Big Waves - First Accident

[Roger Long]

Lurking back in the mind of every naval architect is the fear of hearing that one of their creations has suffered an accident. Other than crew injuries, inevitable given the thousands of person / sea miles that people have experienced on ships and boats I have designed, this has not happened to me until now.

(Photo: Portland Press Herald)

Story: http://www.pressherald.com/2014/12/...haven-after-trucks-on-board-get-knocked-over/

and:

http://www.workingwaterfront.com/articles/Rough-waters-tip-cement-truck-on-Island-Transporter/16195

It could have been a lot worse. No one was injured and the vessel made it back to port with little damage. Still, it is the first time I know of that one of my vessels had its stability altered, its operations compromised, and required a Coast Guard response due to wind and wave action. I am pleased with how it handled this very severe loading condition.

There are lessons here for us. This vessel has been in service for a long time by operators familiar with the waters. The bay is deep without shoals that can suddenly create much larger and steeper waves. The vessel is operated from a very high helm station from which the run and pattern of the seas can be seen clearly for a long distance. They still got caught by a much larger and steeper wave than they expected, one big enough to tip these trucks on their sides. If it happened to them, it could happen to any of us steering and anticipating from the low viewpoints of our sailboats.

I’ve noticed that I am more careful and cautious about waves than most sailors. That probably has something to do with having seen a 105 foot schooner swept bow to stern and nearly completely immersed by a freak sea. Having been a investigator of sailing vessel accidents and studied wave dynamics also makes it hard for me to maintain the complacency of many sailors in large seas. At all times, when the tops of the waves are breaking the horizon line, you need to keep in mind how a wave twice as high and steeper than the average would affect your craft. Such waves are not common but, if vessel and crew are not prepared for the encounter, you are rolling the dice.

The presence of shoals raises the ante. You can go over a shallow spot where waves are not breaking but one of these large waves can then break heavily. Anytime you are experiencing ocean swells and the water depth is less than twice the average wave height, there is a fairly significant risk.

Remember the wave illusion when you are trying to decide whether to go out. If buoy or weather reports say that there are eight foot seas, you may well think, No problem. I was out in eight foot seas just last week.. If you are basing that on what observed, you weren’t, you were out in four foot seas. Waves generally look twice as high as they actually are, even to me who has studied them closely. I know a rigorous way to measure wave height but just making your best guess and dividing by two works quite well.

For a discussion of why waves look big, see this archived post:

http://forums.sbo.sailboatowners.com/showthread.php?t=147144&#post973854

Be careful out there.

 

[Chief RA]

Roger: Good read and glad ferry did as well as it did. Your council is well recieved here. My home port is Bodega Bay Ca. and is commonly called "Blowdega Bay" for obvious reasons. Saw report of 16' seas this fall while we were in port and needless to say, we did not go out! My friend came out of Tomales Bay a few years ago when he shouldn't have and got hit with a doubling or rogue wave on a 26' sailboat. The fishermen reported that all they could see was his mast. Wiped out his electronics with companionway open and got rid of all that "superfluous stuff" like throw cushions , life jackets, seat cushions etc. . Nothing that many hundreds of dollars didn't clear up!
Happy Holidays! Chief

 

[RIVERCRUISER]

I see the tie-down points in the deck.

Too bad they were not used...

 

[richk]

Very astute observations in your article Roger. Many years ago I was forecasting for USN ops in the Pacific. One of the problems was, as you note, observations of wave height are typically overestimates. Different maritime administrations had different reputations for accuracy of their observations as reported by the (WMO) global telecommunications network. Japan was consistently rated as one of if not the best. What was amazing to me was that such data was reported regularly, at the recommended six hour, synoptic intervals. That says a lot both for the fortitude of the observer and the radio operator. Sometimes they were the same person. Another problem was the lack of observations after hours because in my world of the time (HF, not satellite) comms, the radio operators were the link to the world and paying them overtime was expensive, where it applied to commercial maritime operations.

 

[Pat]

Thank you for sharing Roger, I can remember being on the USS Lexington back when I was a puppy and the Lady would go to sea when hurricanes threatened....We aboard the ship had to make sure the Lexington was balanced as she made way into the wind and waves. It took all department's due diligence to make sure the boat would remain balanced in 35-40 ft. seas....In the dental dept. we were told to balance our weight in the dental chairs and to remain there until "further" notice. I could not go to the top-sides to look at what was going on but you could feel the weight balances change each time we went up and down....esp. as the wind shifted more astern during the gusts and shifts.

 

[Roger Long]

You might also enjoy reading this:

http://www.cruisingonstrider.us/Stability.htm

 

[jibes138]

Thanks for the nice technical summary Roger. Any comments on what went wrong in this highly publicized capsize? I see in the text the company laid off all the employees, looks like they may go belly up in the process.
http://threesheetsnw.com/blog/2014/05/new-10-million-yacht-capsizes-and-sinks-in-anacortes/

 

[Brian M H23]

I see the tie-down points in the deck.

Too bad they were not used...

Sources who work on the state ferry who were familiar with the incident said the vessel was more than halfway to North Haven when the truck tipped. The truck was not tied down, according to those sources. Had the truck been tied to the deck, the wave that tipped the truck may have tipped the Island Transporter as well, they said.

I think that's a question for Roger?

 

[RIVERCRUISER]

Sources who work on the state ferry who were familiar with the incident said the vessel was more than halfway to North Haven when the truck tipped. The truck was not tied down, according to those sources. Had the truck been tied to the deck, the wave that tipped the truck may have tipped the Island Transporter as well, they said.

I think that's a question for Roger?

That certainly is a question for Roger.

My opinion, that the vehicles should have been tied down, is just that. An opinion.

An opinion based on 40 years of flying heavy aircraft where a cargo shift can have, and has had deadly results, many times over.

Just my gut feeling, but I do believe that had the vehicles been secured to the deck we would not be having this discussion because there would not have been an event...

As I said, just my opinion.

 

[Brian M H23]

You know, I just quoted that right out the news article and hadn't really thought about it much. But I can't imagine any scenario where having that truck (and ten+ yards of concrete) in the middle of the boat is worse than having it against the gunwale (or half hanging over)

 

[RIVERCRUISER]

You know, I just quoted that right out the news article and hadn't really thought about it much. But I can't imagine any scenario where having that truck (and ten+ yards of concrete) in the middle of the boat is worse than having it against the gunwale (or half hanging over)

Bingo!

 

[Roger Long]

Any comments on what went wrong in this highly publicized capsize?
http://threesheetsnw.com/blog/2014/05/new-10-million-yacht-capsizes-and-sinks-in-anacortes/

There are too many unknowns to speculate on what happened here. However, launchings are always tricky because the vessel goes through a period when a large and changing portion of its weight is born by the launching cradle. Any portion of the vessel’s weight carried by the keel is, in effect, negative weight down low which has much the same effect as weight up high. It decreases the vessel’s stability.

If you watch your boat go slightly aground, such as when anchoring when low tide has a few inches to a foot less water than your draft, you will experience this. The first thing you notice will be that the boat feels slightly dead since the contact of the keel with the bottom which dampens rolling. This (at least on a boat of modest size) keeps your walking around from starting the boat moving and rolling slightly. Any wave action, such as wakes, will also produce a different motion than you are used to since the keel can’t move from side to side. The boat will be rolling around the point where the keel is fixed in the mud instead of a point near the waterline as it normally does.

As the water drops further, the vessel’s stability is diminished by the upwards weight on the keel. Wind or a person moving off centerline or from one side to the other will cause the boat to heel more than normal. Once you have been on a boat for a while, these very subtle differences at the first contact of the keel with the bottom will be very noticeable.

Imagine the launching of a vessel when the boat quickly makes the transition from having its weight fully carried by the launching cradle to being fully afloat. There is a lot that can go wrong at the point where the boat has enough buoyancy to lift it off the cradle but is not yet stable enough to remain upright without the support of the cradle. Launching calculations for large ships where the stakes of a mistake are very high are exceedingly complex and may be worked on for weeks.

A story I have heard, but have never been able to verify, is a peculiar launching method used in the Northwest. Stuck and collapsing launch cradles can cause problems as appears to have happened in this case. The solution of some builders was to simply set the keel on a line of rollers and prop the hull up with lengths of timber. Once the hull was released, it would roll into the water so quickly that it didn’t have time to fall over. It’s a clever idea which would have been spectacular and fun to watch. I’ve never heard a hint of it being done on the east coast.

 

[Roger Long]

Had the truck been tied to the deck, the wave that tipped the truck may have tipped the Island Transporter as well, they said. I think that's a question for Roger?

"They" is not usually a very informed source. I can imagine a dynamic motion situation in which the tipping over of the trucks prevented the vessel from continuing on into capsize but it would be a very particular and narrow set of circumstances. It would also be highly improbable from what I know of this vessel's characteristics. As has been pointed out above, once the trucks tipped and the weight was off center, the stability was severely compromised and it was much more vulnerable to capsize.

In hindsight, the trucks certainly should have been tied down but this is a major operation and it is not often done. They would have been more likely to have simply have delayed the trip if tying down was felt necessary. There are other bad things that can happen in such a sea state. The state ferries suspend operations all the time.

The "Island Transporter" has years of service on that run and an experienced crew. The vessel is very capable and they perhaps got a little over confident from their previous experience. The kind of wave that could cause an event such as this in conditions in which the vessel was still able to make port with such extreme list would have been a freak. An operator could be out there every day for decades and never be in just the right time and place to encounter one and have an accident like this.

The lesson is that these kind of waves can rear up or, down. The damage from freaks is often from the large trough that opens up in front of them. The trough effect can also make them hard to see coming. Trough or crest, once you are in them, it is just a big, steep wave. When you are asking yourself questions like, Should we be tied in? - Should I close the companionway? Should I let the crew cook a hot meal?, you should be basing your answer on the possibility of a wave about twice as large and steep as what you are generally seeing.

 

[Daveinet]

This reminds me of the time I rode the Ferry to Washington Island in my motorhome. I had a discussion with the crew as to if they were going to take me or not, because the water was so rough. They seemed to be more worried about stuff getting thrown around inside the RV than the RV its self staying secure. I asked about tying it down, and they said there was no need, as it would not go anywhere. I was a little concerned. They parked me next to the outside wall, with 2 cars in front of me. Just out of the harbor we took a huge roll. Scared the living daylights out of me. I can't accurately say how far we heeled, but I would say that from low point to high point had to be over 15 feet. I was sitting in the driver's seat, hanging on to the steering wheel for dear life, although not sure hanging on was doing anything. We finally headed into the waves. There was a car next to me that as soon as they got on, they both pulled out newspapers and began to read. I figured it was safe to assume they were locals, so I watched them closely for any indication of concern. There were a couple of times I saw the paper come down quick, and they looked up, as a response to a surprise wave. 2 cars in front of me, yet some of the waves were landing half way back on the roof of the motorhome. We did survive, but talking to the locals, they stated it was about as rough as they had ever seen. While I'm not sure that my coach ever moved, for the kicking around, I'm not sure why they didn't tie stuff down, or at least the big vehicles. They was some evidence that some of the cars did move a small amount.

As sailboat owners, I suppose the take away that I would see is that beyond the choice to go out or not, if one does go out, what steps does one take as extra precaution. Of course wearing your life jackets comes to mind first, but are there things you need to secure? What resources to you want out where you can get at them if conditions are much worse than expected. Do you just sail on the main, so you only have one sail to deal with, when things get ugly?