View non-flash version
Suez Canal Tugs (continued from page 44) ant that the tugs be designed to fulfill their role in assisting in the stopping maneuver, it is ex- pected their use in such a role will be infrequent and they must, therefore, function equally effi- ciently while being towed behind, or escorting ahead of a VLCC. Similarly it would obviously as- sist in operational planning if a common design could be derived to fulfill each role associated with escort duties, which might at times involve the need to per- form a conventional tow. Tugs with a bollard pull of 60 tons would be required to handle safely either 260,000-dwt laden VLCCs in phase 2 or 375,000-dwt ULCCs in ballast in phase 1. By analogy, the existing 40-ton tugs should be adequate to escort 150,- 000-dwt laden tankers in phase 1. Normal Canal transit speed for large vessels is up to 16 km/hr so that in order to be effective the escort tugs should have a free running speed of 20 km/hr. Propulsion systems should be of the multi-directional type and in view of the stable behavior of the duckpeller tugs, the use of At Sembawang Shipyard... . . you will gain most from the services of South East Asia's leading fully integrated shiprepairing organisation which caters for vessels engaged in servicing the international and regional trade. Fast and efficient repairs, quality workmanship and cost effectiveness are always carried out to the satisfaction of our clients. Such standards are possible to maintain only because of the Yard's expertise, experience and the vast engineering back-up available round the clock which are com- parable to the best in the world. At Sembawang Shipyard, few ship-repair jobs are too sophisticated for us as we undertake a wide range of repair work from annual and special surveys, damage and emergency repairs to highly sophisticated conversions. If you are repairing in Singapore, Sembawang offers most. Sembawang Posi OKtce Box No 3. Singapore 8175. Tel 2573511/257! 12! /257046172571216 (3SlineS) Cable SEMDOCK Telex S£MSHIPRS 21345 Agent, for United Stale* Canada: a Midland Marine Corporation. One Penn Plaza. New Yoik NY 10001.USA Telex 232081 MIOL UR Cable Mxlmarcorp New YofhTet (212) 7362666 Houston Texas 77079. twin rotatable propellers located aft was incorporated in the con- sultant's design. The stern tugs need not be of the multi-direc- tional type but such a tug would seem advisable to give maximum operational flexibility. Deck equipment should include a forward towing hook, cruciform bollard and rope/wire handling winches. Towing equipment also should be provided aft, and some tugs should be equipped with fire- fighting equipment. Tug Attachment The main purpose of the stern tug during the stopping maneu- ver is to assist in the directional coursing of the ship which itself provides most of the stopping power. The bridle rig, Figure 2, is considered to be more effective than the American rig, Figure 3, in performing this role, and in addition would: 1. Interfere less with naviga- tion buoys due to its more com- pact nature; 2. Not be sensitive to the back- wash from the ship's propeller during the latter most critical stages of stopping; 3. Involve handling fewer lines when being made fast. In addi- tion, all line handling onboard ship would be carried out on the poop deck where there always is an ample number of winches, etc. This is not usually the case on the main deck of a VLCC, which is the area where the American rig would need to be attached; 4. Avoid the possibility of a tug becoming trapped between the ship and the Canal bank. 5. Give rise to less bank ero- sion from tug propeller wash, and 6. Be less expensive to the ship operator in terms of transit dues. The bridle legs on either large vessel would be about 30 meters in length, and in rigging the bri- Figure 2 — The bridle rig is considered best for use of the astern tug in the Canal. LIKEly MAX WHEN PUSHING UNDERWAY RESTRICTED ANGLE WHEN PULLING TO \30° AVOID EXCESSIVE TENSION IN ONES Write 307 on Reader Service Card 46 Figure 3 — The American rig used in the Canal would require more room than the bridle. Maritime Reporter/Engineering News
