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To enter Ovens we must first climb the tower to get us to deck level. This gives us a good opportunity to get an idea of her construction. The core is the pressure hull to either side of this are the ballast and fuel tanks that allow the submarine to dive and surface. On top of these we have the casing which acts as the deck and stowage space which is free flooding as is the conning tower or fin, on American boats it is also called the sail. This holds and streamlines the periscopes, snorkel, exhaust, radar and communication masts. It also provides a position to command the boat from when it is on the surface, we will look a little closer at that later in the tour. |
| How do the ballast tanks fill and empty? There are three tanks each side and one aft a total of seven at the bottom of these are flood holes, the water is kept out by the pressure of air within the tank. When a boat dives these tanks are vented through Kingston Valves on the top of each tank. Many of you will have seen pictures of submarines diving with what looks like steam spouting from them, this is air being vented from the tanks . When it comes to surfacing stored high pressure air is fed into the tanks displacing the water and making the boat more buoyant. Once on the surface the remaining water is forced out by low pressure air blowers which draw air from outside the boat. |
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Arriving on deck if we look forward there is the streamlined housing of one the several Asdic or as called in America sonar arrays which Ovens is fitted with. This system is both active [sends and receives signals] and passive [receives passive signals] The dome houses a 'Krupp' sonar array, its cylindrical shape likened to a 'crown of thorns' [196 transducers] when we get below we will see how the signals are processed.
The wing like things either side are Hydroplanes these are control surfaces and act like ailerons on an aeroplane. They are used to control the submarine once dived, another pair are fitted at the stern |
Aft of the planes is forward escape hatch we will see more of below. The cover we are standing on protects one of the two emergency buoys which can be released to indicate the position of the boat and provide communications. Release of this buoy activates its EPIRB which automatically starts a "SubSmash Alert" This is the code name given to procedures that are implemented if there is an accident involving a submarine. A search and rescue operation starts, to find and save the crew. |
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Looking aft we see the conning tower this which is made of fibreglass and floods when the boat is submerged. From here you can see the scull and cross bones flag. The tradition of that dates back to the First world war and it was flown by Royal Navy submarines when entering port to denote a successful patrol in which they had sunk a ship. Ovens earned her flag when she sank the decommissioned HMAS Colas during an exercise. All fittings on the casing retract to reduce underwater noise except the three fin like hydrophones and the forward power winch. |
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