Royal New Zealand Navy Discussions and Updates

[ThePuss]

I can’t remember if this has been discussed before, but I think a relatively cheap and simple way of making Canterbury more stable would be to have a portable weight system. This could be as simple as a collection of concrete filled shipping containers that could be brought onboard and placed in the vehicle deck when she otherwise unladen.

As discussed above vehicle ferrys are designed for their optimum stability to be achieved when fully laden. So by adding these portable weights when empty of other cargo would lower the centre of gravity which would increase the metacentric height and thus increasing the righting arm, which would make her more "Stiff". She is obviously designed to carry the weight so why not put it in her?.

I post script the above in saying that I only know enough about stability to be dangerous

 

[t68]

I can’t remember if this has been discussed before, but I think a relatively cheap and simple way of making Canterbury more stable would be to have a portable weight system. This could be as simple as a collection of concrete filled shipping containers that could be brought onboard and placed in the vehicle deck when she otherwise unladen.

As discussed above vehicle ferrys are designed for their optimum stability to be achieved when fully laden. So by adding these portable weights when empty of other cargo would lower the centre of gravity which would increase the metacentric height and thus increasing the righting arm, which would make her more "Stiff". She is obviously designed to carry the weight so why not put it in her?.

I post script the above in saying that I only know enough about stability to be dangerous

I would have thought as it is a ferry design it would not always be loaded on the return journey, and would have some way of making her more stable, it might not be a problem from where it was suppose to operate.

Did someone from the RNZN/Tenix point out it flaws in her design and not learn any thing from the HMNZS Charles Upham.

How much weight would it need to make her stable when empty?

 

[Sea Toby]

I would have thought as it is a ferry design it would not always be loaded on the return journey, and would have some way of making her more stable, it might not be a problem from where it was suppose to operate.

Did someone from the RNZN/Tenix point out it flaws in her design and not learn any thing from the HMNZS Charles Upham.

How much weight would it need to make her stable when empty?

I would think any user of a ro-ro ship would do their best to avoid heavy seas when sailing empty. While I understand doing so is almost impossible for long voyages, its very possible for short voyages of a few days. Its not like amphibious operations are being conducted in sea state 10. Troops would drown before they reached the beach. Cruise lines don't tender in rough seas either.

I have seen cruise ships sail around storms at sea. I am sure a ro-ro could do so too. I would think if one is being used as a tender or as a supply ship, they would stick close to the troops or whatever its tendering.... These ships for military purposes aren't at sea 24-7 365 days of the year. Most of the time they are anchored...

Sometimes one has to bite a bullet, considering other factors.

 

[OPSSG]

I would think any user of a ro-ro ship would do their best to avoid heavy seas when sailing empty. While I understand doing so is almost impossible for long voyages, its very possible for short voyages of a few days. Its not like amphibious operations are being conducted in sea state 10. Troops would drown before they reached the beach. Cruise lines don't tender in rough seas either.

I have seen cruise ships sail around storms at sea. I am sure a ro-ro could do so too. I would think if one is being used as a tender or as a supply ship, they would stick close to the troops or whatever its tendering.... These ships for military purposes aren't at sea 24-7 365 days of the year. Most of the time they are anchored...

Sometimes one has to bite a bullet, considering other factors.

@Sea Toby, would this problem also apply to Singapore's Endurance Class (given that it is 6,000 tons empty and 8,500 tons at full load) or other such vessels too, given that the tank deck that runs the length of the ship? What about filling up the ballast tanks?

BTW, I'm a novice in naval matters and I'm struggling to understand some of the discussions.

 

[Todjaeger]

@Sea Toby, would this problem also apply to Singapore's Endurance Class (given that it is 6,000 tons empty and 8,500 tons at full load) or other such vessels too, given that the tank deck that runs the length of the ship? What about filling up the ballast tanks?

BTW, I'm a novice in naval matters and I'm struggling to understand some of the discussions.

Such a difference in weight I would expect would have an impact on how well/stabile a ship is when at sea or underway. Perhaps someone like Alexsa could comment, but as I understand it there are a number of factors which come into play. These are the length, beam, height and draught of a vessel, when both at full load, and 'empty', as well as (or perhaps more importantly) the location of a vessel's centre of gravity when fully loaded vs. empty.

If Singapore's Endurance-class normally has the vehicle deck fairly high above the waterline, that would suggest to me that the class would have a fairly low centre of gravity and should therefore be more stable in most conditions. Something which I have been trying to check without too much success unfortunately is what the unladen displacement of the Canterbury is, as well as where most of the extra laden weight is located on the vessel.

-Cheers

 

[ThePuss]

If Singapore's Endurance-class normally has the vehicle deck fairly high above the waterline, that would suggest to me that the class would have a fairly low centre of gravity and should therefore be more stable in most conditions. Something which I have been trying to check without too much success unfortunately is what the unladen displacement of the Canterbury is, as well as where most of the extra laden weight is located on the vessel.

-Cheers

Any vessel needs to as is much possible to place its heaviest components as low as practicable. So that is why all ships keep their heaviest items, i.e. engines, fuel and cargo as low as possible. Having a high vehicle deck would actually have the opposite effect to what you suggest. Cheers

 

[Todjaeger]

Any vessel needs to as is much possible to place its heaviest components as low as practicable. So that is why all ships keep their heaviest items, i.e. engines, fuel and cargo as low as possible. Having a high vehicle deck would actually have the opposite effect to what you suggest. Cheers

Perhaps I did not articulate that particularly well, but then again, I was a bit tired.

If the vehicle deck was located comparatively high above the waterline, my understanding has been that would raise a vessel's centre of gravity when the ship is fully laden, and by raising the center of gravity it reduces a ships stability. Is this correct?

WRT the Endurance-class, if the vehicle deck was located fairly high, but empty, would this not cause the vessel to have a lower centre of gravity, because the remaining displacement is things like the engines, machinery, fuel, etc which could be lower or below the waterline?

Please let me know if this (now somewhat re-worded) is correct so that I make sure I understand the concept correctly.

Thanks!

 

[ThePuss]

Perhaps I did not articulate that particularly well, but then again, I was a bit tired.!

All good mate, I do most of my posts in an inebriated state so I can relate. :drunk1

If the vehicle deck was located comparatively high above the waterline, my understanding has been that would raise a vessel's centre of gravity when the ship is fully laden, and by raising the center of gravity it reduces a ships stability. Is this correct?!

Absolutely.

WRT the Endurance-class, if the vehicle deck was located fairly high, but empty, would this not cause the vessel to have a lower centre of gravity, because the remaining displacement is things like the engines, machinery, fuel, etc which could be lower or below the waterline?!

If that was the case then yes, however my understanding is that on designs such as the Endurance the vehicle deck is either on the water line or on the waterline and the deck above.

Please let me know if this (now somewhat re-worded) is correct so that I make sure I understand the concept correctly.

Thanks!

No probs, Here to help

 

[RWC]

There is a difference between a seakeeping problem (as questioned by Lucasnz) and a stability problem. Stability is just as the name implies. Seakeeping is the vessel's motions in weather. They are very different and more often than not have conflicting solutions.

A vessel either meets stability requirements in a given condition or it does not. If it does not, it doesn't sail. Thus, I'd guess that it's more likely that the Canterbury has poor seakeeping characteristics than poor stability characteristics.

Stability problems are relatively easy to fix as noted by ThePuss. You can ballast down to reduce your VCG either with water ballast, solid ballast, or permanent solid ballast (concrete poured in the bilge). Seakeeping is a trickier issue.

The most common issues for seakeeping are pitch and roll. Pitch depends primarily on the length of the vessel, so there's really not much you can do about that. Roll depends on the metacentric height, but not in the same way as stability. The vessel will have a natural roll period depending on its shape and the metacentric height. If the natural roll period is close to the wave period, you get a lot of roll and people fall over. If the natural roll period is substantially less than the wave period, you get less roll, but the motions are quick (this is what happens with a "stiff" vessel, with a high metacentric height), which can also be bad for motion sickness. If the natural roll period is substantially more than the wave period, then you get slow, lazy motions, but this requires a low metacentric height, which often conflicts with stability requirements.

There are a couple of other solutions to roll problems which do not require adding or removing weight. You can add an anti-roll tank, you can add active fin stabilizers, or you can add bilge keels. These three are most often employed rather than trying to tune the VCG, as they don't require as many compromises in other aspects of the design.

I don't know what problem the Canterbury has, but I just thought I'd clear up the confusion between stability problems and their set of potential solutions and seakeeping problems and their rather different set of potential solutions.

 

[RWC]

For completeness, I'll also mention that seakeeping involves some elements other than motion, for example:

Propeller immersion - depends on length and draft
Water on deck - depends on freeboard and motions

I did a little reading on the Canterbury problems. It sounds like it has motion problems in high sea states and propeller immersion problems. Since the length and draft can't be changed, nothing much can be done about the propeller immersion except to derate the machinery and take best headings in high sea states.

Roll motions could be corrected by the methods mentioned above, but most likely won't be. I'd guess operational restrictions on heading in high sea states.

The interesting aspect (to me) of the evaluation is the critique of the choice to use a commercial design. It seems to be accepted by the NZ government that commercial designs have some intrinsincally inferior seakeeping ability to naval vessels. But really, the problem was in trying to convert a coastal RORO vessel to an open water MRV. Seakeeping doesn't have anything to do with commercial vs. naval design.

 

[OPSSG]

^^ Todjaeger, ThePuss and RWC, Just a note of thanks for all the above replies. It's much appreciated guys - it really helps.

 

[Twickiwi]

Ineressing

UK, Australia begin talks on future ship projects

"The UK has also engaged with its counterparts in New Zealand with regard to its ANZAC frigate replacement plans.

The UK Ministry of Defence (MoD) is expected to announce in February the start of a four-year assessment phase for the Future Surface Combatant (FSC) C1 variant.

Under a separate funding line, concept phase activities for a Future Mine Countermeasures/Hydrographic/Patrol Vessel (FMHPV), previously identified as FSC C3, are expected to commence in April 2010."

The discussion of C3 in the RN pages talk around a 2500t vessel and whether it should have a SAM. Rumours swirl around Venator as a C3 template.

Is C1/C2 really suitable as an ANZAC replacement?

 

[harryriedl]

UK, Australia begin talks on future ship projects

"The UK has also engaged with its counterparts in New Zealand with regard to its ANZAC frigate replacement plans.

The UK Ministry of Defence (MoD) is expected to announce in February the start of a four-year assessment phase for the Future Surface Combatant (FSC) C1 variant.

Under a separate funding line, concept phase activities for a Future Mine Countermeasures/Hydrographic/Patrol Vessel (FMHPV), previously identified as FSC C3, are expected to commence in April 2010."

The discussion of C3 in the RN pages talk around a 2500t vessel and whether it should have a SAM. Rumours swirl around Venator as a C3 template.

Is C1/C2 really suitable as an ANZAC replacement?

seems what goes around comes around as the AUS Navy joint funded few frigate programs with the RN the last being I think the T-21. Im not sure if they helped fund the Leander.

 

[StingrayOZ]

This is interesting. Some of the RN and RAN vessels could end up using the same systems or even the same hulls. Its interesting they also engaged the NZ, Im assuming NZ and Aust are also sharing data regarding the Anzac replacements.

Australia's ANZAC replacements are 7,000t as defined in the public white paper (and much has been disclosed to imply they are based on AWD hulls). Capable of BMD defence. Most likely with Auspar. Australia seems to pretty much know what it wants. I would assume this type of vessel would be able to meet the C1 requirements. The UK might perfer to buy into this program and get a very capable ship for not a whole lot of money and a common partner with 8 vessels. I would assume NZ would also be interested in 2 although no commitment has been made.

The C3 is very simular to the OCV project. Again, they might end up sharing systems, or even hulls.

It would be interesting for the RN, RAN and the RNZN if they ended up sharing two classes of ships. Training, development etc would be greatly enhanced and as a 10 (RN) + 8 (RAN) + 2 (RNZN) fleet thats 20 ships you start to get Burke like volumes and efficencies. Even if the RN goes for aster instead of SM, the ships would be very simular and need only differ in VLS.

C3 would tap into the RAN huge 20 ship order and add another 8 of which I would think NZ would also want some (atleast 3). Resulting in 30 hulls.

The requirements are pretty simular. That doesn't mean they will get the same ship (although there is hope), but it does mean everyone benifits from shared info and possibly shared systems.

 

[recce.k1]

Interesting indeed (and does anyone have subscribed access to the rest of that Jane's article)? As it only initially mentioned that UK was talking to NZ about the ANZAC replacements (but not NZ about the C3 vessels, despite NZ needing to replace its diving/MCM tender Manawanui and survey/towed array vessel Resolution in the next several years etc)?

Not wishing to delve into intergovernmental politics but is it an issue that the UK is talking with NZ (rather one would thought, Aust-to-NZ, seeing the operate the same Frigate type)? Probably not as I suppose this is quite normal (or is it a hint the original Australian Future Frigate is too large for NZ needs ... and possibly even the UK's??? ... hence talks to establish the optimum baselines and configurations ... for when tenders are called)?

Anyway the T23 Dukes were on the original ANZAC Frigate short list, back in the late 80's weren't they (T23/Meko 200 and a mod'ed OHP I vaguely recall??) but lost out (for whatever reason?) hence this cooperation is probably not unsual (and maybe a sign that with BAE Australia now a major player in the region, is being quick off the mark)....?

 

[spoz]

Interesting indeed (and does anyone have subscribed access to the rest of that Jane's article)? As it only initially mentioned that UK was talking to NZ about the ANZAC replacements (but not NZ about the C3 vessels, despite NZ needing to replace its diving/MCM tender Manawanui and survey/towed array vessel Resolution in the next several years etc)?

Not wishing to delve into intergovernmental politics but is it an issue that the UK is talking with NZ (rather one would thought, Aust-to-NZ, seeing the operate the same Frigate type)? Probably not as I suppose this is quite normal (or is it a hint the original Australian Future Frigate is too large for NZ needs ... and possibly even the UK's??? ... hence talks to establish the optimum baselines and configurations ... for when tenders are called)?

Anyway the T23 Dukes were on the original ANZAC Frigate short list, back in the late 80's weren't they (T23/Meko 200 and a mod'ed OHP I vaguely recall??) but lost out (for whatever reason?) hence this cooperation is probably not unsual (and maybe a sign that with BAE Australia now a major player in the region, is being quick off the mark)....?

The full article suggested that all three governments were talking on the sides of PAC 10. Australian requirements for MCM and SML replacements were mentioned but I don't have any memory of Resolution or Manawanui being specifically in there.

The two finalists in the ANZAC design were the Meko 200 and the Dutch M (Karel Doorman) Class. The Type 23 had been there early on but was (from memory) eliminated because it had too much of an ASW focus for what was then intended to be a Tier 2 patrol vessel (revisit DoA 87 is you're unsure aboutwhat that meant).

 

[alexsa]

The interesting aspect (to me) of the evaluation is the critique of the choice to use a commercial design. It seems to be accepted by the NZ government that commercial designs have some intrinsincally inferior seakeeping ability to naval vessels. But really, the problem was in trying to convert a coastal RORO vessel to an open water MRV. Seakeeping doesn't have anything to do with commercial vs. naval design.

Hmmm........... to say commercial designs are less capable than miltary designs in tesm of stability is a bit of a gross generalisation and not strictly correct. The issue is the approach.

In most cases commecial hulls are intended to operate over a proportionally larger displacement range than most military vessels. To do the the stability of the vessel must be flexible and calcuatled for all conditons expected during the voyage. Generally it is intended that commercial vessles sail loaded to a degree and light loading will casue problems including propeller immersion in heavy weather and the vessel being too stiff in some cases.

IMO criteria (if obeyed) and operating requirements of the vessle stability book should resolve isue of the vessl be so tender it will roller over but 'stiffness' is si sperate issue. Again the vessle will have operating limitatios and recommedation is its stability book but this does allow the vesle to be reasonably stiff where the conditions allow it.

The problem is where you thave purchased a vessel that allows you to carry a large load, relative to its dispalcement, for amphib purposes (which is where the commercial hull has a beniifit) this is likely to become a factor where you ty to operate it in a light condition as a patrol vessel..... particularly in trying conditions.

Permenant ballast and other options would have ot be very carefully considered as such mechanism detract from uplift capacity and may result in the likelihood that it is hard to avoid the vessel being stiff. Mobile ballast is a better idea but adding and removing such ballast take time and it needs to be secured.

A stiff vessel is not a good thing in respect of comfort as discussed, but it also has adverse consequences in respect of cargo securing (greater forces on lashing), hull stress and .......... dare I say it, helo operations.

 

[StingrayOZ]

Not wishing to delve into intergovernmental politics but is it an issue that the UK is talking with NZ (rather one would thought, Aust-to-NZ, seeing the operate the same Frigate type)? Probably not as I suppose this is quite normal (or is it a hint the original Australian Future Frigate is too large for NZ needs ... and possibly even the UK's??? ... hence talks to establish the optimum baselines and configurations ... for when tenders are called)?

The article does mention Australia, but then refers to communication to NZ counterparts, I assume they were already in contact with Aust already. I don't think it excludes any Australian options, but it is a bit ambigious.

No one has really decided on anything yet. The F-100 comes in a variety of sizes/displacements and it may not be what Australia builds its Anzac replacements on. But as I said previously, even if they don't share the same hull, systems I would imagine would be atleast compatable if not actually the same. I don't think the 7,000t is too big for what the UK is looking at, if it is at the right price. It proberly is too big for NZ. That 7,000t figure is created by lowering the draft. The F-100 floating in the water now are currently 6,250 full load as a full AEGIS ship. In reconfiguration that might drop to 5,900 ish depending on the load out, hangers etc. F-100 is only about 20m longer and 4m wider than a ANZAC, and approximately the same length as a Type-22 frigate and the displacement is not widely off the batch 3's.

Australia is deeply involved in Seapar and Auspar development, which is relevant for all involved.

I hope the bare minium to come out is that all navies are CEC compatable and capable.

 

[recce.k1]

Thanks for the clarifications Spoz and Stingray OZ.

I since re-read some other old info which mentioned the original ANZAC project came about when an Australian defence review from the early 80's identified a need for new RAN patrol Frigates. But that leaves me with further questions eg why didn't the RAN at the time acquire more FFG7's and simply run one class of ship (instead of both FFG7's & ANZAC's)?

Also if the T23 had too much of an ASW focus, was the Australian concept of the time to use the FFG7's mainly for ASW (and area air defence) and thus this left the door open for another (cheaper) class of vessel for general patrolling eg Meko200/ANZAC?

But that was then and this is now, and as you say Stingray the important thing, especially for NZ is to ensure whatever they replace their ANZAC's with, is indeed CEC compatable and capable with its partners. Otherwise presumably NZ has a (future) fleet that cannot realistically interoperate that well. Presumably too, seeing that the current RAN ANZAC's are starting to receive their ASMD/sensor upgrades that the current NZ ANZAC's receive a similar upgrade when(ever) that commences ...

 

[Tom Tom]

Thanks for the clarifications Spoz and Stingray OZ.

I since re-read some other old info which mentioned the original ANZAC project came about when an Australian defence review from the early 80's identified a need for new RAN patrol Frigates. But that leaves me with further questions eg why didn't the RAN at the time acquire more FFG7's and simply run one class of ship (instead of both FFG7's & ANZAC's)?

Also if the T23 had too much of an ASW focus, was the Australian concept of the time to use the FFG7's mainly for ASW (and area air defence) and thus this left the door open for another (cheaper) class of vessel for general patrolling eg Meko200/ANZAC?

But that was then and this is now, and as you say Stingray the important thing, especially for NZ is to ensure whatever they replace their ANZAC's with, is indeed CEC compatable and capable with its partners. Otherwise presumably NZ has a (future) fleet that cannot realistically interoperate that well. Presumably too, seeing that the current RAN ANZAC's are starting to receive their ASMD/sensor upgrades that the current NZ ANZAC's receive a similar upgrade when(ever) that commences ...

The NZ ANZACs are to defend NZ and its interests. They are not to defend Australia and their interests (or any other foreigners). If Australia cannot defend itself then they should look at themselves rather than whinging about some other country.

Be strong, NZ. Let the whingers deal with themselves - and if they cannot then to hell with them. Why should they bludge off us, the losers?