The watertight bulkheads for the engineroom shall by regulation extend to the bulkhead deck. The forward bulkhead seemed not to be damaged that’s probably why the forward part is still afloat. Keep in mind that a minesweeper is built mostly of wood, including the deck, with bronze and stainless steel fittings and engines to minimize their magnetic signature.
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I’m pretty sure the sweeper is all fibreglass/plastic and Aluminum, which would account for the extent of damage from the reportedly low speed of impact.
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Agree, on both points.
https://www.seatrade-maritime.com/casualty/greek-minesweeper-loses-stern-maersk-boxship-collision
The container ship had just left Piraeus container terminal which is opposite the naval base bound for Cannakkale, Turkey, when the accident appears to have happened as the vessels left the more crowded waters.
Apart from the colregs you don’t mess with your 60 m with another ship of 266 m and 84 times your weight. It’s a mystery to me how this, with clear visibility, could have happened.
In the mean time the Maersk Launchton is still moored in Piraeus.
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This was the track of Maersk L (copied from Gcaptain), the minesweeper apparently was in silent mode…
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The enormous damage, Greek TV reported, is due in part to the construction materials of the warship. It is made of reinforced plastic and fibreglass, which makes it vulnerable to impact.
Kallisto‘s fibreglass hull was built by Vosper Thornycroft in the early 1980s (then called HMS Berkeley) before being moved to Greece between 2000 and 2001.When built in the 1980s, Kallisto was one of the largest warships ever built with a fibreglass hull. Mine countermeasures ships are typically built with non-metallic hulls, in part to help reduce their vulnerability to magnetic mines. This also reduces their acoustic signature, which, in turn, makes them less likely to trigger acoustic mines.
How does a non-metallic hull reduce acoustic signature?
The fibreglass is much thicker than steel and acts as a sound insulation.
The purpose of the fibreglass construction is also to create a monocoque construction and reduce the requirement for framework as would be normal for steel, alloy or wood. This is to reduce the variation of strong and weaker parts of the hull shell caused by frames and much thinner shell plating.
Mine countermeasures ships are designed to withstand the pressure waves of exploding mines and the hull shell has consistent resistance to that because there are fewer weak areas and strong areas. The whole hull can flex consistently after an explosion and the machinery and equipment is all resiliently mounted.
There are far more very expensive variations in the construction of MCM ships. An interesting one might be that the metal wear treads on each step of a ladder in one ship I visited were made in several parts to prevent creating induced currents causing tiny magnetic fields as the ship moved. No metal coathangers are allowed. The beer is in aluminium cans - bottles in the old days when only steel cans were otherwise available. Magnetic hygiene is very important, and every magnetic item on or off the ship is recorded.
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I would add that propulsion system is designed to be very quiet using active rudders.
The sound absorption coefficient is the quotient of the reflected sound energy divided by the incident sound energy and varies from 0 to 1. If this coefficient is for instance 0.1 then this means that only one tenth of the energy is reflected and nine tenth is absorbed by the insulation material and/or is transmitted beyond the material, sound leakage you could say. This is very favourable for the detection of the mine sweeper, it is hardly “seen”. Thicker insulation material means much more absorption. The coefficient for steel is 1 or very close to 1, the energy is almost completely reflected which is bad.
Sound absorption coefficients of 4mm thick composites with various fiber loadings. The sound absorption coefficient is clearly dependent of the frequency.
Carbon reinforced fiber is by far superior to wood for building mine sweepers. I donot know whether for the Kallisto glass fiber or reinforced carbon fiber was used. These last fibers, hollow straws, contain air which improves the absorption very much as compared to glass fiber.
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An similar, less severe, accident took place on September 23 in Danish waters. The Russian Parchim class navy vessel Kazanets collided with the Swiss-owned container ship Ice Rose near the Oresund Bridge linking Denmark and Sweden. The collision took place in foggy weather conditions. The AIS of the Russian 800 ton ship was said to be turned off.
The Ice Rose, which was sailing from St. Petersburg in Russia to Gothenburg in Sweden, collided with a Russian frigate early on Wednesday morning.
The above water damage of the reefer.
The damaged bow of the Kazanets.
The Maersk Launceston is now at anchor. I don’t know why but it looks like they are going to hold on to the ship until at least November 11, the date of the captain’s testimony.