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PostPosted: Thu Sep 12, 2019 12:03 pm 
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Since the last post was long, I will summarize the appearance of 688 stern stabilizers:

Flight I and II
1970s (as launched) - no towed array blister and no towed array tubes at all
1970s (as commissioned) - most had the towed array blister and towed array tube on the port stabilizer
1980-1985 - all had the towed array blister and towed array tube on the port stabilizer
1985-1990s - some may have had additional towed array tube on the starboard stabilizer
1990s-present - probably all have additional towed array tube on the starboard stabilizer
2005-present - possibly some have additional WSQ-9 fairings on both stabilizers

688I
1980s (as launched/commissioned) - all had the towed array blister and towed array tube on the port stabilizer and possibly the tube on the starboard stabilizer
1990s - probably all had additional towed array tube on the starboard stabilizer
2000s-2005 - all have additional towed array tube on the starboard stabilizer
2005-present - most, if not all, have additional WSQ-9 fairings on both stabilizers

The WSQ-9 is an active intercept sonar fitted to the Virginia-class and retrofitted to the 688Is and possibly earlier 688s. This is what it looks like on the Virginia-class,

Image
Image
Image

Jacob

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PostPosted: Thu Sep 12, 2019 2:25 pm 
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Hi Jacob,

That is very complete and extremely useful information, thank you a lot! And your sketch is invaluable for us modelers. :worship_1:

And of course I was confused using the VLS abbreviation, thanks for the correction!

Maarten

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PostPosted: Thu Sep 12, 2019 9:19 pm 
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Just out of curiosity, I was wondering if any body has knowledge about the USS Cheyenne SSN 773. I recently ran across a picture online of the sub in dry dock and it has the three large sonar panels on the sides like the Virginia Class subs. I have not found any of the other Los Angeles subs with them yet so I was wondering if any one knew when they were added.


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PostPosted: Fri Sep 13, 2019 2:06 am 
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JordinR wrote:
Just out of curiosity, I was wondering if any body has knowledge about the USS Cheyenne SSN 773. I recently ran across a picture online of the sub in dry dock and it has the three large sonar panels on the sides like the Virginia Class subs. I have not found any of the other Los Angeles subs with them yet so I was wondering if any one knew when they were added.

You are right, USS Cheyenne is the last build of the class and seems to have been the test platform for the Virginia sonar panels. https://en.wikipedia.org/wiki/USS_Cheyenne_(SSN-773) I would appreciate if you could upload that picture you found! In return here the drawing of her.
Attachment:
0877335a.jpg
0877335a.jpg [ 148.25 KiB | Viewed 2717 times ]

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PostPosted: Fri Sep 13, 2019 4:30 pm 
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JordinR wrote:
Just out of curiosity, I was wondering if any body has knowledge about the USS Cheyenne SSN 773. I recently ran across a picture online of the sub in dry dock and it has the three large sonar panels on the sides like the Virginia Class subs. I have not found any of the other Los Angeles subs with them yet so I was wondering if any one knew when they were added.


Could you post that photo? As far as I am aware, the only 688 ever to receive the BQG-5 WAA (Wide Aperture Array) was the Augusta. The 688Is only had about 30 tons of weight margin (i.e. extra lead ballast), and the boats with the improved propulsion plant (SSN 768-773) had a zero weight margin. This would make it difficult to accommodate the weight of the WAA arrays. But if a photo exists, they must have figured out a way to do it.

Jacob

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PostPosted: Sat Sep 14, 2019 11:52 am 
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Hello again. I found these pictures on the Pearl Harbor Naval Shipyard Facebook page. If anyone wants to look up there page there are several interesting sub pictures in there going back through the last 5-6 years. I am going to try to post the direct link to these pictures. The first one I want to post here is dated May 2016 of USS Olympia SSN 717 which I thought gives an interesting look on a fresh older 688 ready to hit the seas again. https://scontent-ort2-2.xx.fbcdn.net/v/ ... e=5E0A71F9


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PostPosted: Sat Sep 14, 2019 11:57 am 
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The next picture I have found is from a dry docking of the USS Tucson SSN 770. One can see some of the little detailing down the side of this 688i boat. https://scontent-ort2-2.xx.fbcdn.net/v/ ... e=5DF7DAFA


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PostPosted: Sat Sep 14, 2019 12:03 pm 
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And lastly, here is a few of the pictures from April 2014 which say they are part of the Cheyenne Project. https://scontent-ort2-2.xx.fbcdn.net/v/ ... e=5E0A29C1 https://scontent-ort2-2.xx.fbcdn.net/v/ ... e=5E0F176C https://scontent-ort2-2.xx.fbcdn.net/v/ ... e=5DF2E98A


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PostPosted: Sat Sep 14, 2019 12:10 pm 
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Yep, those are definitely WAA panels. I wonder it was the advancements in COTS sonar equipment as well as the Light Weight WAA (LWWAA) that allowed for enough margin to carry those arrays.

Jacob

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PostPosted: Sat Sep 14, 2019 12:32 pm 
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Cold Warriors by Roy Manstan (p. 209) claims that an engineering development model of the WAA was installed on the Cheyenne, which implies it was done in the '90s:

https://play.google.com/books/reader?id=kZWmAwAAQBAJ&printsec=frontcover&pg=GBS.PA180.w.3.0.15

I still don't understand how the Cheyenne had enough margin for the heavy arrays, but obviously they were able to lighten the boat enough.

Jacob

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PostPosted: Mon Jan 20, 2020 7:20 pm 
pascalemod wrote:
Vepr157 wrote:
Pascalemod,
Do all LA classs boats sit lower by the stern, so the muck line is NOT parallel to the red lower half of the hull it seems. Can you confirm this and why this is?


Yes ... 688's sit at a 1-1/2 degree up-bubble pierside. this is due to the center of gravity being located aft of the center of buoyancy ... basically, they have a "heavy" reactor & engine-room aft.

When they come up to speed the hydrodynamic forces on the hull cause the bow to suck down to a zero bubble. ... and of course, when submerged, the boat is trimmed to a zero bubble.


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PostPosted: Mon Jan 20, 2020 7:36 pm 
JordinR wrote:
Just out of curiosity, I was wondering if any body has knowledge about the USS Cheyenne SSN 773. I recently ran across a picture online of the sub in dry dock and it has the three large sonar panels on the sides like the Virginia Class subs. I have not found any of the other Los Angeles subs with them yet so I was wondering if any one knew when they were added.


Actually the WAA (Wide Aperature Array) was prototyped on USS Augusta (SSN-710). We did an underhull on her in the Bahamas back in 1988 and could clearly see the individual sonar array bulges.

I'm not certain if Cheyenne had a WAA (never operated with her) ... but from my discussions w/ some of crew she was the test bed for the propulsor that was eventually used on the VA class.


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PostPosted: Tue Jan 21, 2020 1:56 pm 
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Just to add to the previous post. I actually have a coffee mug with a very nice (and still quite crisp) color rendition of the Augusta with the WAA. The caption says "USS Augusta SSN-710" and "AN/BQG-5", with the three WAA blisters on the submarine's side. Picked it up when I was living in the Groton area.

Tom

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PostPosted: Thu Jan 30, 2020 8:54 pm 
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I'm trying to catalog the number of different screws for the LA class, and I've come up with three.

OG:
Image


Vortex Attenuator:
Image

Image


Ice ring guard:
Image

Image

Are we aware of any others? Is there any understanding of the timeline of introduction? The Ice Ring Guard variant, is that swapped on and off as needed? And what are current LAs running?


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PostPosted: Fri Jan 31, 2020 9:15 am 
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The vortex attenuator was added to the existing 7 blade propellers when it became apparent that the Russian submarines had wake detectors. I guess you could call that a variant. The ring propeller is on the 688I boats, which are capable of under ice operations. Earlier LAs are not, as their sail planes cannot rotate to the vertical (as the Sturgeon class) due to the small sail size. For the 688I, they received retractable bow planes, reinforced sails and ring props.

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PostPosted: Fri Jan 31, 2020 9:42 am 
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Tom Dougherty wrote:
The vortex attenuator was added to the existing 7 blade propellers when it became apparent that the Russian submarines had wake detectors. I guess you could call that a variant. The ring propeller is on the 688I boats, which are capable of under ice operations. Earlier LAs are not, as their sail planes cannot rotate to the vertical (as the Sturgeon class) due to the small sail size. For the 688I, they received retractable bow planes, reinforced sails and ring props.


So do all 688i have the ring screw? Are there exceptions (that is, a 688i with the vortex attenuator screw)? And to clarify, "688i" and "Flight III" are synonymous designations?

Yes, sans vortex attenuator would seem to be a forth then, thanks for pointing that out.


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PostPosted: Wed Feb 12, 2020 1:09 pm 
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Woodstock74 wrote:

So do all 688i have the ring screw? Are there exceptions (that is, a 688i with the vortex attenuator screw)? And to clarify, "688i" and "Flight III" are synonymous designations?

Yes, sans vortex attenuator would seem to be a forth then, thanks for pointing that out.


I haven't seen a 688I with a non-annular screw, and I have only seen the vortex attenuator on non-688I screws, but this is a sample size of only a handful of photos. Since submarine screws are made up of two main parts (the hub with the blades, and the boss cap) I assume that the vortex attenuator (that specific type of design is commercially called Propeller Boss Cap Fins) is just added on to the original screw design. Whether or not it's connected to the Russian interest to non-acoustic ASW, I don't know, but it certainly does increase propulsive efficiency. As for the annular screw, it may help with ice protection, but it also probably increases propulsive efficiency and decreases propeller tip cavitation by eliminating the blade tip vortices. The ring also might help reduce flexing of the blades.

And yes, 688I and Flight III are synonymous.

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PostPosted: Tue Feb 18, 2020 12:15 pm 
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Vepr157 wrote:
Woodstock74 wrote:

So do all 688i have the ring screw? Are there exceptions (that is, a 688i with the vortex attenuator screw)? And to clarify, "688i" and "Flight III" are synonymous designations?

Yes, sans vortex attenuator would seem to be a fourth then, thanks for pointing that out.


I haven't seen a 688I with a non-annular screw, and I have only seen the vortex attenuator on non-688I screws, but this is a sample size of only a handful of photos. Since submarine screws are made up of two main parts (the hub with the blades, and the boss cap) I assume that the vortex attenuator (that specific type of design is commercially called Propeller Boss Cap Fins) is just added on to the original screw design. Whether or not it's connected to the Russian interest to non-acoustic ASW, I don't know, but it certainly does increase propulsive efficiency. As for the annular screw, it may help with ice protection, but it also probably increases propulsive efficiency and decreases propeller tip cavitation by eliminating the blade tip vortices. The ring also might help reduce flexing of the blades.

And yes, 688I and Flight III are synonymous.


Thanks for the clarifications!


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PostPosted: Sun Mar 15, 2020 4:10 pm 
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The first I ever head of the 11-bladed vortex dissipater (that's what they (crew) called it) was after the LA used one while she was in Pearl, after arriving in '78. Supposedly, it was removed after evaluation to add a little extra speed to what was already a fast quick and silent boat. --As in spooky silent.

They passively ranged us during a training exercise, and then proceeded to perform an under-hull, with us blissfully unaware just a few yards above. We had been told this op was going to happen but when it did, we were . . . blissfully unaware. The only way to detect them would have been to use our fathometer, but that was tagged out after diving, --as per the CO's Standing Order. After we returned to port, our CO was pretty pissed-off, but our equipment was NO match to theirs. That didn't prevent him from taking it out on any sonarman he crossed paths with for a long time thereafter.


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PostPosted: Fri May 29, 2020 10:33 am 
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Regarding the LA's screw diameter, digging into this data base, here:
https://www.parttarget.com/?userguid=72 ... 92E6E12160

Looking at the 688's propeller entry, here:
https://www.parttarget.com/2010-00-106- ... 28E17F6A13

Says:

AGAV End Item Identification Propeller assy 216.000IN od 250.964IN pch rh

216 in OD...= 18'

But what's the 250.964" indicating (20.8')?

Pretty cool it gives diameter of the vortex attenuator (dissipator) at 5.5' and verifies the blade count (11).


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