CRACK goes the HULL!

[FAST FRED]

On another site I mentioned the concept that LARGE commercial vessels (oil tankers, freighters, etc.)are built so the mid ship wave supports the hull underway , and any attempt to go faster could provoke a disaster.

Pretty sure I read that someplace , any tech support for or against for this position?

FF

[innomare]

Where did you read that, Fred?
The waves a ship encounters on the ocean (swell) are quite a bit worse than the bow wave the ship makes herself. It's statistics about sea states that govern the structural design, not the self-generated wave pattern.

Or am I missing something here?

Bruno

[FAST FRED]

I understood the large boats (Non military) 700 -1000 + were built to operate at a low enough speed so there supported by a midship wave for structural purposes.

And that an attempt at "Hull Speed" where the vessel is ONLY supported by the bow and stern wave might lead to failure of the structure.

Where did I read that? . Wish I could remember, with over 500 books in my library its a long task.

FF

[Guillermo]

You could not run a tanker at hull speed, though, as you'd need a huge amount of power for that! Tankers, bulkcarriers and the like go at very low Froude numbers and they have many bow waves lengths within their length.

For their structural design both static and dynamic loads, as well as important corrosion and fatigue allowances, are taken into consideration nowadays. The static, or still water, components typically represent the loads associated with vessel operation loading conditions such as lightship weight, cargo, ballast, external buoyancy conditions, etc. The dynamic, or wave-induced, components represent the loads associated with the vessel motions and accelerations imposed from the vessel reacting to the seaway. Nowadays rules specify the loading conditions and tank loading patterns to use and then impose corresponding dynamic loads to be applied.

What you mention is probably an exemplyfying concept. I remember to have read something in that line a long time ago, i.e. that tankers would break if only supported by a full length wave, or even if unproperly loaded at still waters.

Cheers.

[CDBarry]

The hull girder of a tanker is designed for a wave of the vessel length, in both hog (crest midships) and sag (trough midships), and extensive studies of wave statistics and so one are done to evealuate fatigue.

A tanker can be damaged by improper loading, especially in combination with wave loads, and has a load computer on board that the mate uses to check stress, draft and trim and stability.