Talk:Bulbous bow

Sonar Dome

I fail to see how Sonar Domes are related to bulbous bows. Most sonar domes are located on the bottom hull of the ship not on the side surfaces. Also this section is completely unreferenced. --66.54.184.41 20:26, 29 May 2007 (UTC)

Antisubmarine ships routinely use bow-mounted sonar, see [1] for a good photo of a DDG-51 class destroyer with its bulbous bow sonar. Georgewilliamherbert 21:06, 29 May 2007 (UTC)

I can understand the first comment. However, location on the hull and pictures, many people will think there is some relationship. The point of on bottom not side is key. Although visible similar- SONAR domes do nothing to reduce drag and fuel consumption. SONAR domes are now place at bow for maximum distance from noise of propeller for better performance. (UTC) Wfoj3 (talk) 02:24, 8 January 2010

The section needs to be kept here, have people realize there is NO relationship. SONAR domes are not always at the bow - for reference see US FFG-7 class. (SQS-56) - "SONAR domes do nothing to reduce drag and fuel consumption" I don't know about that - the do change the hydrodynamics, change how and where the bow wave is, I guess under certain cases it does reduce drag and fuel - but certain not in heavy seas. It is a weird feeling on a ship in heavy seas when the sonar dome re-enters the water after emerging from the waves shape. Wfoj3 (talk) 16:32, 1 September 2013 (UTC)

I don't think the sonar dome affects to the bow wave since it's located largely below the baseline and not at the surface. As for "weird feeling", I would expect slamming in such case. Tupsumato (talk) 13:03, 11 September 2013 (UTC)

Comment

While 'bulbous bow' is the tern commonly used for this feature, it is strictly a bulbous forefoot. The forefoot being the junction between the keel and the stem. As structural features, both stem and keel as narrowly defined, have been superseded by plate structures but their positions in the structure of the ship are recalled when naming these parts of the hull. The flow characteristics around sharp and bulbous forefoots are analagous to those investigated in the early years of the development of modern (motorised) torpedoes. The earliest ones were pointed but it was soon found that a hemispherical fore end permitted more efficient passage through the water.

"Large seas"?

However, neither of these explanations accounts for the fact that vessels with bulbous bows handle better in large seas.

What does "large seas" mean here? Deep? High waves? --Doradus 16:21, Apr 1, 2005 (UTC)

Heavy seas? Rmhermen 16:25, Apr 1, 2005 (UTC)

Ok, what is that? I think we should strive to use minimal jargon, and failing that, we should define our terms. --Doradus 18:23, Apr 4, 2005 (UTC)

When I wrote that I meant "Heavy Seas", which indicates large (i.e. amplitude) waves which are usually (though not by definition) accompanied by high winds and rain/sleet. -Lommer | ^talk 21:20, 4 Apr 2005 (UTC)

Yamato?

Wasn't the design of Japanese battleship Yamato one of the earliest successful examples of bulbous bow? I remember they tried several wax models to reach the final 3 meter long design. -- Toytoy 08:13, Apr 17, 2005 (UTC)

Andrea Doria

The image caption has been changed from bulbous bow to sonar dome. If this is true (and it looks like it to me), I think that the image should be removed from the article. What do other people think? --Apyule 08:19, 10 November 2005 (UTC)

I think it still qualifies as a bulbous bow, especially given that the "additional benifits" section of the article explicitly addresses this point. I've clarified the caption to reflect my interpretation... how's that? -Lommer | ^talk 18:40, 10 November 2005 (UTC)

Yeah, looking at it that way I think I've changed my mind. It should stay now. --Apyule 01:07, 11 November 2005 (UTC)

I'm not so sure, bulbous bows are generally only used for hydrodynamic purposes, a sonar dome is a completely different object, it's not really relevant to the topic. I've taken it out for now, and edited the "Additional Benefits" section to make the distinction clearer. Kupos 19:30, 2 March 2006 (UTC)

History of bulbous bow

I have read in some books that the effect of bulbous bow on the speed was observed during the American Civil War. Those days ships used to ram each other with pointed iron rods fixed to the bow under water. It was observed that those ships which had these rams traveled faster. And the scientific study followed from that observation. —Preceding unsigned comment added by 202.1.192.7 (talk) 17:01, 25 January 2008 (UTC)

I will try to be more complete in future and add to the page, but a few key points: 1. the bulbous forefoot was developed by the US naval constructor David Taylor and used on several battleships in the 1920s 2. The US passenger ship Malolo was the first commercial vessel to use a bulbous forefoot (it was designed by Gibbs and Cox, who had close ties to the US Navy and Admiral Taylor) 3. The German ships Bremen and Europa followed suite. It is not clear whether German naval architects developed the concpet independently or they learned of the American research 4. The Russian naval constructor Vladimir Yourkevitch used the bulbous forefoot on his battleship designs in the 1920s, but they were never built. He emigarted to France where, famously, he designed the hull of the passenger liner Normandie with a bulbous forefoot. 5. The bulbous bow we know and love today was developed in the late 1950s in Japan by Takao Inui, now an emeritus professor at the University of Tokyo. He developed it after carefully studying the wave theories of Havelock in Britain (Havelock and Wigely had come up with the concept of a wave-cancelling bulb in the 1920s and 30s, but never built one). It took some time for the concept to come to be accepted in the maritime community.

Ferreiro 01:45, 17 February 2007 (UTC)Dr. Larrie D. Ferreiro

Semi-displacement speed range - jargon in second paragraph of lead

The phrase "semi-displacement speed range" appears to be jargon. I can figure out the pieces and guess meaning from context, but given its position at the top of the article it should be readable for a well-informed non-expert, yet it is not. Is there a link that can be provided, or could this be re-worded? --Scray (talk) 11:39, 25 February 2009 (UTC)

I put Maximum Speed. That should do. -- Justsail (talk) 06:24, 20 March 2009 (UTC)

Squiggle Keel

Neither this article nor any other on Wikipedia explain what a "squiggle keel" is, talked about in this article under "How it works": "...the bulb dampens pitching movements like a squiggle keel." Lriley47 (talk) 01:36, 9 November 2010 (UTC)

Hull markings?

When you look e.g. at the picture of the black and red painted ship with the yellowish bulbous bow in this article you can see markings for the b.b. and the bow thrusters...

Shouldn't there be a mention for this marking/signage in the article?--109.91.42.96 (talk) 23:45, 8 May 2012 (UTC)

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Best speed?

An IP editor commented on the following passage in this edit:

Thus, large vessels that cross large bodies of water near their best speed will benefit from a bulbous bow. This would include , cargo ships, and passenger ships. All of these ships tend to be large and usually operate within a small range of speeds.

By saying, "This is nowhere near true for many naval vessels. Their cruising speed is typically much lower than their maximum (e.g. around 14 knots compared with top speeds of around 30 knots), both for fuel efficiency and for 'discretion' - speed equals noise, which undermines acoustic sensor performance."

I've brought this comment out of the article to hear for further discussion. HopsonRoad (talk) 20:42, 16 March 2019 (UTC)

I've checked now when this claim was supported with a reference, it's here. The link of the reference is no longer valid, however, there exists a snapshot from some months later here at archive.org. This text does not support that naval ships are usually proceeding at or near their top speed most of the time.

I must admit I have no idea how naval ships are usually operated, however the claim they proceed usually near their top speed is just unreferenced. Therefore I think it is the best to remove this from the article. I've done this now and also replaced the link by its archive.org capture.

--Cyfal (talk) 13:15, 17 March 2019 (UTC)

Design conditions

@Cyfal and Tupsumato: The lead paragraph includes the following, using a 1936 reference:

Bulbous bows have been found to be most effective when used on vessels that meet the following conditions:

• the waterline length is longer than about 15 metres (49 ft)
• the vessel will operate most of the time at or near its maximum speed

The reference would appear to be outdated and is not available on line, so it's difficult to confirm whether it is correctly paraphrased. Barrass suggests other constraints on ship design, as does Bertram. Additionally, there is no modern concept of "maximum speed"; we speak in reference to Froude numbers. It's more correct to say that a bulbous bow is designed according to a vessel's planned operating speed. Cheers, HopsonRoad (talk) 21:23, 17 March 2019 (UTC)

References

Where is the bulbous bow of USS Lexington ?

The photo in the article does not show the bulbous. It rather seem to shows slim neck. Did she really bear bulbous bow? Bored boar (talk) 02:31, 4 July 2019 (UTC)

The text (and presumably the reference) explains that it is a predecessor design, called a "bulbous forefoot". HopsonRoad (talk) 02:37, 4 July 2019 (UTC)

Contradiction in text

the opening says that the bulb "reduces pitching by adding buoyancy to the bow". The closing sentence says "Bulbous bows also decrease a ship's pitching motion, when they are ballasted, by increasing the mass at a distance removed from the ship's longitudinal centre of gravity." So is it the buoyancy or the extra weight? Those seem like kind of polar opposites. I feel like the first one makes more sense since there is nothing at all to stop builders from just packing a normal bow with lead weights for ballast if that really helps reduce pitching. Adding ballast to a bulbous bow seems more or less like a way of cancelling out the added buoyancy. Idumea47b (talk) 08:35, 12 August 2024 (UTC)

Buoyancy is not the opposite of mass. Mass isn't the same thing as weight, and adding mass needn't add overall weight if it also adds volume and thus buoyancy. Andy Dingley (talk) 12:24, 12 August 2024 (UTC)