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airship · 11-26-2007, 06:56 PM

The last photo in AMG's link shows that the antifouling at least, appears to be in excellent condition...?!

I remember having read an article in some yachting magazine at least 20 years ago which explained that just a Ø2 inch hole (say, complete loss of a thru-hull fitting) 4-5ft below the waterline would be sufficient to sink a modern 40ft GRP sailboat in under 5 minutes. I'm not 100% sure of the facts, but I'm sure that our resident naval architects will be able to elaborate...?!

When it comes to larger, ice-classed double-hulled steel vessels equipped with bilge pumping systems on a wholly different scale to the average Johnson / Jabsco / Rule etc. pumps found on a 40 footer, they still share the same constant: the seawater pressure applied on a hull at a certain depth...

It's one thing to know that you've got a breach in the hull somewhere. And quite another to identify exactly where it's located in order to try to plug it. All bilge-pumping systems have their limitations (said with a Dirty Harry frown). Double-hulled vessels (where the fuel, water and ballast tanks) form part of the double-hull are not a panacea. Double-hulled oil super-tankers won't completely shield us from Exxon Valdez or Torrey Canyon-like oil spills in the future. They all rely on the gap created between the outer and inner hulls being of sufficient distance and the "inner hull" resisting the initial impact / grounding or whatever.

What we need to have is some form of 3rd "sensitive skin" that could be applied all-over the internal hull surfaces of at least passenger vessels opearating in far-flung areas in hostile conditions. Which when breached, would be able to alert the crew of both the size and precise location of the breach. It's one thing to know that there's at least a "fist-sized" hole in the hull "somewhere in a certain space" which contains a water-level sensor. Quite another to have rapid access to the damaged area in order to try and plug it. How many square metres of bilges (or m3) does the average water-level sensor cover? Just how are today's crews expected to identify and gain access in order to try to plug any breaches? I'll tell you: they probably don't / cannot. And once the water level reaches the deck plates, can you blame anyone for abandoning ship...?!

Lots of yachts are effectively double-hulled too. But as they get older, one wonders whether the methods used to conduct metal-thickness tests on the outer hull are also used on the tank-tops too? But just supposing new yachts were all equipped with these "3rd skins", how many engineers or crew would take a sledge-hammer to the marble-floor of that guest bathroom...?!

11-26-2007, 06:56 PM	#12 (permalink)
airship Senior Member Join Date: Jul 2006 Location: French Riviera... Posts: 302	The last photo in AMG's link shows that the antifouling at least, appears to be in excellent condition...?! I remember having read an article in some yachting magazine at least 20 years ago which explained that just a Ø2 inch hole (say, complete loss of a thru-hull fitting) 4-5ft below the waterline would be sufficient to sink a modern 40ft GRP sailboat in under 5 minutes. I'm not 100% sure of the facts, but I'm sure that our resident naval architects will be able to elaborate...?! When it comes to larger, ice-classed double-hulled steel vessels equipped with bilge pumping systems on a wholly different scale to the average Johnson / Jabsco / Rule etc. pumps found on a 40 footer, they still share the same constant: the seawater pressure applied on a hull at a certain depth... It's one thing to know that you've got a breach in the hull somewhere. And quite another to identify exactly where it's located in order to try to plug it. All bilge-pumping systems have their limitations (said with a Dirty Harry frown). Double-hulled vessels (where the fuel, water and ballast tanks) form part of the double-hull are not a panacea. Double-hulled oil super-tankers won't completely shield us from Exxon Valdez or Torrey Canyon-like oil spills in the future. They all rely on the gap created between the outer and inner hulls being of sufficient distance and the "inner hull" resisting the initial impact / grounding or whatever. What we need to have is some form of 3rd "sensitive skin" that could be applied all-over the internal hull surfaces of at least passenger vessels opearating in far-flung areas in hostile conditions. Which when breached, would be able to alert the crew of both the size and precise location of the breach. It's one thing to know that there's at least a "fist-sized" hole in the hull "somewhere in a certain space" which contains a water-level sensor. Quite another to have rapid access to the damaged area in order to try and plug it. How many square metres of bilges (or m3) does the average water-level sensor cover? Just how are today's crews expected to identify and gain access in order to try to plug any breaches? I'll tell you: they probably don't / cannot. And once the water level reaches the deck plates, can you blame anyone for abandoning ship...?! Lots of yachts are effectively double-hulled too. But as they get older, one wonders whether the methods used to conduct metal-thickness tests on the outer hull are also used on the tank-tops too? But just supposing new yachts were all equipped with these "3rd skins", how many engineers or crew would take a sledge-hammer to the marble-floor of that guest bathroom...?!