Virginia class SSN

[lesrae]

Originally Posted by GrayFox

Arent the planes on the 688&688(i) class on the sail like the pic under the huge yellow SUBSIM.COM Radio room?

I think the 688I boats had the foreplanes moved to the hull + the sail strengthened, for under-ice ops.

[GrayFox]

i just saw, all the improved 688s have their planes on their hull.



All the 688s in SC are (i) improved. Above is the SSN-700 Dallas, a non improved one, and it has them on the sail.



above is the USS Greenville, second to last of the 688(i) class. no planes on the sail.


But i would really like to see them on the sail, to me it just looks better.

[cowman1009]

Originally Posted by GrayFox

i just saw, all the improved 688s have their planes on their hull.



All the 688s in SC are (i) improved. Above is the SSN-700 Dallas, a non improved one, and it has them on the sail.



above is the USS Greenville, second to last of the 688(i) class. no planes on the sail.


But i would really like to see them on the sail, to me it just looks better.

It's actually better to have the bow planes below the waterline on the 688I class for such events as periscope depth; on an older 688 if you broached (came out of the water) the sail then once you started going back down the fairwater plains would slap the water and rattle the whole boat unless you were quick about it and put them to full rise.

[TLAM Strike]

Originally Posted by cowman1009

It's actually better to have the bow planes below the waterline on the 688I class for such events as periscope depth; on an older 688 if you broached (came out of the water) the sail then once you started going back down the fairwater plains would slap the water and rattle the whole boat unless you were quick about it and put them to full rise.

But in the event of a collision head on its better to have them on the sail like on the USS San Francisco.

[sonar732]

Originally Posted by TLAM Strike

But in the event of a collision head on its better to have them on the sail like on the USS San Francisco.

Did you forget this pic?

Copyrighted from www.subguru.com

[XabbaRus]

My mistake with the Virginia,

However,

Originally Posted by Kapitain

Id doubt the american's would go down the russian path after all these years.

Despite the hydrodynamic efficentcy of the sail on russian submarines it can prove unstable during high speed turns, and can roll over where the america blockish type sail can keep the sub upright.

So a blended sail can have advantages in speed and efficentcy but also disadvantages in other areas.

I thought the whole point of the blended low profile sail was to avoid or at least minimise the instability and risk of snap rolling during a high speed turn. Given that US submarines sails are taller and of a similar chord I would expect the lifting force to be greater than that of a Russian sail.

[Kapitan]

The al'fa had such a squat sail that if it turned full rudder at top speed it would well roll and roll imagine the crew inside a tumble dryer

[XabbaRus]

Hmm, not sure about that...

Take a look at this

http://203.10.217.104/publications/3...TO-TR-1622.pdf

Page 33, apparently the squatter sail loses hydrodynamic efficiency.

There is also a bit about snap roll but it is ambiguous as to whether he is referring to Russian or US sails.

[Sea Demon]

Hmmm...That's interesting Xabba. Just a small question in regard to the Russian sail design. Doesn't it have less turbulent flow at the trailing edge than the American design due to the fact that it has more of a curvature (roundness) in shape? It may be less efficient than American sails hydrodynamically, but perhaps has a better shape in reducing hull flow noise? What is your opinion?

BTW, I had no idea the Russians intended the blended sail for roll risks when high speed maneuvering. But makes sense when you look at what subs like the Alfa could do.

Sea Demon

[Kapitan]

Intresting read ive printed it out and have contacted a friend of mine to see its worth.

Professor P.N Joubert is highly regarded in the maritime engineering world.

Il read the rest when i get time but its intresting

[XabbaRus]

I was of the impression and one given to me by a few ex US navy sumariners I have chatted with that the larger sails of the US submarines increased the snap roll probability due to the fact that although it might have a larger lever action it also generated lifet. We all know that underwater in a turn due to the bernoulli effect (spelling?) you get lower pressure on the side of the sail that is on the inside of the turn, thus the sub rolls in that direction, much like how a wing generates lift. It is from this that I surmised that although Russian sails being squater would have less of a lever moment they would generate less "lift" on the inside of the turn and thus not roll so much.

Hmmm, any of you ex subbies here able to help me out.

You got it right.

It's called 'foil roll' and is different from the vortex shear that precipitates the infamous 'snap roll.'

Foil roll is incremental and is proportionate with the boats angle of attack about the yaw axis as the rudder is put over. Snap roll is sudden and dangerous.

Class design evaluation (physical and computer model runs) and post build, pre-commissioning trials of the lead boat verify or modify the projected handling characteristics. The findings are working into a ships characteristics book that defines the boats performance envelope: such-and-such will happen if you do this-and-that.

These perimeters are drilled into the Ship Control Party. Foil roll, snap roll, c.g./c.b./c.p. shifts and the like are understood in the context of what they mean to ship angle, roll, response, speed, recovery times and excursion depth anticipated. Recovery/avoidance moves are constantly drilled on in both a shore-side team-trainer simulator and aboard the boat.

Simply put, the Conning Officer directs his ship control party to stay out of situations that do bad things to the boat. Where the bad things hide is known, it's simply a matter of running the boat so as to avoid straying into those bad places.

That's a reply to a post I made on another forum where there are quite a few ex US navy submariners.

It seems we are confusing 'snap roll' with 'foil roll' Snap roll being a sudden departure foil roll being a result of water flowing round the sail as described in the quote. Size of sail does influence how much 'foil roll' you get and therefore Russian subs suffer from it less.


This is shown with further clarification below.

OK so it doesn't cause snap roll, but a taller sail does produce a larger bank and would I be right in assuming at a higer rate of roll too for any given speed?


Yup.

Skipjack is the worst.

David,

Also I was passed on a message to the effect that the Alfa had no problems making full speed turns...

[Kapitan]

Seems that way, but having a large sail has some advantages.

For a start dont have to go so shallow at PD and un the risk of exposure (akula's do some times).

[JessIAm]

Originally Posted by GrayFox

I have heard rumors that the USS North Carolina & USS New hampshire (SSN 777 & 778) will have a new sail design.

SSN 777 did indeed introduce a new sail design. The design incorporates fully electronic periscopes and masts from the top of the sail. Since no physical connection is needed between the periscope display in the CIC, the CIC can be incorporated into the hull more (or entirely). This allows the CIC to be larger.

The new sail design doesn't change the outward appearance of the sail compared to previous Virginia class submarines.

[Aktungbby]

JessIam!you are nominated for necro of the year,We've been waiting 14 years for this info!

[Onkel Neal]

All right! Awesome, and it's not even a spammer. Good job!