The total cost of the FORDS concept includes everything except the 

 cost of cable (or pipe string). The costs of the cable and cable handling 

 equipment (or pipe and pipe handling equipment) must be added to the costs 

 of all the above systems. 



It is important to consider the limitations of the above surface 

 vessels. Except for the platforms, there are serious restrictions on the size 

 of the load that can be handled. The ships are relatively narrow and, as a 

 consequence, the outside dimensions of the load will be restricted accordingly. 

 Moreover, there is some question whether some of the smaller ships are large 

 enough to accommodate even the equipment to lower the load, especially if 

 a derrick of adequate size were required. Based solely on the criteria of 

 versatility and size, a custom-built platform would be the most satisfactory. 



As emphasized in the opening paragraphs of this appendix, economy 

 of construction cannot be ignored. It is obvious that the ships offe/ the least 

 expensive means of constructing a heavy-lift system, since they are only to be 

 modified. Even if an entirely new ship were to be constructed, there is a good 

 possibility that the total cost would still be less; the Glomar Challenger, for 

 example, cost $12.6 million. 



Another factor which should be kept in mind is that the FORDS 

 platform is probably more than is needed. It was designed to spend many 

 days at sea, be self-sufficient, and survive the severest seas. It seems logical to 

 suppose that the heavy-lift system will not be required to satisfy such stringent 

 requirements; in other words, that the crew will have some choice as to when 

 they can lower or lift a load. How closely the final system resembles the 

 FORDS platform or the Glomar Challenger depends greatly on the scenario 

 of the desired operation. A fast, mobile system will require a ship-like hull, 

 while a system which requires less mobility could be configured as a stable 

 platform. 



MAINTAINING POSITION OF THE SURFACE VESSEL 



Mooring 



There are three main classifications of major mooring systems: 

 (1 ) single-leg flexible, (2) multileg flexible, and (3) bottom-rest. Brief 

 descriptions of these systems are given below. ■^^ 



Single-Leg Flexible Anchors. A single-leg flexible anchor consists of 

 one anchor and a single slack riser line to the surface vessel. It is the most 

 common form of anchorage and is used primarily to resist horizontal loads. 



97 



