My point was not that it would be the best tactic but rather that the assumption that in all cases loosing power automatically means that the vessel is going to be in a much worse situation is not necessarily correct. It depends on the GM, the ship’s rolling period, and the wave period.
This is from Nichols"s Seamanship and Nautical Knowledge by Cockcroft chapter 11, Heavy Weather;
An alternative method is to lie beam on to the sea with the engine stopped. The stress associated with heading into the sea will be avoided but the vessel may roll heavily causing racking stress and greater risk of cargo shifting. This method is therefore not suitable for a vessel which is stiff. When lying beam on to the seas a ship is likely to drift rapidly to leeward so there needs to be plenty of sea room in that direction.
Like I said it not a well known tactic and it is controversial. Aside for the book, I have actually experience in heavy weather (winds 70 kts, seas 15 meters) with a large ship DIW at sea.
I believe that your assertion that a ship lying a-hull would require an excess righting arm is incorrect, it is contrary to both my experience, understanding and to the section in Nicholls’s Seamanship which is a standard text-book.
[QUOTE=Kennebec Captain;170138]My point was not that it would be the best tactic but that the assumption that in all cases loosing power does not automatically mean thatit is going to be in a much worse situation for the vessel. It depends on the GM, the ship’s rolling period, and the wave period.
This is from Nichols"s Seamanship and Nautical Knowledge by Cockcroft chapter 11, Heavy Weather;
Like I said it not a well known tactic and it is controversial. Aside for the book, I have actually experience in heavy weather with a large ship DIW at sea.
I believe that your assertion that a ship lying a-hull would require a excess righting arm is incorrect, contrary to both my experience, understanding and to the section in Nicholls’s Seamanship which is a standard text-book.[/QUOTE]
I use to “lay to” routinely in fishing boats. I’ve done it once in big blow on a sailboat. Never had to try it in a tugboat, but I have always assumed that it would be feasible. We sometimes tow in the trough of a big sea and make good time, as long as the cargo will stay on the barge.
[QUOTE=tugsailor;170141]I use to “lay to” routinely in fishing boats. I’ve done it once in big blow on a sailboat. Never had to try it in a tugboat, but I have always assumed that it would be feasible. We sometimes tow in the trough of a big sea and make good time, as long as the cargo will stay on the barge.[/QUOTE]
Yes, if you end up with synchronous rolling it’s going to roll the guts out. But if the vessel’s rolling period is longer then the wave period you might be able to get away with it. In general a low GM is required, certainly not an excessive righting arm, that’s ass backwards.
[QUOTE=Kennebec Captain;170142]Yes, if you end up with synchronous rolling it’s going to roll the guts out. But if the vessel’s rolling period is longer then the wave period you might be able to get away with it. In general a low GM is required, certainly not an excessive righting arm, that’s ass backwards.[/QUOTE]
I have been on a vessel which had a perfect righting arm and rolling period to match the swell period and when running in the trough, did not heel even though the entire time is actually was rolling away from the inclining forces of the swell but this was in a situation where the swell period was long. This could not work in a situation where the period of wind driven seas was short unless the vessel had a very stiff righting arm and fast rolling period. I do not hope to ever test that one.
If the ship’s rolling period matches that swell period the result will be synchronous rolling. If the rolling period is longer then the swell period then the ship will behave as you describe, at times actually rolling opposite the slope of the wave. A ship with a high GM is going to
try and match the slope of the swell, like a raft. You’d get a wicked snappy roll.
On the other hand, a ship having very high metacentric height (GM) would show the following behaviour: A stiff ship will tend to respond to the wave profile more rapidly, tending to assume the slope of the passing wave.
So, even though a stiff ship will develop rolling moment easily in a passing wave, it will also require less force to return to an upright position, rendering the ship more stable.
Also, the time period of the rolls would be shorter.
[QUOTE=Kennebec Captain;170138]My point was not that it would be the best tactic but rather that the assumption that in all cases loosing power automatically means that the vessel is going to be in a much worse situation is not necessarily correct. It depends on the GM, the ship’s rolling period, and the wave period.
This is from Nichols"s Seamanship and Nautical Knowledge by Cockcroft chapter 11, Heavy Weather;
Like I said it not a well known tactic and it is controversial. Aside for the book, I have actually experience in heavy weather (winds 70 kts, seas 15 meters) with a large ship DIW at sea.
I believe that your assertion that a ship lying a-hull would require an excess righting arm is incorrect, it is contrary to both my experience, understanding and to the section in Nicholls’s Seamanship which is a standard text-book.[/QUOTE]
I’m sure its possible and in very rare circumstances you might ride better with beam to seas, but what…less than 5% of the time? There is a reason why no where will you find it suggested and written that in hurricane force winds and waves you try putting the beam into the sea.
[QUOTE=greatlakesmaster;170171]I’m sure its possible and in very rare circumstances you might ride better with beam to seas, but what…less than 5% of the time? There is a reason why no where will you find it suggested and written that in hurricane force winds and waves you try putting the beam into the sea.[/QUOTE]
Not sure how rare. As I said it depends on the GM and rolling period of the ship and the period of the swell. As you know, often the ship rolls worse when it synchronizes with the seas on the quarter because the rolling period of the ship is longer then the swell but the quartering seas lengthens the actually apparent wave period. If the ship were to turn and put those waves on the beam it would roll less.
Also the tactic is not to put the seas on the beam but to drift without power. With cyclonic storms is swell/wave direction is often not the same as wind direction so the ship does not necessarily settle down with the seas on the beam.
[QUOTE=greatlakesmaster;170171]I’m sure its possible and in very rare circumstances you might ride better with beam to seas, but what…less than 5% of the time? There is a reason why no where will you find it suggested and written that in hurricane force winds and waves you try putting the beam into the sea.[/QUOTE]
Also, not saying necessarily it will ride better, I’m saying it might not be the worse. If you are drifting and not synchronous rolling in fact you can make your situation worse by getting way on and finding a course where you are synchronous rolling, or at least doing it more frequently.
In a hurricane force winds and seas the ship is not going to have a good ride. If the ship is DIW and, as long as it’s not synchronous rolling, when you restore power you not going to then find a course that gives you a good ride. You may only be able to marginally improve your situation. This is likely counter-intuitive to many mariners because they associate beam seas with synchronous rolling.