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Surcouf propellers

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  • Surcouf propellers

    I read somewhere that the Surcouf propellers were not inline, one was forward of the other. Can anyone throw any light on this?

  • #2
    Here is a link to plans, it does indeed look like they are not on the same plane. From the rear view the diameter of the props overlap and may be the reason it was done that way.
    If you can cut, drill, saw, hit things and swear a lot, you're well on the way to building a working model sub.


    • #3
      Many thanks.


      • #4
        Great time to clarify this Question in my head-With the propellers offset fore and aft, you would think that the differential thrust would affect the track of the boat...ah, but wouldn't it be possible to offset the thrust bearings to compensate. Is it not so much the placing of the propellers but the placing of the thrust bearings pushing on the structure that determines differential thrust?


        • #5
          I've yet to have my 48th scale OTW Surcouf on the water, but she has the authentic offset props. I really don't know that the minimal offset would be of notice for something this large, though, as pointed out, there must be some sort of effect, as the props are angled toward the centerline and each would create a slightly different turning moment about the center axis.

          I'm going to hypothesize that no effect will be noticeable, but we can certainly experiment once she's completed and taking her sea trials...


          • #6
            I would suggest, to insure a cancellation of any lateral thrust from a two or more shaft running-gear, that all shafts would be toed in so that their respective thrust lines intersect at a common point along the vehicles longitudinal axis. Most ships and submarine see this vector nexus ahead of the c.g. and most who conn these type craft are familiar with the ability to employ differential thrust to effect yaw forces. Those few vehicles with the vector nexus behind the c.g. (type-21 drivers for example) are a special breed, as the same technique is used to yaw the craft -- but it's backwards from the norm.

            Last edited by He Who Shall Not Be Named; 10-28-2019, 07:57 AM.
            "... well, that takes care of Jorgenson's theory!"