. The 

 increased distance from the top of the upper barrel to the bottom of the lower barrel causes additional 

 strain on the vertical members where bent, and they must be reinforced with iron straps. The straps 

 are made of 2- by ^i-inch flat stock, drilled with holes as shown in the sketch. The barrels, if non- 

 returnable ones are used, are held in place by tightening the tie rods, fitted with washers, so that the 

 barrels will be held firmly between the vertical wooden members. If returnable barrels are used, they 

 are held in place by slots burned out of the rolling tracks into which the vertical members fit, as 



<4 :----:>© 



lA^ 



SCALE IN FEET 



FiGi'EE 46.— Two-barrel survey buoys > tiree arransfinciits. 



