DESIGN, CONSTRUCTION, AND OUTFITTING 



79 



Emergency exit is forward through a 30-in. hatch. Access on the surface is through the 

 upper conning tower hatch, a 30 psi surface ship weather deck hatch, and the lower hatch, a 

 30-in. hatch. The 48-in. main access hatch was specially fabricated, while the two 30-in. hatches 

 are standard submarine escape trunk side hatches. 



Lifting pads are provided for both the dry maximum weight lift and the negative buoyancy 

 lowering. Special slings are designed for each operation. Towing chocks are provided fore 

 and aft. 



When on the bottom Sealab n is 13 tons negative and the bearing surfaces, two pads extend- 

 ing athwartships fore and aft, are designed for 300 psf, the bearing strength of the bottom at 

 the site. Corner spades 15 in. in depth allow a firm implacement and increase resistance to 

 sliding. No provision is made to level the pads, such leveling is the task of the occupants if 

 possible by a washing process using compressed air and water. 



Stowage racks for 24 - 1300 cu ft gas bottles are provided port and starboard forward. 

 The bottles contain make-up helium (10), make-up oxygen (11) and a helium -nitrogen-oxygen 

 mixture for emergency breathing (3). 



There are 11 viewing ports each 24 in. in diameter. These ports are designed to withstand 

 15 psig internal pressure and are protected at full internal pressure by hinged steel covers. 

 An equalizing line allows maintenance of a Ap = across the glass while submerging. This 

 line is capped at depth and the steel covers opened. 



Hull Interior 



The variable water ballast tanks are three feet deep and located in the overhead (Fig. 46). 

 These tanks are "soft" tanks, i.e., the bottom boundary cannot withstand aAp of greater than 

 15 psi. These tanks provide, with the conning tower, the negative buoyancy necessary for ini- 

 tial submergence and lowering, and the negative buoyancy necessary for firm seating on the 

 bottom. 



Fig. 46. Sealab II fixed and variable ballast 



