Visby-class corvettes HSwMS Härnösand (K 33) and sister-ship HSwMS Helsingborg (K 32) at the Swedish Navy Base at Karlskrona. (Photo: E. H. Lundquist)
Posted on 12/22/2010 8:40:24 PM PST by sukhoi-30mki
Swedish corvette is engineered for stealth
By Edward Lundquist
The Swedish corvette Visby is stealthily to the core, right down to the all-composite shaft.
From the carbon fiber hull and radar absorbent coating to the enclosed gun mount, flush antennas and telescoping mast, this ship has extremely low signatures. The camouflaged appearance is hard to see, and the engine exhaust being ducted into the water jets reduces the infrared signature (the engine exhaust mixed with the water does create a visible vapor “exhaust”). The machinery sits on vibration isolation mounts, and non-magnetic materials are used throughout.
Despite this unique approach to warship design, Lt. Cmdr. Bjorn Spangberg of the Royal Swedish Navy’s Third Naval Warfare Flotilla doesn’t see a downside.
Spangberg is head of Trials Unit Visby technical division with the Third Naval Warfare Flotilla, and before that was aboard the Visby class as chief engineer.
“Regarding the composite shafts I can’t come up with any cons at all,” Spangberg says. “They are almost maintenance free. We only have to perform visual inspections of the shaft surface, flexing elements and bulkhead seals. Existing bolts are checked regarding tightness once a year.”
The composites weigh about half as much as steel. If the ship was built with tradition construction materials it would displace 1,300 tons instead of 650. And the composites contain the heat and smoke, so compartment fires do not spread before the installed firefighting system can extinguish it. Every thing aboard is fire retardant, even the bed sheets.
Five ships of the class have been built or are building. The lead ship was commissioned in 2000.
HSwMS Härnösand and sister-ship HSwMS Helsingborg were commissioned Dec. 16, 2009. They are the two newest Visby-class corvettes, says Cmdr. Patrik Norberg, who commands the Härnösand.
According to Royal Swedish Navy Capt. Anders Olovsson, 3rd Naval Warfare Flotilla commander at the Karlskrona naval base, Visby has “lean manning,” with 27 officers and 16 ratings, for a total of 43.
With the two Detroit/MTU diesels she can make 15 knots, and with the diesels and with the four Vericor TF50A gas turbines, the 238-footVisby can move out smartly at 35 knots.
I accompanied Härnösand to sea in the Baltic for a gunnery exercise. The steerable KaMeWa waterjets make Härnösand very maneuverable during mooring evolutions, and the bow thruster makes it even easier. Helm controls are operated by one person. The ship comes up to speed rapidly. While underway at 35 kts., I watched from the bridge as the ship made a 180-degree turn inside its own wake.
Gas turbines exhausts gases are cooled with seawater, Spangberg says. “We also cool gases produced from boiler, auxiliary machinery and low speed machinery in order to keep the heat signature low. The internal seawater cooling systems are used for cooling everything but the exhaust gases from the gas turbines. When the main engines are running, their exhaust gases are cooled by seawater drained from the waterjet units via a regulating system for optimal cooling effect due to specific power used.”
The cooling system for the gas turbines are built by Mecmar, a Norwegian company. “They have built systems like ours for high-speed ferries around the world. One unique thing is that we have two gas turbines that come together in one exhaust system on each side (port and starboard). The exhaust system leads from the engine room aft and up to the cargo deck, and then turns down through a horizontal surface in front of the transom. The advantages include reduced heating signature, reduced gas volume, reduced size of exhaust piping, and reduced weight,” Spangberg says.
“The Visby-class corvettes for Sweden have been in the limelight. They took a long time. They cost a lot. But we are leaving the conscript navy and this flotilla is rapidly evolving into a standing operational force,” Olovsson says. “These ships are warfighters. They can fight in all dimensions.”
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Captain Edward Lundquist, U.S. Navy (Ret.) is a principal science writer with MCR Federal LLC.
Visby-class corvettes HSwMS Härnösand (K 33) and sister-ship HSwMS Helsingborg (K 32) at the Swedish Navy Base at Karlskrona. (Photo: E. H. Lundquist)
The modern equivalent of the Viking Long Boat.
damn I clicked on it thinking it was a car!
There is absolutely no way that the Rats would allow the US to build such ships.
They don't know...got a friend, naval Architect, working on design of a stealth composite attack boat now.
I thoght it was a car also! At least there’s post three. ;)
Not sure we would want to anyway. They don't look very big, and that's fine for the Swedish Navy. Maybe not so good for ours.
How many tons do these stealth ships displace? How do they handle heavy weather? How long can they stay on station without resupply and refueling?
Smaller ships tend to be less stable and more susceptible to wind and wave action in the open ocean. They also tend to have shorter range. Not a problem for the Swedes, who are rarely far from a Swedish port or convenient fjord. The US Navy has ships in every ocean, and ships can be stationed thousands of miles from a friendly port.
There may be a place for such vessels (littoral combat, maybe) but not as front-line vessels.
The car was named for a class of sailing ship.
“...points sittin’ way up high...”
“...points sittin’ way up high...”
#####
Bjourn Seeger.
BWAHAHAHAHAHHAHAHA! Um... sorry...
My point is that the Rats wouldn’t allow us to get an advantage because that wouldn’t be fair to our enemies.
They could be used to interdict smugglers coming in from Baja, the Gulf or the Keys; to chase down pirates in the Red Sea, and/or to escort in or to patrol in short to medium length commercial channels e.g. from India to the Suez, or from the Suez to Sweden. The stealth part I don’t really figure as critical but maybe it’s got a future in the front line of a sea-based landing, or maybe it is just one version proof of concept for future, larger ship with a different purpose.
A stretched-Visby class ship would have been perfect for the littoral role which the USN is buying the hugely expensive LCS, which is currently plagued by performance and equipment issues.
Those points in #3 are covered with a light absorbing stealth material that makes it impossible to see them.
Unfortunately, everything the US tries to build ends up costing far too much. The Zumwalt Destroyer class will have a ship in the water in 2013, I think. It’s a very advanced 14,000 ton stealthy destroyer. Closest thing to a battleship that any nation has built in decades. It’s darn cool. We were originally going to build 32 of them — imagine! Thirty-two stealthy ships capable of doing serious damage in a land attack scenario! The range on these ships is very high so anything near the coast becomes a viable target. But the cost was too high and we are going to end up with only 3 of these.
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