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    David Merriman's Nautilus...

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    Tom(ADMIN)
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    Posts : 3024
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    Post  Tom(ADMIN) Sun Dec 08, 2013 4:14 pm

    David asked me to add this about the Nautilus in the 'painting and weathering' section, so here it is, copied and pasted from David's email:

    ''Some may question how the 31-inch long NAUTILUS was able to maintain depth and maneuver credibly underwater without any practical bow or stern planes. The secret to getting around these traditional control surfaces was to gimbal the propeller about the pitch and yaw axis. Works great and avoids adding any non-scale control surfaces that would otherwise ruin the 'look' of the Disney NAUTILUS''.

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    nigele(ADMIN)2
    nigele(ADMIN)2
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    Post  nigele(ADMIN)2 Sun Dec 08, 2013 4:57 pm

    Why not just move the battery backwards and forwards ?,I very rarely use the dive plains I drive the boat by moving the battery
    merriman
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    Post  merriman Sun Dec 08, 2013 7:46 pm

    At any rate above a critical speed, the short moment arm of the shifting c.g. can't beat the magnitude of the moment arm of the upsetting forces that result from asymmetric dynamic forces acting upon the submerged hull and appendages working to upset the submarine about the pitch axis.

    Shifting fixed ballast weight, pumping trim water, and pixie dust work to effect pitch control below the critical speed.

    David
    nigele(ADMIN)2
    nigele(ADMIN)2
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    Post  nigele(ADMIN)2 Sun Dec 08, 2013 7:51 pm

    "WOW"
    merriman
    merriman
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    Post  merriman Sun Dec 08, 2013 8:12 pm

    ... and that makes me the Master of the run-on sentence!

    David
    nigele(ADMIN)2
    nigele(ADMIN)2
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    Post  nigele(ADMIN)2 Sun Dec 08, 2013 8:29 pm

    It sure do David.
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    Tom(ADMIN)
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    Post  Tom(ADMIN) Sun Dec 08, 2013 8:37 pm

    There's no arguing with that, really...
    david f
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    Post  david f Mon Dec 09, 2013 9:19 am

    So for subs at low speed, the only control methods available are ballast/weight shifting. (My mental picture is always an airship at hover - not at New Jersey and not with flames licking out from it!)

    At higher speeds dynamic forces are much more significant so dive planes, the hull shape and angle of attack and NOW prop pitch and yaw can all be used. (Think of an airship motoring along rushing through the air)

    I had never thought of moving the prop like that. That is clever! Thanks.

    David
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    Tom(ADMIN)
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    Post  Tom(ADMIN) Mon Dec 09, 2013 9:28 am

    Similar sort of effect (in a way) to movable side thrusters, maybe?
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    Post  bwi Thu Feb 19, 2015 8:15 pm

    Making way trough the forum and stumbled on this......this is a fine example of “Improvise, Adapt and Overcome!”.
    grtz,
    Bart
    merriman
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    Post  merriman Thu Feb 19, 2015 9:39 pm

    bwi wrote:Making way trough the forum and stumbled on this......this is a fine example of “Improvise, Adapt and Overcome!”.
    grtz,
    Bart

    Then, you'll like this:

    I made the dorsal 'heeling' rudder at the trailing-edge of the phase-2 ALBACORE sail practical -- its deflection driven by a servo controlled by an athwartship oriented angle-keeper; as the boat rolls into a high-speed turn, the dorsal rudder produces a roll moment to counter the heel. Just like the real thing!

    I found this to be a great way to 'put on the breaks', when needing to kill head-way; just start fish-tailing the rudder and the hull and control surfaces work to produce a great deal of drag.

    The last shot is of a phase-3 ALBACORE model, with the counter-rotating propellers and X-tail configuration -- turned on a dime and gave back nine-cents change!

    David


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