When did they decide to abandon ship's bows?

[Captain Sub]

Dear folks,

so I recently came across a picture of probably one of the last subs (post-war) that were built in ship's bow design.



I'm wondering when and why they decided to abandon that design and why they never built belly-bow subs in WW2.



kind regards,

Paul

[Raptor1]

Post-WWII submarines differed from earlier ones because they were designed to operate underwater most of the time rather than most WWII-era dive boats. The teardrop hull (Pioneered by USS Albacore) is much more hydrodynamic, allowing for greater speed and maneuverability underwater (Along with some other advantages), wheras the WWII-style design was designed to increase performance on the surface much like a normal ship.

At least, I think that's what you're talking about...

[msxyz]

The "bow" in post war subs is actually a dome containing an array of transducers. The principle is more or less the same of a sinthetic aperture antenna but this is designed to pick up sound, not radio waves.

That looks like a soviet Romeo submarine or a similar class. It has a slight, protruding bow that helps breaking the waves but it's not the main function of that bow, as it holds a U-shaped sonar array.

Basically, when submarines began spending more time underwater than surfaced, the classic bow shape (that helps seakeeping) was dropped in favour of designs that guaranted lower resistance underwater.

[TLAM Strike]

Originally Posted by msxyz

That looks like a soviet Romeo submarine or a similar class.

That is a Soviet Foxtrot class boat.

Interestingly the first modern subs (The Holland boats) used a cigar shape for greater underwater performance much like the ones today, it was Simon Lake (John Holland's competitor) who came up with the idea of a sub that was faster on the surface and had a surface ship like bow- this design philosophy became the Fleet Type Submarine. It wasn't until the 1950's with the USS Albacore that submarines returned to Holland's origional design philosophy.

(Don't take the above paragraph as disparaging of Simon Lake, he had many good ideas including the Conning Tower, Dive Planes and the Rotating/Retractable Periscope.)

When submarines were no longer required to operate and transit on the surface, the requirement for hull forms optimised for surface travel could be replaced by designs optimised for undersea travel.

As far back as the 1917 R Class of the Royal Navy it was recognized that high underwater speed required different shapes than surface seaworthyness. The R's were the first submarine hunter-killers and even if the technology was not mature enough to make them successful in that role they had some features, the bulbous bow shape in particular, that greatly improved their submerged performance relative to those boats with ship-like stems, either straight or flared.

USS Albacore (AGSS 569) is generally considered the forerunner of the teardrop shape submarine whereas the Soviet Navy retained a basic Type XXI hull form as late as the Project 641B (NATO Tango Class) introduced in the late 70's. The OP's linked photo looks to be a Project 641 (NATO Foxtrot Class) which preceded the Tango's into service. Cold War accounts of Foxtrot and Tango operations indicate that these boats spent more time surfaced than submerged so retaining a flared stem for improved seaworthyness made sense.

The first true teardrop hull in Soviet service was probably the Project 671 (NATO Victor Class) first reported from 1969 although Soviet designs had featured much smaller and very streamlined sails as far back as the Project 627 (NATO November Class) and Project 569 (NATO Echo Class) from the late 1950's and early 1960's.

For the R Class see:

http://www.battleships-cruisers.co.uk/r_class.htm

For USS Albacore see:

http://www.ussalbacore.org/

[TLAM Strike]

Originally Posted by Randomizer

As far back as the 1917 R Class of the Royal Navy it was recognized that high underwater speed required different shapes than surface seaworthyness. The R's were the first submarine hunter-killers and even if the technology was not mature enough to make them successful in that role they had some features, the bulbous bow shape in particular, that greatly improved their submerged performance relative to those boats with ship-like stems, either straight or flared.

As I said in another thread the R class boats wouldn't have look out of place in the 1950's. Go UK!

USS Albacore (AGSS 569) is generally considered the forerunner of the teardrop shape submarine whereas the Soviet Navy retained a basic Type XXI hull form as late as the Project 641B (NATO Tango Class) introduced in the late 70's. The OP's linked photo looks to be a Project 641 (NATO Foxtrot Class) which preceded the Tango's into service. Cold War accounts of Foxtrot and Tango operations indicate that these boats spent more time surfaced than submerged so retaining a flared stem for improved seaworthyness made sense.

Actually it appears they have retained the Type XXI hull style today!



Sat photo of Sarov class submarine. Note the Stern- twin screws with control surfaces much like the Whiskey. Also note the bow shape:

[msxyz]

Project 627 actually looks like a giant torpedo when it's out of the water. Its lenght far exceeds the other dimensions. Its bow, however has a proper drop shape. There aren't many shots of November class submarines in drydock, not even after the fall the USSR when they went to the scrap yard. This is the best I could find:



Notice the bulge under the bow. The first vessels in the class lacked this dome which housed a huge cylinder that is the sonar "antenna".

No wonder the XXI shape was so popular. It was designed using water tunnels, so it was extensively tested through trial and error. Possibly the most elegant offspring of this design was the Project 651 juliett

Actually it appears they have retained the Type XXI hull style today!

I think the OP was concentrating on the existance of a flared stem as opposed to actual hull form or cross-section. It would certainly be strange if the 21st Century Sarov's were optimized for surface operations and this is not at all apparent in the photo links you provide.

There are certainly advantages to not using a teardrop shaped hull if it is not required for high underwater speed.

That some Type XXI hull characteristics are still being utilized is a nice engineering example of how form follows function regardless of nationality.

[Kapitan]

First of all tear drop shape was pioneered by the K3 the first november class submarine, the K3 rendered the nautilus obsolete if you go by paper v paper side of things, it out classed nautilus it dived deeper was faster and carried more weapons and had alot more space inside.

the last boats for the russian navy built with a type 21 hull form would have been the tango class the follow on from the foxtrot.
The picture in the first post is a foxtrot, by the time the last boats entered service in the 1980's they were obsolete replaced by the tango who again was of a obsolete design most tangos didnt see past 20 years service, only one has been retained for training uses.

The introduction of the kilo made the conventional hull form extinct in the russian navy and has been adopted even in 3rd world countries, they have ditched the older hull form boats such as foxtrots (india poland) in favour of the newer more effective tear drop boats.

The thing is hydrodynamically tear drop is far better it achieves greater submerged speeds, and it also reduces noise, the foxtrot was incredibly loud as it had three screws where the kilos have just one.

I only know of about 3 navies who maintain non tear drop hull submarines, egypt (romeo improved) china (romeo improved, golf II) tiawan (whiskey)
Note the world status of these countries.

[msxyz]

Noise in a hull generated by flowing water depends on the bow shape and from apertures in the flooded parts of the hull, both of which contributes to create vortexes. Classic WW2 submarines like the type VII or IX had myriads of slots in the outer skin to allow water passage and reduce diving time by quickly flooding the space below the deck and avoid bubbles of gas to be trapped between the skin and the hull. In a later type XXI (or in a similar post war submarine) the number of slots was reduced and their placement and shape became extremely important.

Another critical area is the sail and, of course, anything sticking out of the hull itself, ie a rudder, a plane or -in past times- a deck cannon. Everything that can create local vortexes is a potential source of unwanted sounds and drag.

Back on shape and hydrodynamic efficiency...

If we have to observe fishes and marine animals, Mother Nature solution for a perfect underwater craft, there are several different shapes that appear to be optimized for speed and fuel (err... food) economy.

Sperm whales, for example, don't adopt a teardrop shape, yet they are among the biggest marine animals that ever traveled oceans and they are capable and fast swimmers (up to about 40km/h - 22 kts). Interestingly, the hull shape and the bow of several post war German submarines resembles more the shape of a sperm whale than that of a blimp. (Type 206-209, TR1700)

[Subnuts]

Originally Posted by Kapitan

First of all tear drop shape was pioneered by the K3 the first november class submarine,

Really?
http://www.ussalbacore.org/html/albacore_story.html

[TLAM Strike]

Originally Posted by Kapitan

First of all tear drop shape was pioneered by the K3 the first november class submarine, the K3 rendered the nautilus obsolete if you go by paper v paper side of things, it out classed nautilus it dived deeper was faster and carried more weapons and had alot more space inside.

Kapitan that is a common miss understanding. You see there are two post Type XXI hull designs, the teardrop and the cigar. Teardrop designs are based on the USS Albacore while the Cigar is based on the November (which is derived from pre-WWI Holland boats). Here is a great photo where you can compare the differences.


That is an Alfa on the left and a November on the Right. See how the November is bullet shaped on the bow and uniform along the hull- that is a cigar shaped hull. The Alfa on the other hand is not uniform along the hull (for the most part) it is tapering from the fin to the ends of the hull.

I only know of about 3 navies who maintain non tear drop hull submarines, egypt (romeo improved) china (romeo improved, golf II) tiawan (whiskey)
Note the world status of these countries.

Taiwan dosn't have a Whiskey, I think you ment a Tench class GUPPY.

North Korea also has some Romeo/Mings kicking about.

Pakistan has a few Damphine' but they may have been retired by now.

Originally Posted by msxyz

Noise in a hull generated by flowing water depends on the bow shape and from apertures in the flooded parts of the hull, both of which contributes to create vortexes. Classic WW2 submarines like the type VII or IX had myriads of slots in the outer skin to allow water passage and reduce diving time by quickly flooding the space below the deck and avoid bubbles of gas to be trapped between the skin and the hull. In a later type XXI (or in a similar post war submarine) the number of slots was reduced and their placement and shape became extremely important.

Those are called "Limber Holes" even today submarines have them- especially Russian submarines although the Los Angles class has a few near VLS tubes. Today they have doors that close once the hull spaces are filled to reduce flow noise.

[Kapitan]

I see what you mean now about cigar and tear drop,

[Captain Sub]

Originally Posted by Kapitan

I only know of about 3 navies who maintain non tear drop hull submarines, egypt (romeo improved) china (romeo improved, golf II) tiawan (whiskey)
Note the world status of these countries.

China and their military could take over North America any time they wanted.

But they wouldn't even have to do that. They could destroy The United States alone by simply stopping to buy their debt.

How would the US-submariners fight without food?




The submarine hulls today vary so greatly as if noone knew what's truely efficient.

The German 206 seems to totally imitate a sperm whale!

[msxyz]

Originally Posted by TLAM Strike

Those are called "Limber Holes" (...)

Thank you, I didn't know the proper English term for them.