Aratere.....oh boy.

[wheels 543]

First of all, I am not going to take the Media reporting as Gospel.

I forget who our Creworg member is that is on the "inside", but can he get us up to date with some accurate info if he is reading?

So from what I can confirm, the thing is going slow. The Media are saying 15min slower on a trip across, but I don't think that is quite correct...maybe... because it was reeeeealy late docking this morning and then they canceled the next trip back across. So either it is so slow it might be almost quicker to swim....if it wasn't so darn cold.....or there are other problems that delayed it.

Plus it didn't help that the Arahura used the Brail method of docking yesterday.

I bet there is a Manager or two banging their heads against a wall right now.

[Island Time 1,239]

Yep, seems like more of the same. Hayden (SOWID) whats the real story??

[waikiore 400]

Word is smaller props so less speed, presumably to lessen load on the shafts.

[Guest]

Radio is saying they put the old props back on but they can't keep up with the 11m extension whatever the f*ck that means

[Island Time 1,239]

Well, if that is the case it's incompetence. Should have been easy enough to have performance requirements written into the upgrade contract. Standard practice...

And how about the sea trial in Singapore? Surely they tested the speed and consumption?

[wheels 543]

You won't believe this, but she is probably going to Oz middle of next year for new Props. They are looking at having two new larger props made for it. Apparently the two props are too small. Yes I agree IT, surely they should have worked that out while still over there and even when she was back here, how did they not pick up the problem before she entered back into passenger service. She spent a week or more on Freight only. First sailings on Passenger service and they find its a problem??

I dunno, maybe we are not getting the whole story, but from what we are getting, it makes it all look rather pathetically managed.

[Brendon 0]

My understanding is that they put the props back on that were replaced with bigger props when the extension was made.

I guess that they thought that the bigger props were loading the drive system too much contributing to the shaft failure, so they returned to the smaller ones.

They did sea trials in Singapore which showed that they could get up to speed with the old smaller props. But that was in calm waters and perhaps not fully loaded, very different from Cook Strait.

Now it is here they find that she cannot maintain a fast enough speed in Cook Strait conditions to keep to a 3 sailing schedule, it is only in the order of 15 min per sailing, but that throws the whole schedule out. As the ferries share berthing facilities when one is behind schedule it can affect the others.

 

And so the saga continues...

[sow1ld 2]

OK I guess I better enter into the conversation. Imho the main issue the tere has, is it's time table. The extension very publicly cost a lot more than budgeted or expected. The only way to get those costs back was to make the tere work to earn her keep which meant three return sailings a day.

The down side to three sailings a day is that it only leaves 50minutes turn around. That's 50 minutes to unload passangers, cars, trucks, trains and then reload passangers cars trucks trains & take on fuel. Planes don't even load unload this quickly! You can see how one truck that won't start, a sick passenger requiring a ambulance, spring tides, a southerly makes that time impossible to keep.

Tere runs 6 days a week 3 sailings a day. The 7th day is a maintenence day but what happens is during the week she runs later and later and in order to NOT cancel sailings the 7th day (maintenence) day gets canceled so she can take sailings.

This means not only does maintenence day not happen but the engine's get pushed harder and harder to try and find time. The tere gets absolutely thrashed.

The bigger props and the two extra engines installed during the extension where to be called on help maintain time table if there was stronger tides or if she was late leaving the berth etc it was never intended to be pushed that hard day in day out. This break when driven hard continually as we all know.

The smaller props may only be 15 mins slower per trip which doesn't seem like much and isn't really but it's a huge deal on that time table. I think it's great they've found some props that will get the speed back up without working at near peak shaft loading. Let's not forget where not dealing with your standard 16"x12 briski here.

 

Testing at dry dock is basically to make sure it floats and that's about it. Dry docks cost over 30k a day. Everyday it's empty costs the yard money. The moment you're out of the dock there's another ship waiting to go in. I've had a main engine crap out 30 mins into a return trip home after a dry dock.

 

So during testing they discovered the ship was a tad slower. What could they do about it? Go back into the dock and wait until next year until the new props are made? Or put the bigger props that are on the verge of peak shaft hp? Or head for home and get the service going again and work on the next step.

 

Let's keep in mind that choosing a prop for a roro ship like the tere takes month's and month's of pretty clued up people running number's and calculations like you wouldn't believe. It's not like picking one for the 36 yanmar.

 

The prop shaft engine loadings are calculated for loadings that your likely to see with some level of redundancy. Just like building a boat and plenty of them break all the time just like in the last fiji race. Sometimes the loads are just too high.

 

And finally phew marathon post sorry guys! Parking these things.

 

From time to time you do hit the warf the average roro has 1hp to ton. So putting that into perspective next time it's blowing it's ass off and you're running late to be some where try parking with only 6hp and see how u get on.

Repeat that operation 2190 times (number of docking procedures a year) andc get back to me with your results!

[wheels 543]

Thanks SOW, and no it's not too long a post. I had thought the Ship sailed night crossings also. Or is that just a summer thing?

Sooo could it be said that at a very upper level management area, or perhaps a bad set of numbers supplied by the Designers, there has been a major stuff up by lengthening the Ship and not taking into consideration the loads the Shafts have to take??? I certainly understand that Props are not simple and off the shelf. But someone somewhere in the picture has made some poor judgment. As you say, these ships are being used in a tuff piece of Ocean, but alterations should have taken that into account.

[sow1ld 2]

They run 24/7 normally late night sailings are dangerous goods (I use to think bombs and stuff but mainly chemicals doh) so limited number of passengers.

Lengthening ships is very common throughout the rest of the world and has worked very successfully I think the major problem here is the part of the world we are in. Normally sea state pattern frequency wave period etc are taken into account when contemplating lengthening. The issue wellington has is that the sea state etc can very so much. Big ocean swells in the strait, big short confused seas at karori, 6 return trips a day. I think this may have been overlooked or not understood fully when considering the lengthening job .

[snippys_dad 0]

This makes me wonder if its all my fault eg left booking at xmas to last minute due work , finally went to book prop fell off , 12 hours late , que easter wek end still slack to book , secured a booking only to have it cancel d last minute due to replacement ferry hitting a inanimate object , must be boats and me .

[sow1ld 2]

Does seem like it all adds up to be your fault lol. You havnt book on any planes lately? !

[Guest]

Sounds like the Aratere has been thrashed harder than Winnies liver....he should remember that next time he slings mud!

[Guest]

I am not a marine engineer, but I've owned a few boats and listened to a few experts over time.

 

My take on the Aratere case is as follows:-

 

If you increase engine horsepower you increase torque on the shaft.

Similarly, if you increase prop size or pitch you increase torque.

 

When altering Aratere, they increased the length (therefore the displacement) of the vessel and, to compensate, added larger props.

 

Quite obviously, they didn't allow for the increased torque on the shafts and one propeller literally screwed its shaft to breaking point. It was only a question of time before the other shaft suffered a similar fate.

 

Now, without admitting any of the above, they have replaced the larger propellers with the originals. The

vessel suffers, in consequence, from inadequate power.

 

I guess the real question now is can they fit higher grade steel shafts to accomodate larger propellers - i.e. increased torque.

[wheels 543]

You have it pretty much in the Nutshell David.

One question I have, is this Ship Diesel Electric? SOW has commented a couple of times now about the Ship having added two more engines to make a total of Four. So unless they are added in front of the originals and driving in tandem, I was wondering how they would be coupled to the shafts.

[w44vi 17]

I though the diesel motors were just connected to generations and so only electric motors on the shafts

[grant 40]

I though the diesel motors were just connected to generations and so only electric motors on the shafts

 

correct, they added more generating capacity, i think part of the reason was so that the generators providing power to the shaft motors don't have to provide power to the other parts of the ship as well.

[sow1ld 2]

She's got a total of 6 engines running on heavy fuel. 4 are around 4,500kws each and the other 2 are around 1,200kws each. They run constant rpms and feed electrical power to a main board which then sends power to two megastars (basically eletric motors) that drive to shafts.

The beauty of this system is that any engine can feed power to the board which supplies power to the bow thrusters and also ships supply (lights hydraulics, galley ac etc) the board megastar conbination also makes changes in load easier on the main engines.

The downside is that the props aren't cpp (controlled pitched propellers) so docking becomes harder as the shafts have to come to a complete stop before changing direction and the megastar requires a large amount of cooling.

When extra load is applied the weakest link is usually the cooling system which causes concern first, generally long before any mechanical failures present themselves.

Normally we run a lt and a ht system. The lt is basically a fresh water system cooled by salt water and variation in temp isn't that critical. The ht hight temp cooling is very critical in how it's controlled and monitored. Ht cools things like the turbos injectors liners etc as an example liners don't like much more variation than ten degrees between the water entering and the water exiting. Much more than that and they start cracking and at 500kgs each it's and expensive fix!

This shaft thing is highly usual and no one so far in their entire careers has seen this sort of failure before.

Maybe we should do away with this whole shaft thing and get some big ass jet units. Imagine the rooster tails

[rigger 47]

The downside is that the props aren't cpp (controlled pitched propellers) so docking becomes harder as the shafts have to come to a complete stop before changing direction and the megastar requires a large amount of cooling.

 

Could never understand why they went for FPP over CPP. Probably made it a cheaper build...

[sow1ld 2]

Me either especially with the amount of docking it had to do. I hear the whole build was on the c#@&p!