Slender non-planing foil assist catamaran?

Discussion in 'Hydrodynamics and Aerodynamics' started by S V, Dec 28, 2020.

  1. S V
    Joined: Jan 2019
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    Location: Lithuania

    S V Junior Member

    There is not much to be added...
    -Type/area of service: rivers, laggons and other protected waters, sea state 2 at most. Salty and fresh water. Lets assume, that clean wters without debris of floating objects.
    -Operation profile: 1+ hours between stops, 90+% at service speed. At least 1000hours/year.
    -Autonomy: 7 hours at service speed.
    -Passenger boat, 45-55 passengers in bus/airplane configuration. A bit more comfort and legroom than in economy airlines. 3-3 single isle I guess.
    -Maneuverability: average, no need for rapid change of directions.
    -Dimensions: length - any. Width 5 m at most. Air height - 4m at highest part, one deck. Draft - as low as possible, 0,8m for hull is ok, if the propulsion is propeller - a bit more.
    -Propulsion: any.
    -Hull type: any.
    -Fuel type: diesel. I am not dreaming about solar or cold fusion boats.
    -Service speed: >=34knots
    -Fuel efficiency: <=175 kg/hour fully loaded at cruising speed
    -Ship total displacement with fuel and fully loaded: ~20 000kg, but can be any to meet the other requirements
    -Construction, building materials: any, but with ability to mass produce. So, it has to be affordable and have of the shelf components.
    Requirements can bend a little if there is something that blocks all the project.

    As I know there is no such ship in the market except some of the exotics, which I have mentioned in this and others threads.
    Overall - it has to be a replacement to old soviet hydrofoils with about of 110% of their fuel economy but with simpler construction. Dont say, that this cant be done - there is a lot to improve on those ships. If you seen or been on one, you will know.

    Please, no hovercraft or SES ideas... It will not work...

    If there is a need for official SOR, I can fill any of the template.
     
  2. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    So, let me get this right:-

    Such an descriptive set of requirements for a boat that runs for:
    7 hours with seating, hey whatever, length - whatever, propulsion, hey, whatever, type of hull, whatever....and construction of said hull, hey - whatever.
    And this then has to be:

    An exact 20 tonnes, but then again...whatever if it doesn't comply.

    This is not an SOR, it is a school boys idea of dreaming with no roots in reality or a requirement based upon real world expectations.
    But hey, whatever...

    Now that, is a starting point. The rest above it...is nonsense.
     
    BlueBell likes this.
  3. Mr Efficiency
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    Mr Efficiency Senior Member

    What does "110% of their fuel efficiency" mean ? you want at least 10% better, or will accept 10% worse ? I just can't see it happening with twin engines, with either of those two.
     
  4. S V
    Joined: Jan 2019
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    S V Junior Member

    10% worse is ok, the speed has to be at least 1-2 km/h faster for obvious marketing reasons. The waterways are really really limiting in depth and in width. One, or more engines is ok.
     
  5. BlueBell
    Joined: May 2017
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    BlueBell "Whatever..."

    Well that's good because Sea Sleds tend to work best with two engines.
     
  6. S V
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    S V Junior Member

    Defining max width of the ship and seating quantity is not nonsense, and sadly I am older than a schoolboy, so if you want to show you superiority you just failed. This supposed to be forum for sharing knowledge, and you show none of it.
     
  7. BlueBell
    Joined: May 2017
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    BlueBell "Whatever..."

    Also S V, what is the budget and timeframe for completion and in-service?
     
  8. DogCavalry
    Joined: Sep 2019
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    DogCavalry I aim to misbehave.

    Well, some of your thoughts on pressure/suction etc, are correctish. Not actually correct, but I understand where you got the misconceptions. But no, foils don't always win, and there's nothing the least bit magical about suction vs pressure. Dynamic lift happens solely by momentum transfer. It is irrelevant whether its on the above ambient side of a lifting form moving on a fluid, or below ambient side. Momentum is transferred to the fluid in the wake, equal to the lift. And foils give dynamic lift with low surface area and high aspect ratio, so they are useful in lifting a displacement form above the air/water interface and reducing drag thereby. But high aspect ratio lifting forms with high finess have very unforgiving lift vs angle of attack characterics. And foils in water, in reality, hit stuff. Best case there is minor damage that is very harmful to efficiency. Just as easy to bend one slightly, leading to dynamic instability, leading in turn to emergency stopping, or total loss of vehicle and lives.
     
  9. S V
    Joined: Jan 2019
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    S V Junior Member

    There should be one, but I have none, as the world pretty much stopped in year 2020... Tourism is dead ATM.
     
  10. BlueBell
    Joined: May 2017
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    BlueBell "Whatever..."

    Oh.
    Well that's going to be a tough build then with no budget.
    Good luck.
     
  11. S V
    Joined: Jan 2019
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    Location: Lithuania

    S V Junior Member

    Oh no, maybe I expressed myself wrong! The project may be on hold, as the tourism pretty much stopped.
    The budget is from 0.8M EUR for ship, depending on "trim" and performance :)
    The timeframe is undefined, as it is still unknown when majority will be immune from COVID-19
     
  12. Mr Efficiency
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    Mr Efficiency Senior Member

    Foils are more efficient lifting surfaces than the bottom of a boat, partly because they have reduced ambient pressure on the top surface, a boat bottom does not.
     
    S V likes this.
  13. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    So: -
    length - any
    beam -any
    hull - any
    construction - any
    Propulsion - any.

    Yup..that sounds like me just failing to grasp the exact nature of the design!

    That wholly depends if there is a real requirement at hand or just a pipe dream not rooted in actual real-world variables...like something as simple as... money:

    So, that's a no again!
     
  14. S V
    Joined: Jan 2019
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    S V Junior Member

    I mentioned passenger quantity, mentioned limiting beam and so on. There are many things that I simply dont know, thats why there are smart people who can help and make their offers, ideas, suggestions. But overall... you know, that I am in a big dilemma: to reply to your posts or not. I dont want to discuss in nonnative language about smth that at the end is your psichologic problems, because I cannot express that good, so I will write in my native language just for you:

    Tu debilas ir tiek. Būk geras berniukas ir nelysk į šitą diskusiją.
     

  15. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    And that's the point!
    You can't expect others to give you an answer if you don't know what it is you want, or can afford, or understand.. etc etc.

    Design requires an exact set of parameters, not guesses.

    I have a lot of respect for those coming into a forum where English is not their native language...i struggle big time with Japanese.
    But engineering .... is universal. It is based on facts...not endless unknowns and guesses.
     
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