Is it possible to combine a sailboat, motorboat and submarine?

Discussion in 'Motorsailers' started by tahroo, Sep 14, 2012.

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  1. whitepointer23

    whitepointer23 Previous Member

    this topic came up a while back but i still can't get it through my head that a submerged vessel can be more efficient than a surface vessel. the fastest boats run with almost no hull in the water so you are saying they would go faster under water.. there is just no way a sub can be more efficient.
     
  2. viking north
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    viking north VINLAND

    Interesting -- Increased drag from wetted surface but possibly decreased drag from form. When considering overall drag(combination of the two) if skin resistance be the much lesser factor then it is possible underwater form design allows a reduction in drag when compared to the design necessary for a displacement /floating hull. Another consideration might be the underwater vessel operates in one medium, water while the surface vessel operates in two , air and water. Two mediums generate not only interaction in design but also in operational dynamics. Old subs were slower under water but then again their hulls were cluttered up with all sorts of arms and comm. gear causing drag. Modern subs are faster under water thanks to streamlining and modern propulsion systems aided by computer design, something unavailable to the old sub engineers. I'm sure in there somewhere lies the answer.
     
    Last edited: Oct 15, 2012
  3. Perm. Stress
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    Perm. Stress Junior Member

    in all this discussion big drag question is untouched:
    how to transfer pull of kite deep underwater (a sub has to be quite deep uderwater to benefit a drag decrease due to absence of free surface).
    Even streaming lines are quite draggy devices at speed in the order of 10 knots.
    In our case, line will need to be dragged trough the water at an oblique angle.
     
  4. viking north
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    viking north VINLAND

    Well I hit on a couple of the reduced drag factors but did not know about dept verses reduced drag due to Free surface(have to look that up :). Yes kite string drag from great dept would be a fly in the ointment. One of those strings would be heavy as I suspect it would have to transfer a video signal from a kite camera otherwise how would one see the surface in sub. mode.
     
  5. MikeJohns
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    MikeJohns Senior Member

    But the whole idea of a small sub meeting any sensible SOR for a passage maker is a fallacy with no merit and numerous pitfalls.

    If you want a serious passage making sub it needs to be large, capable and propelled, with several days deep dive time between surfacing. Forget sailing it. I think you'd be lucky to make a knot or two when the sails actually properly deployed when you look at the real drag situation.

    Efficiency does not mean practicality for your SOR. If you want a sailing passage maker and you want a bit more comfort look to reasonably heavy displacement boats with a high roll inertia and a comfortable GM, they start to perform well at around 55 feet LOA Heave is the most significant factor in mal de mere.

    The sea is not calm just below the surface.
    There is a fantasy that the sea is calm just beneath the waves. In reality it's far from it and significant wave orbitals propagate to around one half the wavelength. In otherwords the submersible needs to dive below the surface by around one half the significant wavelength, if it's 200 feet ( pretty common) you need to operate at 100 feet for calm water.
    It's common in rough weather for large military subs to have to dive to at least 200 feet before they can even trim properly.

    In water shallower than one half wavelength the orbitals are of greater amplitude and subs have very little inherent roll damping. Subs also heave relative to their displacement relative to the wave volume passing overhead.

    Consider a developed storm with a significant wave period of 200m and a breaking wave height of 15m . A small sub is the very worst of all options. The surface will be intolerable even fatal for the occupants, but to dive into calm water to avoid motion sickness you will go deep MAybe it will be tolerable at 200 feet. From memory 300 feet was the operational limit of the U Boats mentioned before. Now lets say that storm blows for 2 days and you have to emergency surface for air for some reason during the storm, at that point I suspect you will abandon and lose the vessel the motion will be violent and extreme long before snorkel depth is reached.

    Another issue with submerged objects is that they are subject to the worst affects of adverse current. Also with large surface areas they are particularly prone to significant drag increases through fouling .
     
  6. Squidly-Diddly
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    Squidly-Diddly Senior Member

    the private cruising sub might not be bad starting point.

    http://www.ussubmarines.com/submarines/phoenix.pdf

    Not sure about his claims for "18 knot surface speed", looks kinda rounded at the bow.

    But I could see just adding a couple of masts(folding or not) and the batt-pack keeping her upright even in strong wind, and the streamlined above water shape helping sail up wind.

    To me what this design is missing is a snorkel/periscope, with a radar and radio/satellite on the periscope.

    And some "high speed remotely steered submersibles", AKA torpedoes.
     
  7. rwatson
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    rwatson Senior Member

    This working diesel sub (K$670,000) 10m length, will do 9 knots on the surface

    http://www.ussubmarines.com/submarines/101.pdf

    65 metres long should be able to make 18knots easily with Surface Diesels: 2 x 1500 HP

    Why you would spend

    "Total project cost is estimated
    at $80 million with a design and
    construction period of at least 3 years"

    and stick some crappy mast & sails on the beast to do 3 knots in high wind driving 1500 tons of steel ???

    Once you had spent that much money, filling up with diesel would just be pocket money.
     
  8. Perm. Stress
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    Perm. Stress Junior Member

    To return to "is it possible to combine ..." :)
    Actually, during WW2, there was a few instances, when subs did return to port using improvised sailing rigs, due to diesel/shaft/propeller failure or due to running out of fuel... . Combined with inability to call for external help for some reason.
    With careful search, those stories could be dug out, here I write from distant memories of what I did read years ago.
    Of course, they did it in surface mode only.
    And hulls of subs of that era were optimized for surface sailing.
     
  9. goodwilltoall
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    goodwilltoall Senior Member

    Like the pheonix sub interior.
     

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  10. goodwilltoall
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    goodwilltoall Senior Member

    How about and airship/submarine, is it possible? George Buehler dreamed of the day passagemaker subs would be possible, as safe below the water as above.

    Remember snorkeling in reefs where the bottom was 30' deep with 4' rolling waves and you could see schools of fish near the bottom moving up and down in accordance with the waves above. Assume the sub would behave the same way.

    Before contemplating a submarine, a zeppelin would be more affordable and the gentlemen's way of traveling. Cruising efficiently 7MPH about 300' above land or water, windows wide open and drinking a cheap bottle of wine.
     
  11. peterAustralia
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    peterAustralia Senior Member

    goodwilltoal - are you insane or just pretending to be, just cant tell at the moment
     
  12. Submarine Tom

    Submarine Tom Previous Member

    The best airship / subsmarines I know of are diving birds.

    They are very impressive.
     
  13. El_Guero

    El_Guero Previous Member

    I don't want to hurt feelings, but why would anyone buy a sub from them? They are using WW2 designs .... Yes, some countries still do, but they are SLOW .... and AWKWARD ....

    THREE DECKS? Holy cow, cut her down to two decks, make her a truly rounded submersible, and get her up to about 20kts under water ....

    And then they could brag about 80 million dollars a copy .... just remind them to send me my commission.
     
  14. El_Guero

    El_Guero Previous Member

    OK, they claim 2 million people a year ride civilian submersibles.

    HAS anyone ridden a civilian sub?

    Or, are they including dive assistance devices?
     

  15. WestVanHan
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    WestVanHan Not a Senior Member

    How about a hydrogen powered hybrid diesel-electric motorhome hybrid helicopter/blimp,capable of being powered while submerged powered by hybrid sail/solar panels.
     
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