Submarine's sail

[KAPITAIN]

Ive been reading a declassified defence report on submarine hydrodynamics recently, and found some intresting pointers.

The 73 page document is wirtten by Professor Peter N Joubert, and is intended for use in the submarine world.
As i understand Professor Joubert is said to be one of the leading Professors in submarine hydrodynamics, and advises navies all over the world.

Some pointers i found is that "The sail is a large factor in the overall drag of a submarine" which i found quite astonishing, because i assumed that the sail not only kept the submarine up right but also to stop the submarine from snap rolling, here it says "If the sail is too high it can cause a snap roll".

and through out the two pages its all about Drag and what not how the sail causes the amount of drag but also why its needed.

Can any of the Defence analysts here tell me thier personal views on submarine sail's id like to get the overal view of this guy and your personal remarks.

[gf0012-aust]

Ive been reading a declassified defence report on submarine hydrodynamics recently, and found some intresting pointers.

The 73 page document is wirtten by Professor Peter N Joubert, and is intended for use in the submarine world.
As i understand Professor Joubert is said to be one of the leading Professors in submarine hydrodynamics, and advises navies all over the world.

Professor Joubert is an active consultant for the RAN.

You might want to post the link on the article. There are 4-5 people in here who are either ex submariners or are associated with vessel noise, vibration and acoustic analysis.

[Sea Dog]

Ive been reading a declassified defence report on submarine hydrodynamics recently, and found some intresting pointers.

The 73 page document is wirtten by Professor Peter N Joubert, and is intended for use in the submarine world.
As i understand Professor Joubert is said to be one of the leading Professors in submarine hydrodynamics, and advises navies all over the world.

Some pointers i found is that "The sail is a large factor in the overall drag of a submarine" which i found quite astonishing, because i assumed that the sail not only kept the submarine up right but also to stop the submarine from snap rolling, here it says "If the sail is too high it can cause a snap roll".

and through out the two pages its all about Drag and what not how the sail causes the amount of drag but also why its needed.

Can any of the Defence analysts here tell me thier personal views on submarine sail's id like to get the overal view of this guy and your personal remarks.

Drag is not a major factor in submarine construction--remember that subs do not have to worry about constant wave/wind action in the surface where a sail may just actually act to reduce performance dramatically. Submarines, specially nukes, are sufficiently powerful to generate impressive speed. what drag is created by the sail is negligible.

Also, regardless of the drag issue, the sail is the storage site for invaluable sensors. That in of itself negates any drag issue.

[KAPITAIN]

So whats the big issue about Russian and american submarine sail's ?

One is blended into the hull and one isnt both do the same job.

Il post the link when i get it back through i forgot to book mark it, but a friend of mine has it and hopefully he will give it to me soon.

[gf0012-aust]

So whats the big issue about Russian and american submarine sail's ?

One is blended into the hull and one isnt both do the same job.

Actually the Russians use both. The Germans are leaning towards blended sails.

The Collins had its sail modified for blending at the hull junction. That was an NV issue after some acoustic analysis was done. A full blend wasn;t deemed necessary.

There are different issues though. Some larger subs also tend to use the sail as the diving plane hub. Others use bowplanes on the hull.

The other thing is that sails are easier to modify now for things such as "polyphem concepts" - and they're convenient for non nukes to house snorket apparatus etc.

They may become less relevant on some designs (not all) due to technology changes in periscopes.

The USN is using photonics which are far more efficient than traditional scopes )its like comparing a pair of binoculars to a telescope at a technology level) but they still have elected to maintain a proud sail to house various command items.

[KAPITAIN]

I see.

The russian submarines that dont use blended sails are not high speed submarines though, Kilo Delta Typhoon India and Yankee and now Lada are not realy high speed submarines.

So the blended sail could be said to be something realy for very fast attack submarines?

[gf0012-aust]

The russian submarines that dont use blended sails are not high speed submarines though, Kilo Delta Typhoon India and Yankee and now Lada are not realy high speed submarines.

It's not necessarily related to high speed. eg HDW 212/4. At a certain speed you are going to generate vortexes - esp at hull structural formings. As an issue of acoustic management you want to delay that onset as high as possible and in line with the normal operational profile of that particular sub type.

So the blended sail could be said to be something realy for very fast attack submarines?

No, loosely speaking, at a certain speed a submarine becomes an acoustic transmitter. Travelling at high speed means that you might as well ring up the enemies embassies and tell them where you are - as their ASW teams will be happy as a bee in a flower garden.

High speed is anathema to basic/the majority of submarine work.

It's beneficial for a sub that has a requirement to travel at high speed - but its not what its designed for in absolute terms.

[KAPITAIN]

Yes i have heard alot about that especialy the al'fa class submarine when she hits +40 knots its like standing next to a church bell.

Mind you thier sail is very tiny and squat, i could have climbed up it!
and the opening wasnt big for the men to stan in either that was pretty small we got 4 in there ata tight squeeze.

[Sea Dog]

So whats the big issue about Russian and american submarine sail's ?

One is blended into the hull and one isnt both do the same job.

Il post the link when i get it back through i forgot to book mark it, but a friend of mine has it and hopefully he will give it to me soon.

Flow noise reduction....not drag.

[Francois]

Must be the document in question :
Some Aspects of Submarine Design Part 1. Hydrodynamics (http://www.dsto.defence.gov.au/ publications/3442/DSTO-TR-1622.pdf)

Although the sail is indeed creating some unwelcome drag, we need it to suppress the contra-rotation effect given by the propeller. That is the reason the sail has a 1 to 5 degree angle on the opposite direction of the propeller's rotating force.

There were tests of submarines without a sail (and not a conning tower as stated all around!:confused: ), but the lack of stability made the design simply improper.

At the same time, a higher sail allows to hide longer masts, so th submarine can still sail deeper when at periscope depth.
Could save your life in some occasions.

[EnigmaNZ]

The early nuclear subs certainly were blessed with tall sails. A couple of examples here, a Valiant and Dreadnought class submarine.

http://en.wikipedia.org/wiki/Image:HMS_Warspite_%28Valiant-class_submarine%29.jpg

http://www.royal-navy.mod.uk/server/show/ConMediaFile.15493

This is a Guppy 3 Tench class from the '50's. Again note the sail height.

http://www.navsource.org/archives/08/0841603.jpg

Built in the days before bloat took over, between 240 and 270 feet, 30 knots, 24 weapon load. With automation reducing crew from the 115 odd required then, to a more managable 70 off today (Rubis class), these are more your literal subs than the gigantic neviathons being created for such roles. I love these earlier generation subs.