Romany 21 roll reduction

Discussion in 'Stability' started by Lutefiskgeorge, Nov 28, 2019.

  1. rxcomposite
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    rxcomposite Senior Member

    Post a picture of your boat.
     
  2. BlueBell
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    BlueBell "Whatever..."

    Stabilizer bags like on the side of inflatable life rafts.
    They resist rolling big time.
    But, it sounds like you've tried them already, no?
    And, they'd have to be recovered before making way.
     
  3. Ad Hoc
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    Ad Hoc Naval Architect

    Ok..so, can you define annoying..since an annoying roll can mean anything.
    What is the period of roll, what accelerations do you you experience.
    What sea conditions does this occur in?

    Far too many unknowns to really comment properly.
     
  4. Lutefiskgeorge
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    Lutefiskgeorge Junior Member

    I dont have a picture of the boats hull im afraid.

    Bluebell, thanks. Ive tried buckets, which i guess would be similar, but not as large. I have some strong woven polyprop garden bags with handles, next time i am out i will try them. They are bigger than the buckets, and i have 4, so should make a difference if its going to work.

    AdHoc, thanks for the reply, however i wouldnt know where to start with a roll period or any acceleration forces.
    Boat doesnt roll on calm days, just days where its wind over tide, beam on or blowing 3 plus
     
  5. BlueBell
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    BlueBell "Whatever..."

    A roll period is simply the amount of time it takes for the boat to roll through an entire cycle.
    A stop watch really helps.

    Wait, are you catching fish when you go out?
    If not, that may be why you find this anomaly so annoying.
     
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  6. Lutefiskgeorge
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    Lutefiskgeorge Junior Member

    Ha. Yes im catching fish, well, sometimes!
    Il have to time the roll next time i am out and get back to you.
    Thanks
     
  7. Lutefiskgeorge
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    Lutefiskgeorge Junior Member

    Just a thought, re the stabiliser bag system.
    The woven garden sacks i have are 120litres each, like minature 1 ton bulk builders bags.
    I have 4, but have a couple more at the mother inlaws.
    Would 2 each side of the boat be enough?
    From what i can see from one liferaft manufacturer seago they have approx 240litre bags to act as stability. Obviously the rafts are very light in comparison.
    How many should i use to test with?
    In the past ive tried 2x20litre buckets each side, and if a liferaft is stable with 240litres, it looks like my 2ton boat may need a considerable amount more to have any effect?
    Or would i be better off getting the wife to sew a large tarpaulin into a massive pocket and dangle that on each side?
    Then how far down?
    I like the simplicity of this idea alot Bluebell.
     
    Last edited: Dec 1, 2019
  8. Ad Hoc
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    Ad Hoc Naval Architect

    All boats roll under such conditions.
    But the question is...how much...and is it bad...?
    Thus without putting this into numbers for a measure of understanding...it is impossible to say.
    All I can do is refer you to the 3 questions i noted earlier....without the answer to these...it is pure guesswork based upon thoughts/feelings and suppositions!
     
  9. BlueBell
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    BlueBell "Whatever..."

    Well they don't have to be very deep now do they.
    Even if you pulled one out, past the surface, it would only pull that rising side down more.
    Meanwhile, the other side just plunges deeper!
    The larger the diameter of the bags the larger the dampening effect... to a point.
     
  10. bajansailor
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    bajansailor Marine Surveyor

    Re the roll period, you don't have to be out at sea to measure this - you can do this even if you are moored alongside a dock.
    Just make sure that your lines are very loose so that they do not restrain the motion in any way.
    Two people stepping on to the gunwhale from the dock should be able to heel the boat a reasonable amount - if they then step off the boat on to the dock then she should roll a few times quite happily. The amplitude of roll will diminish with time, but the actual roll period will stay the same. You can measure the time for a few rolls, and then calculate the time for one complete roll.
    A very 'quick' roll period indicates 'good' stability - a 'slow' roll period means that the stability is less, but it might well still be within acceptable limits.
    Sometimes boats can have 'too much' stability where they have a very short roll period, but I doubt that your boat would suffer from this.
    A longer roll period is generally more comfortable for the crew (assuming that the stability is still ok), as the centripetal forces trying to throw them off the boat are less.
    Rolling period test https://www.plato.is/general_precautions/rolling_period_test/

    I am just wondering if it would be possible to build a relatively simple gantry / goalpost type of mast over your wheelhouse? You could use this for supporting a couple of outriggers for hanging your stabilisers. The further outboard you have the paravanes / flopper stoppers / stabiliser bags suspended, the more effect they will have, as they are applying a righting moment that is proportional to the lever (ie the distance from the boat centreline).
     
  11. BlueBell
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    BlueBell "Whatever..."

    What you describe is initial stability.
    Lots of boats with high initial stability have very poor stability characteristics overall.
    While some of the worse initial stability characteristic boats can be the most seaworthy!
     
  12. bajansailor
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    bajansailor Marine Surveyor

    Absolutely!
    It will be interesting to hear from George where he is with his Romany, re if she has high or low initial stability.
     
  13. Ad Hoc
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    Ad Hoc Naval Architect

    BB

    Indeed....

    A stiff short sharp roll period of a catamaran leading to high accelerations is a good example of high initial stability.
    Whereas a very questionable stability for say a Swath...has superior seakeeping and low accelerations.
     
  14. BlueBell
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    BlueBell "Whatever..."

    "Tender" is the word that comes to mind.
    or "tippy" perhaps to the landlubber.
     
    Last edited: Dec 3, 2019

  15. Andy1974
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    Andy1974 New Member

    I’ve got a Romany 21 mines got Perkins 4108 with outdrive leg get at 12 knots
     

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