3. Larger ship meant smaller static underkeel clearances. 4.
Just prior to the capsize, the vessel
developed too great a speed. Tis caused a build- up of a pressure wave at the bow and also excessive squat. 5. Bow doors were leſt open. 6. Water entered through these open bow doors. 7. Ingress of water caused rise of ‘G’ due to loading. As shown in Figure 1, ‘G’ moves to G2. By definition, ‘G’ is the vertical centre of gravity above the keel. It is very dependant of the loading of the ship by the officers on the bridge. 8. Ingress of water caused a rise in ‘G’, due to Free Surface Effects (FSE). As shown in Figure 1, G2 to a higher position of G3. 9. Ship’s G rose above ship’s M because of the addition of loading and FSE. See Figure 1. Vessel is now unstable!. 10. At forward speed, squat is produced additional trim at the bow. Tis was added to the static trim. For values of ship squat at various values of ship speed, see Figure 2. Feedback observations indicate that dynamical trim is always added to the static trim. 11. To initially produce trim by the bow, water ballast was put into No 1 double-bottom tank. Tis was to lower the car ramp so as to be able to drive the cars onto the vessel. 12. At speed, an order was given to turn the ship. Tis would cause the ship to develop an angle of heel. Tis angle of heel will produce loss of underkeel at the bilge strakes, known as transverse squat. Transverse squat depends upon the breadth moulded and angle of heel. For angles of heel up to 70 and for breadth Mld up to 70m, see Figure 3. At an angle of only 70 Herald of Free Enterprise would have had a static transverse squat at the bilges of 1.38m. At forward speed, it would be even more. 13. To bring vessel nearer to even keel, a pump was used to transfer water from No. 1 double-bottom tank (located forward) to No 14 double-bottom tank (located aſt). 14. A more powerful pump was requested. Tis was refused, because cost of the pump was £25,000. 15. Ship’s Lightweight on 6 March 1987 was inaccurate. On 6 March 1987, it was 270tonnes more than at her delivery date. 16. Vessel was overloaded at time of departure from Port of Zeebrugge.
The Naval Architect April 2009
17. Te exact number of passengers onboard was not known. 18. Aſt draſt was unable to be read. 19. No end draſt indicators linked to the bridge were fitted. 20. Herald of Free Enterprise departed five minutes late. Was this why the bow doors were leſt open? 21. No stability data onboard regarding a condition with the vessel trimming by the bow. For even keel condition? YES. For bow trim condition? NO. 22. Estimates of individual car weights were incorrect. Some were assumed to be
1.00tonnes when in fact they were each 1.25tonnes - 25% underestimation for quite a number of cars. 23. No audio, telephone or television linkup between ship’s bridge and the bow doors. 24. Other occasions had occurred when bow doors had been leſt open whilst leaving port. On some ships, this still occurs, in March 2009! 25. Fatigue problems with officers and crew. 26. Too many changes in sailing schedules. 27. Very wide open transverse spaces in car-deck levels, very much like a shore-based indoor car park. Incoming water can flood
Figure 2. Squat curves for Herald of Free Enterprise.
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