Celebrity Edge bow-shape

[chengkp75]

There's some misconceptions here, even in "data" from the web.  It is true that the longer the waterline length (so the "inverted" bow on these ships makes the waterline longer for a given overall length) gives a hull a faster "hull speed" or the most efficient speed the hull can be pushed through the water, that does not make the inverted bow "more efficient".  It just means that the ship with the inverted bow has a higher optimum speed than the bow with the flared bow.

 

The trade off is that the inverted bow does not flare outwards as it goes up the way a "normal" bow does.  This flaring increases the internal volume of the hull at higher levels, so when the flared bow digs into a wave, that increased volume provides increased buoyancy, and the bow rises to ride over the wave.  A non-flared bow like the inverted bow does not do this, and the ship will dig deeper into waves and not ride over them.  In fact, these bows are known as "wave piercers", as they will pierce through a wave and not ride over.  This creates less pitching motion, but also results in a "wetter" bow, as the flare also serves to deflect water from an oncoming wave to the side, while the non-flared bow will take it on the forward part of the superstructure.  There can be more "slamming" into the waves in place of the pitching.

 

Cruise lines have decided on fuel savings over ride and green water over the bow.

[ipeeinthepool]

9 minutes ago, chengkp75 said:

There's some misconceptions here, even in "data" from the web.  It is true that the longer the waterline length (so the "inverted" bow on these ships makes the waterline longer for a given overall length) gives a hull a faster "hull speed" or the most efficient speed the hull can be pushed through the water, that does not make the inverted bow "more efficient".  It just means that the ship with the inverted bow has a higher optimum speed than the bow with the flared bow.

 

The trade off is that the inverted bow does not flare outwards as it goes up the way a "normal" bow does.  This flaring increases the internal volume of the hull at higher levels, so when the flared bow digs into a wave, that increased volume provides increased buoyancy, and the bow rises to ride over the wave.  A non-flared bow like the inverted bow does not do this, and the ship will dig deeper into waves and not ride over them.  In fact, these bows are known as "wave piercers", as they will pierce through a wave and not ride over.  This creates less pitching motion, but also results in a "wetter" bow, as the flare also serves to deflect water from an oncoming wave to the side, while the non-flared bow will take it on the forward part of the superstructure.  There can be more "slamming" into the waves in place of the pitching.

 

Cruise lines have decided on fuel savings over ride and green water over the bow.

 

Thanks for the explanation, but I do have a couple questions about "optimum speed" and what it really means to the cruise ship industry.  Exactly what is optimum speed?  Does time matter to the cruise lines?  Is it the cruising speed where the cruise ship consumes the least fuel?  Do the ships typically operate at the optimum speed?  Consider two similar ships one with a normal bow and one with an inverted bow.  Consider the typical case for a cruise ship where the ship leaves one port and sails to the 12 hours to the next port.  If the ship with the normal bow at a lower optimum speeds sails twelve hours and gets to the next port exactly on time and the inverted bow ship gets there an hour early and idles for the next hour, which ship would use less fuel?  I wonder how the fuel consumption of the two ships compares if both ships are operating off the optimum speed.  Given that time is also important to cruise lines, I wonder if they are really saving fuel with the inverted bow design or is this really similar to auto manufacturers putting tail fins on cars in the 50s and 60s.

[chengkp75]

1 hour ago, ipeeinthepool said:

 

Thanks for the explanation, but I do have a couple questions about "optimum speed" and what it really means to the cruise ship industry.  Exactly what is optimum speed?  Does time matter to the cruise lines?  Is it the cruising speed where the cruise ship consumes the least fuel?  Do the ships typically operate at the optimum speed?  Consider two similar ships one with a normal bow and one with an inverted bow.  Consider the typical case for a cruise ship where the ship leaves one port and sails to the 12 hours to the next port.  If the ship with the normal bow at a lower optimum speeds sails twelve hours and gets to the next port exactly on time and the inverted bow ship gets there an hour early and idles for the next hour, which ship would use less fuel?  I wonder how the fuel consumption of the two ships compares if both ships are operating off the optimum speed.  Given that time is also important to cruise lines, I wonder if they are really saving fuel with the inverted bow design or is this really similar to auto manufacturers putting tail fins on cars in the 50s and 60s.

It's not "optimum speed" it is the fastest speed that a hull can be pushed efficiently.  To give an example, the QM2 is a much larger vessel than the old SS United States, but both could reach 30 knots (the SSUS nearly 38 knots).  However, the QM2 needs only 86Mw of power in here propulsion to do this, while the smaller SSUS needed 180Mw (twice the power).  The SSUS was pushing above her hull speed at 30+ knots, requiring all that power to do so, while the QM2 is operating likely close to her hull speed, so she can make that speed with less power.

 

"Optimum speed" is a moving target, as it changes with every passage between ports.  Optimum speed is the minimum speed needed to get to port at the right time.  Getting there early and then "waiting" will not save fuel, typically the opposite, and the longer the passage, the more fuel will be wasted.

 

Time is not that important to a cruise line, but the ability to make a higher speed when desired aids in making itineraries.  Once an itinerary is made, the speed that the ship will travel at between ports is determined by the distance and the time allotted.  So, the faster ship will not "get there" earlier and idle, it will merely slow down so that it makes a constant speed and arrives at the appointed time.  Everyone notes here on CC the way that port times have been reduced over the last few years, and this is so the ships can sail at slower speeds over the same distances between the ports, to save fuel.  The power to move a ship is an exponential relationship to the speed, not a straight line relationship, so the faster a ship goes, regardless of bow shape, the power (and hence the fuel consumption) goes up by a power (like squared or cubed) of the speed increase.  For a cruise ship, steaming along at 14 knots (with a max speed of 20 knots, or about 70% speed) takes about 40% of the power and fuel, so the last 30% of speed more than doubles the fuel consumption.

 

Confusing the calculations is the fact that the diesel engines have their own point of maximum fuel efficiency, which is around 70-80% of max power.  So, if your optimum speed needed to get to port on time results in a lower load on the diesels, you may lose some of your fuel savings.  This is why cruise ships have multiple diesel engines, and often two different sizes of engines, so the engineers can optimize the power generation capacity to the power demand, getting as close to the optimum load on the diesels for the optimum speed the ship needs.

 

No, the cruise lines are very concerned about fuel  consumption, especially with the new sulfur restrictions coming into effect in 2020-2021, which will drive marine fuel prices higher.  A bow design is a major hydrodynamic decision, not like putting fins on cars.  For ships with the same overall length, the ship with the longer waterline length (inverted bow) will require less power to push the ship at any speed up to hull speed, and that hull speed will be higher.

[ipeeinthepool]

22 minutes ago, chengkp75 said:

It's not "optimum speed" it is the fastest speed that a hull can be pushed efficiently.  To give an example, the QM2 is a much larger vessel than the old SS United States, but both could reach 30 knots (the SSUS nearly 38 knots).  However, the QM2 needs only 86Mw of power in here propulsion to do this, while the smaller SSUS needed 180Mw (twice the power).  The SSUS was pushing above her hull speed at 30+ knots, requiring all that power to do so, while the QM2 is operating likely close to her hull speed, so she can make that speed with less power.

 

"Optimum speed" is a moving target, as it changes with every passage between ports.  Optimum speed is the minimum speed needed to get to port at the right time.  Getting there early and then "waiting" will not save fuel, typically the opposite, and the longer the passage, the more fuel will be wasted.

 

Time is not that important to a cruise line, but the ability to make a higher speed when desired aids in making itineraries.  Once an itinerary is made, the speed that the ship will travel at between ports is determined by the distance and the time allotted.  So, the faster ship will not "get there" earlier and idle, it will merely slow down so that it makes a constant speed and arrives at the appointed time.  Everyone notes here on CC the way that port times have been reduced over the last few years, and this is so the ships can sail at slower speeds over the same distances between the ports, to save fuel.  The power to move a ship is an exponential relationship to the speed, not a straight line relationship, so the faster a ship goes, regardless of bow shape, the power (and hence the fuel consumption) goes up by a power (like squared or cubed) of the speed increase.  For a cruise ship, steaming along at 14 knots (with a max speed of 20 knots, or about 70% speed) takes about 40% of the power and fuel, so the last 30% of speed more than doubles the fuel consumption.

 

Confusing the calculations is the fact that the diesel engines have their own point of maximum fuel efficiency, which is around 70-80% of max power.  So, if your optimum speed needed to get to port on time results in a lower load on the diesels, you may lose some of your fuel savings.  This is why cruise ships have multiple diesel engines, and often two different sizes of engines, so the engineers can optimize the power generation capacity to the power demand, getting as close to the optimum load on the diesels for the optimum speed the ship needs.

 

No, the cruise lines are very concerned about fuel  consumption, especially with the new sulfur restrictions coming into effect in 2020-2021, which will drive marine fuel prices higher.  A bow design is a major hydrodynamic decision, not like putting fins on cars.  For ships with the same overall length, the ship with the longer waterline length (inverted bow) will require less power to push the ship at any speed up to hull speed, and that hull speed will be higher.

 

Thanks again

[Denny01]

Zonkers!! Great info.

 

Den

[bobndee]

On 5/14/2019 at 8:18 AM, Xport said:

 

I disembarked Edge's Transatlantic yesterday morning in Southampton after having also spent a week aboard in the Caribbean during March...

 

http://www.rclcorporate.com/celebrity-edges-eye-pleasing-bow-goes-back-to-the-future/ 

 

While I'm not sure I would necessarily agree with Royal Caribbean's assessment that Edge's bow shape is eye-pleasing [and miss the helipad of her Celebrity sisters], it does--in combination with new technologies [among them, a system that generates a "carpet" of drag-reducing microbubbles]--create an consistently smooth ride through frequent high winds/periodic high seas...  Captain Costas indicated that Edge is proving to be extremely fuel efficient.

 

A fire boat--with water cannons creating quite a fountain effect--provided an escort into Southampton port early yesterday morning to welcome Edge to The UK for the first time...  It was quite a memorable experience; many thanks! 

 

 

 

 

 

When I see that bow I wonder about how much reserve buoyancy it has.  That's the ability of the bow to rise above a big wave as opposed to plowing through it.  The traditional forward-leaning flared bow has a lot of extra lift when hitting a large wave.

 

That goes back to my days on sailboats.  A bow that didn't have a good amount of reserve buoyancy was known as a "wet boat" as waves frequently washed over the bow onto the deck.

[so,ton saint]

3 hours ago, bobndee said:

 

When I see that bow I wonder about how much reserve buoyancy it has.  That's the ability of the bow to rise above a big wave as opposed to plowing through it.  The traditional forward-leaning flared bow has a lot of extra lift when hitting a large wave.

 

That goes back to my days on sailboats.  A bow that didn't have a good amount of reserve buoyancy was known as a "wet boat" as waves frequently washed over the bow onto the deck.

Have just seen Edge in Southampton for the first time what a beautiful looking ship, iam more of a traditional person myself having sailed the pond many times on the old RMS Queen Mary as a crew member, am looking forward to Apex next year i think she is doing five cruise from So,ton, she certainly puts her parents company ships in the dark.

[Germancruiser]

so, ton saint- amazing- you sailed the old RMS Queen Mary- that really must have been something! You should write a book or something about it! There are many ship buffs out there- as I am - maybe that´s why i love QM2! At least she is an ocean liner with a nod to the old times..!

[CGTNORMANDIE]

1 hour ago, Germancruiser said:

so, ton saint- amazing- you sailed the old RMS Queen Mary- that really must have been something! You should write a book or something about it! There are many ship buffs out there- as I am - maybe that´s why i love QM2! At least she is an ocean liner with a nod to the old times..!

 

Some of us have experienced the old Queens...amazing.  You would have loved watching the Elizabeth sailing by in the opposite direction of the Mary in mid ocean.  Now that was really something.  I am not a big fan of the reverse bow...but I will abide by it if it boosts fuel efficiency.  

[Germancruiser]

Oh yes- that would have been a sight so see. I was on board the QM2, when for the first time the three Queens- QV- QM2 and the old QE2- met in New York! 2008 i thing it was! Wonderful experience!

[so,ton saint]

4 hours ago, Germancruiser said:

Oh yes- that would have been a sight so see. I was on board the QM2, when for the first time the three Queens- QV- QM2 and the old QE2- met in New York! 2008 i thing it was! Wonderful experience!

Hi yes they were the days, yes you could see the LIZZIE on the horizon midway, at a steady 27 knot,s translantic then was four day,s 17 hours,but now QM 2 as you know is more like six day,s, with that other greyhound  SS UNITED STATES, well say no more three days ten hours say no more the blue ribbon girl.

[Germancruiser]

Oh my- only three days for a TA- faaaaaaaaaar to short! LOL. In them days ment as a competition to flying- but even that was to long for the Liners to survive!

They really should  scrape the United States- such a waste,  they let her rot for some 40 years now- so many tried to save her and always turned back. A swift ending would be better then let her layed up there.

 

[Jammu2]

Reminds me of Fedship.

 

 

[so,ton saint]

5 hours ago, Germancruiser said:

Oh my- only three days for a TA- faaaaaaaaaar to short! LOL. In them days ment as a competition to flying- but even that was to long for the Liners to survive!

They really should  scrape the United States- such a waste,  they let her rot for some 40 years now- so many tried to save her and always turned back. A swift ending would be better then let her layed up there.

 

Hi all i know iam going of the topic but if you go into www.queenmaryassociation.com its were the old crew have a reunion four times a year,but going back farther germancruiser my father shoveled coal in the old berengaria formally the ss Imperator an old german translantic liner transferred to cunard after the war, her sister was the vaterland renamed leviathan taken over by the USA.

[TeeRick]

On 5/15/2019 at 5:52 AM, chengkp75 said:

There's some misconceptions here, even in "data" from the web.  It is true that the longer the waterline length (so the "inverted" bow on these ships makes the waterline longer for a given overall length) gives a hull a faster "hull speed" or the most efficient speed the hull can be pushed through the water, that does not make the inverted bow "more efficient".  It just means that the ship with the inverted bow has a higher optimum speed than the bow with the flared bow.

 

The trade off is that the inverted bow does not flare outwards as it goes up the way a "normal" bow does.  This flaring increases the internal volume of the hull at higher levels, so when the flared bow digs into a wave, that increased volume provides increased buoyancy, and the bow rises to ride over the wave.  A non-flared bow like the inverted bow does not do this, and the ship will dig deeper into waves and not ride over them.  In fact, these bows are known as "wave piercers", as they will pierce through a wave and not ride over.  This creates less pitching motion, but also results in a "wetter" bow, as the flare also serves to deflect water from an oncoming wave to the side, while the non-flared bow will take it on the forward part of the superstructure.  There can be more "slamming" into the waves in place of the pitching.

 

Cruise lines have decided on fuel savings over ride and green water over the bow.

chengkp75,

Thank you very much.  You have taken the conversation past "Do you like the bow shape on Edge" with some good information.  You add a lot of value to these boards with your knowledge.  Much appreciated!

[Chanbre]

The Captain of the Constellation gave a lecture on navigation during the cruise last week. He said (although I may have mis-interpreted what he said) that a lot of ships are long and narrow and have an underwater cross section that approximates the letter V. Such ships can usefully have a bulbous bow. Modern cruise ships typically are quite wide and have a flat bottom. That means that having a flat (and non-bulbous) bow makes sense.

 

Perhaps one of the ship experts on this site can explain the merits of ships with distinct keels versus those with flat bottoms and also how those shapes relate to bulbous bows.

[chengkp75]

2 hours ago, Chanbre said:

The Captain of the Constellation gave a lecture on navigation during the cruise last week. He said (although I may have mis-interpreted what he said) that a lot of ships are long and narrow and have an underwater cross section that approximates the letter V. Such ships can usefully have a bulbous bow. Modern cruise ships typically are quite wide and have a flat bottom. That means that having a flat (and non-bulbous) bow makes sense.

 

Perhaps one of the ship experts on this site can explain the merits of ships with distinct keels versus those with flat bottoms and also how those shapes relate to bulbous bows.

I don't believe that any ship built in the last century and a half has had a v-shaped hull, or a "distinct" keel.  Every ship is flat bottomed, and most have bulbous bows, including most cruise ships.  There is no wider or more flat bottomed than a supertanker, and nearly all of these have a bulbous bow.  The purpose of a bulbous bow is to create a secondary bow wave that negates the principal bow wave, decreasing the drag of the hull through the water.  Also, without a bulb, most ships will have their bow "rise up" onto the bow wave, sinking the stern deeper and increasing drag.

 

Here is a picture of Oasis of the Seas, the widest cruise ship around, and see the flat bottom and a bulbous bow.  Yes, the bow is v-shaped, but so is every ship with a flared bow (98% of ships today), but 80% of the ship's length is flat bottom.

 

[Germancruiser]

I sure will check the site so,tonsaint. Oh my , Vaterland, Imperator, Bismark - those were wonderful looking ships. I have old postcards from my great grandfather from those ships- he was a ship buff - like me- maybe a inheritens thing! LOL! Leviathan, Majestic and Berengaria- as they were later known. Thx and greetings

Michael

[Chanbre]

10 hours ago, chengkp75 said:

I don't believe that any ship built in the last century and a half has had a v-shaped hull, or a "distinct" keel.  Every ship is flat bottomed, and most have bulbous bows, including most cruise ships.  There is no wider or more flat bottomed than a supertanker, and nearly all of these have a bulbous bow.  The purpose of a bulbous bow is to create a secondary bow wave that negates the principal bow wave, decreasing the drag of the hull through the water.  Also, without a bulb, most ships will have their bow "rise up" onto the bow wave, sinking the stern deeper and increasing drag.

 

Here is a picture of Oasis of the Seas, the widest cruise ship around, and see the flat bottom and a bulbous bow.  Yes, the bow is v-shaped, but so is every ship with a flared bow (98% of ships today), but 80% of the ship's length is flat bottom.

 

Thank you for that explanation and for giving some extra details to add to my understanding of the topic.

[so,ton saint]

On 5/18/2019 at 12:05 AM, Germancruiser said:

I sure will check the site so,tonsaint. Oh my , Vaterland, Imperator, Bismark - those were wonderful looking ships. I have old postcards from my great grandfather from those ships- he was a ship buff - like me- maybe a inheritens thing! LOL! Leviathan, Majestic and Berengaria- as they were later known. Thx and greetings

Michael

Hi mike

i see the fourum is quiet, though iam well past my sell by date i still do a little job with the cruise ships in so,ton, i have my licence  to transfer passengers to various cruise ships with my company i take 8 pax and cases down to all cruise ships , saturday we had five ships in port

Braemar

azura

indy of the sea

Brittania

Sapphire princess

and sunday Arcadia   celeb silhouette and Queen Vic

have you a cruise booked, this year we are going back to Barbados with virgin doing a stay and cruise with Carnival  facination

and a week in Barbados my favourite  island, take care

HOWARD

[so,ton saint]

31 minutes ago, so,ton saint said:

Hi mike

i see the fourum is quiet, though iam well past my sell by date i still do a little job with the cruise ships in so,ton, i have my licence  to transfer passengers to various cruise ships with my company i take 8 pax and cases down to all cruise ships , saturday we had five ships in port

Braemar

azura

indy of the sea

Brittania

Sapphire princess

and sunday Arcadia   celeb silhouette and Queen Vic

have you a cruise booked, this year we are going back to Barbados with virgin doing a stay and cruise with Carnival  facination

and a week in Barbados my favourite  island, take care

HOWARD

Hi mike

i see the mein schiffs are doing well do you like the shape of there products or stay as they are, my last cruise was the old Celebrity galaxy now Marella Explorer well travelled  but a very good ex millennium  cruise ship.

[Germancruiser]

What a wonderful idea to keep in touch with ships and great opportunity to get very close to the ships! I usually use South Coast Chauffeurs to get to and from the ship in Soto!

The Mein Schiff´s are huge succes I agree- not for me however- never- ever would i set foot on a ship with only Germans as passengers! Much more interessting to meet foreigners and talking to them...! Germans can be a pain in the backside on holiday! I did that once- on the old Berlin of  Deilman - Reederei! NEVER EVER!