Feature 4 | RO-RO FERRY REPORT Herald of Free Enterprise revisited
Although 22 years ago, the capsize of Herald of Free Enterprise still has lessons for ro-ro ship designers today, says Dr Bryan Barrass, FRINA.
lorries, trailers, trains, cargo and passengers. They may be single-screw or twin-screw design. Ro-ro vessels are ideal for short fast trips
T
across shipping lanes such as the English Channel, North Sea and the Irish Sea. Socially, as more people take early retirement and go on holidays in Europe, the demand for new ro-ro vessel designs has, in the last decade increased. Cars and trailers can be driven into the
ship at the stern, at the bow or through several side openings along the length of the ship. Following several recent disasters with this type of vessel, entering the ship via the Bow has become less popular for new orders
TECHNICAL PARTICULARS Herald of Free Enterprise
LOA ....................................................131.9m Breadth Mld.......................................22.70m LBP ......................................................126.1m Service speed ............................. 22.00knots Ship’s displacement .................8874 tonnes to 9250 tonnes
Mean draft (static) .............5.68m to 5.85m Draft forward (static) ..........6.06m to 6.26m Draft aft ...............................5.31m to 5.43m Trim by the bow (static) .....0.75m to 0.83m VCG (fluid) with slack tanks ..............9.73m to 9.75m
GMT (fluid) with slack tanks ...............2.04m to 2.09m
Ship speed, just prior to grounding .... 18.00 knots to 18.50 knots
Cb @ Draft Moulded of 5.30m ........... 0.525 Three props aft, one prop for’d Brake Power ..................................20,142kW Sulzer Diesel engines fitted CP propellers fitted Hinged stabiliser fins fitted Deadweight .............................2000 tonnes. Cost .................... of the order of £30million. Number of lives lost ................................ 193
54
he design basic concept of a ro-ro vessel is that of a moving multi-storey indoor car park. They carry cars,
for these vessels. On this point of disasters, it should be
remembered that the history of ro-ro ferries includes the fact that, aſter being involved in a collision with another vessel, they can capsize and sink in only 1.50 minutes. Mainly this is due to the very wide spaces athwart ships. Teir fully loaded deadweight values range
from 2000tonnes to 20,000tonnes, their LBP values range from 100m up to 210m and their breadth moulded values range from 20m up to 32.26m (Panamax). Range of draſt moulded is 5.00m to 9.00m. When fully loaded, their Cb values range from 0.525 up 0.575, with a service speed in the range of 18knots to 30knots. Bulbous bows are usually fitted to give, for
similar input of engine power, extra forward speed. Alternatively, for a similar forward speed, oil fuel consumption is reduced, thereby producing savings in operating costs. Generally, the faster the designed service speed, the lower will be the Cb value. To facilitate turning characteristics,
meanwhile, ro-ro vessels have larger than usual rudders working together with bow or stern thrusters. In port, this can lead to a quicker turn round without having to call for the assistance (and cost) of tugs.
HFE reconsidered. On 6 March 1987, the ro-ro vessel Herald of Free Enterprise capsized shortly aſter leaving Zeebrugge in Belgium. She was a passenger and freight ferry and was bound for Dover. This Zeebrugge to Dover transit was scheduled to be 4 crossings per day with each crossing taking about four hours. Herald of Free Enterprise leſt Zeebrugge at
6.05pm, about 78 minutes aſter high water. When static and when at forward speed she was trimming by the bow. She leſt the Port of Zeebrugge with both bow doors open. She turned to starboard and capsized to port. When capsized, her starboard side was above the water with approximately half her breadth moulded showing above the waterline. She eventually ended up about 930m off the centreline of the navigation channel. Te
Figure 1. Transverse stability details.
disaster unfolded in just 1.50 minutes in calm water conditions. At the time that she went aground it was
suggested by the maritime press that her forward speed was of the order of 18knots to 20knots. 193 people lost their lives. In considering the possible causes for this
ferry to capsize in this manner, I suggest 30 factors. Drawing on these, I go on to consider improvements that could be made to existing ferries by way of retrofit, and future policy for new ro-ro ferry designs.
30 factors 1. Larger ship than normally used was selected for the run to Dover. Herald of Free Enterprise was usually on the Dover-Calais run. Herald of Free Enterprise was a replacement vessel for a smaller one that had developed engine troubles. 2. To bring cars on board, Herald of Free Enterprise had to be trimmed by the bow.
The Naval Architect April 2009
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68