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[alexsa]

I understand that you are an Super Moderator. Do you think that I'm NOT being insulted when they tell me to read books and asks me to ask Polynesians from 1000 years ago? How do you think I feel? Is it possible for me to ask any Polynesian that were probably dead 900 years ago? I was not asking questions but rather expressing my opinions. Is it because these posters are identified as Defense Professionals that they're given the benefit of the doubt and have been here longer than myself? I could possibly give you my credentials and also be identified as Defense Professional. Just tell me what documentation you want me to submit. Thank you.

OK here we go. Displacement is just that. If the total ship mass is 2000 tonnes then it will displace 2000 tonnes of water. Aluminium does not make it displace less it is just the ships structural mass may be than the similar structure in steel (noting Al need additional reinforcing given different yield and elastic deformation points).


The issue is hull form and submersion. The Austal LCS is a stabilised long mono-hull (yep the sides are outriggers) with the middle hull providing the majority of the buoyancy (look in derrets to see what that means in upward force). The problem is the speed requirement means there is little margin for additional immersion of the hull. As such there is little scope for large increases in weight without significant performance losses. The material of construction is simply one element of this problem but doe not change the impact of how much mass the vessel displaces and the impact additional immersion has on performance.

 

[alexsa]

I understand that you are an Super Moderator. Do you think that I'm NOT being insulted when they tell me to read books and asks me to ask Polynesians from 1000 years ago? How do you think I feel? Is it possible for me to ask any Polynesian that were probably dead 900 years ago? I was not asking questions but rather expressing my opinions. Is it because these posters are identified as Defense Professionals that they're given the benefit of the doubt and have been here longer than myself? I could possibly give you my credentials and also be identified as Defense Professional. Just tell me what documentation you want me to submit. Thank you.

Sorry one last point on the Def Pro issues. You are certainly not a marine Def Pro as evidenced by your lack of understanding of the basic laws that allow a ship to float.

 

[the road runner]

The issue is hull form and submersion. The Austal LCS is a stabilised long mono-hull (yep the sides are outriggers) with the middle hull providing the majority of the buoyancy (look in derrets to see what that means in upward force). The problem is the speed requirement means there is little margin for additional immersion of the hull.

Alexsa as i understand it ,that's the reason it is a Littoral combat ship,because the hull dose not sit as deep in the ocean ,making it able to work in shallow waters?

 

[Bonza]

I understand that you are an Super Moderator. Do you think that I'm NOT being insulted when they tell me to read books and asks me to ask Polynesians from 1000 years ago? How do you think I feel? Is it possible for me to ask any Polynesian that were probably dead 900 years ago? I was not asking questions but rather expressing my opinions. Is it because these posters are identified as Defense Professionals that they're given the benefit of the doubt and have been here longer than myself? I could possibly give you my credentials and also be identified as Defense Professional. Just tell me what documentation you want me to submit. Thank you.

Read Rob's post, he hit the nail on the head. For the record they're being given the benefit of the doubt because they have track records of engaging in good and constructive discussion on the forums, and you do not, in fact you seem to be intent on doing the opposite. And you feel insulted when you are given a list of books to consult? For god's sake, Alexas even indicated the broad context of each book, it was a genuine suggestion for you to expand your knowledge. And your response to this was to ask for something concrete while in the same statement disavowing the value of books (which are rather concrete) and suggesting Alexas is backward thinking because he doesn't agree with you. And your response to Abe might as well have read "la la la, not listening".

You're behaving like a childish hypocritical twit, so you're getting treated like one. You don't like it, you don't have to post here.

 

[alexsa]

Alexsa as i understand it ,that's the reason it is a Littoral combat ship,because the hull dose not sit as deep in the ocean ,making it able to work in shallow waters?

The hull form is also optimised for speed. The frame used by Austal provides a bucket load of space but they are still constrained by Mass.

 

[justsomeaussie]

Perhaps one could simply look at the difference in range between LCS-1 and LCS-2 to see the differences in the steel semi planning hull and the aluminium trimaran hull. Its almost 1,000nm. The fuel budget was 18% less on the Indy too. Thats quite a lot over the life of a vessel.There is still of a lot of Falkland aluminium myths getting around which I think slows a lot of thinking.

 

[alexsa]

Perhaps one could simply look at the difference in range between LCS-1 and LCS-2 to see the differences in the steel semi planning hull and the aluminium trimaran hull. Its almost 1,000nm. The fuel budget was 18% less on the Indy too. Thats quite a lot over the life of a vessel.There is still of a lot of Falkland aluminium myths getting around which I think slows a lot of thinking.

But that may not just be due to be due to hull form and it is hard to assess that without information on bunker capacity and engine fuel burn figures.


But in fair conditions and 'efficient speed of 18 knots' they get a fair range....... but this is a great deal less than the 6000nm at the same speed by the ANZAC class.

 

[phrank]

Wouldn't 3000 tons of steel give you less ship than 3000 tons of aluminum or the same ship for less weight? I think one thing that is missed is that you not only have the max they can carry but you have to have the space for whatever you are going to carry. The LCS to me seem to have a great deal of internal carry but not so much external.

 

[ASSAIL]

Wouldn't 3000 tons of steel give you less ship than 3000 tons of aluminum or the same ship for less weight? I think one thing that is missed is that you not only have the max they can carry but you have to have the space for whatever you are going to carry. The LCS to me seem to have a great deal of internal carry but not so much external.

I'll answer this with patience as the previous 2 dozen or so posts have been discussing just this point.

Two identical ships, one alu and one steel. The steel one will sit lower in the water because it is heavier. The alu one will load cargo/fuel/stores/weapons whatever until it sits at the same level sitting in the water as the steel ship. Both ships can then load further cargo until they reach their designed dead weight tonnage ie all that fuel cargo weapons etc.
The difference between the carry capacity of the two ships is the amount of cargo the alu ship could load until it reached the same freeboard/sinking level as the steel ship before the steel ship loaded ANYTHING.
All this is not rocket science and is stability 101. Alexsa has posted a comprehensive reference list if you are interested.
Space is not relevant to deadweight, it is a design function of what the ship is required to do. eg a bulk cargo ship carrying iron ore is huge with lots of space but when it is fully loaded with iron ore which has a specific gravity of about 8 IIRC (ie it is 8 times heavier than water) only about 40% of the ship's volumn is filled.(Alexsa would have the better figures than me) The ship needs to be huge because it needs the wetted surface/underwater volumn to displace enough seawater to carry the load. The other 60% could be filled with fairy dust which takes up a huge amount of space but weighs nothing.
I hope this answers your query.
Cheers

 

[Blackshoe]

Somewhat ironically, the refrain of db2646's questioning (especially the parts about just moving into the 21st century) is pretty much exactly what the LCS proponents inside the US Navy say, as well.

At this point, the LCS is starting to feel like matter of necessity of getting hulls to do anything with vice fulfilling actual missions.

 

[alexsa]

Somewhat ironically, the refrain of db2646's questioning (especially the parts about just moving into the 21st century) is pretty much exactly what the LCS proponents inside the US Navy say, as well.

At this point, the LCS is starting to feel like matter of necessity of getting hulls to do anything with vice fulfilling actual missions.

sorry I could get the gist the last sentence, can you please claify?

 

[colay]

From the Jan 2013 issue of Proceedings Magazine, more useful insight into the LCS Program.

Littoral Combat Ship: All Ahead Full! | U.S. Naval Institute

Littoral Combat Ship : All Ahead Full!
By Rear Admiral Tom Rowden, U.S. Navy

The LCS has weathered some controversial heavy seas in the past—some real, some perceived—but the program is still a major player in the U.S. Navy’s immediate future...

Three points must be made up front.

First, the LCS was conceptualized nearly a decade ago to address warfighting capability gaps that still exist today: littoral surface warfare (SUW), littoral antisubmarine warfare (ASW), and mine countermeasures (MCM). Second, LCS remains the most economical available ship to address these gaps while providing global forward presence. Finally, we have very little experience with modularity and how to man, train, equip, maintain, modernize, sustain, and tactically employ this ship. The Navy is incorporating lessons learned with a sober sense of the necessary cultural, organizational, and operational changes required to ensure that LCS is successful.

 

[alexsa]

From the Jan 2013 issue of Proceedings Magazine, more useful insight into the LCS Program.

Littoral Combat Ship: All Ahead Full! | U.S. Naval Institute

Littoral Combat Ship : All Ahead Full!
By Rear Admiral Tom Rowden, U.S. Navy

The LCS has weathered some controversial heavy seas in the past—some real, some perceived—but the program is still a major player in the U.S. Navy’s immediate future...

Three points must be made up front.

First, the LCS was conceptualized nearly a decade ago to address warfighting capability gaps that still exist today: littoral surface warfare (SUW), littoral antisubmarine warfare (ASW), and mine countermeasures (MCM). Second, LCS remains the most economical available ship to address these gaps while providing global forward presence. Finally, we have very little experience with modularity and how to man, train, equip, maintain, modernize, sustain, and tactically employ this ship. The Navy is incorporating lessons learned with a sober sense of the necessary cultural, organizational, and operational changes required to ensure that LCS is successful.

And he also made the point that the trade off between speed and capabiltiy is still being evaulated. I have no doubt that LSC and the modular weapons systems are an economical approch for the 'near land' domain but that also relies on support from other fleet units. The USN is equipped to provide this sort of support which is why this works for them.


There is still the issue of how the ship wouel deal with heavier modules should technology require that. With about 180 tonnes of deadwieght (remembering this the tonnage above light ship ...... i.e it is emply of all stores and fuel) this may mean additional compromises.
However, I return to the theme I have been running that this works for the USN because of their ORBAT and the operational doctrine they use. This wealth of assets allows them to deploy a number of LSC with modules for particular roles.


This is unlikley to work for a mid size or small navy where LCS would replace a GP frigate which is essentailly a major fleet unit.

 

[FormerDirtDart]

And he also made the point that the trade off between speed and capabiltiy is still being evaulated. I have no doubt that LSC and the modular weapons systems are an economical approch for the 'near land' domain but that also relies on support from other fleet units. The USN is equipped to provide this sort of support which is why this works for them.


There is still the issue of how the ship wouel deal with heavier modules should technology require that. With about 180 tonnes of deadwieght (remembering this the tonnage above light ship ...... i.e it is emply of all stores and fuel) this may mean additional compromises.
However, I return to the theme I have been running this work for the USN because of their ORBAT and the operational doctrine they use. This wealth of assets allows them to deploy a number of LSC with modules for particular roles.


This is unlikley to work for a mid size or small navy where LCS would replace a GP frigate which is essentailly a major fleet unit.

I'm not sure where you are getting that the LCS classes have about "180 tonnes of deadweight" from.

The Naval Vessel Register list the Freedom class vessels as having a Dead Weight of 585 metric tons: http://www.nvr.navy.mil/nvrships/details/LCS1.htm

While listing the Independence class Dead Weight at 797 metric tons: http://www.nvr.navy.mil/nvrships/details/LCS2.htm

This compares to the Perry class frigates whose Dead Weight varies from ship to ship, with the USS Halyburton at 896 long tons, and the USS Rentz at 999 long tons. Though, on average the classes listed Dead Weights are at the higher end above 950 long tons. All active ships of the class list the full displacement as 4100 long tons: http://www.nvr.navy.mil/nvrships/s_FFG.htm

I am not sure if those Dead Weight listing take into account the retirement and removal of the Mk 13 missile launchers.

 

[alexsa]

I'm not sure where you are getting that the LCS classes have about "180 tonnes of deadweight" from.

The Naval Vessel Register list the Freedom class vessels as having a Dead Weight of 585 metric tons: http://www.nvr.navy.mil/nvrships/details/LCS1.htm

While listing the Independence class Dead Weight at 797 metric tons: http://www.nvr.navy.mil/nvrships/details/LCS2.htm

This compares to the Perry class frigates whose Dead Weight varies from ship to ship, with the USS Halyburton at 896 long tons, and the USS Rentz at 999 long tons. Though, on average the classes listed Dead Weights are at the higher end above 950 long tons. All active ships of the class list the full displacement as 4100 long tons: http://www.nvr.navy.mil/nvrships/s_FFG.htm

I am not sure if those Dead Weight listing take into account the retirement and removal of the Mk 13 missile launchers.

Happy to admit my error that. That's what comes from using very old material........ However the dwt on LCS is still calculated without modules and all supporting gear. As you note the DWT on the other GP frigates is not higher by a massive order of magnitude but that is inclusive of all weapons systems. Effectively this mass is for liquids, crew and stores ( including weapon load out).


On LCS it has to include the mission modules as well. Otherwise it's fit out is the 57mm, HMGs, RAM or SeaRAM and sensors and baseline combat system.

 

[db2646]

Happy to admit my error that. That's what comes from using very old material........ However the dwt on LCS is still calculated without modules and all supporting gear. As you note the DWT on the other GP frigates is not higher by a massive order of magnitude but that is inclusive of all weapons systems. Effectively this mass is for liquids, crew and stores ( including weapon load out).


On LCS it has to include the mission modules as well. Otherwise it's fit out is the 57mm, HMGs, RAM or SeaRAM and sensors and baseline combat system.

Now that you admitted that you made an error, maybe, just maybe, it means that you're NOT always correct and you're just human after all? Nobody is perfect all the time? I could probably get in big trouble with the moderators for asking you that question?

 

[db2646]

The hull form is also optimised for speed. The frame used by Austal provides a bucket load of space but they are still constrained by Mass.

I think your assumption that the commercial Austal trimaran design and the Independence design are identical is totally incorrect. The bow of the Independence is of the "Wavepiercer and the main hull is of the Tumble home designs. The only similarity between the commercial Austal trimaran and Independence is the "trimaran" designation. Even the outside configuration of the two vessels are different. The Longitudinal, traverse, and vertical centers of gravities of the Independence vs the commercial Austal trimaran are completely different.

You're correct when you stated that the Independence is optimized for speed but at the same time it is optimized for stability due to the outriggers. If you take a look at the Independence's design, the center gravity of the vessel is basically located close to the superstructure and distribution of weight even with the inclusion of the modules is always close to the center of gravity. Austal and General Dynamics made an amazing design but it is not totally exclusive to them with this amazing design as the NAVSEA was basically been experimenting with the trimaran design since 1995. Also, the NAVSEA design and mathematical model was made of steel material.

 

[gf0012-aust]

I think your assumption that the commercial Austal trimaran design and the Independence design are identical is totally incorrect. The bow of the Independence is of the "Wavepiercer and the main hull is of the Tumble home designs. The only similarity between the commercial Austal trimaran and Independence is the "trimaran" designation. Even the outside configuration of the two vessels are different. The Longitudinal, traverse, and vertical centers of gravities of the Independence vs the commercial Austal trimaran are completely different.

I've had some involvement with Austal a few years back - and had access to some of their line drawings/drafts

It was made pretty clear to me that the USN class of platforms were derived from the Benchijigua Express

 

[alexsa]

I think your assumption that the commercial Austal trimaran design and the Independence design are identical is totally incorrect. The bow of the Independence is of the "Wavepiercer and the main hull is of the Tumble home designs. The only similarity between the commercial Austal trimaran and Independence is the "trimaran" designation. Even the outside configuration of the two vessels are different. The Longitudinal, traverse, and vertical centers of gravities of the Independence vs the commercial Austal trimaran are completely different.

Sorry as noted by GF that is just rubbish. This is is a stalised mono hull as is evidenct by the drawings. The majority of the displacement occurs in the cetre body (hence the jets are located there) with very little draft on the out riggers. The differnece between the 127m commercial ferry and the LCS 2 is not in the hull form but the upper works and the internals. They call it a SeaFrame and even their own blurb notes the realtionship, have a look on their web site. In addition a lot of us have been to the works and have been involved in thier ferry production. Trust me GF is correct. If in doubt write to them and ask.

You're correct when you stated that the Independence is optimized for speed but at the same time it is optimized for stability due to the outriggers. If you take a look at the Independence's design, the center gravity of the vessel is basically located close to the superstructure and distribution of weight even with the inclusion of the modules is always close to the center of gravity. Austal and General Dynamics made an amazing design but it is not totally exclusive to them with this amazing design as the NAVSEA was basically been experimenting with the trimaran design since 1995. Also, the NAVSEA design and mathematical model was made of steel material.

I am happy to admit figures, however, the fundamental issue is uplife (if you had read my post that would have been evident). An LCS has less DWT with less on it than a comparable convention hull. If weights less and displaces less water (it has to to get the speed). It also has less range at economical cruising speed than many GP frigates which are fitted with a greater array os systems and carry more weapons than the base LCS.


Stability............ yep the out riggers provde you transverse stability (how this is suddenly evidence of my culpability is beyond me as this has not been discussed). You have no way of know where the transverse or longtitudinal CoG is unless you have the intact stability data which I suspect you don't. The vessel design will be optimised for a given trim and I am certain that Austal have this sorted in the configuration of the ship, then are well versed in this................... but this does not mean you can increase the load on the ship beyond the design limits without impacting on performace. Sink the hull deeper and performance will drop off. Performacne will also drop off in a seaway due to issues such as tunnel slam and buring of the ourriggers ........... in addition to structural design. The LCS 1 will be less prone to the fun and games that comes with a multihull.


The other issue you miss is the vessel is built to a military version of he High Speed Craft Code. This permits certain relaxations with structure (including structural fire protection) in order to cater for the need for a lighter structure that can achieved the desired sustained speeds. The HSC code came into being largely due to efforts in Australia for fast ferry design and was adopted by the IMO.


Agree with "if a hull weighs less it displaces less water" and we have been saying tis since day 1. The fact is even if you can cut a hull weight to 2500 tonnes it does not mean you can then load it to the same maximum displacement of say 4000 tonnes in the same manner as a comparable convention vessel (length only). The problem with a small water plane area is it sumerges pretty quickly with weight. In short the total scope for crew, stores (including food and personal gear), helicopters (and all their stores, spares and weapons), weapons carried for fitted systems, fuel, water, other liquids (trust me there will be a few), any spares and tools (excluding fitted equipment) and the Mission Modules and all spares, stores, tools, liquids, weapons and ammunitions associated with them will come off your 500 to 700 tonnes.


Add more and you will increase your submerged area and impact upon performance. You may also apply additional stresses to the hull with may impact on hull integrity. There have been a number of steel cat designs and there are some which are built under the HSC CCode. This makes no fundamental difference to the general principal that there will always be a balance of how a vessel can be loaded and the greater the resistance of the sumerged area the more power required to push it as speed and the lower the limiting hull speed.


Basically you cannot suggest that reducing hull weight will result in greater uplift where the vessel has to operate at certain limits (max draft) in order to achieve its operattional speed.


Finally I am happy to agree where I err, you on the other hand choose to see this as justifiying your suggestions which are in error.

 

[justsomeaussie]

It is directly based off the commercial ferry design.

US Navy 21st Century LCS Freedom & Independence Classes

The design for Independence (LCS 2) is based on a proven high-speed trimaran (Benchijigua Express) hull. This trimaran hull will enable the ship to reach sustainable speeds of nearly 50 knots.