Hard a Starboard Norwegian Sky vs Titanic

[Cal Haines]

Here's an interesting news item from May 21, 2001:

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Quote:

SEATTLE, Washington -- The autopilot on a cruise ship failed and caused it to make a jarring turn and then list, sending plates and glasses crashing and injuring more than 70 people, the Coast Guard said.

The 853-foot Norwegian Sky's autopilot malfunctioned Saturday near the mouth of the Strait of Juan de Fuca, causing the rudders to swing and turn the ship hard to the left. A crew member had to disengage the autopilot, Coast Guard Lt. j.g. Scott Casad said at a news conference Sunday.
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(source)
http://www.cnn.com/2001/TRAVEL/NEWS/05/21/cruiseship.injuries.ap/index.html

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Other stories about the incident:

Hawaii Group Jostled On Cruise Ship
http://dailynews.yahoo.com/h/kitv/20010521/lo/405866_1.html

16 Injured in Cruise Ship Mishap
http://dailynews.yahoo.com/h/abc/20010521/ts/ship010521_1.html


This is what I would have expected to have happened aboard Titanic if the rudder was put hard over. Yet there are no reports of anything close to this. Comments?

Cal

 

[Erik Wood]

Cal, I think this was discussed in my private thread.

Erik

 

[Michael H. Standart]

Hi Cal, at 11:40 at night, I doubt that many people were up and about to take notice save those crew on watch and some die hard card players or lounge lizards among the passangers. As many of them had made crossings befor, they may not have considered the heel worth mentioning.

Cordially,
Michael H. Standart

 

[Erik Wood]

It is also important to remeber that the helm was shifted before the ship really began it's swing. The problem with Hydraulics and auto pilot is the auto pilot doesn't know (unless you tell it) how fast you want to turn and can throw the rudder over in one direction in less then 5 to 8 seconds. Or both rudders whatever the case may be.

Erik

 

[Cal Haines]

Hello Mike & Cap'n Erik,

Based on my limited experience, it's not something that would escape notice. Boxhall and Olliver would have had trouble walking, the lookouts would have reported more that a slight lean, the card player's drinks would have slid off the tables, etc.. Particularly if the rudder is held over as Hichens reports.

As to the speed of the rudder, Hichens could (and undoubtedly would) turn the wheel more quickly than the steering gear could respond, so the rudder would be moving at its maximum rate.

Cal

 

[Michael H. Standart]

Hi Cal, I don't think it would escape notice either. It's just that sailors and seasoned travellers might not think it worth mentioning. Unfortunately, none of these people are available to ask anymore.

The ambiguities and uncertainties of Titanic research bite again.

Cordially,
Michael H.Standart

 

[Per Erik Kjepso]

This is an interesting point. There has been several incidents on cruise ships with wheel hard over on full speed. FX, a RCCL ship making 25 knots gave full rudder and this resulted in a 14 degree list. 14 degree list is something you will notice if you are onboard. In this case, the pools overflowed, people were injured from falling and from falling objects and the technical damage was 80000 USD.

Cruise ships dont have much stability (GM), they are very top heavy. Does anyone know how the GM and so was on Titanic? Would think the stability is better as the superstructure was relative smaller than the hull and there were no swimming pools on Titanic.

However, the amount of list is a result of speed and the rate of turn, not directly the rudder angle. Or to be precise, list is determined by how fast the rate of turn is increasing.

If you dont have a propeller stream on the rudder, ie only the ships speed through water gives force to the rudder, it wont be a very sharp turn.

It could be that Titanic made a very slow turn after all, possibly a result of stopping the centre propeller giving no propwash on her only rudder. And that is the reason a list was not noticed.

Per E

 

[Samuel Halpern]

>>Does anyone know how the GM and so was on Titanic?<<

Best estimate for GM is 2.6 feet or 79.25 centimeters.
For Titanic in a hard turn with full rudder at full speed, the maximum heel angle works out to about 5 1/2 degrees. Also, due to hydrodynamic drag, the speed in the turn would be reduced from 22 knots to about 17 knots.

 

[David G. Brown]

To put Sam's post into perspective, I have a lot of experience in passenger sailing vessels. Very few people notice any heel angle below 5 degrees. Between 5 and 10 degrees the awareness grows among the passengers. At 10 degrees people begin to ask questions.

-- David G. Brown