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

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  • #91
    You are dealing with nothing, you are just commenting like I do. David is dealing with his built, and he can build whatever he wants. Top rudder, blunt superstructure, dive plane guards the shape he wants. All fine to me. Btw, what you think are rectangular dive plane guards are in my opionon outlines for bigger dive planes. David is working of the same plans that I have and they show a generalized version of the Type from U-19 to 56. All the same basic deisgn but with lots of alterations (like removed top rudders). The dive planes were enlarged because they were so ineffective as they are positioned in front of the props and not behind them. Same on my SM U-1 or Bernhard Wenzel's SM U-9.


    • #92
      At ease, Mr., for i did not intend to put that matter on a personal level nor do i - with all appropriate respect - appreciate you lecturing me.

      Beeing usually not that serious about forum chatting , I at this point feel obliged to give a crystal-clear commentary defining my intention:

      I am refering to David's ongoning request for input on the U-23 and sisters of that specific series of U-boats. It is my experience that plans-especially on such a rarely documented subject-are often different from the actual "real" thing. Now the photographs do not lie, pennant numbers neither. On the contrary, what we cannot see is open for qualified guessing.

      Once again:

      The thread is about U-23. The pictures show the knife stern with a top rudder. One cannot deny that.


      Your argumentation suggests one may also call a VII A an VII C on the base of beeing Type VII.

      I it not my responsibility to make use of that knowledge or leave it as-is.

      Furthermore, by pointing out the existance of details i deem vital to contributing to a scale model i have every right to "speak" out freely as long as demanded and welcomed just like you did by directing attention to the stern transition. Until this very moment, i experienced the recent conversation beeing a discussion of producing character, not a contest.

      I fail to see your justification in critizising my usage of the term "to deal with something". Both our native language is not English.

      I do not use google translate, do you?

      This very model is the brainchild of David Hughes and he commands the outcome of his project. His critizism and opinion towards my writing is the only force to be acknowledged here, certainly not yours or mine.Agreed.

      Last edited by JHapprich; 08-16-2021, 05:01 AM.


      • #93

        Please don't argue over my U-boat. I have asked for feedback and both of you have given valuable feedback that I appreciate. You have both convinced me to change the rear end. It is advice I am grateful for. It has come at a good time in proceedings. I knew that when I started this project there would be lots of question marks. I have a habit of picking rare and obscure projects. I am coming to the realization that unless I get clear pics of U 23 then I will only get drawings that cover a range of U -Boats and not ones specific to U-23. As a result I will inevitably misinterpret details in drawings. The drawings cover such a wide range of boats that variations are going to occur. Being able to narrow down to U-23 is hard.

        So to cover as many possibilities I will create extra parts. I will create the Rudder horn to fit over the tiller and mark on the raised deck side the exit points for the push rods. I will then also create a upper rudder. Customers can fit either, or both as maybe seen in the lower image. Awesome image by the way...

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        I really like that this pic just shows a hint of the stern tubes just like my other pic. I will never get this boat absolutely right. I just want to create something that looks realistic on the water and gives customers another choice rather than just another type VIIC.

        Dave H



        • #94
          Hello all,

          I've done some drastic work on the stern after some solid feedback from the resident German's among us. Who am I to argue?, an Aussie building a German boat! Outrageous.. However, more on that later. Small bits for now.

          I have gone back to looking at the Torpedo tubes and thinking about producing the tube doors. I decided that I would produce a small part that could simply be glued on the front of the round flat section at the front of the tube. So I decided to start be getting on the lathe and machining up some shallow round Brass bar. Brass is my favourite material to turn. I am a bit scared of steel. Brass also looks nice. So I measured the inside diameter of the tube area and then turned down a thin section of about 2 mm and then parted off. I did that twice, checking for fit within the tube entrance.

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          After making both these parts I then cut out some small pieces of styrene to make the supports for the spring mechanism. Then I took as very small piece of round dowel to simulate the spring mechanism that sits in the middle. Unfortunately I don't have a photo here. As far as I am aware the hinge is inwards and the door opens inwards.

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          These will simply be glued to the front of the tubes on the kit. I then turned back to a feature that I had been deliberating over for a while. There is evidence to indicate that the stern and forward planes have slight bulges where the pivot shafts run along their width. From pics of other boats that I have seen and also having details like this featured on the vertical rudder I decided to recreate the bulge along the width of the planes where the shaft enter. I measured this position although It already coincides with where the shaft hole is. I then cuts some very fine slivers of balsa and glued them along the lines laid down. I couldn't find any dowel or material with a small enough radius that I could easily cut to do the job. So balsa and some initially fine sandpaper would see the balsa turn to the round profile that It would need to be.

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          Filler and sanding. The bulge will certainly add character and I would expect the planes to look like this from a boat of the early twentieth century. I would be interested to know if the designers of these early U-boats did tank testing. It would be really interesting to know what the hydrodynamic thinking behind these designs was.

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          Then after lots of sanding and filling a shot of the blue spray filler. Then more sanding...

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          After this I decided to work on some fittings that appear on the conning tower. There is what looks like a 'helm' a steering wheel for the officer on the conning deck. I decided that this would once again be made using a small brass shaft turned on the lathe. I then carved a small round wheel to be attached the side of the brass shaft and then drilled a small recess in the top forward section of the conning deck to place this helm in just behind the front of the steel and fabric frame covers.

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          Some styrene straps around the side to increase the thickness at points. After this I repeated the process for the vertical pole section that extends from the forward lower tower section up till almost the deck. I have no idea what it is but it is on the drawings. Can someone illuminate? Looks cool..

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          David H


          • #95
            Hi dave, that could be a compass daughter. I will see to send some helm post pictures of the conning


            • #96
              Hello all,

              Still more small appendages. A couple of weeks ago i posted some pics showing all the stern pieces in position. These included the hydroplane guards. Like most things on this class of boat, trying to work out exact shape and geometry has been a challenge, as what has been made abundantly clear to me is just how much variation there has been in the design over the successive boats. I am at a stage of creating to the masters where I have to consider what detail to put on the hull from here on. I could put a lot more scribing work into creating a set of hull ballast tank vents along the bottom of the boat ,but I simply don't know where they are located and how much variation could there be across the entire range of boats in this class. The plans simply don't give the information and there are almost no photos showing clearly the very underside of these boats. Oh, to have the documentation that comes with the Type 7C.

              Anyway, the drawings do show guards. These guards are curved rails around the front of the forward and stern planes and I believe serve two purposes. One is to protect the planes from damage from piers when alongside. The other I guess, is to ride the mine cables around the outside of the plane and not get stuck on a shaft and seriously end badly for the crew. The drawings show a generic shape. I decided to make sure that the clearance would be acceptable for both so created a set of guards for both the front and then back.

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              So I took a piece of brass 2.3mm rod and placed it in the lathe. Tapered am mm in down to about 1mm. This is tricky as it wants to deflect when the tool goes in. If you push to hard it will simply bend and go wacky on you. Then just a fine file and a little more smoothing down. This is to allow the point to sit in the tip hole at the outside shaft exit. The shaft connecting the two sides wont go all the way through. I wont be making the forward planes move. Never have. I then take some pliers and then bend the two bends making sure that when I do this I start the bend at the right point and don't need to bend back otherwise it will simply snap off.

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              The stern plane guard has a little more room forward. The arm length is less than the front at the curve of the hull is moving inwards as opposed to the front where it is moving outwards. The inner section of the plane is angled outward as this will allow the plane to move up against the curve of the upper hull above it.

              I have no information on where the guards have a airfoil type profile to their root sections. This is very clear on WW2 German Uboats. Clearly documented on the Type 7C but unsure or WW1 boats. I decided to go with profiles anyway along the trailing edge of the guards.

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              To do this I took some really small bits of Renshape and glued them to the inner surfaces of the guards. Them sanding and some filler. More sanding and some more filler and....

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              The line is to mark out the distance to the small divitt that will indicate where the guard is to sit forward of the plane. The gouge beneath is the location of the shaft exit point that will be covered over by an exit gland.

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              The next step is to work out how the rudder shaft is held. The lower half will be made using a hard shell glass mold. These molds aren't really the best for fine detail and small parts. Also because they are rigid then getting parts out could be seriously difficult. Draft angles and such. The small cut out are as seen above by the Rudder where the shaft is exposed by the square cut out begs for a small extension of the extreme end of the keel to house a small bracket to hold the rudder shaft. Mold this would be near impossible with F'glass. So I intend on cutting out a rectangular section along the bottom and then casting a small rectangular block with a hole in one end. This block will have the brass rod pushed through and then glued in the bottom back end of the keel to secure the rudder.

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              The Saga continues next week....

              David H


              • #97
                Hello all,

                For quite a while I have kept the stern raised middle deck section broad without much taper. I had in the back of my mind been thinking about tapering it and at the same time not being sure how to interpret the drawings. Did the stern raised deck taper very sharply like is the case with the U9 class. My lack of pointy rear end on the U-23 class ended up causing a bit of a stoush with the previously mentioned German members. Friction over an Australia U-boat. Well pretty quickly it became clear that the stern was going to have to be quite tapered. Time to break out the hacksaw, files and sandpaper.

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                First thing to do was to cut two angled cuts emanating from the center back and finishing at the same point either side further forward. I would then have to take the hacksaw and cut horizontally along the base of the deck and file down smooth the transition point.

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                As I was cutting I would be breaking through a combination of materials such as Balsa, Renshape, Expandable foam and filler. This means that as you are cutting and filing you can tear away at the material at different rates if you are not careful. I had to move between various tools and grades of sandpaper.

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                I decided once again that i would use Renshape replacement strips in the back end. So to accommodate their thickness I had to cut back a little further below the raised deck and make sure that the expanding foam wouldn't get in the way of the new strips. The main problem that I had was that the old profile created an inner curve and stop to the material behind. You can clearly see the outline of where the vertical sheet sat and behind this was just void. This would mean the need for some extra filler and material placed in their. So I got some small bits or Renshape and blocked them in and the rest would be filler.

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                Below is the scrubbed up and looking a little more respectable back end. Still more fine tuning with the pointy bit but in the meantime I thought I would also do a write up over the next point of contention amongst the German contingent. Rear upper rudders.

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                I have decided to go with two options for this kit. I will make an upper rudder for those who wish to give the boat a rearward upper rudder and pushrod connections for those who don't. Jorg even managed to find me a photo that showed one of the U-boats had the best of both worlds. Push rod connection and rudder over the top. Way to Go! I am not going to offer that combination, sorry.

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                So I made another rudder out of Renshape. I don't have any really clear photos of rudders on the U23 class, there are only some grainy ones. So I am speculating.

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                More next week.



                • #98
                  When I train someone in the Craft, the first thing I tell them is to be contemptuous of the project: It is not your master, you are the master. Take whatever measures, ruthlessly, to put right an error.

                  Your above example of the stern correction is a shining example of courageous model building. Slash away, Jack! You're my kind of model-builder.

                  Yes, your finished product is still crude looking and needs much refinement to be classified as 'museum quality', but you have, over the years, embraced so many new techniques and tackled so many tough projects, that eventually you will be able to dedicate yourself to becoming proficient at refinement of the completed display.

                  You are model-builder in the classic sense.

                  Go get 'em Tiger!

                  Your fan, David
                  Resident Luddite


                  • #99
                    Thanks David,

                    Its nice to get feedback and I appreciate the comments.

                    Last week i hacked away at the stern upper deck section and majorly tapered it to comply with what everybody is telling me it should look like and is suggested on the drawings. I am happier with how it looks and know that It fits in with the design principles of the time. The taper has seen some more filling and sanding and is looking alot smoother now. It then started looking at the creation of the stern upper rudder for those so inclined because with the U-23 class its not totally certain that it had a top rudder. Photos certainly suggest it but this is a class of boats that theoretically extend as far as U-41 so i thought I would add some flexibility to the design.

                    The next step is creating the push rod mechanism for the rudder if you don't go with the top rudder. This detial is best shown by the photo that i have of the U-39's rear end. You can clearly see the upper push rod connections in a 'hub' like structure. For want of a better term it looks like a servo horn with some solid looking push rods either side. I have seen several photos showing this design. As mentioned in a previous post I am intrigued as to why its on the outside. Did it need regular maintenance? Is could be more exposed to battle damage..

                    I created the push rod hub by turning up a really tiny piece of Renshape. I turned it down to about 5 mm. I then drilled a 2 mm hole through the center. I parted it off and gave it a delicate sanding as this is a really small part. I then took a piece of the Renshape strip that I had and used the mill to shave off a couple of mms. I then cut it to size to create the flat plate section that effectively makes the horns either side.

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                    I then turned up an even smaller diameter piece and drilled an even smaller hole for the outside push rod supports.

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                    Then some spray putty and some really fine filing.

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                    I then see how they ft over where the top of the rudder shaft is positioned. I then need to work out the exit points into the pointy stern raised deck section. I am not going to make the push rods, that will have to be down to the customer. The Calipers shown the distance needed between the push rod movements. It is about 17 mm from centers. The photos that I have shown push rod exits either side as a wide tube exiting either side of the rear raised stern section inside a rectangular plate with rounded ends. I will be making the push rod exit pieces, tiny as they are.

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                    The exit tubes will have to be a bit wider than the shaft rods as like a servo push rod you have radial movement not purely linear so there will be some sideways movement that needs to be catered for. First thing that I do it take some of the tube of the Renshape that I turned up for the outer push rod supports and parted them off. This was soo tiny I parted off with a Stanley knife. I then take a section of flat strip and then mill the slot for the tube to be glued in at a tangent.

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                    Once this is done I then need to cut the profile after checking for the size and fit of the tube.

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                    I then need to carve a groove for the push rod as it will run inside the surface of what would have been the side of the deck. I have run the file right through to give as much flexibility to the pushrod exits and allow that radial movement. I then cut out the profile and then glue the tube in at the right angle.

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                    I then repeat the exercise with the other side by making two. I will be scribing the outline of the part on the side of the deck. If a customer wants to do the rudder they simply fill in the scribed outline. If not then the drill or mill out this section and place the push rod exits in an attached their own push rods that are wither working or dummy.

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                    The above photo of U 31 also shows the outline of the lapped metal plate outline around the torpedo tubes. I have been meaning for some time to address this and give it some detail. So i took some styrene and then cut some very fine strips. I then wrapped then around the shape to create a 'v' shaped profile.

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                    Nice little bit of Styrene trim on the side. The Hull is approaching being ready for mold making and tooling. So much fine checking filling and sanding, filling and sanding....

                    More next week.

                    David H


                    • Wow, thats really small! You could have used brass instead.

                      New 3D-Printer?


                      • Hi Jorg,

                        I could have but I really like using Renshape. I had company in the workshop today, a big fat Bluey. ( Bluetongue lizard.) This one was big, about 300mm long.

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                        • Nice pet! What's it's name? Doe's it like subs,too?

                          Last edited by JHapprich; 09-12-2021, 02:53 PM.