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  • Originally posted by redboat219 View Post
    https://youtu.be/5v9RURr5hjg

    I bet Ellie looks at you like laser beams are gonna come out of her eyes.
    Not far off the mark, pal. I fear only one person on this planet.

    David
    The Horrible
    "... well, that takes care of Jorgenson's theory!"

    Comment


    • Got the propeller done and started to back-fit the proper torque-rod type rudder actuator -- got ride of the two pushrod-bell crank arrangement (an artifact from bum documentation that originated with one of the boats builders well after the event.

      The rip-out of the two pushrods produced holes at the upper stern. These had to be filled, and most of that work was done with CA and baking soda.

      The operation starts with a back-up of the hole from the inside -- wax paper if you want to be neat. A paper towel if you don't give a damn. While holding the back-up tight to block the hole from the inside, some baking soda is sprinkled on and thin formula CA applied, which instantly hardens. Repeat till the mass is higher than the surrounding structure. At that point the back-up is pulled out.



      The mass is then ground down with a sanding drum followed by a course file, then sandpaper.



      Drilling a hole to accept the rudder torque rod tube.



      I'm jumping ahead a bit to show you the end-game: the completed propeller and pitch gimbal, all installed. The objective is to achieve positive control of the boats pitch-angle while submerged through the use of active thrust vectoring -- tilting the propeller up and down will produce the torque needed to keep the boat on a near zero bubble angle.



      From .030" thick sheet brass I cut out three propeller blade blanks. Then, from dense RenShape, I carved out a blade pitch mandrel that would be used to form the annealed blades to the correct helical twist demanded by the blade-chart.



      The cartridge brass is much too stiff to bend easily, so it it taken to a red heat and allowed to cool back to room temperature without quenching. The softened propeller blades are now malleable enough to be easily bent to the required twist by hand and light hammering over the mandrel. (if you look carefully you can just make out Exeter's image on the view screen as it cools... joking!).



      Here I've ground, filed, and sanded the helical twist into the blade forming mandrel. The oxidation on the blade blanks is a consequence of the heat treatment and is later abraded away after the blades are formed, and soldered to their solid brass hub.



      Most twisting of the blades was done between thumbs and forefingers. The final work was done with repeated light hammer blows with the work sitting on the face of the mandrel. The mandrel was temporarily glued atop an anvil. The constant hammering 'work hardened' the blades, making them stiff enough to handle and assemble without fear of accidently bending them out of shape.



      Three slits were cut into the solid brass hub to receive the propeller blades. A rotary table, angled to the saw to produce the correct blade-hub interface slits. As the rotary table is indexed it was an easy matter to dial in the three equally spaced slits.



      I love my cheap-ass Chinese milling machine, but sometimes (like here) I wish I had sprung for a proper Bridgeport machine with the ability to tilt the spindle-head instead of having to jury-rig this Rube Goldberg fixture to angle the rotary table to the saw. Oh, well.



      From the blade-chart I was informed that the angle at the hub where the root of the blades fit is 55-degrees. So be it -- I hear and obey!



      The blade roots were a tight fit to the hub slits so there was no need for a holding fixture as the blades were soldered in place. Friction is our friend! Here I'm slathering on some acid flux to insure a nice clean, strong wetting of the metal as the molten solder is applied.



      60-40 solder is fine for this kind of work -- plenty of adhesive area, buttressed with heavy fillets. The soldering operation only took seconds to perform. Soldering is adhesion, not welding; it's glue, boy's and girls.



      Files, sandpaper, and a rotary wire brush cleaned up the assembled propeller.



      And the completed propeller assembly.








      "... well, that takes care of Jorgenson's theory!"

      Comment


      • David,
        Didn't you have a dedicated thread on propeller making?
        Make it simple, make strong, make it work!

        Comment


        • Originally posted by redboat219 View Post
          David,
          Didn't you have a dedicated thread on propeller making?
          Yes, I think there is one buried somewhere on the site -- Bob is going to streamline searches for such documents when he gets the time. Why? Am I starting to get redundant?

          David
          "... well, that takes care of Jorgenson's theory!"

          Comment


          • Redundant? No.

            I'm sure some of the newcomers would like to know how to fabricate their own prop from scratch. As you said some of the good stuffs tend to get buried under. Hope Bob can find it and place it in a dedicated archive.

            Redundant? No....
            Make it simple, make strong, make it work!

            Comment


            • Originally posted by HardRock View Post
              Oh thanks for that. Now I have a mental image of a big male nurse shaving your nut sack! Another mental scar I can't wash away!
              Happened to me, several times...its not fun!
              A man of true Frankenstinean proportions!!

              Comment


              • That prop is BEAUTIFUL...absolutely spot-on
                A man of true Frankenstinean proportions!!

                Comment


                • Originally posted by He Who Shall Not Be Named View Post

                  Yes, I think there is one buried somewhere on the site -- Bob is going to streamline searches for such documents when he gets the time. Why? Am I starting to get redundant?

                  David
                  Fantastic work on the new Hunley propeller and gimbal!

                  Here’s a link to more of your propeller work from the older type XXIII build.

                  https://forum.rc-sub.com/forum/gener...h-scale/page10

                  Not sure if this is what you guys are referring to, but a great informative build thread nonetheless.

                  Nick

                  Comment


                  • I'm currently engaged in creation of tooling that will be used to produce GRP (fiberglass) hull and resin and metal parts of a 1/96 scale kit of the American STURGEON class attack submarine. Most of the masters I'm handling here were created by Matthew Thor who sold them to Nautilus Drydocks, an outfit I've been affiliated with for a number of years now.

                    Details concerning the STURGEON and the other thirty-six boats of the class can be found here: Sturgeon-class submarine - Wikipedia

                    The quality of the masters I received were, for the most part, exceptional in regards to their scale fidelity and craftsmanship; very, very good work.

                    However, there were a few problem areas that had to be addressed before using them to produce the tooling. As research is everything when dealing with scale models, I took pains to study my files and external sources – the objective was to create masters that would depict the first 'short hull' boats of the class. I leave it to future customers of the kit to make the appropriate modifications needed to configure their model to suit the characteristics of a specific boat they wish to represent in miniature. I only supply the canvas, not the paint.

                    The principle document I used to further detail the STURGEON masters was a 1/96 scale, five-view orthographic drawing produced by the famed Canadian r/c submariner, Greg Sharpe. His work lofted off official documents. I consider them source material. Someone correct me... I dare you!



                    Buttressing the drawings were hundreds of photos and other documents I've been collecting the last forty years.



                    There are two schools of thought as to how tooling intended for GRP production should be made.

                    One is the 'hard-shell' type mold – typically a stiff GRP lay-up over the master. This type has the virtue of being simple and cheap to produce. The drawback to this type tool is the need to avoid deep draft items; the master has to be compromised as to depth of engraved lines in order to prevent entrapment of the master (and later the GRP part produced) within the tool that gave it form.

                    Any significant depth of engravings invariably leads to tool damage during the extraction process. You just can't get the level of engraved and/or high relief detailing into a hard-shell tool than you can with a rubber tool. Also, the hard-shell tool is most unforgiving if you fail to correctly apply the correct type mold-release system between lay-up cycles – get it wrong and you trash the tool!



                    The resulting GRP hull part produced in the hard-shell tool will capture engraved lines, yes, but by necessity the depth of those engraved lines must be shallow and unreasonably wide. The result is engraved detail that is not deep or narrow enough to throw significantly stark shadows, greatly reducing the visual impact of the engravings.



                    The preferred tool is of the compound type, made up of two elements: a flexible rubber glove-mold, backed by a stiff mother-mold. This type, owing to the flexible nature of the rubber glove has no problem separating from the master and later production parts regardless of draft depth or angle – this type tool will easily pull away from parts of negative draft without damage or wear. Such as this 1/96 THRESHER hull tool.



                    Once the GRP has been laid up in the rubber glove, the glove is pulled away from its backing mother-mold and peeled – like a glove – away from the GRP part. No matter the engraved or high-relief items unique to the subject, the glove nor the part is damaged during the de-molding process. Pretty damned slick!

                    All that needs to be done is to re-seat the glove into the mother-mold, spray on a few coats of poly vinyl alcohol, and you're ready to start another GRP lay-up. No waxing, no buffing, no bull-****.



                    The result of the mother-glove type tool are deep, crisp, narrow engravings. The bow of this completed 1/96 THRESHER class model, formed in such a tool, so demonstrates. Compare the engravings on this model to those on the hull produced in a hard-shell type tool. A world of difference.



                    The two STURGEON hull masters – an upper half, and a lower half – were mounted on a mold-board. The flat face of the mold-board would later form the parting flange shared by the hard and rubber faces of the compound tool. One tool for the upper hull, one tool for the lower hull.

                    Each hull master was secured to its mold-board with the aid of three deck-screws passed up through the bottom of the mold-board.



                    Most of the STURGEON hull tooling work involves building the support structure for the eventual mother-mold element of the tool. These structures, called 'egg-crating', provide a stable support for and convenient table upon which the inverted tools cavity is accessed for part glass lay-up. The egg-crating only goes onto the mold board after the rubber glove has been built up over the hull master and over that the first layers of mother-mold tooling resin applied. Eventually the tooling resin will bond to the ribs of the egg-crate forming the ridgid and easy to handle assembly.





                    Enhancement of the hull masters included inclusion of a radial engraved line near the stern. This will denote, on the GRP hull parts, where to cut away the end of the assembled hull to make way for a hollow cast resin stern cone that will come complete with attached horizontal stabilizers, stern tube and bearing, and rudder and stern plane interconnecting yokes. Good kit engineering strives to produce a product any mouth-breathing idiot can assemble with the minimum of fuss.



                    A vertical fence was temporarily screwed in place over the mold board to permit use of a waterline marking tool to lay off a radial pencil line onto the stern of a master. I would later remove the master from the mold-board and with careful use of a razor saw I would engrave a very shallow, narrow cheat-line.



                    The one major fault with the Thor STURGEON hull master we received (I suspect there are more than one set of 'masters' out there) was the height of the two escape trunk hatch 'flats'. Instead of the plane of the flat being flush with the top of the hull the flats stood .040” over deck level. That had to be fixed. Fortunately this portion of the master was a cylinder of easily ground, scribed and filed plastic rod. After that work the deck hatch outline was re-scribed

                    Once the two escape trunk flats had been taken to deck level I ran a length of pencil 'lead' over the hull – the fragile lead strengthened by gluing it to a scrap piece of plastic sheet that also served as a handle. Resting a portion of the lead on the circular rim of a flat I circled it around to that the outboard portion of lead contacted the hull, denoting where the eventual fairing between flat and hull took place.



                    I set about the work of fairing the outboard areas between circular flat and gentile compound curve of the hull. I'm showing the work at the bow, but the same job had to be performed as I worked the engine room escape trunk hatch flat as well.



                    A mask was prepared to confine the Bondo to only those ares on the hull where there would be a fairing. Those masks went a long way in reducing the work involved in filing and sanding the Bondo to shape.



                    The second major chore was to deepen – and in only a few instances, correct – engraved lines that denoted access hatches, line lockers, capstans, main ballast tank vents, salvage plates, buoy markers, reversible cleats, bull-nose, torpedo tube shutters, ballast tank flood-drains, anchor, main and auxiliary sea water penetrations; and portions of safety-track.

                    What a job the engraving enhancement turned out to be! You see here just some of the stencils, engraving scratch-awls, abrasives, fillers and putties, files, and measuring tools required for the work.



                    These masters, apparently, were intended for creation of hard-shell type tools. But, as I was going to produce a proper set of glove-mother molds intended to capture deeper engravings and significantly raised details (not present on the masters as delivered), I was compelled to deepen the existing engraved lines and add those appendages.



                    When I took on the job I assumed that that hull master halves were wood, but was delighted to find that it was a GRP copy. Not the original pattern. So. Are there more than one set of Thor 'masters' out there we don't know about?? Not my problem … I'm only the idiot model-builder with a job to do. The proprietary aspects of this property are not my concern.

                    Any way, it was a relatively easy matter to deepen the engraved lines in a GRP substrate than it would have been had the underlying material been wood. I was grateful for that. Inevitably, as I worked the engraving with scratch-awl and razor saw I invariably buggered up some of the work with over-strikes and miss-directed passes. I would work a section then lay down some air-dry putty, chasing out the properly engraved lines before the putty could dry thoroughly. After sanding, what was left were deepened, narrow of width engraved lines.



                    Special sanding tools were employed -- specifically brass strips with #400 glued to one face and #600 to the other – to insure only the puttied areas were knocked down as I wet sanded the dried putty. Particular care was taken on the escape trunk flats and surrounding fairing.



                    Once happy with a section of the hull, I applied a light coat of gray primer. Repeating the examination-putty-sanding-priming steps as many times as required.



                    Additional scribing included enhancement of a cheat line for the anti-foul boarder on the deck, as well as the designed waterline had to be completed forward of the sonar dome radial line – that radial line can't be seen in any photos of the real boats, so I softened it with putty.





                    The master did not represent the raised portion of safety-track welded atop the pressure hull portions of the submarine. I built the raised portions of track from Bondo between three plys of masking tape. Making the masking strips narrow gave them the flexibility to negotiate the tight radius jogs you see here:



                    A small amount of Bondo was catalyzed and screed between the two parallel masks.



                    Before removing the masking the top of the Bondo safety-track was coated with thin formula CA to strengthen the porous Bondo. The masking was removed and a little work with file and sandpaper, and the safety-track was done.



                    Three hydrophones are prominently displayed sitting atop the hull on most units of the STURGEON class submarine. These items would be impractical protuberances on a master used to create a hard-shell type tool, but are a welcome enhancement when captured faithfully and without fear of entrapment when giving form to a glove type mold. These items were formed from 40 lbs. RenShape pattern making medium and glued to the deck of the hull master.







                    Along the deck of a STURGEON class submarine are situated brackets that stand slightly proud of the hull, these foundations accept and make fast to the hull 'portable cleats' used to secure mooring lines between ship and pier – these heavy, hard to hold toe-crushers had to be shipped up and down the escape trunk ladders every maneuvering watch. Total nightmares for the deck gang I heard.

                    Square indentations in the hull master would impart the same to the eventual model parts. Cast metal brackets would fit those hulls during model assembly.

                    I first drilled then gouged out rough square holes, then back filled these depressions with Bondo and before that hardened I placed a square tube in the depression to refine its square shape. The form removed once the filler had hardened. Saliva, as it turns out, is a fine part-release!



                    The hull masters are just about done. Now to rub down a few layers of mold-release wax, mount the masters to their respective mold-boards, and to start laying down repeated layers of brushable RTV mold making rubber to form the glove-mold.







                    "... well, that takes care of Jorgenson's theory!"

                    Comment



                    • One last detail item I put to the upper hull master was little indentations around the two escape trunk hatches -- these cheat-marks denote were little holes will be drilled into the eventual GRP hull to accept padeyes. These representing hard-points used by the McCain Rescue Bell hold down turnbuckles during a crew rescue operation.

                      Incidentally, the STURGEON class boats were the last American combatants configured with marker buoys and hold-down padeyes. From LOS ANGELES on all American submarines would rely on the DSRV system to rescue a crew on a stranded boat. Guess, what, sports-fans?... We don't have DSRV's anymore. WTF?!



                      Before mounting the two hull half masters to their mold-boards I first laid shown a sheet of parchment paper between the base of each master and the face of the mold-board -- this to keep the very sticky glove making rubber from sticking too tightly to the mold board.







                      I used a pen loaded compass to mark off a stand-off between base of a hull master and where I wanted the eventual build up of RTV glove rubber to stop.



                      I waxed the masters to insure a clean, easy parting of the eventual RTV glove mold when the time came. I've made gloves without the wax without any stick problems, but I'm getting ever more conservative and careful with old age.





                      After rubbing the wax into the work I used a sharpened dowel to chase out wax from all the engravings.



                      And finally starting to lay down the, what will be many, layers of 'brushable' RTV mold making rubber.



                      The catalyzed rubber has to be mixed thoroughly, which folds in a lot of big air-bubbles. These have to be eliminated before application by subjecting the mix to a hard vacuum.










                      "... well, that takes care of Jorgenson's theory!"

                      Comment

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