Close encounter - with a submarine......

snowleopard said:
I had what I believe to have been a very close encounter about 3 years ago. Crossing from the Chenal du Four towards Plymouth at night the depth gauge went down to 4 metres for an hour or more. At one point it jumped back up to the usual 80+ for a few minutes then went back to 4, finally returning to normal a few miles south of the Eddystone.

I have heard that subs hide under the sonar or radar signature of yachts. I can think of no other explanation.
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Absolutely no chance whatsoever!! Its not a Tom Clancy world.

http://upload.wikimedia.org/wikipedia/commons/7/7c/Royal_Navy_Dolphins.jpg
 
AntarcticPilot said:
I am 400 miles away from my charts, but I was under the impression that submerged activities NORTH of Arran were forbidden, except in specified test areas like Loch Long? I stand to be corrected!

That patch north of Arran is plenty deep enough - my echo-sounder usually loses the bottom in that region!
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Don't know about forbidden areas, but we were to the north east of Arran, somewhere off Sannox Bay
 
Apologies for the poor quality of the photo

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She was on on collision course with me this summer in the Inner Sound. I was the stand on vessel.

Not being sure she had seen me in the poor vis, I called her up on Ch 16 addressing her as "Surfaced Submarine": she did not answer, maintaining radio silence I suppose.

She altered course and went round my stern. I suppose these things have some smart gizmos so they don't depend solely on their eyes.

Not bad, a vessel costing billions and capable of destroying the planet giving way to an MAB with only one person aboard. (well I was impressed)
 
Old Glow In The Deeps said:
What’s the range of the human ear (16hz to 16khz?), what is our transducers signal strength and at what frequency?
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Ehm, they don't actually listen with their ears to their hulls. The most expensive part of the sub is the nose cone, which hosts the listening devices (basically a microphone, but of a quality you can't afford, even if you could buy it).

And yes they can monitor infra sound and ultra sound, they *will* pick up you depth sounder. They can hear a whale fart from miles away and identify the specific individual by said fart.

Your sound transducer has a bigger sound footprint than a missile boomer.
 
kingfisher said:
Ehm, they don't actually listen with their ears to their hulls. The most expensive part of the sub is the nose cone, which hosts the listening devices (basically a microphone, but of a quality you can't afford, even if you could buy it).

And yes they can monitor infra sound and ultra sound, they *will* pick up you depth sounder. They can hear a whale fart from miles away and identify the specific individual by said fart.

Your sound transducer has a bigger sound footprint than a missile boomer.
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Lots of good ideas! But it's not a Tom Clancy world. Cheers.
 
Obviously not!

kingfisher said:
Ehm, they don't actually listen with their ears to their hulls.
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Obviously not, but they do listen with a set of headphones within our own audible range.

? what’s the bandwidth and carrier frequency of our £50 tranducres ?

If at all concerned just run your engine.
 
iirc and off the top of my head the bog standard leisure depth transducers run at 50Khz or 200Khz depending on make ...

and even if the submariners are listening in on headphones they can hear things outside the normal human hearing range - by way of audio modulators.

If a sub couldn't pick up the sound from a yachts depth transducer then I would be very concerned!!
 
You are right.

fireball said:
iirc and off the top of my head the bog standard leisure depth transducers run at 50Khz or 200Khz depending on make ...
and even if the submariners are listening in on headphones they can hear things outside the normal human hearing range - by way of audio modulators.
If a sub couldn't pick up the sound from a yachts depth transducer then I would be very concerned!!
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You are right about audio modulation, but the system with the guy listening on the headphones is configured to a Broadband frequency range best suited to detection of engine and propeller (cavitation) signatures.
Active Sonar Intercept suite/system is what will detect (in the main) your transmission/echo sounder.
 
West Coast said:
Has anyone ever had an unexpected close encounter with a submarine?
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My Clyde experience was that RN submarines were careful and courteous while US ones were a bunch of cowboys. I am convinced that the good ol' boys used yachts for practice - on more than one occasion I had one (with escort boat, so they must have known I was there) turn directly towards me, dive under me and come up on the other side. I like to think that my vigorous application of lump hammer on keel bolt as they passed below hurt their hydrophone operator more than it hurt me.
 
Do they not have any kind of computer thingy that visualizes the location and type of sounds etc?

Is there really just a bloke sat there with headphones on?
 
Boats Everywhere But Not One Insight

Off Arran I had the bigger of the two periscopes right behind my yacht for about 10 minutes, just following me at a constant distance. I would have estimated it to be no more than 20 m away. I remember it being grey, about 1 - 2 feet in diameter and what looked like two lenses behind a clear panel. It had a dome shaped top.

Within 5 minutes there was a distant whine as a frigate accelerated, turned and at a very fast speed headed right towards us. The sonar ping started to get louder as the frigate drew near. By this time the periscope had gone. The frigate turned sharply right around our yacht healing at an incredible angle and the sonar very, very audible.

Later a yellow smoke float appeared over at the Holy Isle, off Arran but we never saw the submarine again.

On frequent occasions I have noticed small periscopes (assumed) with what looks like a tin can on top, popping up and down. I have been passed close by at night with the only evidence being the smell of diesel and a subdued thrump thrump noise as the snorkel passed by.

Off the Point of Ayr (IOM) in heavy seas at night, I got cut up on the inside by a USA Polaris boat (fins on the con), the only evidence was the flashing yellow light.

All this was between 1985 and 1990. Today it's all rather boring with the demise of our Naval fleet and big exercises.
 
My closest was as a young man on a drilling rig off the coast of Tunisia. The Tunisian authoroties had broadcast our position incorrectly and we were in very deep water. We were attached to the sea bed by the steel riser when an impact shook and moved the whole rig. One hour later we were buzzed by US fighter planes. Several days later a badly damaged riser was finally brought up and paint scrappings sent off for analysis - and never came back!!!!
 
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