Why the bulb on the bow

[thomasale]

Why have I noticed a bulb on the bow of some ships? You know the thing that looks like a ramming tool at and below the water line on the bows of some ships. Do all have it?

[Tinknock50]

I think all large ships have them. It was discovered many years ago that the biggest detriment to speed and fuel consumption was the suction a ship creates as it cuts through the water. The bulb basically "punches" a hole in the water for the ship to pass through reducing drag along its sides.

[HALOnlyCruiser]

Hi Thomasale,

It's called a "bulbous bow" and is usually not seen as it is always below the waterline (except in dry dock). It makes water flow around the bow in a more aerodynamic fashion, and reduces drag. This affords better speed with more fuel efficiency. They are most effective at speeds that cruise ships sail. You won't find them on small vessels. And if it's a very fast ship, the drag can actually increase with a bulbous bow. So they are used for any large ship that travels between, say 10 and 35 knots. But it's ugly, isn't it?

P.S. Sean posted while I was composing. His answer is a better explanation.

[wrp96]

Hi Thomasale,

It's called a "bulbous bow" and is usually not seen as it is always below the waterline (except in dry dock).

 

Or when your ship runs aground on a sandbar in Bermuda.

[Tinknock50]

Hi Thomasale,

It's called a "bulbous bow" and is usually not seen as it is always below the waterline (except in dry dock). It makes water flow around the bow in a more aerodynamic fashion, and reduces drag. This affords better speed with more fuel efficiency. They are most effective at speeds that cruise ships sail. You won't find them on small vessels. And if it's a very fast ship, the drag can actually increase with a bulbous bow. So they are used for any large ship that travels between, say 10 and 35 knots. But it's ugly, isn't it?

P.S. Sean posted while I was composing. His answer is a better explanation.

 

You explaination was just as good.:) I didn't know about the speed thing....interesting.

[bepsf]

But it's ugly, isn't it?

Bulbous bows were invented back in the 20's by a brilliant Russian naval architect named Yourkevitsj – his design was first used on ships built for the Russian Navy, thereby proving his hydrodynamic theories correct. Hearing of plans for a great new CGT liner, he sent his hull designs (un-bidden) to the French shipyard which was comissioned to design and build Normandie back in the 30's, where they tested several hull configurations (including his) before concluding that his design was the best for their new flagship. Queen Mary (I) had already been designed and eventually completed without a bulb and therefore required much more horsepower (and fuel) in order to make the speeds that Normandie was capable of. Some estimate that the bulb alone increases hull efficiency by 6-7% (QM(I)’s aerodynamically “dirty” superstructure cost her an additional 6-7% horsepower/fuel inefficiency compared to Normandie)

One can see from old photographs of the two ships underway the noticable differences: great bow waves caused by Queen Mary versus the much diminished bow waves for Normandie. Needless to say, Queen Elizabeth and all subsequent major ships were built with versions of the bulbous bows from then on.

[Copper10-8]

RCI (Jewel of the Seas) has been known to use the bulbous bow to bring wales in to port

[Tinknock50]

 

 

Bulbous bows were invented back in the 20's by a brilliant Russian naval architect named Yourkevitsj – his design was first used on ships built for the Russian Navy, thereby proving his hydrodynamic theories correct. Hearing of plans for a great new CGT liner, he sent his hull designs (un-bidden) to the French shipyard which was comissioned to design and build Normandie back in the 30's, where they tested several hull configurations (including his) before concluding that his design was the best for their new flagship. Queen Mary (I) had already been designed and eventually completed without a bulb and therefore required much more horsepower (and fuel) in order to make the speeds that Normandie was capable of. Some estimate that the bulb alone increases hull efficiency by 6-7% (QM(I)’s aerodynamically “dirty” superstructure cost her an additional 6-7% horsepower/fuel inefficiency compared to Normandie)

 

 

One can see from old photographs of the two ships underway the noticable differences: great bow waves caused by Queen Mary versus the much diminished bow waves for Normandie. Needless to say, Queen Elizabeth and all subsequent major ships were built with versions of the bulbous bows from then on.

 

Some more interesting "bulbous bow" facts........ North German Lloyd's Breman and Europa were the first liners to have them in 1929. It enabled the Breman to beat Cunard's Mauretania crossing time by 8 hours. In those days, the steel plates of the hull overlapped and on these ships the butt edges that stuck out faced foward instead of aft as on previous ships.... another way to reduce drag.

[mim100]

Wow....great question and great answers...thanks to all....I'll be looking at ships' bows more carefully in future...

[Tinknock50]

Brian......I have been looking through my books and an American Admiral by the name of Taylor invented the boulbous bow. First large vessels to use it were the Bremen and Europa in 1929..... and then used by Yourkevitch's on his masterful hull design of the Nomandie.

[jessemon]

I just thought it meant they were "male" ships....:p

Sorry.

[Tinknock50]

I just thought it meant they were "male" ships....:p

Sorry.

 

:rolleyes:

[thomasale]

I have thought about this whenever I am near the bow of a cruise ship. Unfortunately that has been the only time until NCL Crown/ The picture that shows its' Bulbous Bow with what appears to be a hole in it.

 

BTW I didn't know that was what it was called (bulbous bow) but my thread title would appear that my thoughts were the same as the original designers.

 

My thanks to all those for their replies.

 

Danka

[Krazy Kruizers]

John

 

I remember when RCI had that "whale" problem - there were pictures of it everywhere - even in our local newspapers.

 

Yonnie

[jhannah]

Next time you see an old war film, notice the large bow waves created by the Naval vessels. Then notice on your next cruise how the waves are originating a number of meters aft of the bow. They are rolling off the hull instead of being rammed by the bow. It's an amazing difference.

[Tinknock50]

John

 

I remember when RCI had that "whale" problem - there were pictures of it everywhere - even in our local newspapers.

 

Yonnie

 

I also seem to recall the old Rotterdam carrying back a dead whale on its bulbous bow into Vancouver. I think it was in 1998.

[RuthC]

I also seem to recall the old Rotterdam carrying back a dead whale on its bulbous bow into Vancouver. I think it was in 1998.

Don't know if she did or didn't, but do know it couldn't have been in '98. The ss Rotterdam discharged her last passenger on 9/30/97.

I was one of them. :(

[Copper10-8]

Don't know if she did or didn't, but do know it couldn't have been in '98. The ss Rotterdam discharged her last passenger on 9/30/97.

I was one of them. :(

 

Plus I'm pretty sure (Doug can correct me) that the Rotterdam V did/does not have a bulbous bow;)

[cruzincurt]

Quote: "I just thought it meant they were "male" ships...."

 

Then why are ships called "she"?

[bepsf]

Plus I'm pretty sure (Doug can correct me) that the Rotterdam V did/does not have a bulbous bow;)

 

I'm looking for a clear pic of her bow...

...but I think she does have a bulbous bow in a similar style to the ships of her era - back then the bulbs did not project far forward as they do today.

 

[C 2 C]

Why have I noticed a bulb on the bow of some ships? You know the thing that looks like a ramming tool at and below the water line on the bows of some ships. Do all have it?

 

For more info:

 

http://en.wikipedia.org/wiki/Bulbous_bow

 

"I just thought it meant they were "male" ships...."

 

Then why are ships called "she"?

 

I don't think it is politically correct to discuss the sexual orientation of any cruise ship...

[Tinknock50]

Don't know if she did or didn't, but do know it couldn't have been in '98. The ss Rotterdam discharged her last passenger on 9/30/97.

I was one of them. :(

 

I wasn't sure of the date....I did think it might be '97.

That was the 1st year I cruised Alaska and I was at Canada Place checking out all the HAL ships. I did see the Rotterdam docked there then.

[Tinknock50]

Plus I'm pretty sure (Doug can correct me) that the Rotterdam V did/does not have a bulbous bow;)

 

That would be strange if it didn't.....given the obvious advantages.

 

At any rate, the Jewel of the Seas was not the only cruise ship that has caught a whale on the bulbous bow. I know I heard the story in the late nineties and I think it was a HAL ship.....if not the Rotterdam.

 

It was carried right into Vancouver harbour.:eek:

[Copper10-8]

That would be strange if it didn't.....given the obvious advantages.

 

Don't forget she was built in 1959! Here's some pics of her in drydock in Cadiz, Spain in January of this year. She does not have the pronounced and protruding bulbous bow of modern cruise ships but she does have somewhat of a fairing to her bow

[Copper10-8]

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