Why Are These Ships Designed To Sink?

how do you transport a ship on the verge of sinking from one side of the world to the other say something like this nine thousand ton 154 meter Destroyer this is the USS coal and in October 2000 she was attacked in the Gulf of Aden but later repaired in the United States having been transported across the oceans on the back of this massive ship carrying ship while this was probably the most public example of one of these transports arguably more impressive was that when the hmas canberra's hull was moved from Spain to Australia via the Cape of Good Hope in 2012. her Hull was over 230 meters in length making it even bigger than the ship that was carrying her so what's going on what are these extraordinary ships and how do they work normally when you have cargo that you want to move you get yourself a ship and just lift the cargo on smaller things might be containerized and moved in standard size boxes other things might be lifted onto the deck as they are and just strapped in place either way you need a crane that can lift your cargo regular Harbor cranes typical quickly have the capacity for lifting maybe a couple of hundred tons specialist cranes do get into the low thousands but if you're needing close to 10 000 tons lifted you really don't have many options add in the complication of operating in less than ideal conditions like the Gulf of Aiden and you quickly realize that cranes just aren't suitable so in the case of the USS coal and the hmas Canberra the solution was to instead use a ship called a semi-submersible heavy lift chip they are really specialized vessels designed to lift and carry immensely heavy floating objects like oil or eggs and occasionally other ships in both of our examples the heavy lift vessel used was called the Blue Marlin she's around 225 meters in length and capable of carrying in excess of 75 000 tons the way this sort of ship works is that you have a series of ballast tanks throughout the hull which can be freely filled up with seawater by flooding them the ship gets heavier and sinks lower eventually the main deck submerges and then the more you continue to flood the lower it gets get low enough and there is then space to float buoyant cargo over the top it's then just a case of gradually pumping out the water from the ballast tanks and letting buoyancy do all the heavy lifting in the case of the USS coal she was small enough to fit across the deck so that's exactly what they did in the case of the HMS camera however even though blue marlin had been enlarged by then she was still slightly too big so had to overhang the stern that doesn't actually matter though as it's all about where the weight is distributed rather than the size as long as you keep the overall size and weight of the heavy lift vessel and its cargo within limits you're good to head to sea with Canberra loaded on board blue marlin left Spain and headed south she went around the Cape of Good Hope and across the Indian Ocean towards Port Phillip in Victoria they chose the longer route simply because they didn't want to chance the high risk areas in the Gulf of Aden and Around the Horn of Africa anyway the great thing about semi-submersible heavy lift ships is that once the cargo on board they behave in the same way as any other vessel and can navigate in the same way then when they get to their destination and need to unload it's just a case of doing everything in Reverse they fill their ballast tanks in a controlled manner so that the heavy lift vessel slowly sinks lower into the water as the cargo begins to submerge buoyancy starts to lift it off the deck until eventually it reaches the point where it's floating free on its own tugs are then used to maneuver it clear of the deck after which the heavy lift vessel is free to refloat herself and make her way towards the next loading Port although the two examples we've discussed both involve moving ships around the world the original purpose of these vessels was a little different they were actually designed for the oil and gas industry moving ships is more like a side hustle to them they were designed to move floating offshore structures that would otherwise need to be towed while Towing platforms around is fine for short distances it becomes much harder if you want to move them across the entire world say you want to construct a new oil rig in a yard in Asia and then bring it to the golf of Mexico for operation tugs would need to be in place for weeks typically Towing at only a few knots with the weather and political instability adding unknown risks throughout the passage instead of that you could use a semi-submersible vessel to load the rig right onto its deck and trouble at much more normal speeds with a single ship's crew considering the scale of the finances involved massive savings are possible which in turn means that it's possible to make massive investments into these sorts of ships when she was built blue marlin was the largest one in the world but she's since lost her crown to the Vanguard Vanguard is so big that she was actually one of the options for removing Costa Concordia in 2013 although ultimately she wasn't used she has been used as a dry dock for other cruise ships though notice the similarity between the Vanguard and the blue marlin you can very easily identify these sorts of vessels from their wide open deck space and upright buoyancy casings these are necessary as they provide extra buoyancy when the main deck submerges and prevents the stern from Simply dropping away from the bow without them once the main deck is underwater any further submerging will act to quickly move the center of buoyancy towards the bow potentially destabilizing the ship longitudinally anyway this combination of large buoyancy casings with a vast open deck area is a quick giveaway if you ever see one of these vessels on the horizon otherwise it will be very easy to mix them up with other sorts of vessels that also take project cargo but don't actually submerge they are pretty much regular cargo ships as they still rely on cranes lifting the cargo on and off for most things that's fine and certainly cheaper than designing all the ballast systems needed for a semi-submersible vessel it's only for the very large items oil rigs and other ships that you need a semi-submersible vessel not that many need moving which is why the worldwide Fleet is so small and now before we go I just wanted to remind all members that the directors commentary to this video is now live for second mates and above Link in the description down below for anyone considering joining check the description to find out more

Channel: Casual Navigation

Views: 605,811

Keywords: casual navigator, marine, shipping, casual navigation, maritime explaination, merchant navy, sailing, marine animation, semi submersible, semi submersible ship

Id: FmJOvekHYvs

Length: 6min 1sec (361 seconds)

Published: Fri Dec 30 2022

Reddit Comments

[u/Nogohoho]

The reason is literally right in the splash image.

Gods I hate clickbait.