I have years of experience as captain in the Gulf of Alaska and the Bering Sea. I administrate a fleet of vessels about 240’ LOA and 2000 IGT. Some are house forward, some house aft. These vessels carry palletized cargo below decks, and a variety of cargo chained down on deck, everything from lumber to automobiles to containers.
Heaving-to in 40-foot seas is a commonplace activity on our freighters.In heavy weather we hove-to bow on to the seas, with just enough way to maintain steerage. If the rolling doesn’t exceed 25 degrees we call things good. If she rolls to 30, that’s to be expected. At 35 degrees, you curse. At 40 degrees, you wonder what you’re doing out there–just like you’ve wondered a thousand times before.
You might stay hove-to like that for days, making little or no headway, keeping just enough way ( 0. 5 kt. to 1 knot of SOG ) to maintain steerage. Lying-to in any other position causes severe rolls (35 to 45 degrees) and waves breaking over the side of the deck.
For years I have read authors advocating lying “a-hull”. For years I have seen what happens to the class of the vessel I have just mentioned, if they get anywhere near abeam to heavy seas. All I can say is that for the size/type of vessel I have noted here, lying a-hull is dangerous, as wold be instantly apparent to anyone who tried it.
I am not prepared to say what happens on ships of other sizes. I have sailed on 800’ container ships but do not have heavy weather experience on them.
I must also add that, for the size/class of vessel I have noted here, the safest point of steaming in heavy seas is with them on your stern. Again, I am being very specific here. I am talking about steaming in extra-tropical cyclones in the North Pacific. where the primary wave and swell set is coming from a single direction. Not the confused seas often found in a hurricane. In my experience, 50-foot seas coming from one direction are far safer than 30 foot seas coming from several directions.
My brother captains and I on the Aleutian Run have beaten our brains out for days heaving-to bow-on to heavy weather for more days than we would like to recount. We have learned that when the seas get to about 40-feet turning about and putting the seas on the stern, steaming as slow as possible to maintain steerage, provides the best ride. The difference between putting the seas on the stern as opposed to the bow is the difference between night and day. Rolling decreases. Pitching is less abrupt. The hull is not getting hammered. Waves no longer break over deck.
Riding even 45 degrees to the seas causes severe rolling and seas breaking over the ship, in excess of the the other two points of steaming. To be avoided at all costs.
Again, I’m being specific here. 160’ to 240’ LOA. 700 to 2500 IGT. 1500-to 3000’ HP. At least 6’ of freeboard, and enough cargo to keep the wheel in the water as the wave passes; without the latter you lose steerage. A host of caveats.
I have read authorities who state categorically that running before huge seas is dangerous, because of he danger of broaching. I can state that, in as far as they are being categorical, they are dead wrong.
One last word on the subject of heaving-to in heavy weather concerns deck inspections, Sometimes we have to heave-to bow-on to heavy weather because the wind is coming from the direction of our destination. We are waiting for the low to blow over us, until we can make headway again. This may take a couple of days. When seas are 30-feet or less, experienced captains will often turn the vessel about at mid-day and put the weather on the stern for an hour, to give the mate and crew an opportunity to check the deck for dangers, and check cargo lashings. Chief among the dangers are cargo hatch bolts and hatch dogs which have backed off after days of hull flexing, allowing flooding in the holds.
This practice of putting people on deck may seem dangerous, but as I have said, on this class of vessel, running with the weather on the stern, the experience of 30 years and 1800 voyages without a man overboard says it is safe, if the officers and crew are experienced, and precautions are taken. We’re not talking about a situation where waves are breaking over deck, which is the whole point of turning about.
In heavy weather, even on runs where heavy weather is common, like the Aleutian run, flooding must be assumed to be happening until you have actively determined it is not. This pertains to tank vents and chain lockers. Get water in your fuel and you are in a world of hurt. Witness the Aiviq/Kulluk fiasco.