Submersible hulls

Discussion in 'Boat Design' started by Collin, Mar 20, 2012.

  1. Collin
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    Collin Senior Member

    I'm wondering if there would be some performance advantage from catamaran hulls that would be so low that they would submerge themselves in waves. we see wave piercing hulls, so why not go all the way into wave submerging?

    Wouldn't this do a lot to remove pitching in waves? Also, we'd eliminate windage. :confused:
     
  2. Leo Lazauskas
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    Leo Lazauskas Senior Member

    SWATH might be similar to the arrangement you are proposing.
    http://en.wikipedia.org/wiki/Small-waterplane-area_twin_hull

    The disadvantage is the large increase in wetted surface area which will
    increase the resistance of the vessel.
     
  3. tugboat

    tugboat Previous Member

    nothing wrong with the idea in my opinion- but your not going to go fast...
    think submarine...civil sub about three knots-- also-then you need hydrodynamic hulls shaped like blimps or torpedos...why not make a test model? tihis would be my approach..would you use sails or power? again-whole new ballgame...sub hulls are the most efficient..this is why i laugh at guys like Micheal Phelps- who spend an entire lifetime learning to swim in the most inefficent way possible--on the surface...this concept you are talking about is called -semi-submersible hullforms--they dont dive but are submerged while running--it would be inefficient too to use two hulls--why not then use one..?
     
  4. Collin
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    Collin Senior Member

    I also had that exact idea for a boat! I reasoned that if wave making resistance was such a limiting factor, we could get around it by keeping the hulls under the surface.

    What I was talking about here wouldn't be exactly that. In calm conditions, the hulls wouldn't be submerged, but when sailing in big waves, they could just torpedo through them without any fuss.

    So it would be like a hybrid between the small-watwerplane hull and a conventional wave-piercing hull
     
  5. Leo Lazauskas
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    Leo Lazauskas Senior Member

    And he laughs back at you. There are rules that preclude swimming under
    water for more than a prescribed distance. :)
     
  6. tugboat

    tugboat Previous Member

    which is silly because its so inefficient...:D let them all laugh! fools!!:p

    some companies toyed with the idea of using submarine towing-thereby decreasing fuel costs...semi submerged running - the idea was abandoned...
     
  7. whitepointer23

    whitepointer23 Previous Member

    i am having a bit of trouble understanding this. if the fastest sailboats run on foils to reduce drag from the water then how can it be more efficient to run the hull underwater. wouldn't the speed records be in subs.
     
  8. Leo Lazauskas
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    Leo Lazauskas Senior Member

    You might have to make some clear limits on what is allowable in your "speed record" set.
    Top speed of some nuclear subs is at least 70 knots, which is not bad for a
    large vessel. About 100 knots for an SES is pretty slick too, but that's for a much smaller displacement.
     
  9. rwatson
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    rwatson Senior Member

    the world powered water record is over 300 mph - try getting a sub to do that.

    Water is far denser than air, so the more exposure to water the hull has, the slower you must go.

    Sub hulls are as efficient going the water as they can be, but they can never outperform an equivalent surface vessel.

    "Earthrace was intended to showcase environmentally friendly technologies. It broke the world record for circumnavigating the globe in a motorized boat.[4] It set the record in 60 days 23 hours and 49 minutes. This beat the record of 74 days, 20 hours, 58 minutes set by the Cable and Wireless Adventurer (then the Ocean 7 Adventurer)[17], in 1998, by 13 days 21 hours and 9 minutes. It is unclear if the circumnavigation was faster than the disputed time set by the US Navy's USS Triton nuclear-powered ( powered by two nuclear reactors.) submarine during Operation Sandblast.[18] The time established by Earthrace did not supersede the overall record set by the multi-hulled sailing yacht Groupama 3 of 48 days, 7 hours 44 minutes and 52 seconds"

    http://en.wikipedia.org/wiki/MY_Ady_Gil

    "The top speed of a nuclear submarine is a bit over 70 knots in a full speed run of 1.5 NM. I was on the Submarine Wolf off Hawaii during trials and we topped out at 71 knots at a depth of 180 ft."
     

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    Last edited: Mar 20, 2012
  10. Leo Lazauskas
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    Leo Lazauskas Senior Member

    That's why I suggested that we need some clear limits (e.g. on displacement) before thumping the tub for one class of vessel or another. (A case could be also be made for WIG's, proposed Shkval torpedoes, and many others as contenders.)
     
  11. FAST FRED
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    FAST FRED Senior Member

    "I also had that exact idea for a boat! I reasoned that if wave making resistance was such a limiting factor, we could get around it by keeping the hulls under the surface."

    The Atkin box keel boats used a simpler concept.

    The "box" (canoe body) underwater took 85% of the hull weight so the small bit of hull skimmed over the surface easily ,like a water ski.

    Claimed to be efficient up to SL 2.8 or 3 ,but full plaining is quicker at higher speeds.

    Loads easier to build (and live with) than submerged cat hulls .

    FF
     
  12. Ad Hoc
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    Ad Hoc Naval Architect

  13. tugboat

    tugboat Previous Member

    not faster underwater--just more efifcient...less windage-friction, and its almost weightless when neutrally bouyant., it doesnt have to over come wave resistance. it doesnt drag a wave behind it. nor does it push waves with the bow---there are other reasons...im not sur eonm this but a sub would be classified as a displacement type hull and would have limits...
    gettign a large object like a sub to go 70 knots it impressive! they outrun ships... when a boat goes 300 mph--its not really touching much water--its up on tiny specific points such and ihas little wetted surface.
    they ride on hydrofoils, sponsons or a tunnel effect makes it more like an airplane than a boat...who knows maybe a small sub could go 300 knots if it had the proper high speed engines?
     
  14. tugboat

    tugboat Previous Member

    hi Leo--a wig..is more like an aircraft isnt it..it actually flies a few feet off the ground? "wing in ground effect" vehicle
     

  15. Leo Lazauskas
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    Leo Lazauskas Senior Member

    Yes, or over water.
    There also AAMV's (Aerodynamically Alleviated Marine Vehicle) and variations on the theme.
     
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