Scratch Build project SM U-23 Class World war one U-boote. Zero Bubble model design.

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  • Davidh
    Captain
    • Nov 2010
    • 719

    #31
    Hello all,

    Hello HWSNBN, David, I’m not sure if you saw my request in the last thread about exit shaft locations on my U-Boat hull. Do you have any suggestions or techniques as to how to determine this without punching too many holes as a result of bad guesswork? I appreciate that you should be enjoying your retirement but I really do appreciate your advice.

    thanks,

    David H

    Comment

    • gantu
      Commander
      • Apr 2009
      • 360

      #32
      Hello david ,
      a friend of mine do always pipes in the section and then plank the hull.













      Regards Gantu

      Comment

      • Davidh
        Captain
        • Nov 2010
        • 719

        #33
        Hello All,

        Thanks for the pics Gantu. That is certainly a different way of doing things. I'm still awaiting to hear from DM if he has any gems about how to go about aligning shafts and working out the shaft exits without making a dogs breakfast of everything.

        After grinding back the sides of the rear hull where the bottom round section of the hull transforms to the emerging Keel and adding extra polyurethane foam on the insides to support it I decided to lay up the hull once again and create the concentric profiles around the hull at the bulkheads. These help give an idea of the consistency of the hull shape and looking down the length allow you to see any areas of deviation in frame profile. I made a vertical profile that I could run a pen around to accurately get the vertical sectional profile of the bulkheads.



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        Once the bulkhead frames have been drawn on and lots of eyeballing later I then filled undulations and low points. Once done more sanding. Particular points are marked with pen just so that I can work reasonably quick before the filler sets. I use a plastic flat surface cut from an Ice cream container and then screed the filler over the low point in a smooth action that creates a very flat mostly smooth surface.




        Here, next to the hull marked with pen is the top section of flat Renshape that will make the middle deck section and also the lower section of the small conning tower. The hooks are in place to anchor down the upside down hull in place, resting on small Renshape blocks after careful checking that the keel of the hull is a consistent distance away from the board.

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        I eventually came to the point where I would lay down the layer of weave that would greatly add to the rigidity of the hull and further increase and seal the hull and give a little more surface area to sand down and eliminate undulations and low points. After slowly going over the hull and sanding it back thoroughly I mixed up some further resin and brushed it onto the hull and then laid up the 6 oz weave. I did this in sections and whetted it up as I laid it down and then slowly brushed and made sure that there no bits sticking up.

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        Initially I laid the weave down before brushing down the hull, in order to get the fit right and minimize overlaying.

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        Once done and whetted up I left it outside and let it cure. Even now in March we are still getting residual summer heat , a nice 25 degrees. Once cured, I marked out the high points and then lots of sanding with 80 grit and hardboard backing it. My Biceps ain't bad. This was about an hours worth of sanding. Slowly taking it from 80 down to about 600 grade wet and dry.

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        Once I was happy with this I then gave a light primer coat. This spray did'nt cover over too much of the frame indications.

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        Once the primer is dried, it's only a light coat, then I once again marked out the high and low points in the surface that are more noticeable now with the primer and fill and sand. Repeat...
        I really need to start looking at the stern shaft exists. As mentioned in the previous post, I would really love to hear from people as to strategies to make this work without making too much of a mess of the rear end.


        David H

        Comment

        • gantu
          Commander
          • Apr 2009
          • 360

          #34
          U8 web tour. Cutting edge educational web tours with full admin management. 3D VR, panoramas, super high resolution images, RTI and more!

          Regards Gantu

          Comment

          • He Who Shall Not Be Named
            Moderator
            • Aug 2008
            • 12253

            #35
            To establish the toe-in and the other off-sets of propeller shaft-to-hull-centerline hold both shafts at the correct angles in a table mounted jig that establishes the desired off-sets. Plunk the stern down onto the table, sleeve the stern tubes over the shafts, drill holes in the ass-end of the hull, and slide the stern tubes into the hull (the jig tells you where they enter the hull) and glue in place.

            A variation on these torpedo tube shutter-door scribing jigs is what you're after, David.

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            David
            Who Warships at the Alter of Rube Goldberg
            Last edited by He Who Shall Not Be Named; 03-13-2021, 10:32 AM.
            Who is John Galt?

            Comment

            • trout
              Admiral
              • Jul 2011
              • 3545

              #36
              David,
              ‘great jigs, but how do you figure or build the jig to get the torpedo doors where they need to be?
              If you can cut, drill, saw, hit things and swear a lot, you're well on the way to building a working model sub.

              Comment

              • He Who Shall Not Be Named
                Moderator
                • Aug 2008
                • 12253

                #37
                Originally posted by trout
                David,
                ‘great jigs, but how do you figure or build the jig to get the torpedo doors where they need to be?
                You loft the orthographic 'front-view' onto the face of the jig. find the center of the doors, and that becomes the center of rotation.
                Who is John Galt?

                Comment

                • trout
                  Admiral
                  • Jul 2011
                  • 3545

                  #38
                  Ah, got it. So, good set of plans is imperative otherwise it is a lot of guess work?
                  If you can cut, drill, saw, hit things and swear a lot, you're well on the way to building a working model sub.

                  Comment

                  • He Who Shall Not Be Named
                    Moderator
                    • Aug 2008
                    • 12253

                    #39
                    Originally posted by trout
                    Ah, got it. So, good set of plans is imperative otherwise it is a lot of guess work?
                    If guess work, at least the jig will assure symmetry between the two shafts -- they will be wrong... equally!

                    David
                    Who is John Galt?

                    Comment

                    • Davidh
                      Captain
                      • Nov 2010
                      • 719

                      #40
                      Thankyou David.

                      David H

                      Comment

                      • trout
                        Admiral
                        • Jul 2011
                        • 3545

                        #41
                        Gantu, that is pretty cool link.
                        David, thank you for explaining.
                        If you can cut, drill, saw, hit things and swear a lot, you're well on the way to building a working model sub.

                        Comment

                        • Davidh
                          Captain
                          • Nov 2010
                          • 719

                          #42
                          Hello all.

                          Torpedo Time!....


                          Torpedo Tubes that is...

                          The space for the torpedo tubes at the moment currently is a big oversized rectangular box that is begging for something more in terms of details. As mentioned over previous logs I had the dilemma of not knowing whether the torpedo tubes had a boxy appearance rather than having a half round curve. Bernhard Wenzel to the rescue with a picture showing an early U-boat in dry dock with a curved front section of the torpedo tube. The picture looks doctored or even a hand drawing but it was the best I have. The earlier boats such as U-9 have a box like forward tube structure.

                          I decided to start doing some more detail work at the front end of the boat rather than the back end even though I will be going over both. The rear end is especially needing some attention at the moment but I though I would go with the front.

                          I measured the area around the box frame that would make up the tube area and measured the width or diameter of the tubes on the original drawings that I was working off. I used various sizes of drill bits to get a feel of the side and dia of the torpedoes and the corresponding tubes.


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                          The width of the torpedo tube space as seen here is about 16mm. This varies as it heads towards the bow. I haven't bothered with sanding and getting the width consistent as it will be filled over with the tube details. I then took a couple of drill bits and placed them inside the tube opening to get an idea of the diameter of the torpedo and tried to get it as close to the original size in the drawing.

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                          To make the curved outer surface of the tubes I decided to take a piece of Renshape and then machine it down to the 16mm width of the outlet then took it a little further just for good measure. I made this piece as long as the length of the outlet. I then took the drill bit shown here and placed in the tail stock drilled a hole through the Renshape to create the hole for the Torpedo.

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                          This is the two turned Renshape pieces that will feature in the torpedo areas to be come the front of the tubes or scoops as I'll call them for want of a better term. The second one hasn't been drilled through yet. Back and front denote the back and front end. Once made I then place them inside the recess area for the tube and mark out the line that will see them sliced in half in a gradual curve to follow the profile of the front of the boat and create the scoop. I had to dremel out some of the recess especially at the back of the box section to accommodate the half tube.

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                          I have had to give some though to the geometry of the Torpedo tube doors. On these early subs they seemed to have the door exposed, unlike later and WW2 U-boats there were no outer shutters. As a result it would seem that the doors opened outwards and as far as I can tell they opened inwards with the hinge on the inside of the tube. In order for this to happen then you would need to have space for the door to open which means that you couldn't have the curved section of the tube in the way for this door to open without jamming. As a result I deiced to create a square section immediately in front of the Bow door to give space to the door top open. The torpedo then moves forward sliding past the open door and runs along side the scoop and then on to target.


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                          The buried torpedo tube terminates with a bulged section as the outer corner of the tube exceeds the curved profile of the hull. As a result there is the bulge that terminated at the door. This was created by
                          cutting a left over piece and shaping it to coincide with the front edge of the tube. I then placed a small Renshape block in place immediately before the tube door outlet and glued into place. This provides the space for the door to swing back. It makes the tube look a bit awkward and not smooth and streamlines but I don't see any other way they could have made this geometry work.

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                          The bulge and block in place. The front section needed to be raised at the back end to make sure that it would be in line with the axis of the tube as it comes out of the hull. This meant putting down a bed of filler and at the right time pushing the back end of the tube into the soft filler and aligning it so that theoretically the torpedo wouldn't glance off the scoop as it was heading out of the tube. Then I cut out two small circles of Balsa sheet to cap off the door area and glued them to the bulge sections that would sit as the back of the recess and signify the front of the tubes. Line them up and glue them in place.

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                          Early filler, lots more needed.


                          Stay tuned, more torpedo's next week....


                          David H

                          Comment

                          • Davidh
                            Captain
                            • Nov 2010
                            • 719

                            #43
                            Hello all,

                            At this point both tubes are in. They have both had a layer of filler applied around the edges of the Renshape tube forward of the tube doors. Once sanded back and another layer added, more sanding. Then a paint brush with some resin around the scoop area. I will need to carefully add some more filler around the gar between the doors and then scoop. ( This is the space for the doors to open inwards). I will have to get into the square corners and smoothly sand back..

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                            The hull has also had a light sanding back to get out some of the high points and undulations caused by the thicker coat of resin and weave. It is pretty smooth. Once the bumps have been taken out with something thicker I will move through 600, 800, 1000 grit. The formers have received all sorts of spray coats, splatter of resin and splashes of water and as a result look a bit aged.


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                            Primer grey on the other side and repeat the process.

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                            Looking from the front back towards the door show small areas where the filler hasn't quite covered over the gaps. Once tube door is slightly forward of the other, so I will need to address that. I also need to define further and make sharp the bow line. I will still need to add more filler along the edge of the scoop line to get the transition between scoop and hull sides just smooth and consistent.

                            For some time I have been working on interpreting the the middle deck section hull detail. Having never built a U-boat before and certain not one that is over 100 years old meant that I was unfamiliar with the layout and parts that would be found on the center deck. Certainly will not find any red and white hatches like I have always worked with on my soviet boats. My inspiration for working out the deck arrangement has come from the main drawings that I have and the images of the U-9 kit that I have had to rely on when the 2-dimensional-ness of the drawings doesn't quite give me enough. The U-9 model has been good for getting the low down on raised items on the main deck. I am going on the theory that from Class to Class there are only incremental changes and wouldn't be a huge change between the U-9 class and U-23 deck arrangements.

                            So I have aligned up the middle section of deck that is made of a 4 mm sheet of Renshape and started marking out the placement of hatches and access panels. Once marked out in pencil I could then start on scribing. I have taken a small fine file and have ground it down to a tiny round point. Renshape is fantastic for scribing into. Scribing on a flat surface is definitely easier than trying to with the Renshape strip already attached to the hull.


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                            I have used an array of circle and square templates to attain some consistency. On this boat many of the features seen up front are also duplicated towards the stern.

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                            I now have to work through which parts have raised components and which don't. Any more pics that people have of the front deck space would be greatly appreciated.

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                            David H

                            Comment

                            • Davidh
                              Captain
                              • Nov 2010
                              • 719

                              #44
                              Hello all,

                              At this point both tubes are in. They have both had a layer of filler applied around the edges of the Renshape tube forward of the tube doors. Once sanded back and another layer added, more sanding. Then a paint brush with some resin around the scoop area. I will need to carefully add some more filler around the gar between the doors and then scoop. ( This is the space for the doors to open inwards). I will have to get into the square corners and smoothly sand back..

                              [ATTACH=CONFIG]n148723[/ATTACH]

                              The hull has also had a light sanding back to get out some of the high points and undulations caused by the thicker coat of resin and weave. It is pretty smooth. Once the bumps have been taken out with something thicker I will move through 600, 800, 1000 grit. The formers have received all sorts of spray coats, splatter of resin and splashes of water and as a result look a bit aged.


                              [ATTACH=CONFIG]n148724[/ATTACH]

                              Primer grey on the other side and repeat the process.

                              [ATTACH=CONFIG]n148725[/ATTACH]

                              Looking from the front back towards the door show small areas where the filler hasn't quite covered over the gaps. Once tube door is slightly forward of the other, so I will need to address that. I also need to define further and make sharp the bow line. I will still need to add more filler along the edge of the scoop line to get the transition between scoop and hull sides just smooth and consistent.

                              For some time I have been working on interpreting the the middle deck section hull detail. Having never built a U-boat before and certain not one that is over 100 years old meant that I was unfamiliar with the layout and parts that would be found on the center deck. Certainly will not find any red and white hatches like I have always worked with on my soviet boats. My inspiration for working out the deck arrangement has come from the main drawings that I have and the images of the U-9 kit that I have had to rely on when the 2-dimensional-ness of the drawings doesn't quite give me enough. The U-9 model has been good for getting the low down on raised items on the main deck. I am going on the theory that from Class to Class there are only incremental changes and wouldn't be a huge change between the U-9 class and U-23 deck arrangements.

                              So I have aligned up the middle section of deck that is made of a 4 mm sheet of Renshape and started marking out the placement of hatches and access panels. Once marked out in pencil I could then start on scribing. I have taken a small fine file and have ground it down to a tiny round point. Renshape is fantastic for scribing into. Scribing on a flat surface is definitely easier than trying to with the Renshape strip already attached to the hull.


                              [ATTACH=CONFIG]n148726[/ATTACH]

                              I have used an array of circle and square templates to attain some consistency. On this boat many of the features seen up front are also duplicated towards the stern.

                              [ATTACH=CONFIG]n148727[/ATTACH]

                              I now have to work through which parts have raised components and which don't. Any more pics that people have of the front deck space would be greatly appreciated.

                              [ATTACH=CONFIG]n148728[/ATTACH]



                              David H

                              Comment

                              • Davidh
                                Captain
                                • Nov 2010
                                • 719

                                #45
                                Hello,

                                I have just posted up my latest build update. It is coming up green with ‘unapproved’ and I guess not showing for everyone else. Could this be fixed please?

                                David H

                                Comment

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