Submarines

[Goldie fish]

I know it is part of the RN submariners course to take photos of coastlines and harbours. Cork Harbour has been photographed in this way in the past.

[Rooster]

"Water depth of under a few hundred meters, together with islands, shoals and currents create a lot of noise, making it more difficult to detect objects"

- that's what ambient noise is Victor, and the sub is more likely to be at about 30ms
Good point though, the sonar ray does'nt actually strike the bottom but due to the great depths the speed of sound increases by 1.7m/sec for each 100m increase in depth and as sound rays are bent away from areas of higher sound speed you should get a cz at about 28-32nm.
I've never heard about reflectance, what is it?

[Goldie fish]

I remember seeing a periscope and snorkel while transiting the english channel back in the 90s,and a few miles away a number of RN frigates,operating lynx with dunking sonar....we were going to radio to tell them where to look...but we decided not to bother....
If it was in time of war we would have been sunk.

[sba]

Thank goodness for some common sense Goldie! I think we're all agreed that the Irish government will never purchase a sub for the INS. Whereas it's nice to talk about such things, in reality, it'll never happen.

As I said in an earlier post, I've seen one of these beasts up close and personal, along with, I'm guessing, quite a number of NS personnel who ever travelled along the Northern coast back in the 80's. We've seen these subs, and so, have a fair idea of what we're talking about

As for the subs being a navigation hazard, well then, I think we can all agree that they used to pose a certain problem to the likes of trawlers, and yachts (i.e. those vessels who would operate WITHOUT their engines running).

And, if someone says that they think they saw a periscope off the coast, then perhaps they did! Who are any of us to question what they did or did not see on a particular day.

End of lecture!

[Goldie fish]

Victor, I am not as tolerant of long posts where you repeat or quote the posts of other members as on other sections of the board. If you have a point to make..Make it.
In this section I pay more heed to people who have been there rather than those who have read about it.
Keep this in mind. Some of those you are lecturing to have actually worked aboard a naval vessel.

[Victor]

I very much doubt anyone has seen a persicope from the shore, whatever about a surfaced submarine on a port visit - they need to surface away from the shore so as to not be a navigation hazard.

Originally posted by Rooster
It is true that submarines will come in "relatively" close to the coast, known as the "littoral zone" and use the ambient noise of the coast to avoid detection but we're not talking a couple of hunrede yards were people on cliffs and beaches can actually see them!

Water depth of under a few hundred meters, together with islands, shoals and currents create a lot of noise, making it more difficult to detect objects, especially a submarine on batteries.

Originally posted by Rooster
is'nt as the deeper the water then the more likely it is that a ships sonar will bounce of the bottom and get greater ranges, (known as convergence zones)

You are thinking about reflectance (works like a mirror) not diffraction (like a stick looking bent when you put it half into water). Convergence zones occur at multiple of about 30nm in deep water, whereas bottom bounce only works in the first few miles at medium depths.

Originally posted by Rooster
Ireland could afford a small diesel electric, an ex-RN one like what the Canadians are purchasing or even better a german 209, this would open up a lot more oppportunities for the defence forces but again would the tax payer be happy about footing the bill.

Unless we plan on sinking something, we have no need for submarines (submersibles are another matter). Second hand the 4 U-class subs cost in the order of €1bn. How many patrol craft would you get for that?

[hptmurphy]

the eithne is equiped with passive sonar. On operation purple warrior in 1987 which we gate crashed we were tracking an undentified sub for a while when the bastard took off doing about 30 knots.....the most offensive underwater weapon the NS have is a lead line!

Thanks for that Goldie fish!

[Rooster]

As for ASW, the NS would need far more ships with far better sonars and so far more investment, the only navies that have developed this capability are the navies that are intending to sink the subs they find, if Ireland is'nt prepared to do this the whole arguement becomes pointless!

[Rooster]

It is true that submarines will come in "relatively" close to the coast, known as the "littoral zone" and use the ambient noise of the coast to avoid detection but we're not talking a couple of hunrede yards were people on cliffs and beaches can actually see them!
There is a deep trench south of Cork, the Porcupine sea bight but a deep sea trench although to most people this may sound good for the sub it actually is'nt as the deeper the water then the more likely it is that a ships sonar will bounce of the bottom and get greater ranges, (known as convergence zones)
Even spotting the periscope from a warships deck is difficult, the idea of the NS purchasing a sub is an interesting one , but, and its a big but, how do the advatages compare to the cost of the vessel and the crew, Ireland could afford a small diesel electric, an ex-RN one like what the Canadians are purchasing or even better a german 209, this would open up a lot more oppportunities for the defence forces but again would the tax payer be happy about footing the bill.

[Goldie fish]

Click Here

Goldie Fish any idea where is a good place to start looking: re NS opening fire.

[Goldie fish]

Hedgehog Launcher on HMCS Sackville

[yooklid]

Originally posted by John
You mean to say that not everyone knows what a hedgehog is?

Amazing.

I guess nobody reads Monserrat anymore

You mean to say that not everyone knows what a hedgehog is?

Amazing.