Anyone Interested in Ships

[KeithMacdonald]

2 hours ago, jjb1970 said:

No idea what this is.

 

 

J.F.J. De Nul, a dredger

https://www.vesselfinder.com/vessels/details/9260677

[WessexEclectic]

14 hours ago, jjb1970 said:

The arguments for catamaran designs are nothing like as clear cut as advocates insist, it's down to use case which makes more sense.

Pentamaran's are where it's at....

[The Johnster]

My somewhat inexpert view is that multihulls are fine for smooth water use such as rivers, smaller lakes, coastal inshore &c, and as sailing craft are very effective and fast downwind.  I am less convinced of their value in offshore/open sea situations, where they offer fast passages but are vulnerable to cancellation in heavy weather and seem even in moderate seaways to spend a lot of effort lurching about in a way that a monohull doesn't. 

[jjb1970]

11 hours ago, WessexEclectic said:

Pentamaran's are where it's at....

 

I remember the RV Triton which was built to trial a catamaran future frigate concept. At the time there was a lot of advocacy that the T23 replacement should be a multi-hull, the problem was that as with the 'short fat' advocates those promoting it stressed the virtues without also considering whether those virtues were necessary in a sub-hunter or compatible with the fundamental performance need of a sub-hunter (to be quiet and provide a good sonar platform/towed array carrier). The BMT penta form seemed to evolve from all the work they did on multi-hull combatant concepts which led to Triton.

[jjb1970]

When this ship hit the water in 1996 it would have been quite a big ship, now it's a feeder ship.

 

[admiles]

22 hours ago, jjb1970 said:

No idea what this is.

 

 

A dredger according to Marine Traffic.

[KeithMacdonald]

13 hours ago, The Johnster said:

My somewhat inexpert view is that multihulls are fine for smooth water use such as rivers, smaller lakes, coastal inshore &c, and as sailing craft are very effective and fast downwind.  I am less convinced of their value in offshore/open sea situations, where they offer fast passages but are vulnerable to cancellation in heavy weather and seem even in moderate seaways to spend a lot of effort lurching about in a way that a monohull doesn't. 

 

Portsmouth to Jersey is c.10 hours on the Condor Commodore Clipper (monohull). Slow and relaively sedate.

Poole to Jersey on the Condor Voyager is c.4 hours. My wide calls it the Vomit Comet.

[jjb1970]

On our recent long weekend in Batam the outbound ferry was a twin hull wave piercing type and coming back was a monohull. The wave piercing design was much smoother, the monohull was slamming quite heavily, especially when crossing the wake of ships going through the strait.

[Flanged Wheel]

In 2017, we took the fast catamaran vehicle ferry from Portland, Maine to Yarmouth in Nova Scotia. This was a sizeable craft, leased from the US Navy who had originally purchased it to work in Hawaii.

 

The sea state was not particularly high but it had a terrible motion. Most people were lying around and not enjoying the trip. My main memory of the crossing is watching the news coverage of the USS Fitzgerald collision, particularly poignant as I was working with the US Navy at the time.

 

When we got there, Nova Scotia was superb and if you get chance to go, I thoroughly recommend it. They have a floating Flower Class corvette in Halifax!

[jjb1970]

There's been a huge amount of research and development on Hull form in recent years to improve comfort, reduce Hull stresses and improve efficiency (I will let people form their own view on the relative importance of these drivers).

 

A lot of this (most) has focused on bow form, followed by the stern. At one time (and still today for many designs) the bow form maximised bouyancy, and controlling the bow wave with deigns optimised for calm conditions. However heavily flared bow contours above the waterline lead to riding over waves and heavy slamming which is uncomfortable and causes high hull stresses.

 

Modern theory is to go through waves and swell and to design for efficiency in a wider range of representative conditions. Hence the prevalence of ships using the X-bow, axe bow and similar configurations. The difference to comfort levels can be huge, especially ships with fwd accommodation. I spent time on an offshore vessel with an X-bow and afterwards would be loathe to return to a more conventional design.

[jjb1970]

I posted pics of the X-bow somewhere in the distant past of the thread, but for those who have never seen a ship with the X-bow here is an example.

 

[peach james]

On 15/04/2024 at 19:44, jjb1970 said:

 

I remember the RV Triton which was built to trial a catamaran future frigate concept. At the time there was a lot of advocacy that the T23 replacement should be a multi-hull, the problem was that as with the 'short fat' advocates those promoting it stressed the virtues without also considering whether those virtues were necessary in a sub-hunter or compatible with the fundamental performance need of a sub-hunter (to be quiet and provide a good sonar platform/towed array carrier). The BMT penta form seemed to evolve from all the work they did on multi-hull combatant concepts which led to Triton.

But, in a more realistic look at multi hulls, is the SWATH ships of the SURTASS system.  So there potentially is an argument in favor of the use of multi hull forms for the role of the T23's.  (which, like the CPF, are designed as very quiet ships for ASW work...)

(I snipped some rather specific RCN stuff...)

James

[jjb1970]

Some ships going in/out of Pasir Gudang through the passage between Changi Beach and Pulau Ubin in Singapore. Pasir Gudang is a port in Johor, Malaysia, just to the East of Johor Bahru. There is a container terminal in Pasir Gudang but it's been overtaken by the newer port of Tanjung Pelepas on the West side of Johor Bahru which is massively bigger than Pasir Gudang container terminal. 

 

[jjb1970]

On 17/04/2024 at 11:35, peach james said:

But, in a more realistic look at multi hulls, is the SWATH ships of the SURTASS system.  So there potentially is an argument in favor of the use of multi hull forms for the role of the T23's.  (which, like the CPF, are designed as very quiet ships for ASW work...)

(I snipped some rather specific RCN stuff...)

James

 

SWATH is one of those ideas which has persuasive arguments in its favour for very specific use cases, particularly where stability in the sense of vessel movement (as opposed to naval architectural stability) is important. However I'm not sure it'd be appropriate for a combatant design as they tend to be problematic in damage scenarios (as with most multi-hull types). 

[KeithMacdonald]

2 hours ago, jjb1970 said:

However I'm not sure it'd be appropriate for a combatant design as they tend to be problematic in damage scenarios (as with most multi-hull types). 

 

Like a three-legged stool after one leg breaks off?

 

[peach james]

On 19/04/2024 at 08:59, jjb1970 said:

 

SWATH is one of those ideas which has persuasive arguments in its favour for very specific use cases, particularly where stability in the sense of vessel movement (as opposed to naval architectural stability) is important. However I'm not sure it'd be appropriate for a combatant design as they tend to be problematic in damage scenarios (as with most multi-hull types). 

I'm really quite doubtful of the usefulness of most designs post combat damage- survival of crew is vital, but of hull is likely unimportant beyond keeping the crew alive.  Lets face it, no ship's taking even a Harpoon  Exocet inboard and still fighting.    So SWATH which has some quite serious advantages with regards to ASW may be appropriate to a ASW Frigate design.  I'm equally sure that since most designs are now back to being "generalists" that ASW Frigates are somewhat right now passe.

[Johann Marsbar]

It's that Condor moment........

 

 

 

 

...all at St Peter Port last week, plus this deposited a load of rather lost looking tourists on Guernsey for about 8 hours last Thursday......

 

[St Enodoc]

A short holiday let me take this:

 

[jjb1970]

On 24/04/2024 at 00:10, peach james said:

I'm really quite doubtful of the usefulness of most designs post combat damage- survival of crew is vital, but of hull is likely unimportant beyond keeping the crew alive.  Lets face it, no ship's taking even a Harpoon  Exocet inboard and still fighting.    So SWATH which has some quite serious advantages with regards to ASW may be appropriate to a ASW Frigate design.  I'm equally sure that since most designs are now back to being "generalists" that ASW Frigates are somewhat right now passe.

 

The ability to absorb a missile strike without total loss is subject to multiple variables, but as with almost any engineered system the risk controls for warship design aren't based on worst possible scenario (which tends to be impracticable) but either worst credible scenario or a scenarios defined by regulation or user. Documents like the naval ship code/ANEP77 basically call out the concept of operations to define the degree of damage and functionality but most damage incidents aren't missile strikes but regular accidents such as allision and collision.

[J. S. Bach]

8 hours ago, jjb1970 said:

 

 ..snip...  but regular accidents such as allision and collision.

Thank you, I learned a new word today! I have honestly never heard it before. From Merriam - Webster:

"Allision is an obsolete word that means the action of dashing against or striking upon, or the running of one ship upon another ship that is stationary."

[jjb1970]

54 minutes ago, J. S. Bach said:

Thank you, I learned a new word today! I have honestly never heard it before. From Merriam - Webster:

"Allision is an obsolete word that means the action of dashing against or striking upon, or the running of one ship upon another ship that is stationary."

 

Sadly, few maritime regulators other than the USCG seem to know it these days and use collision for ships hitting both moving and stationary objects. Another one is riparian, in Europe many maritime regulators no longer know the difference between riparian and littoral. 

[chipbury]

I first learned of the word allision after we (an offshore windfarm vessel jacked up in port) were hit by another vessel. 
They still tried to say it was our fault!

[WessexEclectic]

13 minutes ago, jjb1970 said:

Another one is riparian, in Europe many maritime regulators no longer know the difference between riparian and littoral. 

Meanwhile, in the UK, some inland Local authorities appear to have never even heard of the former, despite having a major UK river flow through their boroughs...

[KeithMacdonald]

On 25/04/2024 at 14:08, St Enodoc said:

A short holiday let me take this:

 

 

Goodness gracious me! I've been on that. Picton to Wellington.

[jjb1970]

Some visitors today.