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Topic review - Calling all Los Angeles class (SSN-688) fans
Author Message
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
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!
Post Posted: Tue Feb 18, 2020 12:15 pm
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
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.
Post Posted: Wed Feb 12, 2020 1:09 pm
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
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.
Post Posted: Fri Jan 31, 2020 9:42 am
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
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.
Post Posted: Fri Jan 31, 2020 9:15 am
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
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?
Post Posted: Thu Jan 30, 2020 8:54 pm
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
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
Post Posted: Tue Jan 21, 2020 1:56 pm
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
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.
Post Posted: Mon Jan 20, 2020 7:36 pm
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
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.
Post Posted: Mon Jan 20, 2020 7:20 pm
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
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
Post Posted: Sat Sep 14, 2019 12:32 pm
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
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
Post Posted: Sat Sep 14, 2019 12:10 pm
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
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
Post Posted: Sat Sep 14, 2019 12:03 pm
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
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
Post Posted: Sat Sep 14, 2019 11:57 am
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
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
Post Posted: Sat Sep 14, 2019 11:52 am
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
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
Post Posted: Fri Sep 13, 2019 4:30 pm
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
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.
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Post Posted: Fri Sep 13, 2019 2:06 am
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
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.
Post Posted: Thu Sep 12, 2019 9:19 pm
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
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
Post Posted: Thu Sep 12, 2019 2:25 pm
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
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
Post Posted: Thu Sep 12, 2019 12:03 pm
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
Maarten Schönfeld wrote:
I have just been browsing through the lot of 688 photos on Navsource, but photos where the stern stabilizers are in view are very rare, and in fact I have seen NO towed VLS or thin line array tubes on any photo at all! In all these cases the stabilizers are bare, just as if they were Sturgeon stabilizers - but without the end plates!
So if anyone can provide good shots of these tubes, either stbd or port, would be a great help! Otherwise we should all start cutting them from our models, Italeri, Hobby Boss, Riich or whatever. As for now I had deleted them from my 688 Los Angeles already.


Maarten,

If there's a fairing for the towed array along the starboard side (the long blister that runs from bow to stern), there will always be a towed array tube on the port stabilizer. This is the TB-16 ("fat-line") towed array. The array itself was thick and inflexible ("fat"), thus it had to be kept relatively straight inside that fairing on the starboard side. It was streamed out of the tube on the port stabilizer on a much longer cable that was stored in the forward ballast tanks (because the tow cable was thinner and more flexible, it could be wrapped around a winch). A few of the early 688s were launched without towed arrays, but they were added soon after the submarine was commissioned. By about 1980, all 688s had TB-16 towed arrays. To reiterate, if the long blister on the starboard side is there, there must be a tube on the port stabilizer. Having neither the blister or port-side tube is only correct for a few boats in a limited time period.

Before the TB-23 was introduced, the starboard stabilizer was bare, like you described. The TB-23 ("thin-line") was longer, thinner, and more flexible than the TB-16, thus it could be wrapped around a winch with its tow cable. The array and cable were stored in the aft ballast tank and the array was streamed out of a tube on the starboard stabilizer. The TB-23 was developed in the mid '80s, and my impression is that they were fitted to the new 688Is before they were retrofitted to the early 688s. The TB-29 was another type of thin-line array that was developed in the mid '90s, and the tube on the starboard stabilizer was almost certainly unchanged for boats that got the TB-29.

Here is a photo of the Columbia which shows both arrays,

Image

as does this youtube video of the La Jolla,

https://www.youtube.com/watch?v=tfcNIAEDsPM

Here is a drawing I made showing the top-down view of a 688 with both TB-16 and TB-23 tubes,

Image

By the way, VLS refers to the Vertical Launch System (the nest of 12 tubes on the Flight II and Improved 688), and not a towed array.

Jacob
Post Posted: Thu Sep 12, 2019 11:44 am
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
Quote:
As for the stern stabilizers, at that time they probably just had the towed array tube on the port stabilizer. The tubes on the kit look a little long to me. The port tube should only extend about 2 feet past the stern plane trailing edge, which is just 1/16 inch in 1/350 scale. I don't think the thin-line array on the starboard stabilizer was added until later, so the tube on the starboard stabilizer should be cut off so that the end is flush with the stern plane like the picture of SSN 703 on page 4.

I have just been browsing through the lot of 688 photos on Navsource, but photos where the stern stabilizers are in view are very rare, and in fact I have seen NO towed VLS or thin line array tubes on any photo at all! In all these cases the stabilizers are bare, just as if they were Sturgeon stabilizers - but without the end plates!
So if anyone can provide good shots of these tubes, either stbd or port, would be a great help! Otherwise we should all start cutting them from our models, Italeri, Hobby Boss, Riich or whatever. As for now I had deleted them from my 688 Los Angeles already.
Post Posted: Thu Sep 12, 2019 3:26 am

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