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PostPosted: Sat Aug 01, 2015 7:23 pm 
Wow. I have never seen such detail, you can even see the zincs. Thank you.


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PostPosted: Sun Aug 02, 2015 12:49 pm 
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Quote:
aken from Vepr157's amazing prop album: http://imgur.com/a/IQBOi


It is a nice collection of photos. One error which could affect model building is that the photo of Scamp's five bladed screw is printed in reverse. This is from the Friedman book and was printed with the negative reversed. The blades should be pitched so that the screw turns clockwise when viewed from behind the boat.

The explanation of the noise caused by the original Scamp screw (water boiling and cavitation) is also incorrect. The original five bladed screw had problems with "blade rate" noise, which is a low frequency emission caused by the large flat blade entering and exiting the disturbed wake caused the rudder and stern planes. The individual blades abruptly entered the disturbed wake and vibrated. This low frequency sound carried great distances in the deep sound channel. The skewed back propellers had dampening features (pure Wasatch sand in their hollow shafts), smaller surfaces (hence 7 blades instead of 5) and entered and exited the wake more gradually due to their shape. SOSUS hydrophone arrays were placed in the deep sound channel, and could pick up Soviet subs (which lacked the 7 blade, damped propellers) often at great distances.

The George Washington (SSBN 598) originally went to sea with a five bladed propeller, and it is said that SOSUS could track the Washington during transit to Holy Loch, Scotland from Groton.

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PostPosted: Tue Aug 18, 2015 1:12 pm 
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Tom Dougherty wrote:
Quote:
aken from Vepr157's amazing prop album: http://imgur.com/a/IQBOi


The explanation of the noise caused by the original Scamp screw (water boiling and cavitation) is also incorrect. The original five bladed screw had problems with "blade rate" noise, which is a low frequency emission caused by the large flat blade entering and exiting the disturbed wake caused the rudder and stern planes. The individual blades abruptly entered the disturbed wake and vibrated.


Is this not exactly what I said in the album? In shallow water, there was cavitation at flank speed, but as the submarine went deeper, the cavitation noise decreased and eventually stopped at some depth, and all remaining noise was from blade-rate. It's in the chapter notes in Submarines Since 1945.

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PostPosted: Tue Aug 18, 2015 5:20 pm 
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Sort of… My point was that the reason for the replacement of the screw with the J-propeller was almost solely due to blade rate. Cavitation is a problem at shallow depths for all propellers at high turns, but is is blade rate that allowed long range detection by SOSUS arrays in the deep sound channel. This is, of course, why the details of the design of the J-propeller and later designs were so closely kept for years. During the Cold War in the 1970-early 80's time frames, the USSR equipped their submarines largely with standard propellers, which allowed tracking at long range by SOSUS which was used to vector in trailing submarines. For example, all of the Alfa's had a standard propeller and were detected at high speeds up to thousands of kilometers range by SOSUS.

As I said, it is a very nice collection of photos of the propellers you have assembled.

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http://www.usni.org/store/catalog-fall-2012/project-azorian


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PostPosted: Fri Oct 23, 2015 3:45 pm 
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Hello
I'am not quite sure, that, I'am a SSN688 fan
but :
http://www.koga.net.pl/forum/viewtopic. ... 23&t=23122
http://www.koga.net.pl/forum/viewtopic. ... 23&t=45318
http://www.koga.net.pl/forum/viewtopic. ... 35&t=46284

If, I make mistake with post on this forum, I'am very sorry.

With regards
Andrzej Korycki


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PostPosted: Sun Feb 28, 2016 10:50 am 
Ok, I understand that the anhedrals were introduced on the Flight III Los Angeles class boats to counteract rolling tendencies induced by the sails during high-speed maneuvers. In addition, the ends of anhedrals have additional countermeasure dispensers at their ends.

Unless the snap roll was aggravated by moving the planes to the bow, it would seem that they would also be helpful on the earlier boats, as well as providing additional countermeasure dispensers. So, does anyone know if these have been retrofitted on the earlier boats?


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PostPosted: Mon Feb 29, 2016 8:24 pm 
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I don't know why they were not retrofitted to the rest of the class (perhaps the structural modifications weren't worth the trouble). Memphis is the only non-Improved 688 that I've seen with the anhedral fins, but she was a test bed for all sorts of things.

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PostPosted: Sat Mar 12, 2016 7:10 pm 
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FRAMSailor wrote:
Ok, I understand that the anhedrals were introduced on the Flight III Los Angeles class boats to counteract rolling tendencies induced by the sails during high-speed maneuvers. In addition, the ends of anhedrals have additional countermeasure dispensers at their ends.

Unless the snap roll was aggravated by moving the planes to the bow, it would seem that they would also be helpful on the earlier boats, as well as providing additional countermeasure dispensers. So, does anyone know if these have been retrofitted on the earlier boats?



The anherdrals have nothing to do with countering any rolling at high speeds. When the subs are operating at high speeds they a switch in between the helm and planes man that they switch on to limit the amount of movemnet the planes surfaces or rudder can move. The anherdrals just contain additional countermeasures and maybe additional towed sonar gear.

I served on US subs for 8 years.

Duane

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PostPosted: Sat Mar 12, 2016 8:34 pm 
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Seems like a lot of weight and drag just for more countermeasures (judging from some excellent close-ups, they don't seem to be associated with any towed arrays).

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PostPosted: Sat Mar 12, 2016 9:51 pm 
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Nope. They're there to counter roll and increase yaw stability. Secondary purpose is to get towed line and 'devices' outside the propeller disc.

David

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PostPosted: Sat Mar 12, 2016 10:14 pm 
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Here's a photo of the fins in question (USS Columbia):

http://i.imgur.com/2l2f8No.jpg

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PostPosted: Fri Aug 05, 2016 5:19 pm 
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I'm interested in building USS Chicago in 350th and the idea of representing a deployed towed sonar array appeals.

In an earlier post Vepr says the flight II boats the array "is streamed from a small tube on the port side diving plane".
I believe there's a photo (but can't seem to relocate it) of an arrangement with a pipe, supported by a v-bracket, leading from the aft edge of the hull storage fairing to the outboard end of the aft plane. Is this the arrangement Vepr refers to? Can someone help with a link to this photo?

Assuming the deployment arrangement can be reasonably nailed down, I'd think in 350th the array could be modelled with something like piano wire with maybe a cone shaped drogue at the far end and some wrapping in front of that to represent the phone housings. Shaping up to be a pretty lengthy (and perhaps droopy) display but still an interesting possibility.

Any help or comments would be greatly appreciated.


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PostPosted: Sat Aug 06, 2016 4:00 pm 
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It sounds as if you may be confusing the towed array installation on the Sturgeon class with the LA class. The Sturgeons had the arrays adding post construction and the array had an external support. Here's a model showing that:
http://thatravenmagic.com/cavallaaft.html
and: http://www.navsource.org/archives/08/0865005.jpg
and on the Sturgeon class USS Aspro in dry dock: http://www.navsource.org/archives/08/0864801.jpg
and this painting from Undersea Warfare magazine: http://www.navsource.org/archives/08/0866804.jpg

The LA class towed array was all internally housed, and deployed from the ends of the stern planes:
https://upload.wikimedia.org/wikipedia/commons/9/94/USS_Greeneville_(SSN_772)_-_dry_dock_Pearl_Harbor_(1).jpg
and https://upload.wikimedia.org/wikipedia/commons/8/8b/USS_Greeneville_(SSN_772)_-_dry_dock_Pearl_Harbor_(2).jpg
and: https://upload.wikimedia.org/wikipedia/commons/8/8b/USS_Greeneville_(SSN_772)_-_dry_dock_Pearl_Harbor_(2).jpg

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PostPosted: Sun Aug 07, 2016 9:34 pm 
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Adding on to Tom's comment:

The TB-16 (and successive fat-line arrays) are stored externally in a blister on the starboard side, and stream out of the port stabilizer. Only the thin-line array (probably only carried on later 688s; not sure about Chicago) is stowed was stowed inside the outer hull. Your model should include the blister as well as the little tubes protruding from the stabilizers.

Something I didn't realize until a few months ago is that the first ten or so 688s did not have the towed array when launched. If you look at photos of the newly-commissioned 688s (see links), they don't have the towed array blister until about 1980 or 1981. I wonder if they were built so that the towed array could be added later or the were completely retrofitted.

http://navsource.org/archives/08/688/0868837.jpg
http://www.navsource.org/archives/08/0868802.jpg
http://www.navsource.org/archives/08/0869706.jpg

Jacob

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PostPosted: Mon Oct 24, 2016 2:08 am 
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I want to do a model of USS Tucson SSN-770. what model should i work use to work with and what are the things i should look for and consider?


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PostPosted: Mon Oct 24, 2016 2:07 pm 
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AZMadHatter wrote:
I want to do a model of USS Tucson SSN-770. what model should i work use to work with and what are the things i should look for and consider?


You basically three options in 1/350: the old Dragon kit, and the newer Riich and Hobby Boss kits.

In terms of accuracy, I think the Riich is the best (though the anhedral fins are not perfect); the Dragon is the worst. The only bad thing about the Riich is that the hull comes as a waterline section and two lower sections, which are a pain to get a good fit on. Otherwise it's pretty good.

None of the screws that come with these kits are very accurate. Besides being not properly shaped, they need to have a ring connecting the tips for the Improved 688s.

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PostPosted: Tue Oct 25, 2016 12:24 am 
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thanks, vepr157

what about 1/700? i think i've seen a couple out there.


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PostPosted: Tue Oct 25, 2016 4:21 pm 
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AZMadHatter wrote:
thanks, vepr157

what about 1/700? i think i've seen a couple out there.


Your best bet is probably the Hobby Boss kit. The anhedral fins are incorrect and you'll have to fill in the weird circumferential groves (supposed to represent non-existent weld-lines, I guess).

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PostPosted: Wed Oct 26, 2016 5:24 pm 
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Vepr157 wrote:

Your best bet is probably the Hobby Boss kit. The anhedral fins are incorrect and you'll have to fill in the weird circumferential groves (supposed to represent non-existent weld-lines, I guess).


I saw that when I comparing photos of Tucson and Greeneville. I have Testor's putty that I can put to good use. did Tucson carried the ASDS used in the Greeneville model kit? if not, I probably have some work to do in that location. Also, where I can get decals to depict USS Tucson? I ordered then hobby boss kit on Monday, and should get both submarine and cruiser models by this weekend to do both Tucson ships that served the navy. I'm probably going to do the submarine first before i do the cruiser model because the cruiser has way too many questions at this point.


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PostPosted: Thu Oct 27, 2016 6:40 am 
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Vepr157 wrote:
None of the screws that come with these kits are very accurate. Besides being not properly shaped, they need to have a ring connecting the tips for the Improved 688s.

Hi guys,

There are screws available in 1:350 scale that may stand some scrutiny I believe. These are available from Naval Models in the Netherlands, you best write an email to Michiel Woort (the owner) at info@navalmodels.com. I think these screws are not advertized (yet) in their webshop.

Below I show these on two HobbyBoss LA 688 models, the right of course a Flight III 688i with the anhedrals repositioned to the correct 20 degrees below the horizontal.
Attachment:
IMAG1674a.jpg
IMAG1674a.jpg [ 62.48 KiB | Viewed 2740 times ]

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