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RC submarine lateral stabilization structure

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  • #16
    Originally posted by Sam Victory View Post
    Hi, Nate! I accept your criticism, but I'm afraid you can't judge a theory without a basis. Not to mention that it's a theory that has been proven correct for a long time. My personal understanding of the rc model is that the rc model is a reflection of those big real things that are related and similar in some way. So the basic theory is connected. Maybe it is possible that adding internal bilge keel is not very effective, but the teachers in school told us how to prove things right: first have a conjecture, then design an experiment to prove it. Applying the theory to practice, and just talking without doing is useless! Finally come to a conclusion. With this in mind, I did a simple experiment. Since I had just returned from the lab, I didn't have the better tools to do it. So I used a plastic bottle with a weight mounted on the bottom and put it into water ballasted to the set water line. Then I used my hand to make the bottle shake from side to side until the bottle was stable, calculating the stability time several times to 7 to 8 seconds or even longer. Then I put cardboard on both sides of the bottle to simulate the bilge keel, and after the same operation, the stabilization time was 3 to 4 seconds. In fact this is very correct theory and I don't think it is necessary to practice it anymore, maybe it is better by mathematical modeling. But I still did the experiment and came up with the results....


    V
    Did you place the keels on the inside or outside of the bottle?
    Make it simple, make strong, make it work!

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    • #17
      Originally posted by redboat219 View Post

      Did you place the keels on the inside or outside of the bottle?
      just outside , they are in a whole part.


      V

      Comment


      • #18
        Originally posted by Sam Victory View Post
        When I have time, I will definitely try it, just may be a long time from now. Just because I don't have enough time, I'm hoping that other members of the forum can apply my ideas in a practical way.

        Sincerely
        V
        If I ever get to 3D printing that Gotland class, I will definitely test this idea out.

        Nate

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        • #19
          I, personally, love that Sam has shared this bit of marine physics with us. I completely understand the reasoning behind it and how it applies in real life. Again, the scale application may be different, but the physics are sound.

          To simplify for anyone not following, adding external keels has a twofold benefit. First off, it provides a surface that water acts against to improve stability of the boat if an outside force (such as wind) creates a rotational force about the longitudinal axis of the boat. The water reduces the ability of the wind to accelerate the mass of the hull, dampening the effect.

          Secondly, moving the weight of these keels from inside to outside increases the moment arm for the weights, thereby increasing their effectiveness at stabilizing the boat. The caveat to this is that putting them at 45 degrees to the vertical centerline, as Sam suggested, reduces their effectiveness at increasing static stability. You'd need double the weight to create the same static stability. More effective would be an external bilge keel placed in line with the center of buoyancy and the center of mass.

          At the end of the day, we are somewhat hampered in playing around with this as we are, for the most part, trying to create scale replicas of existing boats, and are thereby limited in terms of external modifications.


          Bob

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          • #20
            Originally posted by RCSubGuy View Post
            I, personally, love that Sam has shared this bit of marine physics with us. I completely understand the reasoning behind it and how it applies in real life. Again, the scale application may be different, but the physics are sound.

            To simplify for anyone not following, adding external keels has a twofold benefit. First off, it provides a surface that water acts against to improve stability of the boat if an outside force (such as wind) creates a rotational force about the longitudinal axis of the boat. The water reduces the ability of the wind to accelerate the mass of the hull, dampening the effect.

            Secondly, moving the weight of these keels from inside to outside increases the moment arm for the weights, thereby increasing their effectiveness at stabilizing the boat. The caveat to this is that putting them at 45 degrees to the vertical centerline, as Sam suggested, reduces their effectiveness at increasing static stability. You'd need double the weight to create the same static stability. More effective would be an external bilge keel placed in line with the center of buoyancy and the center of mass.

            At the end of the day, we are somewhat hampered in playing around with this as we are, for the most part, trying to create scale replicas of existing boats, and are thereby limited in terms of external modifications.


            Bob
            Not sure if this fits the discussion about keel stability or not!

            Click image for larger version

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            The HMS Holland l That I am currently build has these keel faring's on both sides of the hull.

            Click image for larger version

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            Rob
            "Firemen can stand the heat"

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