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Japanese BI I-25 in 1/72

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  • There is a new pond reopened here in Adelaide, South Australia.

    It is a lot larger than any of the others and the water is clear. It's not very deep, only about 2 feet but the surface of liner of the pond is a sand colored smooth membrane.

    Took I-25 down to it yesterday just to have a look. She still is not turning as good as I would like but even without a ADF I was able to keep it running submerged for the most part of 3 laps.

    I also took the ALFA down to play with and as always it was fun to play with. Also there were several 1/72 TARGETS.

    Several of the guys that were there took lots of photos but I have only see 2 of them so far.

    Can you see the sub?


    • Really looks good. If you can get someone to help you take pictures and video , you could post some operational shots. Just curious, did you get any leaks in you water tight areas?


      • The photos were taken with a phone camera, not to bad hay. The water tight thingy did it's job well and if I can only get it to turn better I will be a happy chappy.

        I am going to try an aircraft mixer on the motors and rudder to see if that helps.

        The idea is that when the rudder is turned one of the motors speeds up and the other slows down.
        Because I-25 only has one rudder and 2 props it will be a bit of trial and error to figure out which motors to speed up and which one to slow down.
        Will it turn better with the fast prop pushing clear water or pushing against the inside of the rudder? If it had twin rudders it would be a lot easier.

        Got some more photos of the day from Bruce and his phone camera.

        Last edited by oztruck; 07-13-2011, 09:06 AM. Reason: another photo


        • A few more photos were sent to me

          Starting to dive

          Doing what a sub should do

          One of the targets


          • Im thinking "Fast prop pushing clear water" and slow down and even stop and reverse the inside prop. You may have to resort to using a seperate channel for each prop and control them independantly so that you can go ahead on one and stop or reverse the other one.


            • Are the shafts parallel with the boats centerline or toed-out? If toed-out then they will be less effective at differential steering -- the closer the shafts nexus is to the boats center of gravity, the shorter the turning moment arm, the less effective differential throttle will be to effect a yawing force.

              Enlarge the lower rudder and blow water off it with the screw opposed to the direction of turn.
              Resident Luddite


              • Thanks for the input gentlemen. Yes David the Shafts are toed out just a bit so I will give it a go with the stronger inside wash hitting the rudder. That is how I set it up last night. If it does not improve it is a simple matter of changing the ESC leads over to make it work in the other direction. While I am at it I will enlarge the rudder, got nothing to loose. Again thanks for the help.


                • You've done a magnificent job so far. Now, it's just fine-tuning things.

                  Resident Luddite


                  • Update:

                    I fitted an air craft type mixer to mix both the rudder and the ESC to see if it improves the turning. It would slow or reverse the outside prop when turning the rudder. Although it did work it did cause other problems. Like whenever I mover the rudder one of the motors would run so i could not just coast along and steer with the rudder like you do when coming along side. It was like trying to ride a bike on ice, it can be done but it is too hard.(not fun)

                    I then tried using the inbuilt mixer on my radio and that was even worse. Back to the drawing board.

                    What I have now done is enlarge the control surface and give it a bit more movement from side to side.

                    It is raining here in Adelaide so I have to wait till it stops before giving it another run and wait for the pond to be fixed. The water has gone GREEN


                    • Couldn't help myself. Went to the "green sea" today to see if there was any improvement in the handling of the boat.

                      VERY happy with the results. With the larger rudder and different shaped front dive planes it was like a different boat.

                      The turning circle is a lot tighter than before and the response to change of direction is now good.
                      A guess would be about 4 boat length radius, it's not a sports boat so it's not going to handle like one.
                      The rudder is a winner. And I am happy

                      Even with the green water I still wanted to see if I had improved on the submerged running by changing the shape of the front dive planes and I am happy to say that after a bit of fiddling with the angles I had to adjust the rear dive planes UP by about 5 deg to stop the bow from trying to rise all the time.
                      She now runs at periscope depth with no hands with only a slight movement up and down about an inch, as she runs, .

                      The water is just too green to do anything fancy submerged, so it was only straight runs but as I was leaving some workers from the City turned up with some chemicals.

                      I will as soon as I can get some video of the boat doing its stuff. But it is winter here and it's hard to get my camera person (wife) to spend a winters afternoon by the side of a wind swept pond.


                      • Sorry about the lack of input over the last few weeks, but I have been called to Sydney on our East coast to look after my Dad for a few weeks.

                        When I was flying in I spotted something that took my interest and as soon as i got a bit of free time found what I was looking for.

                        It's there, It's complete, and open. The photos are from my phone, so there is not many to show

                        I will be here for another week or two, but when talking to my wife on the phone this morning she said there is a package back at home for me
                        It is the control valve for my emergency blow system so I will be able to get the boat finished and post progress photos and text


                        • Will they let you up into the sail?


                          • The sail and the lower deck area are closed off to the public. The climb up to the top of the sail might be too much to control. Only a single ladder and a long climb up and down. The boat is in great condition and as you can see in the couple of photos VERY well fitted out and complete


                            • I'm back.

                              Got home today, kissed the wife and opened the mail.
                              What I had ordered had turned up, it is a valve that I am going to use for my emergency gas ballast blow system.

                              The plan is to have the valve connected in such a way that it can be operated manually and/or by the fail safe.
                              That's the plan.

                              This is the "Robart" valve, it is originally built for air operated landing gear on RC aircraft

                              Next is a clear gas cylinder to hold the gas supply. Because it is clear I can tell at a glance how much gas is left.

                              And here is the housing for the gas cylinder, still a work in progress

                              Now all I have to do is fit it all together and get it to work.


                              • These never fail to help the turn radius when installed on the TE of a rudder, simple too.