the long guideline; and its maximum capacity would be too small to deploy 

 and recover the guideline anchor. Had the guideline been lightweight 

 ropes, slack at the lower end might have been avoided. For best results 

 in future designs, the guideline should be high-strength, lightweight 

 ropes, such as the newly developed ropes made of Kevlar 29 and Kevlar 49 

 materials, to take reasonably high tensions with less tension variations 

 along the line. 



Deck Handling 



The guide frame and the payload can be attached to the guideline 

 system either on deck or under the surface by divers. The method used 

 in this study was to attach the guide frame on the deck of the support 

 vessel. The payload assembly was first placed under the bow A-frame by 

 a deck crane. The load was then transferred to the lift line support by 

 a block. 



Sometimes the payload swung, and it was quite difficult for the 

 riggers to align the guideline with the slots on both upper and lower 

 guide cones. The problem was solved by reducing the number of guide 

 cones to one on the single guide frame and to two on the double guide 

 frame, thus enabling the riggers to quickly place the guideline into the 

 guide cones. 



Another problem that was encountered with the single guide frame 

 was its tendency to tilt from its own dead weight when suspended by the 

 lift line. A tilted guide frame will not slide properly on the guide- 

 line and also makes it impossible to place the guideline into the guide 

 cone. A straightforward solution to the problem was to attach a short 

 length of chain across the top of the guide frame and to shackle the 

 lift line to a selected point on the chain to level the guide frame 

 (Figure 12). Because these problems were not severe, it is felt that 

 deck rigging by riggers is superior to underwater rigging by divers. 



The method of using two parallel guidelines for lifting and 

 lowering the anchor block proved completely successful. The positive 

 control of line tensions by air-operated winches and the low center of 

 gravity of the payload contributed greatly to the entanglement -free 

 operation. 



Motion Compensation 



Large dynamic tension was observed by a load cell when the load 

 was suspended at the 50-foot depth. However, the resiliency of the 

 nylon lift line was effective in providing motion compensation at depths 

 beyond 300 feet. At the 600-foot depth, the dynamic tension in the 

 nylon guideline was so small that the air winches did not operate. 

 Therefore, surface motion compensation was not needed for the long 

 nylon guidelines. 



For guidelines of steel wire ropes, the air winch worked as expected, 

 The dynamic tension in the guideline was greatly reduced by the motion 

 compensation. The guideline tension was always kept near a preset value. 



10 



