Cruise ship propulsion

[WorldTraveler151208]

I have a technical question, maybe someone will have an idea.

I have recently wondered why some modern cruise ships still have fixed propellers, despite the fact that most ships use the 360 degrees rotating azipods. The advantages of rotating azipods are clear: greater maneuverability and no need to install thrusters on the stern of the ship. So why on some cruise ships is the usual, stationary propulsion still chosen? An example of this are the Msc Fantasia-Class ships. What is also interesting, the ship model shows that this solution will also be used on Msc World Class ships. Is the use of azipods not possible on all cruise ships?

[UniPac]

Same for Seaside/Seaview. I asked the staff about that at the black party, they said they will get back to me with an answer - but didnt.

Too bad I didn‘t ask the Captain when I met hin on an earlier cruise.

Will ask again onboard in few weeks 🙂

Edited February 19, 2020 by UniPac

[cruisesafer]

Time ago I read somewhere that they are much more expensive than conventional propulsion and have a limitation on how much power they can transmit to the propeller, so for big ships it is not ideal. Also they offer different maneuvering characteristics than traditional shaft plus propeller systems that are not ideal for very large ships.

[sidari]

The Meraviglia class all have Azipods as do the Oasis class, it appears size has nothing to do with it.

[cruiseguyinorl]

Azipods tend to have much more mechanical difficulties than traditional propulsion. I imagine the cruise lines might take this into consideration as well.

Bret

[sidari]

A bit about different types of propeller.

 

https://shipinsight.com/articles/different-types-of-propulsion-systems-used-on-ships

 

 

[Bossa Nova]

Here's a Cruise Critic thread about the Smithsonian Channel's Mighty Cruise Ships episode on Celebrity Solstice. In this episode, the captain has to trade off cabin air conditioning vs. ship speed because the sea temperature is too high (>89 F) for the azipods to function properly. The episode also shows a crew member inspecting the inside of an azipod during the cruise.

https://boards.cruisecritic.com/topic/2107125-solstice-on-smithsonian-channel-tonight/

Unfortunately it appears that Smithsonian Channel has taken down all season 1 episodes from YouTube and their own paid service, so I cannot provide a link. (I had season 1 saved on Hulu and it's gone now, too.)

Edited March 1, 2020 by Bossa Nova
fix typo

[Essiesmom]

Where is @chengkp75 when we need him...  EM

[Hlitner]

There are pros and cons to both types of systems.  If Chengkp75 sees this thread he might jump in with the technical facts.  But you might consider that when Princess introduced its latest class of ships they also decided to go with fixed props.  While not getting into technical considerations you might consider that Azipod systems have a higher initial cost and come with their share of maintenance issues.  For example, Azipods will often require a drydock to make repairs that could easily be handled without drydock on fixed prop ships.

 

Hank

[AL3XCruise]

On 2/19/2020 at 1:15 PM, WorldTraveler151208 said:

The advantages of rotating azipods are clear: greater maneuverability and no need to install thrusters on the stern of the ship.

A couple of ship handling experts on this forum have pointed out that a well designed system with high lift rudders and sufficient bow/stern thruster power isn't really any better or worse than azipods in terms of maneuvering, just different in terms of how the crew manages it.  I remember speaking with an RCI captain years ago about this.  He had recently commanded one of the early pod-equipped ships in the fleet and was now master of a conventional one.  His opinion was the pods themselves made no difference versus thrusters and rudders, but he did appreciate that the newer ship had a lot more horsepower. 

 

On 2/19/2020 at 4:09 PM, cruisesafer said:

Time ago I read somewhere that they are much more expensive than conventional propulsion and have a limitation on how much power they can transmit to the propeller, so for big ships it is not ideal. Also they offer different maneuvering characteristics than traditional shaft plus propeller systems that are not ideal for very large ships.

On 3/2/2020 at 12:39 AM, Hlitner said:

  While not getting into technical considerations you might consider that Azipod systems have a higher initial cost and come with their share of maintenance issues.  For example, Azipods will often require a drydock to make repairs that could easily be handled without drydock on fixed prop ships.

 

I can't claim to be an expert, but I've seen @chengkp75 mention several times they are generally less expensive to install than a system comprised of twin shafts, rudders and associated equipment, and two to four stern thrusters.  

 

@cruisesafer: you may be seeing articles that refer to large cargo ships.  They generally use a completely different propulsion system than the diesel electric configuration on cruise ships.  There are no cruise ships currently in service or on the drawing board that exceed the capability of azipods.  

 

Big cargo ships tend to operate contentiously at one speed for days at a time, and most are powered by a single (occasionally two) very large engines bolted directly to the prop(s).  Cruise ships have more variable speed profiles, higher tops speeds, higher non-propulsion electrical loads, and other factors that favor multiple (commonly four to six) diesel generators providing power for electric motors (either in azipods or attached to a shaft).

 

I know current generation azipods have dramatically improved reliability and serviceability.  Some tasks that used to require a drydock no longer do with the newer designs.  The Chief, however, would be far better at explaining the relative details of servicing a modern azipod versus a more conventional system.

 

It is also worth noting that some ships are employing things like Rolls Royce's Promas system, which are largely conventional designs with hydrodynamic tweaks for efficiency.  I'm always skeptical of the marketing hype when it comes to efficiency, but these "advanced" prop and rudder designs seem to be attracting customers, either due to delivering on promises or aggressive pricing.

 

 

[MasterNotCommander]

Pretty much per the above posts, azipod's have increased initial and ongoing maintenance costs. Leaking seals is a common issue and very few ports appreciate seeing oil sheens around visiting ships. 

 Pods can provide significant manoeuvring advantages over stern thrusters for someone who knows how to drive them properly.

[HappyInVan]

You can't have a proper discussion without going into the details of the schematics and sales pitch. ABB has a nice library of these PDFs...

 

https://library.e.abb.com/public/590ce0d16e7d72f5c1257a330027e777/Azipod_XO_Presentation.pdf

 

NavArch64 made a startling discovery about the Nieuw Amsterdam's azipod malfunction.

 

https://boards.cruisecritic.com/topic/2726665-nieuw-amsterdam-azipod-technical-discussion/

 

Enjoy