# What determines a ship's ability to withstand sea state 9?

#### Ibexe

What exactly determines a ships ability to withstand extremely high sea states?

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#### phinds

Gold Member
What research have you done so far? What have you found out?

#### Ibexe

What research have you done so far? What have you found out?
From looking at videos of ships in high sea states and looking at the data for sea states i believe it has to do with length of the vessel and the materials used

#### JBA

That is correct, it is the ratio of the length of the ship to crest to crest wavelength the higher that ratio the less amount of pitching the ship will experience; but, at the same time the ship hull must be designed and built with materials that give it sufficient strength to endure the longitudinal bending forces as it spans the wave troughs. The weight of the vessel is also a factor, because a heavier or well ballasted ship will be better able to cut trough the wave peaks and reduce the pitching height caused by the impacting wave. Obviously, there are additional factors associated with preventing internal damage from shifting of cargo, both solid and liquid.

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#### rootone

Funnily enough I was wondering recently about something similar.
The scenario is you have a container ship coming out of Rotterdam in Netherlands, with goods bound to Cork in Ireland.
The first stage going down the English channel/La Manche should be straight forward enough, but after that the ship has to do hard right turn, whilst simultaneously encountering all the North Atlantic can throw at it.
I guess there must be standard procedure, and if things don't look good they wait in the Channel for a while.

#### Ketch22

Primarily the determination is via the relationship of the center of gravity to the center of buoyancy. As a ship floats at a level that varies by weight for any given actual weight the center of gravity varies by loading and the center of buoyancy varies by overall weight of displacement. A ships stability calculation uses a set of tables known as "cross curves of stability" These are particular to a ship or class of ship and give the righting moments for weight and metacentric height. A little Google search will show quite a bit on how these work.

#### Baluncore

What exactly determines a ships ability to withstand extremely high sea states?
The wisdom of the master is most important. Otherwise it really depends on the type and size of the boat.

A long hull may give you a more comfortable ride, but when a long hull straddles two big waves it will break it's back. I would prefer to survive than be comfortable. The complex wave interference patterns such as found off the SE coast of South Africa have broken the backs and so taken many vessels over 100,000 tonnes.

If you are in a sailing boat and a storm is rising, first reduce sail, next heave to, then run with the wind with a small storm jib, or under bare poles, then if it gets too fast, put the drogue out from the stern.
A light-weight racing boat is a liability. The design rules make winning boats dangerous in challenging seas. The race winner will be the boat that just manages to survive the storm. To win at any cost, costs lives.

#### Ibexe

The wisdom of the master is most important. Otherwise it really depends on the type and size of the boat.

A long hull may give you a more comfortable ride, but when a long hull straddles two big waves it will break it's back. I would prefer to survive than be comfortable. The complex wave interference patterns such as found off the SE coast of South Africa have broken the backs and so taken many vessels over 100,000 tonnes.

If you are in a sailing boat and a storm is rising, first reduce sail, next heave to, then run with the wind with a small storm jib, or under bare poles, then if it gets too fast, put the drogue out from the stern.
A light-weight racing boat is a liability. The design rules make winning boats dangerous in challenging seas. The race winner will be the boat that just manages to survive the storm. To win at any cost, costs lives.
Hmm surprisingly the ship im looking at is going to be used all the way from South Africa all the way to the Kara sea im looking around to find the best design to prevent extreme damage when transporting 3 vehicles around for joyriding around the world lol

#### Ibexe

Funnily enough I was wondering recently about something similar.
The scenario is you have a container ship coming out of Rotterdam in Netherlands, with goods bound to Cork in Ireland.
The first stage going down the English channel/La Manche should be straight forward enough, but after that the ship has to do hard right turn, whilst simultaneously encountering all the North Atlantic can throw at it.
I guess there must be standard procedure, and if things don't look good they wait in the Channel for a while.
I wonder what caused them to take such a hard right.

#### Baluncore

Hmm surprisingly the ship im looking at is going to be used all the way from South Africa all the way to the Kara sea im looking around to find the best design to prevent extreme damage when transporting 3 vehicles around for joyriding around the world lol
Surprisingly ............. lol !
If you keep secrets when asking questions you will not get useful answers and you will waste the time of all the respondents.

#### Mark44

Mentor
Hmm surprisingly the ship im looking at is going to be used all the way from South Africa all the way to the Kara sea im looking around to find the best design to prevent extreme damage when transporting 3 vehicles around for joyriding around the world lol
Is this question an exercise in an engineering class?

#### Ibexe

Surprisingly ............. lol !
If you keep secrets when asking questions you will not get useful answers and you will waste the time of all the respondents.
What secrets am i hiding? Lol you lost me there comrade

#### Ibexe

Is this question an exercise in an engineering class?
No just a curious question when i seen youtube videos on ships in high sea states

#### russ_watters

Mentor
Hmm surprisingly the ship im looking at is going to be used all the way from South Africa all the way to the Kara sea im looking around to find the best design to prevent extreme damage when transporting 3 vehicles around for joyriding around the world lol
For liability reasons, we cannot provide advice on dangerous activites. Consult the ship's builder and follow their safety guidelines. Thread closed.

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