Japanese BI I-25 in 1/72

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  • oztruck
    Commander
    • May 2010
    • 317

    #61
    Oh well, looks like that request went down like a sub with the hatches still open. I guess I will have to make myself one.

    Comment

    • oztruck
      Commander
      • May 2010
      • 317

      #62
      Started on the drive unit.





      They have a 3/1 reduction. Looking that they will give me plenty of power and a good long run time.

      I don't have any clear water here in South Australia to put my boats into.

      Most of the time it is either green or coffee colored.

      The best place I have found uses boar water but it is only 2 1/2 feet deep, so speed is not a big thing with my subs. Long run times and steady depth control as you can imagine are very important.

      It's hard to drive when you can't see where it is.Scuba Diving

      Comment

      • greenman407
        Admiral
        • Feb 2009
        • 7530

        #63
        I think that this is where it gets complicated for me, probably not for the rest of you. Oztruck has determined that a 10" block of styro is what he needs to displace that same volume of water to get his sub trimmed. Well obviously a WTC will add bouancy and weight. So im not sure how sizing a styrofoam block will help. I do it the lazy way. I just ask Dave what size WTC will work. Then I stick it in and then trim for that. Ill be interested in where you go from here. Now if you are going to build a seperate WTC for the ballast tank then you would install the WTC that houses your Battery and electronics first and then see whats left in order to size your ballast tank. Right??
        IT TAKES GREAT INTELLIGENCE TO FAKE SUCH STUPIDITY!

        Comment

        • oztruck
          Commander
          • May 2010
          • 317

          #64
          Think of it this way greenman407.

          The ballast tank size will determine how your boat sits in the water. I might be wrong but I think its size is critical

          1a: If my boat without its WTC is sitting in the water with just the top part of the sail sticking out, it has just a bit of positive buoyancy. correct

          2a: Now to get it to the correct surfaced water line, through trial and error I found my foam block has to be 10" long to displace enough water.

          now take that one step further

          1b: My boat with its WTC is sitting in the water with just the top part of the sail sticking out, it has just a bit of positive buoyancy. Same buoyancy as above in 1a. correct

          2b: Now to get it to the correct surfaced water line, I found my ballast tank has to be 10" long to displace enough water.

          All the ballast tank (10"foam block) is lifting out of the water is the deck, conning tower and the part of the hull above the water line.

          Does that make sense?

          Comment

          • He Who Shall Not Be Named
            Moderator
            • Aug 2008
            • 12503

            #65
            Your assumptions are correct for the conditions established.

            David,
            Who is John Galt?

            Comment

            • greenman407
              Admiral
              • Feb 2009
              • 7530

              #66
              Absolutely but maybe I missed it. Your tests were without a WTC. So until you get one in there and test it you dont know what you have. Unless I am missing something.
              IT TAKES GREAT INTELLIGENCE TO FAKE SUCH STUPIDITY!

              Comment

              • He Who Shall Not Be Named
                Moderator
                • Aug 2008
                • 12503

                #67
                He'll simply re-establish submerged trim with the WTC in place, less the ballast tank, then build a ballast tank that contains the same number of cubic inches as his hunk of exceptionally ugly foam. Done.

                In the early years of the game (the 80's Renascence of r/c submarining in America, led by Skip Asay, Dave Weeks, Mike Dorey, and others) David Copeland advocated just this very method of determining a boats ballast tanks displacement.

                David,
                Who is John Galt?

                Comment

                • greenman407
                  Admiral
                  • Feb 2009
                  • 7530

                  #68
                  Yes, "re-establish submerged trim with the WTC in place", less the ballast tank
                  IT TAKES GREAT INTELLIGENCE TO FAKE SUCH STUPIDITY!

                  Comment

                  • oztruck
                    Commander
                    • May 2010
                    • 317

                    #69
                    As above or with the ballast tank full of water.

                    Did a bit more detail work on the bow today.

                    Last edited by oztruck; 05-18-2011, 04:31 AM. Reason: added photo

                    Comment

                    • oztruck
                      Commander
                      • May 2010
                      • 317

                      #70
                      Started on my Water Tight Thingy. a bit different than the norm

                      Comment

                      • greenman407
                        Admiral
                        • Feb 2009
                        • 7530

                        #71
                        Looks like youve got something in mind like doing what Engle does in their subs with a top that is held down by a bunch of screws? Inquiring minds need to know.
                        IT TAKES GREAT INTELLIGENCE TO FAKE SUCH STUPIDITY!

                        Comment

                        • oztruck
                          Commander
                          • May 2010
                          • 317

                          #72
                          Your guess is correct. What you see is a long box that I have started using 3mm plastic HIP. I will follow up with more photos in the next few days.

                          Comment

                          • oztruck
                            Commander
                            • May 2010
                            • 317

                            #73
                            These are the air pumps that I am going to use on this project. They are large 4 diaphragm air pumps. I will need BIG pumps because of the volume of air that has to be moved.



                            Built the air craft lift crane and it's storage bin. Seems like there is always something to do on this one



                            Last edited by oztruck; 05-20-2011, 03:59 AM. Reason: added photo

                            Comment

                            • Rpmtech1
                              Lieutenant Commander
                              • Dec 2009
                              • 229

                              #74
                              Looking cool, and worth the work when its done.

                              And why are you using a box shaped WTC? man I did one of those once, never again!

                              Comment

                              • oztruck
                                Commander
                                • May 2010
                                • 317

                                #75
                                "And why are you using a box shaped WTC? man I did one of those once, never again!"

                                It's more like have to, than want to. But that is a long story.

                                Any way there are no places around here where I can use my boats that are more than 4' deep. So a box is strong enough for that

                                Comment

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