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Thresher / Permit control surface bearing blocks & Hydrophone end plates

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  • Thresher / Permit control surface bearing blocks & Hydrophone end plates

    I've started researching a bit the different configurations of the Thresher / Permit class & have a couple of questions on the rudder and rear dive plane arrangements.

    Most plans & scale models of the Thresher / Permit class submarines show the rudders and rear planes rotate around a fixed bearing block with a cutout in the control surface. However, launching / construction photos of the Thresher, Plunger as well as one Barb in drydock appear to have the rotation fully enclosed in the control surface. Therefore, is it possible that the bearing block was a later modification or incorporated only specific boats? Unfortunately, I've only found a few photo's of the rear control surfaces.

    Here are links to the specific photos ;

    SSN-593 Thresher launch photo, showing upper Rudder
    http://navsource.org/archives/08/593/0859317.jpg

    SSN-594 Permit Stern section showing dive plane and rudder axes
    http://navsource.org/archives/08/593/0859407c.jpg

    SSN-595 Plunger construction photos, showing upper Rudder and Rear Dive Planes
    http://navsource.org/archives/08/593/0859518.jpg

    SSN-596 Barb Drydock photo showing Rudder
    https://imgur.com/jje70AL


    Interestingly the photo of Barb shows the installation of an element of the BQG-2 Hydrophone array in an end plate on the rear dive planes. A similar arrangement appears to have been fitted to the Thresher at the time of her loss as it is visible in a couple of photo's taken by the Trieste during survey of the wreck in 1963-1964;
    http://navsource.org/archives/08/pdf/0859368.pdf


    Does anyone know if hydrophone endplates were also fitted to other boats in the class?

  • #2
    It really comes down to which generation of fast boat you want to build. A lot of experimentation occurred in the 60's with older sonars adapted to the new hull forms, so accurate class info is difficult to come by,

    The long baseline array for the PUFFS and it's progeny were made redundant by the towed arrays that were back-fitted in the 70's when the Q-5 was retrofitted to the older SSNs and standardized on the 688s. Whereas PUFFS measured the arc of the sound wave as it was detected by each phone in the array to determine range, this calculation was made more accurate by using a similar algorithm to measure the arrival time to to determine the arc via the sphere and the towed array, yielding much greater accuracy. The Q-6 installed on Tridents incorporated a Line array in the ballast tanks angled in such a way to maximize bottom bounce returns and a wide aperture, due to the length made for a good array, though not as sensitive as the towed array (TB-16 / TB-23 / TB-29.)

    As a 21-year sonar tech for both the Navy and DoD, I only encountered PUFFS twice - on the Tang class and Dolphin, where it was more of a curiosity than a necessity. It was long gone on the Permit and Skipjacks in the 70's.

    Comment


    • #3
      Thanks for the information on the sonar array configurations. Indeed I had assumed that the PUFFS end plates would have only been used on some Permit class submarines in the early-mid 1960's, with only the photo's of Thresher and Barb confirming that they were fitted to those boats.


      I found a photo of the later deployable towed array installation on Plunger taken in the late 1980's, which nicely shows the support structure and modification of the rear plane;

      https://www.reddit.com/r/submarines/...dock_note_the/

      Would it be correct to assume that for the earlier generation of towed arrays (attached and removed at sea), were connected to a baseplate on the end of the starboard plane similar to that on photo's I've seen of the Skipjack & some SSBN's?

      Incidently, I have started constructing a CAD model of the Thresher / Permit using Greg Sharpe's plan as the starting point & progressively integrating data from other drawings and photo's. For the Thresher/Barb PUFFS end plates I made a preliminary estimate of the dimensions from photo's and incorporated this into a layer in the model as follows;

      - Length 9.82'
      - Height 8.6'
      - Maximum thickness: approx 1.6' to 1.73' giving a chord/thickness ratio of 16% to 17.5%
      -Plate Position: End 2.32' forward of rear tip edge of dive plan
      - Section: Used a NACA0016.5 section, but need to check again whether the max thickness might be further back along the chord.

      If anybody has an actual dimensions this would be useful for confirming these values. I believe USS SS-581 Blueback has a similar arrangement fitted to the rear planes.

      Also, the plan and construction photo's give a diameter for the rudder/plane bearing blocks of around 22" which confirms that these can be enclosed within the control surface.

      Attached is a screenshot screen shots of the model so far, very much a work in progress. The basic hull shape is fairly easy to model, being axisymmetric (I got quite a good fit to the shape using a Myring hull equation) & the basic hull shape is also shared with the Sturgeon class. Of course adding the details takes a bit more time...
      Click image for larger version

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      Attached Files

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      • #4
        Originally posted by CC Clarke View Post
        It really comes down to which generation of fast boat you want to build. A lot of experimentation occurred in the 60's with older sonars adapted to the new hull forms, so accurate class info is difficult to come by,

        The long baseline array for the PUFFS and it's progeny were made redundant by the towed arrays that were back-fitted in the 70's when the Q-5 was retrofitted to the older SSNs and standardized on the 688s. Whereas PUFFS measured the arc of the sound wave as it was detected by each phone in the array to determine range, this calculation was made more accurate by using a similar algorithm to measure the arrival time to to determine the arc via the sphere and the towed array, yielding much greater accuracy. The Q-6 installed on Tridents incorporated a Line array in the ballast tanks angled in such a way to maximize bottom bounce returns and a wide aperture, due to the length made for a good array, though not as sensitive as the towed array (TB-16 / TB-23 / TB-29.)

        As a 21-year sonar tech for both the Navy and DoD, I only encountered PUFFS twice - on the Tang class and Dolphin, where it was more of a curiosity than a necessity. It was long gone on the Permit and Skipjacks in the 70's.
        Your research here is timely for me. I'm finishing another 1/72 THRESHER and want to do those vertical stabilizers right. If you come up with any new revelations as to position and geometry let me know. Good work, sir.

        Click image for larger version

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        David
        Resident Luddite

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        • #5
          I'm doing a more detailed analysis of the photo's of the PUFFS arrays, with better correction of perspective effects. I'll report back with an update in a couple of days.

          Comment


          • #6
            If you end up doing a late-model Permit class version, here's a render from my extensive CAD library of US boats:

            Click image for larger version

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            • #7
              I measured again the photo's of Thresher's PUFFS array end plates on the rear planes, adjusting for perspective effects on the photo's. The revised estimate I have of the dimensions are the following which gives a more or less square planform;
              Length 8.8'
              Height 8.6'
              Maximum thickness 1.65'
              top and bottom have a curved edge of max height of ~ 4"
              Plate Position: End ~ 2.5' forward of rear tip edge of dive plan

              Centre of array around 9-10" outboard of outer edge of rear plane, the PUFFS array just clears the rear plane control surface with this distance.

              Attached are some screenshots of the new PUFFS array model, with plan side and front view. The section was derived from the photo, adjusting for perspective the max thickness approx 18.75% of chord at 42% chord. For the curved upper surface I took the same section, rotated 90 and then scaled to maximum 4" height.

              Without any better photo's there is some uncertainty in these estimates but the overall form & size looks correct compared to the photos. The planform is very similar to the rear planes PUFFS array on the 1/96 USS Blueback , which makes me think that it is essentially the same installation. If anyone has good photo's / dimensions of the actual installation on USS Blueback this would be useful for comparison. Click image for larger version

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              • #8
                Originally posted by CC Clarke View Post
                If you end up doing a late-model Permit class version, here's a render from my extensive CAD library of US boats:

                Click image for larger version

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                Thanks for posting, that's a nice model - It gives a good overview of the towed array installation on the late model Permit's and also the communication buoy dome.


                What software are you using for the model & rendering? I'm using Rhino 6.

                Comment


                • #9
                  Excellent presentation (your nomenclature takes me back to my unlimited rubber and A-1 tow-line FF design and build days).

                  I have booklet of general plans and TAB drawings of BLUEBACK's vertical stabilizers -- are those authoritative enough?

                  David
                  Resident Luddite

                  Comment


                  • #10
                    Originally posted by jphatton View Post

                    Thanks for posting, that's a nice model - It gives a good overview of the towed array installation on the late model Permit's and also the communication buoy dome.


                    What software are you using for the model & rendering? I'm using Rhino 6.
                    Thanks. Lightwave3D.

                    Click image for larger version

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                    • #11
                      Thanks David. Indeed the Vertical stabiliser drawings from the Blueback booklet of general plans would be an ideal reference for comparison.

                      I have the Modelsvit 1/144 Thresher kit which I'm planning to start on soon as a static build & would like to incorporate the PUFFS end plates in that.


                      Jason

                      Comment


                      • #12
                        Originally posted by jphatton View Post
                        Thanks David. Indeed the Vertical stabiliser drawings from the Blueback booklet of general plans would be an ideal reference for comparison.

                        I have the Modelsvit 1/144 Thresher kit which I'm planning to start on soon as a static build & would like to incorporate the PUFFS end plates in that.


                        Jason
                        Behold!

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                        Resident Luddite

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                        • #13
                          Thanks for the extract from the USS Blueback plans and photo's. I will measure the dimensions later, but the basic planform looks similar to the Thresher. Just as a cross check on dimensions do you have the distance between the hull frames?

                          It is interesting to see that the vertical stabiliser section is not symmetrical. On the Thresher photo the section appears thicker & closer to a symmetrical, but looking again it appears it may have less curvature on the inboard side.

                          Comment


                          • #14
                            Originally posted by jphatton View Post
                            Thanks for the extract from the USS Blueback plans and photo's. I will measure the dimensions later, but the basic planform looks similar to the Thresher. Just as a cross check on dimensions do you have the distance between the hull frames?

                            It is interesting to see that the vertical stabiliser section is not symmetrical. On the Thresher photo the section appears thicker & closer to a symmetrical, but looking again it appears it may have less curvature on the inboard side.
                            I promised BuShips drawings, but could only dig out this 'current condition' plan prepared for/by the museum that now has custody of that boat. The foil section depicted in the drawings is clearly in error -- as can be seen in the provided dry-dock photo of the BLUEBACK's stern -- the foil section of the vertical stabilizers is symmetrical, not Clark-Y as suggested by the drawing. Sorry about that. That obvious error suggests that the other dimensions on that drawing should not be taken as gospel. Sorry.

                            David
                            Resident Luddite

                            Comment


                            • #15
                              Thanks David. Indeed the symmetrical shape is apparent in the drydock photo.

                              Using the rear plane width I got a dimension of 8.9' (H) x 9.4' (L) from the plan drawing, and a bit longer (over 10') using the side drawing and the frame spacing as common reference. This is larger than my estimates from the Thresher photo, but given the uncertainty in the drawing & my photo estimate are at least a similar order of magnitude. Also the overall aspect ratio (H/L) is similar 0.96 vs 0.98. So for the time being I'll keep the current PUFFS plane as in the model, in any case this very easy to update in the CAD if new data becomes available.

                              In the meantime I've continued to work on the CAD model, starting on the masts on the sail. Click image for larger version

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