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Old 04-05-2018, 16:04   #31
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Re: Speed to survive container colision?

It's such an open question that there are no answers except to say "it all depends. . ."
However, if this is really a major concern of yours, buy a steel or alloy boat.
And yes, there are ocean capable alloy catamarans, and in the Mom & Pop range.
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Old 04-05-2018, 16:07   #32
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Re: Speed to survive container colision?

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Originally Posted by Snowpetrel View Post
I'd be far more worried about logs than containers. Far more likely to hit one of them drifting about in oceans than a container.
This is very real,
dependent upon which currents you are in and where you are.
Near somewhere that has significant logging activity this can be of interest.

Having had to negotiate submerged trees as well as cut logs offshore
(after heavy rainstorms flushed them out from river systems)
this is probably not something to find in the middle of the Indian Ocean (?)
[Logs do eventually sink]

Anyway,
an idle thought is that a longish piece of pipe (strapped) on the front of the keel
might be enough to take some of the sting out of such a collision.
It would tax the vessel velocity, of course,
but for someone single-handed and in no particular race this might be
something interesting to consider, as an amusement.
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Old 04-05-2018, 16:38   #33
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Re: Speed to survive container colision?

My nearest "strike" was in the Banda Sea (Indonesia). Our boat of about 35 tons , sailed past a submerged log that was longer than our boat and passed very near the hull. We were traveling at about 7 knots but that log was very large and I am sure there would have been very serious if not fatal damage if we had impacted.
In retrospect, we considered that our momentum (product of mass and velocity) and the inertia of the log would have been the major contributors to damage along with the angle of impact. I really think no number of sealed bulkheads would have saved us.
In areas of intense continuous logging and clear felling of entire islands, this problem is presumably more likely.
However we have also seen large bits of trees after flooding events off the Queensland coast. Have never see a container in the sea though.
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Old 04-05-2018, 18:16   #34
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Speed to survive container colision?

A lot depends on the boats design.
Way my boat is built, I’m sure it would simply sail over a lot of stuff.
Cut away full keel.

There was a thread a year or so ago about a Cat hitting some kind of unlit fish farm at night, it was constructed I think mostly of pipe. The boat suffered serious damage and I think lost a rudder, and almost had one of the drive legs almost torn from the hull, if memory serves.
There was a lot of discussion on how well the boat was built to not sink.
I quietly thought if I had hit the object, I would have sailed right over, maybe with some scratches, but nothing torn from the hull.

Anything hits the sharp end of a telephone pole, or the corner of a shipping container is likely to be holed, but if I hit it sideways at 7 kts, I believe I would survive with minimal damage.

7 kts for me is Warpspeed, only occasionally obtainable, 8 isn’t.
Energy equals mass x velocity squared of course, speed kills when hitting something.
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Old 04-05-2018, 18:57   #35
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Re: Speed to survive container colision?

Just going by what I saw with my very own eyes in a movie with a well-respected actor:

You cannot escape those critters! Robert was minding his business, dozing down below, no wind, the boat was drifting, sails flapping; then there comes this heinous container drifting along and slams into the nice and shiny hull of the boat, turning it into a world of chaos and utter pain.

Seems you can only avoid them by slowly reversing at all times.
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Old 04-05-2018, 20:42   #36
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Re: Speed to survive container colision?

For what it’s worth, I have personally seen and avoided a container. I was crew on a 65’ racing monohull approximately 400 offshore between east coast and Bermuda. We were in very light winds and virtually no sea during daylight hours. We spotted what looked like a large box - dead on our course - and diverted. As we came past, we could clearly see that it was a shipping container and just like an iceberg, only a single corner was above waterline lying at an angle to the surface. We took coordinates and reported to USCG. Had sea state, winds, or visibility been different it might have been more “interesting”. I will never forget that!
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Old 04-05-2018, 21:29   #37
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Re: Speed to survive container colision?

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I forget where I read it, but I read that it's a myth that a container will be "slightly submerged", so with a lookout, in theory, it should never be a problem. There will always be a portion above water level or it will have sunk.

Not sure of the accuracy of the statement.
CaptsWife well that myth should go down with the containers sailed past six floating just submerged or a wash just north of Brisbane .Qld ,Australia it all deepen on wots in side steel and they go down but wood or something containing air they float.
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Old 04-05-2018, 21:37   #38
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Re: Speed to survive container colision?

Assuming that the container is dead in the water and the sea is relatively flat, I think you could hit at up to 3 knots and still be able to keep from sinking. Obviously though, most head-on encounters with a rogue container in less favorable conditions are going to be at much greater risk of sinking and the variables make it nearly impossible to calculate a maximum speed that allows for sustained flotation.
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Old 05-05-2018, 12:23   #39
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Re: Speed to survive container colision?

That's like asking "How fast can I drive my car into a brick wall without spilling my drink?"
There's no standard for how strong the hulls of a boat may be, or for how much they will crumple under impact. The construction standards (i.e. Lloyd's, ABYC) have scantlings designed to provide certain strengths, but those are not designed for ramming containers and manufacturers don't necessarily follow or exceed those scantlings in a uniform manner.

The OP wants to find a marine architect and have a custom made steel hull to their own satisfaction. Otherwise? "Walking speed" is a good limit. But sailing cats aren't really meant to go that slowly, except when docking.
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Old 05-05-2018, 13:45   #40
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Re: Speed to survive container colision?

1: A guy coming up the Delaware river in a popular 45’ish mono hit a nav buoy. Tore a big hole in his bow about 5’ back and maybe 18” above the waterline. Not sure of speed, if the tide was with him maybe 7 knots. Had there been any sea he would have been in trouble.
2: a guy, me, snickered at the above poor fellow. A few years later I wacked a nav buoy on the St Lawrence Seaway. No excuse, just plain made a bad mistake, hot day and drifted off into lala land. Tore up my bow pulpit railing and dented my bow a bit. 10ga Steel boat. 7 knots.
3: a guy, me, trying to avoid a tug and tow on the C&D canal hit a submerged piling. It’s shown on the charts but was “decluttered” on the Navionics chart display. 7 knots, rode straight up over it, picked the whole boat up 1/2 to 1 foot. Narry a scratch or dent on the 40,000 pound boat. Steel 1/4” keel. It’s a real thrill to hit something like that when you are showing 40’.

I think a glancing blow to the bow may be the worst case scenario. You miss the heavy structural stuff and impale the thinnest build up. If it runs along the bow it may compromise even a water tight bulkhead.
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Old 05-05-2018, 15:22   #41
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Re: Speed to survive container colision?

We hauled our ketch 2 years after we bought it and found a decent sized chip out of the bow about 1ft below the waterline with star-shaped cracks radiating out about 6" each way. Impact was too sharp to be a log and it was delivered through an area where the containership "Rena" was being salvaged.

We did have a very small amount saltwater seepage that we couldn't trace. I think 7 to 8 knots is fine.
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Old 05-05-2018, 16:04   #42
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pirate Re: Speed to survive container colision?

Remember the Titanic...
The 'Unsinkable Ship'..
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Old 05-05-2018, 18:49   #43
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Re: Speed to survive container colision?

I'd say the biggest variable would be the angle of impact.


If the end of the container towards the boat is fully submerged, you may be able to ride up over it without sinking the boat at almost any speed.


If you contact a corner of the container when just drifting with a bit of a swell, it could sink you.


So - I'd be fairly confident in saying the answer is somewhere between zero & 100 knots.
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Old 05-05-2018, 19:08   #44
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Re: Speed to survive container colision?

Quote:
Originally Posted by goat View Post
7 knots.
Goat beat me to it.
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Old 06-05-2018, 10:26   #45
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Re: Speed to survive container colision?

Had to pick up the hitting a buoy thing, did it to once on a calm day I have to confess.
Good thing it was Dutch (=here a not to big plastic buoy) and I was on my cat. No damage despite a bit of scratches in paint under the bridgedeck.
Sometimes multihulls have surprising advantages ;-)
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