Making this boat self righting.

Discussion in 'Stability' started by zurk, Apr 22, 2014.

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  1. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    Self-righting depends on the boat being unstable in the inverted condition, obviously once the fire extinguisher broke the glass and flooding occurred, that must have no longer applied.
     
  2. zurk
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    zurk Junior Member

    bladders will be pre inflated at the docks. the idea is to have something like airbags - never needed except in a real emergency. then it adds a cushion for very little investment. The bladders will double as a expensive alternative to boat bumpers at the docks and head protection in the cabin.
    i believe a sunken boat can be made stable just like anything filled with liquid but its best to test these things on a real life scale at the docks and its also relatively cheap to do so.
    naysayers aside - this is perfectly practical and cost effective as an added layer of insurance. its just a matter of getting it to work which i believe it will be able to. as mentioned earlier the bilge pumps are self contained with their own power supply built in and full waterproofed. The bladders are military grade rated with full UV protection, long life and self venting for varying pressures.
    i dont see why it wouldnt work.
     
  3. Mr Efficiency
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    Mr Efficiency Senior Member

    That part I believe ! :rolleyes:
     
  4. PAR
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    PAR Yacht Designer/Builder

    Maybe some more research is in order, start with looking up "free surface effect", which is the butt kicker in swamped vessels. Better yet, borrow a little jon boat, fill it up with water in the shallows, sit inside it and start bailing. The results will be quickly observed.
     
  5. zurk
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    zurk Junior Member

    thats what the baffles are there to reduce. divided into 3 partitions to reduce sloshing.
     
  6. Mr Efficiency
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    Mr Efficiency Senior Member

    What baffles, where ? Maybe baffle-ment is the order of the day !
     
  7. TANSL
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    TANSL Senior Member

    Anything filled with liquid is is much more unstable than if it is empty. And this is not an opinion but an effect studied by the laws of physics, which you seem to know well.

    What sloshing may occur on a stationary boat and head down?
     
  8. zurk
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    zurk Junior Member

    as i said earlier the boat has baffles. 2 of them run crosswise across 80% vertically and double as storage. they divide the interior into 3 sections which reduces sloshing if partially filled.
    dont know how effective they will be but theyre there anyway.
    sloshing occurs if the boat is being drained as the cg shifts.
     
  9. Mr Efficiency
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    Mr Efficiency Senior Member

    I this is the doddle you seem to be suggesting it is, how about some diagrams to indicate the physics and sequence of events that will see the boat floating, just like before ?
     
  10. TANSL
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    TANSL Senior Member

    zurk, in my opinion it is possible that you are confusing the sloshing with the loss of stability due to the effect of free surfaces.
     
  11. zurk
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    zurk Junior Member

    fine. here is the attached diagram. let me know if the unknown free surface effects will cause problems.
    orange = 200lb lift floats, both slightly offset.
    yellow = 1100lb lift. small yellow in hull = 1000lb lift across both (500lb each), in hull side flotation.
    light blue = water inside hull.
    dark blue = water surface.
    hull = 2000lb.
     

    Attached Files:

  12. Navygate

    Navygate Previous Member

    Gee-whiz, you are tenacious Zurk.
    Are you Dutch by chance, that's a wonderful trait.
    So, in the diagram, is the time line linear?
    What happens between the last two images.
    I'm with Mr E, I believe you believe.
    Lets do this!
    When can we start?
    Video please.
    :)
     
  13. zurk
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    zurk Junior Member

    time line is not linear. between the last two images the submersible bilge pumps kick in to drain the water. they can do a max of 1200 gallons with built in batteries @1000GPH.
     
  14. DCockey
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    DCockey Senior Member

    RNLI Atlantic (Class B) RIB lifeboats use a manually actuated airbag to self-right. The airbag is mounted on a frame at the stern.

    Paper on the design of the RNLI Atlantic 85 RIB lifeboat. http://www.rnli-thurrock.org.uk/files/Design-of-Atlantic-85-1-_z9k23z99.pdf Capsize recovery is discussed on pp 4-5. GZ curves and other information are on pp 10-12.

    Video of RNLI Atlantic self-righting: https://www.youtube.com/watch?v=KgLM0z1cjwo

    Boat mounted video of capsize training; shows airbag inflation: https://www.youtube.com/watch?v=EHeB_QgYlCU

    Video of RNLI Atlantic 75 self-righting in capsize drill: https://www.youtube.com/watch?v=xHE9FMj7j6Y

    Capsize training starts at 2:50 https://www.youtube.com/watch?v=8X7Q0WLYNDk
     

  15. TANSL
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    TANSL Senior Member

    If the situation # 1 is produced, you'll be hard. Position # 2 can achieve self upright, but the c. of g. must be very low. He'd better do the test with a weight equal to the motor in the same position.
     

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