Hull protection for floating objects

[ShinyHappy]

Originally Posted by boat driver

sometimes insurance is there for a reason- mines in the red sea come up as a thought

I'm not as concerned about repairing or replacing the boat as much as I am surviving the impact. But I guess the EPIRB and liferaft are the insurance several hundred miles off-shore.

Minefields. Hope I only have to think about shipping containers.

[Scorpius]

As I mentioned previously, in my experience the vast majority of shipping containers have vents in each of the four upper corners. Thus, unless they are filled with cargo light enough, and non-absorbant enough, to provide the necessary buoyancy (I remember a container full of Nike shoes being found floating at sea), they will very likely sink as they fill with water.


For the period 2016 through 2019, according to the IMO (and I have no reason to doubt their figures as they have access to insurance records, etc.) only an average of 779 containers were lost at sea annually. This represents only .0003% of the 228 million containers moved each year in the same period. And as I said above, many of those lost would have sunk.


I think the chances of striking a container are EXTREMELY low. I know it is regularly discussed here as a theoretical hazard - but I don't recall too many reports of actual strikes.

[hpeer]

Originally Posted by Scorpius

Somewhat faulty calculations: Because a container is made of steel (denser than water) if it was completely full of water (40 x 8 x 8) it would sink. And you can't add the weight of the contents because they would displace water - at 62 pounds per cubic foot. Only if the contents were sufficiently less dense than water and there were enough of them to displace quite a lot of water, or if there was air trapped in the container (unlikely as most are vented right up near the roof) would the container float - and it's total weight would be considerably less than your calculations.

Still, even though I have a steel boat, I don't want to test it's strength hitting the corner of a floating container! (There are also lots of reasons other than container strikes that could have sunk that superyacht - including a failed through hull, pirate attack, insurance fraud, etc. Note too that even if it was container strike, he was probably traveling A LOT faster than we would be, thus increasing his momentum substantially, and increasing the force with which he would have hit the container. And, how big was the super yacht? As a boat gets bigger, the ratio of hull plate thickness to vessel weight drops dramatically. A small steel boat is MUCH more resistant to hull strikes than a big one).

Of course its faulty, its a rough estimate. The point being the damn things are heavier than their empty weight.

To be more precise, i simply calculated the displacement based on volume. If the total weight of the container and contents is 1 pound less than the displacement it will float.

You don't want to hit one with any boat, glass or steel. You chances with steel, aluminum, a reinforced bow, or water tight bulkheads are somewhat better, but not guaranteed.

[Mark Johnson]

Originally Posted by ShinyHappy

The cargo ship losing several hundred containers had some discussion about the danger of hitting them and it has been a concern of mine for ocean sailing. I understand the low probability of such a collision, but being that it could be devastating it would seem a builder could provide additional protection for such an event.

A substantial piece of stainless covering the point of the bow below the waterline would take the impact of a hit much more effectively than fiberglass and framing. I'm thinking of 3/8 or 1/2 inch angle just covering the point of the bow.

That would take the brunt of solid impacts and allow the vessel to weather such an event. Glancing blows could still be damaging but it seems the point is lost vulnerable.

It would help even here where we dodge the tree branches floating down river to save scratching the hull.

Is there a reason this isn't done or isn't common?

This is why I chose multihulls. My trimaran will not sink, and floats half way awash with all three hulls breached, or upside down. In warm water at least. It gives a sailor a fighting chance!
Watch the documentaries on the Rose Noel, where they lived in an upturned tri for over 100 days. With modern electronics, it would have been 2 or 3.

[mikecambrai]

Containers usually sink with a corner up rather than purely horizontal. That corner becomes a very potent weapon against a yachts hull. I would prefer to hit one in a fiberglass yacht or a wooden one if I had to hit one at all because they tend to bounce back.
A corner will easily penetrate a 4/6mm steel hull and of all the boats that I have owned that has happened to me twice over 60 years.
I like the idea of watertight bulkheads or at least bulkheads that you walk through with a cutout where the bottom is at least 12 inches above the waterline. The more bulkheads you have the more chance you have of being able to repair the hull and pump out. Better carry a collision blanket as well and have bilge pumps connected to each section.!

[ameehan]

Hello all,
This subject has been a fear of mine forever and your points are well made.
My thought however, after 40+ years at sea is why container ships, which keep getting bigger, are allowed to traverse the oceans with such primitive securing arrangements. The reason is of course that gross tonnage (a measurement of area) is measured on enclosed cargo spaces and does not include deck cargo.
IMHO these mega container vessels should be forced to carry permanent framing on deck to secure these boxes, google ACL fleet to see what I mean. Admittedly these are RO-CONs but the same principle could be applied.
Rant over,
Stay safe all,
AM

[wingssail]

Originally Posted by ShinyHappy

The cargo ship losing several hundred containers had some discussion about the danger of hitting them and it has been a concern of mine for ocean sailing. I understand the low probability of such a collision, but being that it could be devastating it would seem a builder could provide additional protection for such an event.

A substantial piece of stainless covering the point of the bow below the waterline would take the impact of a hit much more effectively than fiberglass and framing. I'm thinking of 3/8 or 1/2 inch angle just covering the point of the bow.

That would take the brunt of solid impacts and allow the vessel to weather such an event. Glancing blows could still be damaging but it seems the point is lost vulnerable.

It would help even here where we dodge the tree branches floating down river to save scratching the hull.

Is there a reason this isn't done or isn't common?

Of course this would help, in some cases, but it is the wrong approach.

It is not reasonably possible to retrofit all boats now sailing with such reinforcement, and it would take decades for new builds to replace all existing boats, and then it only helps if the strike is directly on the bow.

Meanwhile containers will continue to fall off and boats will hit them, potentially causing sinking and deaths.

The solution is to prevent containers from falling off. This solves the problem immediately.

How do we do that? Impose big financial penalties on ships which come to port without all their containers. Of course the shipping companies will have insurance but when insurance rates skyrocket, changes in loading and securing will be made.

[Sofa King Fishy]

Rather than adding weight & drilling holes into the bow, better builders engineer a collision bulkhead. From Catalina, Hunter to Caliber & Amel. Better to design from the get-go than to add on later?

[Scorpius]

There's a lot of sailors on this forum and, collectively, a lot of miles under our keels. Has anyone here actually hit a container floating out in the ocean?

[Adiona]

I would 5ink adding steel reinforcements on any boat would seriously change the weight balance and movement of it. Consider forward looking sonar and keep watch.

[Ianau]

Sinking of SY Asia in Nov 2019 (referred to in a post above) was disturbing. A 2009 29M Steel yacht built by a an experienced NZ steel hull builder.

This is the only info I have seen published:

https://yachtharbour.com/news/29m-sa...an-waters-3555

I have since searched for any subsequent report on the sinking but have not found anything.

Would be interested in Forum advice on possible sources for more info.

[Scorpius]

Originally Posted by Ianau

Sinking of SY Asia in Nov 2019 (referred to in a post above) was disturbing. A 2009 29M Steel yacht built by a an experienced NZ steel hull builder.

This is the only info I have seen published:

https://yachtharbour.com/news/29m-sa...an-waters-3555

I have since searched for any subsequent report on the sinking but have not found anything.

Would be interested in Forum advice on possible sources for more info.

Really? A good-sized steel sailing yacht traveling at maybe 8 knots sank after striking an unidentified submerged object. This is a vessel which previously had been listed for sale then withdrawn from the market - presumably because no-one was prepared to offer the asking price - and then it mysteriously sinks?

I'm not so sure that a container strike is the most probable explanation.

Do we have any CONFIRMED examples of sailors hitting containers in the open ocean and sinking or suffering major damage?

[wingssail]

Originally Posted by Scorpius

...Do we have any CONFIRMED examples of sailors hitting containers in the open ocean and sinking or suffering major damage?

"Confirmed"?

There are many reports of boats hitting objects at sea, mostly race boats, but confirming what they hit is not easy.

[Sonny36]

Instead of loading containers with long dimensions parallel to ship's keel, perhaps they would be more secure of they were loaded with the long dimensions perpendicular to the keel. It would be harder for a container to tip end-for-end, than from side to side. I suppose cranes being set up to load containers parallel to the keel would prevent the arrangement I suggest.

[Pete7]

Originally Posted by Scorpius

There's a lot of sailors on this forum and, collectively, a lot of miles under our keels. Has anyone here actually hit a container floating out in the ocean?

Not a container, but whilst night diving one evening of the Northern Irish coast, I watched a large fridge come floating past in the tide. They are full of foam insulation and float beautifully.

May not have sunk a yacht but it would have made a mess of the gelcoat and propeller.

Pete