Explorer propulsion problem....

On other ships of this class if there is an issue with the center fixed pod they have removed the blades until such time they can make repairs to the pod... usually when the ship goes into drydock. Removing the blades not only reduces drag, but also prevents auto rotation of the pod while the ship is underway possibly aggravating the original problem. Loss of use of the center pod just trims the top speed a tad, the ship can still do close to 20 knots.

Haven't been following this thread too closely, and too lazy to go back and read it all. I remember some early comments about a bent pod shaft causing vibration, but I don't find that too likely. Azipod shafts are fairly short and stout, and not prone to bending. Vibration would more likely be caused by bent propeller blades or bad bearings. If one or more blades are damaged, they could be removing them for repair and getting them back in a couple of weeks. The yard in Freeport is more than capable of repairing blades of this size. If it is a bearing issue, it would be one of the two roller support bearings, not the more common failure of the thrust bearing, and this would, even for the newer style pods, require drydocking to repair, so the fixipod will be out of service until the next drydocking.

Loss of the fixipod is not critical. As you say, they will be able to make at least 19 knots on two pods. Now, loss of one of the azipods would be different, as this removes the redundancy from steering, and would trigger the requirement for tug escorts while entering and leaving ports, particularly in the US.

Loss of the fixipod is not critical. As you say, they will be able to make at least 19 knots on two pods. Now, loss of one of the azipods would be different, as this removes the redundancy from steering, and would trigger the requirement for tug escorts while entering and leaving ports, particularly in the US.

chengkp75, your posts are always so informative. Thank you!

We were on the Explorer last week and did feel some vibration in the aft, but I'm not sure whether it was "normal" or due to propeller issues. We were able to go 19 knots from Saint John to Halifax.

I'm curious what "redundancy from steering" means? Does that mean with only one azipod left, there's no backup?

Pretty smart what they can do now days isn't it

Sent from my iPhone using Forums

chengkp75, your posts are always so informative. Thank you!

 

We were on the Explorer last week and did feel some vibration in the aft, but I'm not sure whether it was "normal" or due to propeller issues. We were able to go 19 knots from Saint John to Halifax.

 

I'm curious what "redundancy from steering" means? Does that mean with only one azipod left, there's no backup?

A rudder and propeller equipped ship will have one rudder for each of the (normally) two propellers. Each rudder will have two electric driven hydraulic pumps to turn the rudder. So each rudder will have two redundant systems, for a total of four means of steering the ship. A ship with two azipods will generally again have two either electric motors, or two electric driven hydraulic motors to turn the azipod, so, again, you have four means of steering.

The problem with azipods is that if the main propulsion motor in the pod fails (like the thrust bearings that have failed on several ships), you not only lose one redundant propulsion system, you lose the two redundant steering systems on that pod as well.

A ship with two propellers and rudders, could lose the port propulsion motor, and still steer with both rudders, or with just the starboard rudder if the steering motors on the port side failed as well. With pods, if the main motor in one pod fails, and the steering motors on the other pod failed, you're out of luck steering. Neither scenario is likely, but possible, and one of the drawbacks of podded propulsion.

So, when a ship loses some redundancy in steering, either an azipod or a steering motor, the USCG in particular, will require a tug escort for the entire time the ship is maneuvering in port (in NOLA for example, all the way up and down the river), to assist if the remaining steering fails.

So, while a ship running on only one azipod does have redundancy in steering (the two motors to turn the remaining pod), loss of the one system (the failed azipod's main motor) has removed two of your layers of steering redundancy. And since ships with azipods don't have stern thrusters, loss of both azipods, while still allowing propulsion on the fixipod, if there is one, severely reduces the ability to maintain the ship's heading.

Even with the prop being bad, we had no problems with our Canada/New England cruise last week. You should be fine. The ship doesn't have to go the high speeds to make the ports.

 

Happy sailing. Hope you have a great cruise. I know we did.

 

 

Gwen :)

The 9 day Bermuda/Caribbean itinerary has been late to some of the ports. It will be interesting to get reports when that itinerary resumes Sep 25th.

I'm on the September 25 th 9 day itinerary. . I'll let you know.

Sent from my SPH-L720 using Forums mobile app

Just read this entire very informative thread - a lot of reading in one sitting! I want to ask about an earlier post that alluded to other problems on the Explorer - namely, "toilet problems" and "Code Delta."

We were on Explorer in 2011 and spent the better part of the cruise talking with fellow cruisers about the "poo poo smell" in the aft elevator shaft. Is this the toilet problems you refer to? I thought this was fixed.

Also please elaborate on "code Delta" problems - isn't that at-sea disaster with multiple casualties???!? :eek:

We are cruising on Explorer on the 10/23 last round trip out of Bayonne, so I am anxious for answers.

Thanks in advance,

Dena

I was on the ship 8/23 to bermuda. Capt James explained it as a problem with an azipod. Ship still made 19 knots after whatever they did in Bermuda. I never felt any abnormal vibration. I can't say as tho I ever smelt any sewer either. The only sewer was Bermudas weather! LOL

My husband and I will be on the ship Sept. 25th as well. Hoping all the kinks and repairs are worked out prior to our sail!

A rudder and propeller equipped ship will have one rudder for each of the (normally) two propellers. Each rudder will have two electric driven hydraulic pumps to turn the rudder. So each rudder will have two redundant systems, for a total of four means of steering the ship. A ship with two azipods will generally again have two either electric motors, or two electric driven hydraulic motors to turn the azipod, so, again, you have four means of steering.

 

The problem with azipods is that if the main propulsion motor in the pod fails (like the thrust bearings that have failed on several ships), you not only lose one redundant propulsion system, you lose the two redundant steering systems on that pod as well.

 

A ship with two propellers and rudders, could lose the port propulsion motor, and still steer with both rudders, or with just the starboard rudder if the steering motors on the port side failed as well. With pods, if the main motor in one pod fails, and the steering motors on the other pod failed, you're out of luck steering. Neither scenario is likely, but possible, and one of the drawbacks of podded propulsion.

 

So, when a ship loses some redundancy in steering, either an azipod or a steering motor, the USCG in particular, will require a tug escort for the entire time the ship is maneuvering in port (in NOLA for example, all the way up and down the river), to assist if the remaining steering fails.

 

So, while a ship running on only one azipod does have redundancy in steering (the two motors to turn the remaining pod), loss of the one system (the failed azipod's main motor) has removed two of your layers of steering redundancy. And since ships with azipods don't have stern thrusters, loss of both azipods, while still allowing propulsion on the fixipod, if there is one, severely reduces the ability to maintain the ship's heading.

But most ships with azis also have plenty of bow thrusters. Which greatly helps the turning radias of large ships. So in the event you lose the motor which turns one pod you still have multiple bow thrusters to aid the remaining functioning pod.

Azipod systems are functionally a better system for cruise ships and the conditions they experience.

But most ships with azis also have plenty of bow thrusters. Which greatly helps the turning radias of large ships. So in the event you lose the motor which turns one pod you still have multiple bow thrusters to aid the remaining functioning pod.

Azipod systems are functionally a better system for cruise ships and the conditions they experience.

The Bow Thrusters only move the bow of the ship from side to side. What Chengkp75 is saying ships also need at least 2 azipods working. If they only have one azipod working and it fails there will be no way to control side movement at the stern of the ship. It will crash into something. That's why the need the tugs if only one azipod is working.

But most ships with azis also have plenty of bow thrusters. Which greatly helps the turning radias of large ships. So in the event you lose the motor which turns one pod you still have multiple bow thrusters to aid the remaining functioning pod.

Azipod systems are functionally a better system for cruise ships and the conditions they experience.

The thing about bow and stern thrusters is that they are designed to be thrusters, not propulsion. The faster the ship goes, the less effect a thruster has, due to the water flow past the thruster tunnels. At 18 knots, the thrusters will have a very low efficiency. Also, when a ship is underway, the turning axis (the vertical axis that the ship will turn around) moves from the midships position (stationary turning) to a point about 1/3 of the length back from the bow. Therefore, when moving ahead, stern thrusters are more effective at turning the ship than bow thrusters. Similarly, when going astern, the turning axis moves to 1/3 from the stern, so that is when bow thrusters exert a greater lever arm in turning the ship.

IMHO, I don't agree that azipod propulsion is "functionally" a better system for cruise ships. The major advantage of pods is a slightly better propeller efficiency, and a lesser capital cost ( 1 pod = 1 propulsion motor/shaft/propeller, 1 rudder, and 1 or 2 thrusters). A twin screw ship, with twin Becker rudders, and bow and stern thrusters, when handled by a good ship handler will maneuver as well as or better than a podded ship.

The thing about bow and stern thrusters is that they are designed to be thrusters, not propulsion. The faster the ship goes, the less effect a thruster has, due to the water flow past the thruster tunnels. At 18 knots, the thrusters will have a very low efficiency. Also, when a ship is underway, the turning axis (the vertical axis that the ship will turn around) moves from the midships position (stationary turning) to a point about 1/3 of the length back from the bow. Therefore, when moving ahead, stern thrusters are more effective at turning the ship than bow thrusters. Similarly, when going astern, the turning axis moves to 1/3 from the stern, so that is when bow thrusters exert a greater lever arm in turning the ship.

 

IMHO, I don't agree that azipod propulsion is "functionally" a better system for cruise ships. The major advantage of pods is a slightly better propeller efficiency, and a lesser capital cost ( 1 pod = 1 propulsion motor/shaft/propeller, 1 rudder, and 1 or 2 thrusters). A twin screw ship, with twin Becker rudders, and bow and stern thrusters, when handled by a good ship handler will maneuver as well as or better than a podded ship.

The efficiency isn't in the open seas. The reason cruise ships use azipods and bow thruster combo's is for the simple fact it allows the large ships to maneuver inside ports and other tight areas that prop and rudder just wouldn't. You would need tugs for those ships. An oasis class ship can park itself without any tugs. Sideways. A prop and rudder ship cannot. That is why all new cruise ships use this system. I agree in the open water the pods are no longer advantageous over the rudder and prop.

The efficiency isn't in the open seas. The reason cruise ships use azipods and bow thruster combo's is for the simple fact it allows the large ships to maneuver inside ports and other tight areas that prop and rudder just wouldn't. You would need tugs for those ships. An oasis class ship can park itself without any tugs. Sideways. A prop and rudder ship cannot. That is why all new cruise ships use this system. I agree in the open water the pods are no longer advantageous over the rudder and prop.

Sorry, but virtually no cruise ship that I know of, many of which are prop and rudder, actually uses tugs to dock (no one wants those ugly tires the tugs use to mark the white paint). I have seen a twin screw ship, equipped with Becker rudders, move the stern directly sideways without using the stern thrusters. I have seen pushboats on the Mississippi river that have three propellers and rudders, but no thrusters whatsoever move sideways. It all depends on the skill of the ship handler. You "split" the screws (one ahead and one astern) and put the rudders hard over to the direction you want the stern to go, and away it goes. The Becker rudders have trim tabs on them to create "lift" like an airplane wing so that the rudder "lifts" in the direction steered, pulling the stern in the opposite direction.

I have been on prop and rudder ships that can turn in their own length in a harbor that was less than twice the ship's length. In fact, the one class of the largest container ships in the world, the Emma Maersk, has only one propeller and rudder, yet is capable of docking unassisted because of two bow and two stern thrusters. The main reason cruise ships use azipods is capital expense. When you are shelling out a billion dollars for a ship, you try to save wherever you can.

On other ships of this class if there is an issue with the center fixed pod they have removed the blades until such time they can make repairs to the pod... usually when the ship goes into drydock. Removing the blades not only reduces drag, but also prevents auto rotation of the pod while the ship is underway possibly aggravating the original problem. Loss of use of the center pod just trims the top speed a tad, the ship can still do close to 20 knots.

I just got back from this cruise today where the screen captures were made. Personally, at the times I went past the barge, I never saw the blades on it. We were at the Top Tier function when were were informed that yes divers were working on the fixipod for the two days we were there and as a result, the captain was not able to attend the function since there was some final paperwork to clear up and that also caused us to have a slight delay in leaving. However, we never had an issue with the propulsion. We did get up to 19+ knots on our way home and yes we were only running on the two azipods. I actually went to the stern going to and from Bermuda and saw the water coming out from the two azipods with nearly quiet water coming out where the fixipod is. BTW, I did ask one of the senior officers and it was stated that there was no bent shaft on the fixipod.

The efficiency isn't in the open seas. The reason cruise ships use azipods and bow thruster combo's is for the simple fact it allows the large ships to maneuver inside ports and other tight areas that prop and rudder just wouldn't. You would need tugs for those ships. An oasis class ship can park itself without any tugs. Sideways. A prop and rudder ship cannot. That is why all new cruise ships use this system. I agree in the open water the pods are no longer advantageous over the rudder and prop.

And actually, my comments were about redundancy in steering, not necessarily for docking, hence my comments about ship's speed. If a ship has lost some of its steering redundancy, whether it is pods or rudders, the USCG will require the tug escort for the entire time the ship is in restricted waters. For NYC that would mean a tug would need to be escorting the ship from the Ambrose light to the dock, in NOLA that would be all the way down the river to the Southwest Pass, in Baltimore all the way to Cape Henry, and in Miami or PC, from the dock until the sea buoy. During some of these long maneuverings, the ship will be doing 10-12 knots, and thrusters will be ineffective at steering the ship. Combining steering and propulsion in one unit like a pod allows for failure of one component to remove two functions.

I just got back from this cruise today where the screen captures were made. Personally, at the times I went past the barge, I never saw the blades on it. We were at the Top Tier function when were were informed that yes divers were working on the fixipod for the two days we were there and as a result, the captain was not able to attend the function since there was some final paperwork to clear up and that also caused us to have a slight delay in leaving. However, we never had an issue with the propulsion. We did get up to 19+ knots on our way home and yes we were only running on the two azipods. I actually went to the stern going to and from Bermuda and saw the water coming out from the two azipods with nearly quiet water coming out where the fixipod is. BTW, I did ask one of the senior officers and it was stated that there was no bent shaft on the fixipod.

Thanks for the update.

Forgive my ignorance.

"only running on the two azipods" - should be running on three?

"We did get up to 19+ knots" - is that typical "top" speed?

Thanks,

IC

Thanks for the update.

 

Forgive my ignorance.

 

"only running on the two azipods" - should be running on three?

 

"We did get up to 19+ knots" - is that typical "top" speed?

 

Thanks,

IC

The ship has 4 bow thrusters to turn the bow and 3 propulsion pods in the stern. The center pod is a fixed position pod meaning it does not turn to assist the steering of the ship. The port (left) and starboard (right) azipods were the ones that were being used as we sailed back to Bayonne. The fixed pod has the issue and is not running (at least up to the point we left the ship in Bayonne).

Top speed for the Explorer is quoted at 23.7 knots but I do not believe they ever run it at that top speed even with all three pods running. I think the most I have ever seen is 22 knots. We did reach just shy of 20 knots on our return home.

The efficiency isn't in the open seas. The reason cruise ships use azipods and bow thruster combo's is for the simple fact it allows the large ships to maneuver inside ports and other tight areas that prop and rudder just wouldn't. You would need tugs for those ships. An oasis class ship can park itself without any tugs. Sideways. A prop and rudder ship cannot. That is why all new cruise ships use this system. I agree in the open water the pods are no longer advantageous over the rudder and prop.

Not all new builds are using pods. A few notable exceptions are Norwegian Epic, Disney Dream and Disney Fantasy.

If I'm reading this correctly Explorer arrived in St. Maarten today at noon, an hour ahead of schedule.

If I'm reading this correctly Explorer arrived in St. Maarten today at noon, an hour ahead of schedule.

If I'm reading this correctly Explorer arrived in St. Maarten today at noon, an hour ahead of schedule.

I think I read this wrong initially.

I'm now thinking:

• arrived Bermuda 8:43 (scheduled 8:00), departed 4:04 (scheduled 4:00)
  
• arrived St. Maarten 1:01 (scheduled 8:00), departed 8:42 (scheduled 8:00)
  
• arrived Puerto Rico 6:13 (scheduled 7:00)
  

On the Explorer. . No issues with propulsion that you would notice. . Except. . Left Bermuda 1 hour early and Labadee scheduled 1 hour earlier departure

Sent from my SPH-L720 using Forums mobile app

We arrived on all ports on time. . Early to pr. .I got up at 530 and we were docked

Sent from my SPH-L720 using Forums mobile app

So strange. We were aboard her in August. The fixed propeller was removed in bermuda on that cruise as well. Seems as though they would have it figured out a month later. As far as the Norwegian Epic, They opted for Prop/Rudder on that build? Wow cool.