Swedish Stealth Corvettes

[Commodore Armiger]

Consider the many methods the military can use to spot a ship: visually (with the naked eye or by satellite), radar, sonar (mainly used by submarines), and even infrared (missiles are now equipped with heat-seeking systems to track enemy vessels).

The Visby, which entered service for the Swedish Navy in January 2005, is designed to minimize all of the above, as well as above-water acoustic and hydroacoustic signatures, underwater electrical potential and magnetic signature, and pressure signatures. How does it accomplish this? For starters, it is the largest vessel ever constructed of carbon fiber -- a super-hard, lightweight plastic that is also used in the making of race car chassis and racing yacht hulls. Specifically, the boat's surface is composed of two layers of carbon fiber filled with a Polyvinyl Chloride (PVC)-like foam, or what Kockums calls sandwich-construction carbon fiber reinforced plastic (CFRP). This composite material has been proven to reduce a ship's "signature," so that not only is it more difficult to pick up on radar, but also less vulnerable to mines and other types of electronic detection, such as infrared. Since the material is not made of steel, it also escapes detection by magnetic waves. And since the Visby, at 600 tons, is about half as light as a conventional corvette, it has quicker escape abilities. That's not even mentioning the lower maintenance costs for a ship composed of plastics as opposed to one built from steel, and the lower fuel consumption costs.

You might think, "How can a ship made of plastic be tougher than one made with steel?" but carbon fiber is one tough material to crack. How tough? Kockums originally used diamonds to cut the carbon fiber in building the Visby, but the diamonds wore out quickly, and thus the engineers had to build a new, tougher cutting technology -- an extreme high-pressure water jet.

All in the Angle

Another critical factor in escaping radar detection is the angle at which radar waves bounce off the surface of your ship. The key is to construct vessels that don't have "right angles," which tend to reflect radar right back to the source. The Visby diminishes radar detection with its flat, outwardly-sloping superstructure, which reflects radar waves at "favorable" angles. This gives it a minimal radar signature, (also known as a "cross-section"), contrasted to the steel-and-aluninum superstructure of a standard ship, which features a "starved horse" pattern that results in uncontrolled reflection of radar waves.

It also helps when you don't have anything to reflect radar waves off of -- thus, the Visby has a fully retractable 57mm cannon which reduces its cross-section still further. And every feature that does not need to be located outside the hull has been built in or concealed under specially designed hatches. Even the gas turbine exhausts have been concealed in hidden outlets close to the water surface at the stern of the vessel.

The Bottom Line

All this talk of angles and materials is all very well, but what's the end result?

In simple terms, because of its stealth measures, if the Visby is 100 kilometers from an enemy vessel, it can pick up the enemy on its own radar, but not vice versa. In fact, the enemy would have to be within 30 kilometers of the Visby to spot it. The Visby get an additional jump on its opponents thanks to its integrated CETRIS system, which incorporates functions for internal and external communications, and includes sensors such as surveillance radar, electronic support systems including a radar warning device, a fire control director, and navigation sensors. The system can also be outfitted with an infrared scanner/tracker, laser warner, jammer, and control for surface-to-air missiles (SAM), and surface-to-surface missiles (SSM), as well as rapidly retractable antennas, some of which are concealed behind frequency selective surfaces (FSS).

All this means is that the Visby is well-prepared to get the jump on its opponent well before the opponent can detect it -- or lay mine traps for its opponent, if the opponent is a vessel or submarine.

It should be noted that the Visby is only a first step towards the dream of a global stealth fleet -- it is only 73 meters long and intended for coastal, or littoral warfare. And despite the "wow" factor of the carbon fiber hull, the Visby is vulnerable, like any ship, to the modern surface-to-surface missile. Questions also remain about how a carbon-fiber hull would hold up under the duress of the high seas. But as a prototype for new technologies and stealth capabilities, the Visby is mighty impressive. Kockums claims that a 120-meter long ship has been designed that is comparable to the Visby's high stealth standards, so a future in which these ships patrol the oceans may be closer than we think.

[astraltrader]

Thank you for the highly interesting account of this innovative Swedish warship. I understand that there are to be a class of six of these eventually. One of the photographs that you kindly provided show that a second one has already been built. What is the name of this please?

[Commodore Armiger]

Lots more info here:

http://www.naval-technology.com/projects/visby/

[romft1945]

Thanks Comm very interesting looks like something out of star wars,
Rom

[Odin]

Thank you very much Commodore for a very interesting post and a useful web site link.

The fact that the Navy has ordered five suggests there is a high degree of confidence in the whole concept. Looks a very interesting approach although I can't quite see how it could accomodate everything (one diagram on the link talks about a hanger!). Any idea what the crew size is? Didn't see any mention of phased array radar technology which I thought it would incorporate.

[Commodore Armiger]

As I understand it the original intention was to install a hangar but there is only a landing pad. Given that virtually all of these vessels' operations would take place in coastal waters, the lack of hangar and maintenance for a helo is perhaps not so vital as it would be for a US or British stealth vessel expected to undertake ocean-going operations.

The crew is 43.

I am not up to discussing the relevant merits of 21st century radars!

Much of the material related to these vessels is of course in Swedish, but the following links should help:

http://en.wikipedia.org/wiki/Swedish_Navy

http://www.youtube.com/watch?v=Bs_Zz4CC7go

http://www.technorati.com/videos/youtube.com%2Fwatch%3Fv%3DmbZUHpk2s8U

http://www.janes.com/defence/news/idr/idr061204_1_n.shtml

http://www.rusi.org/downloads/assets/Grenstad_0207_RDS.pdf

http://awwar.com/Military-Weapons/Warships/Swedish-Navy-Visby-Class-Stealth-Corvette-Ships

[Odin]

Thanks again Commodore for those links - very interesting especially the extreme littoral video.

I'm impressed with the Swedish approach to how they have developed their navy - no real need for power projection but more a realistic fleet of ships based on the geographical location of the country and its' defence aspirations.

It also answered my question on radar although one of the suggestions for improvement would perhaps have a negative impact on the detection range.

I hope more Forum members take time to review this thread as it gives an interesting insight into current warship design thinking.

[astraltrader]

A fabulous looking class of ship IMO.

[BECA@CLEAR.NET.NZ]

These pictures are of the Swedish stealth corvette Visby.
The ship in the shed is the Skrovhall.
Pictures are by kind permission of KockumsAB

[kookaburra]

very sneaky. Looks a little like a small version of the now-cancelled US Zumwalt destroyer class, a ship we'll now never see. Kockums just needs the forward sloping bow. Not much of deck space on these ulta-modern ships, is there.Future sailors are going to suffer a lack of vitamin D.

Ah, this article of July last year says two of the 14,500 ton Zumwalts will be built. I'm not sure if that remains the case. Don't think so from threads elsewhere.

http://www.americanintelligence.us/News/article/sid=5276.html

[Commodore Armiger]

I'll repeat my comment from the other thread: "Skrovhall" isn't the name of the ship, it's the name of the building.

[Wombat]

Becca,
You ask "what will ships look like next" . Here is one example, these are Incats from the Chinese Navy.

Wombat,
(James)

[astraltrader]

Some good pictures there Colin.

As we already have a thread in existence covering these ground breaking corvettes I have moved your post there. Many thanks my friend...

[BECA@CLEAR.NET.NZ]

Some good pictures there Colin.

As we already have a thread in existence covering these ground breaking corvettes I have moved your post there. Many thanks my friend...
Thank you Terry, I did not know that a thread already existed and it is much more interesting than mine. Does this happen often, i.e. a doubling up of input?

[BECA@CLEAR.NET.NZ]

Becca,
You ask "what will ships look like next" . Here is one example, these are Incats from the Chinese Navy.

Wombat,
(James)

Interesting pictures James, do you think the Swedish boats are more elegant?
Regards.

[BECA@CLEAR.NET.NZ]

Consider the many methods the military can use to spot a ship: visually (with the naked eye or by satellite), radar, sonar (mainly used by submarines), and even infrared (missiles are now equipped with heat-seeking systems to track enemy vessels).

The Visby, which entered service for the Swedish Navy in January 2005, is designed to minimize all of the above, as well as above-water acoustic and hydroacoustic signatures, underwater electrical potential and magnetic signature, and pressure signatures. How does it accomplish this? For starters, it is the largest vessel ever constructed of carbon fiber -- a super-hard, lightweight plastic that is also used in the making of race car chassis and racing yacht hulls. Specifically, the boat's surface is composed of two layers of carbon fiber filled with a Polyvinyl Chloride (PVC)-like foam, or what Kockums calls sandwich-construction carbon fiber reinforced plastic (CFRP). This composite material has been proven to reduce a ship's "signature," so that not only is it more difficult to pick up on radar, but also less vulnerable to mines and other types of electronic detection, such as infrared. Since the material is not made of steel, it also escapes detection by magnetic waves. And since the Visby, at 600 tons, is about half as light as a conventional corvette, it has quicker escape abilities. That's not even mentioning the lower maintenance costs for a ship composed of plastics as opposed to one built from steel, and the lower fuel consumption costs.

You might think, "How can a ship made of plastic be tougher than one made with steel?" but carbon fiber is one tough material to crack. How tough? Kockums originally used diamonds to cut the carbon fiber in building the Visby, but the diamonds wore out quickly, and thus the engineers had to build a new, tougher cutting technology -- an extreme high-pressure water jet.

All in the Angle

Another critical factor in escaping radar detection is the angle at which radar waves bounce off the surface of your ship. The key is to construct vessels that don't have "right angles," which tend to reflect radar right back to the source. The Visby diminishes radar detection with its flat, outwardly-sloping superstructure, which reflects radar waves at "favorable" angles. This gives it a minimal radar signature, (also known as a "cross-section"), contrasted to the steel-and-aluninum superstructure of a standard ship, which features a "starved horse" pattern that results in uncontrolled reflection of radar waves.

It also helps when you don't have anything to reflect radar waves off of -- thus, the Visby has a fully retractable 57mm cannon which reduces its cross-section still further. And every feature that does not need to be located outside the hull has been built in or concealed under specially designed hatches. Even the gas turbine exhausts have been concealed in hidden outlets close to the water surface at the stern of the vessel.

The Bottom Line

All this talk of angles and materials is all very well, but what's the end result?

In simple terms, because of its stealth measures, if the Visby is 100 kilometers from an enemy vessel, it can pick up the enemy on its own radar, but not vice versa. In fact, the enemy would have to be within 30 kilometers of the Visby to spot it. The Visby get an additional jump on its opponents thanks to its integrated CETRIS system, which incorporates functions for internal and external communications, and includes sensors such as surveillance radar, electronic support systems including a radar warning device, a fire control director, and navigation sensors. The system can also be outfitted with an infrared scanner/tracker, laser warner, jammer, and control for surface-to-air missiles (SAM), and surface-to-surface missiles (SSM), as well as rapidly retractable antennas, some of which are concealed behind frequency selective surfaces (FSS).

All this means is that the Visby is well-prepared to get the jump on its opponent well before the opponent can detect it -- or lay mine traps for its opponent, if the opponent is a vessel or submarine.

It should be noted that the Visby is only a first step towards the dream of a global stealth fleet -- it is only 73 meters long and intended for coastal, or littoral warfare. And despite the "wow" factor of the carbon fiber hull, the Visby is vulnerable, like any ship, to the modern surface-to-surface missile. Questions also remain about how a carbon-fiber hull would hold up under the duress of the high seas. But as a prototype for new technologies and stealth capabilities, the Visby is mighty impressive. Kockums claims that a 120-meter long ship has been designed that is comparable to the Visby's high stealth standards, so a future in which these ships patrol the oceans may be closer than we think.

WOW!
And I thought that I had found something!
This really is interesting.
Regards.

[astraltrader]

Thank you Terry, I did not know that a thread already existed and it is much more interesting than mine. Does this happen often, i.e. a doubling up of input?


Colin it is good that you have brought this point up.


It used to happen occasionally but now the forum is really starting to grow it is becoming much more of a problem.

It is one of the jobs that moderators are tasked with - to spot them and then merge the two whenever possible.

Members however can play their part in helping with this, by doing their best to check before posting a new thread that the subject/topic/ship has not already been covered.

This I appreciate is not always easy but a quick check using the search facility at the top of every page would prevent most of them.

The thing to remember about our search facility is that the words you use to search must be of 4 letters or more [It is done this way because of the problem that using HMS would cause].

Although this sounds complicated it really isnt in practice. How many warships have a name of 3 letters?? One would type say Vanguard or Warspite or Bismarck.

Using the example provided by your post - the subject would be covered by typing in any of the following: Visby, Swedish, Stealth or even Corvette...

I hope that gives you a better picture my friend!

Finally you mentioned that the original thread was better than yours.
The important fact to consider is that the new thread containing as it now does both the original and your addition, is that much better again!!

[Wombat]

Colin,

Beauty is in the eye of the beholder, but to answer your question I would say the Swedish boats look more elegant. When it comes to performance and capability the Incat has a much wider range of use. The shallow draught and maneuverability coupled with the speed makes them an impressive choice.

At the moment they are mainly in use all over the world as a ferry, as they can carry both passengers and commercial vehicles. But their use as a military vessel is now becoming more recognized. The Americans have them and the Chinese have them in a scaled down version. However what I still find amazing is that even though they are built here in Tasmania and originally an Australian design, the Australian Defence Force don’t use them. :rolleyes:

Wombat,
(James).

[CGRET]

Interesting design incorperating sleath and low-observability with the paint scheme. I think they are on the right track for there defence needs. The mast lowering in possible combat operation's is surley ahead of it's time!

It's about time some of the other countries give credit where credit is due!

Regards
Charles

[BECA@CLEAR.NET.NZ]

Colin it is good that you have brought this point up.


It used to happen occasionally but now the forum is really starting to grow it is becoming much more of a problem.

It is one of the jobs that moderators are tasked with - to spot them and then merge the two whenever possible.

Members however can play their part in helping with this, by doing their best to check before posting a new thread that the subject/topic/ship has not already been covered.

This I appreciate is not always easy but a quick check using the search facility at the top of every page would prevent most of them.

The thing to remember about our search facility is that the words you use to search must be of 4 letters or more [It is done this way because of the problem that using HMS would cause].

Although this sounds complicated it really isnt in practice. How many warships have a name of 3 letters?? One would type say Vanguard or Warspite or Bismarck.

Using the example provided by your post - the subject would be covered by typing in any of the following: Visby, Swedish, Stealth or even Corvette...

I hope that gives you a better picture my friend!

Finally you mentioned that the original thread was better than yours.
The important fact to consider is that the new thread containing as it now does both the original and your addition, is that much better again!!

Thank you Terry.
As always, a gentleman!
I appreciate the advice and will endevour to follow it. A well run site is worth everyones effort to keep it this way. I was not aware of the way to check entries that you have described so I am pleased to get this information, it will save me some embarrasment I am sure.
Regards,
Colin.

[astraltrader]

Thanks Colin - I really appreciate your kind words.

We have really decent and helpful members who all have a part to play in helping to keep the forum moving in the right direction.

[mustang ali]

i love the visby class, i had HMS Helsingborg as part of my screensaver on my old computer. it really looks the part when it comes to stealth, and the paint job is awesome, love the 57mm BOFORS, its great how it folds away, wish the 4.5" guns on RN Ships could do that

[Don Boyer]

Always interesting to see "the latest" technolgy at sea. And I note, thankfully, in passing the Zumwalt piece of drivel is dead. Good for that.

I wonder if anyone can come up with a stealth mast that doesn't look like a dunce cap.

And, in the end, the enormous expenditure on stealth technology, while keeping evil surface ships at bay, matter not a whit to HMS Astute or USS Hawaii. When we go stealthy that way, we'll have something!

Great post guys. I can't keep up with the new stuff like the days of old, so it's always nice to see it posted here.

[mustang ali]

i know the masts all look like "dunce caps" Don, HMS Daring is a good looking ship but with the mast/radar combo it looks like a bell end. but alas, the angles give it is stealthiness and destroyers need bigger masts than corvettes.

but i agree the proposed design for Zumwalt was bloody awful, looked like a schoolboy drew on his computer at school

[mustang ali]

if our Type 26 frigates (if they ever get built) look anything like this i will be a happy bunny

[mustang ali]

http://upload.wikimedia.org/wikipedia/commons/thumb/e/e2/Milgem4.jpg/300px-Milgem4.jpg Turkey's answer to stealth surface ships, looks good, bit big for a corvette though methinks