Macy 



Fig. 3 - Floating single barge (Western Offshore 

 Drilling and Exploration Co., Wodeco V) 



degrees in a vertical plane, the columns become catamaran hulls, and in this 

 mode the unit is moved by self-propulsion. 



There are several special types which are not in common use. One of these 

 is the deadweight anchor type (Fig. 15), consisting of a hull with small columns 

 extending upward to support the platform. When the platform has arrived at lo- 

 cation, very heavy anchors suspended directly below the structure are lowered 

 to the bottom. Then with the use of winches, the unit is pulled under the water 

 so that the hull is below the maximum wave forces, with the working platform 

 remaining above the surface. The proportions of the anchor weights and buoy- 

 ancy members need to meet the following criteria: 



1. The anchors must be heavy enough so that the upward components of the 

 wave forces will not lift the hulls and raise the anchors off the bottom. 



2. The reserve buoyancy of the hulls must be enough so that the downward 

 components of the wave forces will not cause slack in the anchor cables, allow- 

 ing the platform to drop. 



450 



