'V 



characteristics and focused attention on sotse features which could h* re- 

 designed to iaprove its econoolc aspects. 



Developraent of another type of diver lift assist device [2,31 occurred 

 about the sane tirse. A family of these has since evolved. The&t; variable 

 buoyancy devices are invaluable diver support equipment, and sisilar devices 

 are now available concaercially. Several neans are available for providing 

 the buoyancy, including scuba air, bottled pressurized gas, and gas 

 generation, and have been successfully incorporated into various models 

 of the devices. 



PROBLEMS ENCO-'NTERED 



Problems discovered during H-W tests and training exercises included: 



1. The point of surfacing is not predictable. Vhen the de\-ice is 

 released at the ocean bottoo its path to the surface is erratic, causing 

 hazardous operating conditicr.s for personnel and equipment that aay be in 

 the water colunn or on the surface. 



2. The Eass of the device and the padeye projecting from its top 

 coabine to make the device a dangerous weapon during ascent. Tbe in-air 

 weight of the steel device is approxinately 5&0 pounds, exclusive of the 

 ballast shot used to adjust sajor buoyancy. The device displaces about 

 750 pounds of seawater. 



3. The nessenger line is expensive and can be used only once. The 

 line, specially wound with a reverse twist to prevent tangling as it is 

 payed out, is encased in a tub drui. Helted wax is poured into the voids 

 after the line is in place, then allowed to harden. 



4. The buoyancy of the H-W device is varied by initially filling a 

 ballast chamber with up to 250 pounds of lead or steel shot. The quantity 

 used depends upon the in-wacer weight of any equipment to be carried or 

 transported by the device. Shot is added to offset any remaining positive 

 buoyancy. If too nuch shot is added or if tt>e diver wishes to increase 

 buo'.-ancy during a dive, shot aay be bled off through a small gate. If 



the divor wishes to reduce positive buoyancy, he loay partially flood a 



toroidal ballast tank through valves provided for this purpose. Because 



this tank is relatively small, the nunber and extent of adjustaents which 

 can be made are Halted. 



5. Because of its size, the device presents a significant sail area. 

 This makes it difficult for divers to handle in moderate currents and 

 alaost Impossible to handle in heavy surf zones. 



6. The male prod is retained in plice by locking handles. At tiaes 

 divers have difficulty in recoving the handles to disengage the prod. 

 To prevent their loss, the handles are usually tethered to the device. 

 This is a hazardous practice because the diver ray become entangled in 



