The effect of complying with MARPOL requirements is discussed in relation to lightweight/deadweight ratio, and the primary economics of tanker size are examined, with some examples of "economy of size" and of laying-up costs; these latter can be very high for the larger ships. The present demand for MARPOL tankers within the deadweight range of 80,000-100,000 tonnes is significant, and apart from any economic merit in this choice, there may be other advantages in operating tankers smaller than VLCCs. The regulations and recommendations under the umbrella-name MARPOL can be described as defensive, and this approach is criticised in respect of the rudder traversing requirement (SOLAS Chapter 2, Regulation 29). The turning performance of tankers, in relation to their size, is discussed and it is shown that the VLCC has turning performance inferior to that of smaller tankers. Increasing fuel costs have resulted in the large full-form tanker ceasing to be the best earner; a finer and better hull-form (e.g., that of a pre-MARPOL tanker with a C sub B of 0.774) will reduce fuel costs and increase earnings. In the next few years, owners will be demanding better dry-dock facilities for maintaining a smooth hull; time devoted to refurbishing in dry-dock will increase, and this will exercise some measure of control on choice of tanker size. The strength of tankers is briefly discussed in relation to structural failure in grounding, and it is mentioned that MARPOL segregated-ballast requirements allow a "heavy thick structured" tanker to be designed without penalising the cargo deadweight. The owner who is prepared to build such a ship might reasonably expect his classification society to take a favourable view of a demand for an extended renewal/replacement life for the vessel. The high incidence of casualties leads to the conclusion that, even with highly efficient crews, the operational systems on the largest ships are barely adequate. Ship sizes below 100,000 dwt appear to be the best investment for safety and continued economy--a "most contentious conclusion". Order from BSRA as No. 53,336.

  • Corporate Authors:

    Bureau Veritas

    One Western Union International Plaza
    New York, NY  United States  10004
  • Authors:
    • Macduff, T
  • Publication Date: 1980-2

Media Info

Subject/Index Terms

Filing Info

  • Accession Number: 00316627
  • Record Type: Publication
  • Source Agency: British Ship Research Association
  • Files: TRIS
  • Created Date: Oct 8 1980 12:00AM