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Thresher / Permit control surface bearing blocks & Hydrophone end plates

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  • #16
    I've found a bit more information on the period when the BQG-2A Sonar arrays were likely to have been fitted to both SSN-596 Barb and SSN-593 Thresher.

    Navsource has an article detailing the operational history of Barb in the 1963-1972 period;

    The BQG-2A array appears to have been installed during the Post Shakedown Availability refit at Mare Island in December 1963 and is noted as being "replaced" during drydocking at Pearl Habour in December 1969.

    Recently a number of documents on the loss of the Thresher were declassified, including testimony from the court of enquiry. Links to the documents can be found here;

    There are several references to the installation of an updated version of the PUFFS array during the Post Shakedown Availability refit from July 1962 to April 1963 (An earlier version of the PUFFS system was already fitted). Thresher was subsequently lost during her initial post refit shakedown cruise on 9 April 1963.


    • #17
      Nice work on the model! Regarding PUFFS, the Thresher originally had the BQG-1 system, which consisted of four hydrophones mounted in a parallelogram, two of them on retractable masts. The Tullibee initially had the same system, but mounted in a line (two in domes, one in the sail, and one under the superstructure). The Ethan Allen class was designed with BQG-1, and it's possible that they briefly had them (see my reddit discussion:

      The Thresher, Barb, and Blueback subsequently got BQG-2 (six sub-arrays with multiple hydrophones in each) while the Tullibee and various diesel boats got BQG-4. The Haddock had Micropuffs, which was probably similar to BQG-2 (later fitted to Canadian and Australian submarines as BQG-501). The entire Sturgeon class and the Narwhal nominally had space for BQG-2, but it appears that it was rarely, if ever, installed.

      The Baya had the first prototype BQG-5 Wide Aperture Array (WAA), which looked initially similar to BQG-4 with three fin-like fairings, but it was difficult to incorporate amidships ballast tank space on the Los Angeles design to accommodate the arrays a la BQG-2. Thus the WAA design changed radically to six curved panels, which was trialed on the Augusta and later the Cheyenne and are now on all Seawolfs and Virginias.

      By the way, I saw that you fitted the hull shape to a Myring form. The Thresher hull form was based on the Series 58 6th degree polynomials with the addition of a parallel midbody, as was the case of most U.S. submarines in that era, including the Nautilus. The Series 58 report can be found here:

      And the paper outlining the mathematical formulation of the hull equations is here:



      • #18
        The Wide Aperture Arrays on the SSN-21 and VA Class are another step in the evolution of linear arrays decades after PUFFs and it's cousins. There was another array prior to that filled the gap.

        The Q-5 and later Q-6; (neutered for the Tridents) incorporated line arrays oriented and optimized for LF bottom bounce/CZ detection inside each side of the ballast tanks. The Line Array (DT-574A hydrophones) was integrated into the sonar suite as another input corresponding with it's frequency range - it was not a standalone sensor system. The Q-6 Spherical Array used (944) DT-674As too.

        The same phone lives on: The author blows it in this article calling it a "hydrophone sonar transducer" explaining that it's used in passive sonars. Transducers are active elements. Hydrophones are passive elements.

        Navy submarine sonar experts choose Massa Products to design and build DT-574 hydrophone transducers | Military & Aerospace Electronics


        • #19
          Hi Jacob,

          Thanks for the background on the hydrophone systems and evolution of the configurations on successive SSN and SSBN classes. There is a photo on Navsource of Thresher with what I guess is the BQG-1 dorsal mast deployed aft of the sail;

          Would the other deployable mast be on the ventral position?

          The Thresher/Permit CAD model actually started from experimenting with Myring equation & finding that it actually gave quite a good fit to the form. However, I assumed that the actual hull shape was derived from the Series 58 shape, given the research done at the David Taylor Model Basin in the 1950's and the full scale demonstration of the 4165 hull shape on the USS Albacore. The CAD model is done in Rhino 7 and I have made Grasshopper definitions of both the Myring and Series 58 equations. So it is fairly easy to generate different hull forms and compare to plans. So far I've not gone much further with the Series 58 than inputting the parameters from the shapes described in Gertler's 1950 paper. The 4165 shape nicely overlays onto the symmetric part of the USS Albacore hull, only deviating at the stern for the control surfaces and prop.

          There is a further publication from 1955 with experiments with the Series 58 shapes including a 30%-60% parallel mid body section, comparing resistance to the pure 4165 teardrop shape;

          I've slowly been progressing with the CAD model in the meantime, adding in the deck layout and internal structure. This is primarily based on Greg Sharpe's plan, supplemented with details from photo's. The internal structure is based on a basic section of a Sturgeon, taking into account the difference in length and position where the hull was extended between the long/short Permit and Sturgeon classes. At first glance the external features such as hatches and ballast tank vents on the plan line up with the internal components. There is still quite a bit of work to do on the model and I some parts I need rework, but it is quite an enjoyable project to integrate details from photo's and other sources of information into the model. As the Thresher/Permit and Sturgeon classes share the same basic hull form it should be possible to derive models of the long hull Permit and Sturgeon from the base model, taking into account the hull inserts and differences in sail, rudder, dive planes etc.

          Here are a few screenshots to the current version of the model

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          • #20
            This is excellent stuff. Very well done. In all the investigation on this boat has it ever been confirmed if the Thresher had a 5-blade or 7-blade prop when it went down? I know the props are/were a big secret to the Navy and I believe it at least started out with a 5-blade but it seems to be a big mystery.


            • #21
              I found this while doing some digging. Claims that Barb was the first ship to get the AN/BQG-2A which according to another document was in December of 63 which is after the loss of the Thresher. Either this document is incorrect or the Thresher wasn't counted as the first because of its loss.

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