Ocean Liner Question

[DarthGrady]

So this is really more of a technical question, but I am hoping to pick the brains of some of the liner buffs out there, so here goes.

 

Why did the older liners have that bowed design to their hulls? Meaning that when you looked at them straight on from either side, the middle sags down, and the bow and stern are higher. New ships do not do this, as you can stand at one end of a hallway and look all the way down it. When I was on board the RMS Queen Mary, you could only see about halfway down due to the curvature downward toward the middle of the ship.

 

I assume it has something to do with the need for the old liners to be more flexible due to the high seas they operated in. Anyone have any information about this?

[Essiesmom]

i believe it also has to do with aerodynamics and flow of water past the ship, allowing for greater speed. EM

[Druke I]

It's called sheer (or shear?), and it is quite prominent in older ships.

 

I think it disappeared when they started modular building of ships, but I don't know if that is correct, or why that should make a difference.

 

Perhaps a "marine architect" can enlighten us.

[StanandJim]

Why did the older liners have that bowed design to their hulls?

 

Darthgrady-

 

Hope this sheds some light:

 

When ships were much smaller than they are today, their decks were curved upward toward the front and back of the ship (Sheer).

The decks were also cambered (that is, curved higher in the center of the ship, and lower at either side), as another means of draining the decks of seawater that was constantly washing over them.

Over time, the "look" of sheer and camber became so entrenched in the minds of naval architects that the practise was continued, long after it was practically called for.

There was, however, the odd exception.

As early as 1931, the Companie de Navigation Sud Atlantique built their revolutionary flagship L'Atlantique almost entirely without camber or sheer.

Unfortunately, despite having luxurious public rooms and superb amenities, which were often compared to the legendary Normandie; L'Atlantique was also widely considered to be the ugliest ship of her time.

 

It seemed that a return to the drawing board was in order. For a time, maritime architects continued to design with camber and sheer. Later, only the exposed decks were cambered, while those below were built "square" as in a building ashore. Yet "the look" was retained.

Gradually, modular building gained popularity and shipyard costs (driven by the loss of skilled labor) rose dramatically.

Then, the "private verandah craze" killed any hope for external esthetics, and the "shoebox" or "shopping cart" was born.

[PennyAgain]

Fantastic posting! Thank you!

[Druke I]

Excellent post.

 

Certainly makes the issue much clearer than my post.

[sstraveler]

Interesting post. Yes sheer was used to shed water from the decks of the ship. I believe it was still used on all of the liners built to cross the North Atlantic because of the difficult sea conditions they can encounter. By comparison a cruise in the Caribbean encounters much less weather and seas and hence does not require as much ability to shed water off the ship.

 

I remember beautiful ships from the 1960s such as the Shalom (later Hanseatic, Doric, Royal Odyssey and Regent Sea) had lots of sheer especially evident in the forward lounge. Same was true on the Norway if you stood in some of her long straight companionways you could not look end to end of the ship because you could see it dip and then rise .... i.e. sheer.

 

While the emphasis might have lessened I think it has more to do with the deployment of the ships than size. The designer of the QM2 talks a lot about his need to work in sheer and a bow design to shed water .... so it is still a concern in the right circumstances in the 21st century.

[DarthGrady]

Thanks so much everyome for the informative posts. That is why I love these boards, you're always sure to find someone that has just the right information for you! Thanks again!