A modification of this system is employed 

 with the JOHNSOy SEA LINK (Fig. 12.11) 

 where a universal joint is rigidly coupled to 

 the armtip. A diver is required to attach bow 

 and stern steadying lines and to insert a 

 special hooking device into a housing atop 

 the submersible. The pilot's I'ole is to maneu- 

 ver the submersible to a convenient point 

 astern of the ship. The entire procedure is 

 performed underway at low speed and expe- 

 dited by the fact that the boom need only be 

 retracted or extended along the fore and aft 

 line of the ship. In other boom systems the 

 vehicle pad location requires swinging the 

 crane through the ship's roll plane. 



Overhead Rail (Fig. 12.11): The DOWB and 

 NEKTON use an overhead fixed rail system. 



The pendulum effect can be substantial in 

 this case with the added requirement for 

 greater maneuvering by both the ship and 

 the submersible because of the untrainable 

 nature of the rail. 



Ramp (Fig. 12.12): International Hydrody- 

 namic's HUDSON HANDLER is the only sup- 

 port platform known to use this system. The 

 following description of its launch/retrieval 

 procedure is taken from McFarlane and 

 Trice (9). 



''One module of the vessel is hinged 

 along its foremost transverse, the 

 hinge point being almost exactly mid- 

 way between the vessel's stem and 

 stern. The module is watertight and 

 contains internal subdivisions. When 



Fig. 12.12 Hinged rampofHYCO's HUDSON HANDLER. 



598 



