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Cracked subdriver cylinder

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  • Cracked subdriver cylinder


    Cracked Subdriver

    Finally restarted my KILO build after a looooooooooong hiatus.
    Also bought a 1/144 Trumpeter Soryu class along with the recommended electronic V tail mixer.
    Brought out the subdrivers from storage, one for the Kilo another for the trumpeter Seawolf. The Seawolf's 2"SD is a perfect fit inside the Soryu. Plan to use the v tail mixer in the Seawolf SD. If thing don't work out will fall back to the KILO SD and install a mechanical mixer in the stern.

    While inspecting both SDs, I was shocked to find several star shaped cracks emanating around the the screw holes for securing the fore and aft ballast tank bulkheads to the inside of the SD. What's disconcerting is some of the cracks extend from the ballast compartment to the front battery compartment and also to the aft electronic compartment. Hard to see if they superficial or extend all the way through the lexan wall. Need to do a pressure leak test to see.

    Would sealing the cracks with silicone or epoxy/ superglue be a viable fix OR are they already doomed certified fit for deployment in the trashbin?
    Attached Files
    Make it simple, make strong, make it work!

  • #2
    Holy crap...thats a shame, seem like they are pressure cracks from the screws. I have smaller cracks like yours. Maybe rubber gaskets that expand and contract would remedy the stress. I think its a design issue that needs to be addressed imo.

    Comment


    • #3
      It looks like a expansion because of heat or someone cranked down the screws too tight.. As far as sealing, I recall an article that there was a very thin liquid glue that would fill the cracks, but on yours you would need to put a hole at the end of the crack to stop it from spreading. Seal that and fill the cracks. Can you silicon it or epoxy it? Yes, depending how hard up for supplies or availability in your area. The best answer is replace the tube.
      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


      • #4
        Originally posted by trout View Post
        It looks like a expansion because of heat or someone cranked down the screws too tight.
        We did experience extremely hot summers the last few years back, temperature were almost at 100F. The SDs were store in their mailing tubes away from direct sunlight. They were also wrapped in bubble wrap which I think would have serves as insulation.

        As for cranking down the screws too tight, I was the one who assembled the KILO SD and it was my first time building one. I know I didn't crank it down too much. I was even contemplating of sealing the screw heads with silicon to make them airtight. It suffered far fewer cracking as compared to the Seawolf SD which I got already fully assembled from the manufacturer.
        Last edited by redboat219; 11-08-2020, 03:06 AM.
        Make it simple, make strong, make it work!

        Comment


        • #5
          One of the disadvantages of the original version of the SubDrivers was the one-piece tube versus the new MSD's that have a modular makeup. My new MKIII (in final development) cylinder does away with all but a very few cylinder perforations. If you wanted a "correct" repair for your cylinder, it would be to completely replace the tube. That said, you can definitely repair this if you are okay with permanently securing the ballast bulkhead in place.

          What I would do:
          1. Partially drill through the polycarbonate at the end of the crack using a small drill bit. This will stop further spreading.
          2. Use thin CA to wick into the cracks
          3. Remove your equipment tray and motor bulkhead from the cylinder.
          4. Mix up some 2-part epoxy and apply it to the seam around the ballast bulkhead inside the cylinder. I'd also spread a bit on the inside cylinder wall wherever there is a crack (just to be sure).
          In theory, this will take care of the cracks and stop more from occurring.

          Feel free to hit me up by email or phone if you want to talk through this in detail.
          ​​​​​​​

          Bob

          Comment


          • #6
            Thanks for the tip. Will try it.

            BTW, any particular bit size I should use?
            Make it simple, make strong, make it work!

            Comment


            • #7
              Polycarbonate is very notch sensitive, which means any scores or holes drilled into it significantly weakens the materials strength. Coupled with a bending moment from squishing down the seal, plus extruded tubing has quite a bit of stresses in it. PVC seems to be more tolerant in this respect, but hard to find clear which a lot of modellers seem to want.
              DIVE IN! Go on, go on, go on, go on, GO ON! http://www.diveintomodelsubmarines.co.uk

              Comment


              • #8
                PVC will be my fall back option. Unfortunately the only readily available ones locally are orange colored drain pipe.
                Make it simple, make strong, make it work!

                Comment


                • #9
                  Doesn't matter what it looks like- function first.

                  However it's unlikely your endcaps will fit the pipe accurately, as they'll be worked to fit the pipe supplied. Unless you know someone with a lathe or can cut and file to tolerances of around 10 thou (0.25mm) you won't make them fit.

                  You can try the fixes suggested using glues etc. I'll wager problems will eventually reappear though.

                  You have too many irons in the fire, concentrate on the one boat and put the others away. I'd finish the Kilo, easiest and best of the bunch for handling and transport.
                  DIVE IN! Go on, go on, go on, go on, GO ON! http://www.diveintomodelsubmarines.co.uk

                  Comment


                  • #10
                    For some reason my previous post was flagged as a SPAM pending approval.

                    Originally posted by Subculture View Post
                    Doesn't matter what it looks like- function first.

                    However it's unlikely your endcaps will fit the pipe accurately, as they'll be worked to fit the pipe supplied. Unless you know someone with a lathe or can cut and file to tolerances of around 10 thou (0.25mm) you won't make them fit.
                    Fortunately my brother-in-law has a machine shop complete with a lathe.

                    Originally posted by Subculture View Post

                    I'll wager problems will eventually reappear though.
                    Yes, I have a feeling they would. The material is already in a compromised state, it's a ticking bomb.

                    Originally posted by Subculture View Post

                    You have too many irons in the fire, concentrate on the one boat and put the others away. I'd finish the Kilo, easiest and best of the bunch for handling and transport.
                    Yes. Definitely absolutely correct. As a wise cracking man said FINISH YOUR D**N KILO!

                    Actually, I only have 2 ongoing( unfinished) builds, the KILO and a 1/150 Academy Type IX. The Trumpeter Seawolf is in storage for a future build ( only bought it because of an error, the initial SD I got was for a Seawolf and not the KILO), so are the Revell 1/72 Type VII, Bronco 1/35 Type XXIII ( both basically model kits, no WTC or fitting kits etc.), and the aforementioned Soryu, which was more of an impulse/ last one on the shelf don't miss out opportunity/ I can use my current SD on it buy,

                    Thank you.
                    Make it simple, make strong, make it work!

                    Comment


                    • #11
                      Originally posted by redboat219 View Post
                      Fortunately my brother-in-law has a machine shop complete with a lathe..
                      In that case, no excuse for a bad job. You can rework the parts you have to eliminate the screws, cut out the areas damaged, and replace with new tubing of your choice. Or do something of your own choosing.

                      DIVE IN! Go on, go on, go on, go on, GO ON! http://www.diveintomodelsubmarines.co.uk

                      Comment

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