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

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  • #76
    That is a cool building station. Nice view.
    Of the 40,000 men who served on German submarines, 30,000 never returned.”

    Comment


    • #77
      Hello all,

      Thanks Rob, I appreciate the comments and to know that the build log is inspiring someone. Das Boot, yeah its not a bad view of the backyard and the slowly going green pool over the winter. The full sun coming in the morning is also quite nice.

      After sanding back the sides and checking for symmetry with the side decks, I then made a start on the vertical deck sections that join the side and raised middle deck sections. This would require the lower decks to be pushed in and be snug with the profile of the raised bulkheads for the upper deck section. This would allow the vertical deck sections to sit on top and sit next to the edge of the middle deck on either side creating a seam that would be pointing upward along the length of the upper middle deck. With the fitting of these vertical sections you would have the final close out of the hull and would no longer have access inside the hull.

      German U-boats at the start of the war were characterized by large drainage slots that ran along the lower corner of the joint between the outer deck and the sides. These occur a regular intervals and I was keep to put this design detail into the masters. So I took left over Renshape strip and cut the right width with a wider section increasing towards the bow. Then after a lot of fit and slight sanding and adjustment, matched the piece in the correct spot and then drew a line along the bottom to mark and mill the slots. I marked out evenly the position of the slots and then set the piece inside the jaws of my mill and worked out I would move the mill bit down about 1 mm to create the slot. I didn't want to go through the other side.


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      In the shot below I had marked out the location of the vents but had not milled them yet. The slight recessing of the milled vents will allow the detail to be transferred to the silicon mold and the customer will simply have to drill and file out the slots from the impressions. These will certainly aid the evacuation of air during the dive. The rim of the vertical strip is higher then the middle deck, more sanding once glued down.

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      The side decks were glued down and then had a seam of filler around the outer side edge that would eventually get rounded. The challenge with the corner of the deck and vertical section is that there is a radius where the slots meet. I needed to lay down a bed of filler but not get the filler into the slots. Once the sides were glued down I placed some tape on the lower deck and the vertical strip to allow only a narrow channel for the filler. Then wiping some filler into the corner I went along before the filer had time to set and with a wire plucked out any filler that had filled in the slots. The rest would be up to the sand paper.

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      more next week.

      David H

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      • #78
        Hello all,

        For the past 6 weeks the greater Sydney region has been in lock down. So there has been plenty of workshop time. Now my school which is outside the Sydney region (Hunter valley) has also gone into lock down with two COVID cases in my school. I am now housebound ,so when not teaching I can build, amongst other things. Have for the part little while been working on small pieces and finishing them to as high a finish as possible to make way for the next stage which will be the tooling and mold making. So not so much making major parts but attention to detail with tiny things and getting surface and textures looking nice. The vertical deck sections are going to require a whole heap of extra sanding and filing to get the fillet between them to behave. At the moment there is a bit too much of a clear distinction that there is a bead of filler in the middle.


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        Clearly visible is the fillet of filler sitting in the corner. It has been hard to smooth the edges of the fillet to blend into the vertical and horizontal surface with out sanding too much of the Renshape around it and accidentally creating low spots at the edges running along the hull. I also cut off the narrower section of Renshape at the front of the hull and replaced it with a proper shaped larger piece that then received the scribing treatment.

        A couple of weeks earlier I had built the Rudder, just out of Renshape, I didn't bother printing this one as I didn't need an exact copy. The Rudder I believe follows along the lines of a normal ships Rudder design of the time. Initially when I built it It featured the smooth consistent surface of a fin as I would have built it as though on a modern SSN. But this is from 1912 and it s going to require just a little further investigation to see if I had got the shape right. The Rudder features a hole through the top section that is for the rudder shaft to come down through the hull. Curiously on earlier German submarine there was actually a vertically mounted rudder in the upper hull section. On the U -23 class this was not carried on and it had a conventional ships rudder. (I believe.)

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        I would need to take the curve off the top of the Rudder to give it a tighter fit under the stern however there has been some time between this pic and how. After some research, once again looking at old pics and doing the best i can looking at the drawings I seems that the Rudder structure is depicted, so I decided that I would go with some kind of framework that would certainly give the pieces come 'character' if anything.

        So I drew the profiles of the structure that I could see in the rudder. This looks like depressed panel sections that make the Rudder looks like it has a sagging covering. I believe may have been a popular construction method at the turn of the century. I decided that the simulate this I would cut recessed sections, the best way to do this would be on the milling machine.


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        Bigger milling bit and wider cuts. Once done I would fillet filler around the edges to create a gradual transition.

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        Clearly visible is the brass rod that is the rudder shaft. On early U-boats of the U-23 class the push rods for the Rudder protruded up above the hull and could easily be serviced if needed. The push rods dissapeared into the raised deck section. As you can see the raised deck at the back needs some work. More on that later.

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        The rudder before any filler placed around the sides of the recessed sections. I mocked up the stern shaft assembly on dozens of occasions to work out alignment and fit. As you can see the props are too close the swinging rudder. They will be moved forward to just clear it. The stern gland is also too long. will deal with that later.

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        Filling around the sides of the recessed sections leads to a smooth transition for the rubber. Then shots of spray putty and then primer. I intend on creating a small extra piece that will be molded and fitted into the skeg to hold the lower bracket for the exposed shaft. I'm jumping ahead of myself here. This is how the stern bits look at the moment.


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        More later, in the meantime a little video of the build...

        https://www.youtube.com/watch?v=LL9X9ppr3xo

        David H

        Comment


        • #79
          Great job! All those fine derails and those many structured surfaces simply "cry" for airbrush preshading!

          Comment


          • #80
            Thanks Rob,

            Appreciate the comments. It's pretty quiet here most of the time. I think a few people check in now and then. As mentioned last week, mainly the creation of some small parts and a lot of symmetry checking. All my previous boat have been modern nuclear types out of PVC pipe and so symmetry was something that really only occurred around the front and back. With this boat the symmetry needs to be checked everywhere, it is a fair bit more work and can be harder to spot and deal with sometimes. Apart from this its mainly small parts checking and adjusting.

            The back end needed some work done on it as I didn't have the rear section of the top deck closed off. I took a block of Renshape and glued it in under the rear part of the middle raised deck and then placed some other blocks around the side to beef it up before sanding it back. This would need a fair bit of sanding. Once again this is an are in which the drawings are a little vague. They show an outline of the stern section with a curve and another over the same area shown a distinct pointed surface. I have gone with a more rounded back end, bringing the raised deck on a little further distancing it from the vertical position of the rudder shown with the brass pipe. These early U-boats featured an exposed Rudder tiller section with the exposed push rods exposed immediately before the deck starts. I can only assume this is to make them more accessible if there is a steering failure however they could also suffer more immediate damage in an attack.

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            In this image you can clearly see the fillet around the edges of the vertical and lower deck. An ongoing effort to get a smooth transition happening. The small block placed on the side needed some extra back up in the form of filler liberally applied and sanded back. Symmetry was check with a paper profile cut out and flipped either way to ensure consistency.


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            This actually took lots of goes to get the surface just right. Also the Renshape at the very stern of the boat needed some extra filler pushed in underneath and then some smoothing out at check that the deck remained level all the way around the wraparound. Further filler in the seams between the side upright and the top deck.

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            A shot of grey primer to give a lay of the land and show up all the stuff id rather wasn't there... Torpedo tubes look pretty good. What strikes me about this design is that if you look at the drawings there is very little surface detail on the lower side decks. Just the twenty or so access panels and points to mount the radio antenna's and that's about it really.


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            in the meantime i have been doing some design modifications to the the ZB 1/2 endcap. Some minor modifications to the gearbox housing and an Oil lite design change to improve reliability and durability. This was done through feedback from Zero Bubble's Official Chief Tester, Jorg Happrisch. (It's important that you get a German to do this, they are meticulous!)


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            Front torpedo tube doors next week.


            Dave H


            Comment


            • #81
              Thank you Dave!

              Meticulously reading your last post while enjoying a well-deserved hot meal, i immediantly noticed you prompted ZB-1/2, a victim i have already received but not yet guttet and glued back together from small pieces. I however had the pleasure to check over your early ZB-1 (!) and give some surplus commentary here and there.

              I also wonder will you ever get to spell my name correctly

              The rounded stern looks about right, but i think there was a rectangular frame around the rods as U23 class lacked the upper rudder. There is that dock photograph of an u 35? With that frame removed. Besides, open machinary looks cooler!

              Stay Busy

              Jörg

              Comment


              • #82
                I just found pictures of U24 and U25 with upper rudder... odd

                Comment


                • #83
                  The stern looks about right but the superstructure with the deck is wrong. The ending is by far to blunt. the deck ended needle like, very sharp.
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                  Last edited by DrSchmidt; 08-15-2021, 04:13 AM.

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                  • #84
                    A very detailed deck plan.wonder where you got it. But is that a u 23 class? I only know the knife -stern from earlier boats with open rudder gears and the upper rudder. A puzzling spot it seems.

                    Jörg

                    Comment


                    • #85
                      https://www.ebay.de/itm/223709974188

                      U-19 til 56 all had the same basic design with slight variations.

                      The early boats of the Imperial german Navy had top rudders because the engineers feared that the boats, when submerged, would start to roll over because the force of the rudder was not exeted in the line of the center of gravity. only later, when they found out, that there was no base for this fear, the top rudders vanished form the designs. The U-19 and higher classes didn't have top rudders anymore.

                      Comment


                      • #86
                        Thank you Herr Doktor... and official ZB tester.

                        That is really interesting what you've said about the top rudders. I suspected the top rudder info may have been for that reason. Any other gems. So, to clarify, make it pointy? What is the curved line that i have been following? Is it just the outline of a curved plate cover that creates a radius where the vertical sides meet the lower decks either side?


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                        Do you have any other pics of this class other than what I can find online? Thanks for the clarification, in time for me to change it!

                        David H

                        Comment


                        • #87
                          They had top rudders: Click image for larger version  Name:	20210815_134018.jpg Views:	0 Size:	78.6 KB ID:	152444Click image for larger version  Name:	20210815_133854.jpg Views:	0 Size:	71.4 KB ID:	152445


                          And the stern upper deck was a knife-type with 90 degrees transition at the end, following a section with trapezoid diameter (thats your outline, dave) before turning back to 90 degrees again. That part housed the rudder pushrods . U-23 to U-35 were close in design, then the look changed. Conning, stern arrangement etc.. the lines got rounder and more streamlined.

                          There is quite a lot difference in outside appearence between an U-23 stern and the MS-Boat,so one needs to take a good look at existing photos how things actually looked like rather than plans,i believe.

                          Jörg
                          Last edited by JHapprich; 08-15-2021, 08:18 AM.

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                          • #88
                            Hi Jorg,

                            keep those pics coming!

                            Dave.

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                            • #89
                              Well, they had and they had not.... there actually is no U-23 class. U23 was a second batch U-19 class boat, a very heterogeneous class of boat with lost of changes not only from bath to batch but also with lots of changes during the service time of a single boat allot of changes where applied. you might want to check here:

                              http://dubm.de/en/type-u/

                              If you want to make a model of the as built U-23, add an upper rudder and some side extensions to the superstructure (the ones you mistook for the deck line).

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                              Later boats had no upper rudder (e.g. U-29, 3rd batch U-19 class) and on several earlier boats the upper rudders where removed.

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                              So basically there was so much dynamics in the german uboat designs at that time that you hardly can do wrong,

                              Comment


                              • #90
                                Well, batch 4 / u 31 and so on still featured that rudder. We are dealing with u-23 to u-26 here, i believe.

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