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Thread: Dismasted

  1. #21
    Join Date
    Oct 2012
    Posts
    3,288

    Default Re: Dismasted

    Not inertia. While Inertia may have an effect. The main reason the boat rolls faster is the change in the centre of gravity.

    The weight of the Mast is relatively high, it acts at the masts centre of gravity so a small g. Probable close to half way up the mast. Under normal conditions this weights position raises the boats centre of gravity a G.
    The boats stability is a combination of the effects of its centre of G acting down and itís centre of buoyancy acting up.
    They want to be in line. incline the vessel and it will create a righting lever to bring the vessel back upright provided they are both in line.
    The lost of the mast. Will do two things. If lost overboard, the weight is gone, the weight of the boat will be less it will float higher the center of buoyancy change to a position slightly lower.
    The loss of the weight high up will cause the overall boats center of gravity to be quite a bit lower.
    This lower centre of gravity will creat a larger righting leaver when the boat is inclined or heeled resulting in a faster more sudden return to upright.

    The boat will be more stiff.

    The change in stability is often expressed by comparing a theoretical position Metacentric height with the center of gravity.
    Or GM
    The GM will get quite a bit larger with the loss of the mast and rig.

    M is a theoretical position on the centre line through which a vertical line up through the centre of buoyancy acts when the vessel is slightly inclined.
    The centre of buoyancy moves to the low side when the vessel is inclined.

    Sail boats are generally kind of stiff. Take the mast of they get a lot more stiff. So without the mast a sailboat will tend to roll faster and more violently than with the mast.
    Last edited by Uricanejack; 21-11-19 at 08:41.

  2. #22
    Join Date
    Oct 2012
    Location
    Southminster, essex
    Posts
    9,611

    Default Re: Dismasted

    Everyone mentions the actual wire rigging. But on my boat there are lots of ropes leading to the cockpit. Plus all the in mast electrics. Just releasing that lot must take a while. Getting sails clear of the boat must be awkward as they may well be laying across the rigging.
    I broke the mast on a silhouette when I was in my teens, but we drifted to the bank so just hopped ashore (in the mud ) & waited for the tide to go out. The mess was incredible.
    What it must be like on a full blown cruiser, especially with, say, the kite up, must be one hell of a tangle.
    Last edited by Daydream believer; 21-11-19 at 08:55.
    It is all down to the fact that my wife does not understand me !!

  3. #23
    Join Date
    May 2001
    Location
    North Wales, sailing Aegean Sea or Menai Strait
    Posts
    22,130

    Default Re: Dismasted

    Quote Originally Posted by DownWest View Post
    Read about Hammond Innes motoring his new steel boat to UK from Holland. No rig , and it had a nasty short roll. Very unpleasant.
    The inertia of the mast matters.
    Strange coincidence, I am reading that book right now.
    Answers to some technical queries at new website http://coxeng.co.uk

  4. #24
    Join Date
    Jul 2006
    Location
    Emsworth Hants
    Posts
    12,685

    Default Re: Dismasted

    A list of the best bolt cutters: https://www.gearhungry.com/best-bolt-cutters/ What concerns me is the handles are much shorter that the one we carried.

  5. #25
    Join Date
    Aug 2013
    Location
    SW Scotland
    Posts
    19,759

    Default Re: Dismasted

    Quote Originally Posted by DownWest View Post
    JD
    You do speak English as well, don't you?
    I'm an academic and have been fluent in pedantic gibberish so long that my English are rusty.
    "Seamen are always wanting to do things the proper way; and I like to do them my way."

  6. #26
    Join Date
    Mar 2007
    Location
    Atlantic
    Posts
    21,805

    Default Re: Dismasted

    Quote Originally Posted by JumbleDuck View Post
    I'm an academic and have been fluent in pedantic gibberish so long that my English are rusty.
    Its good to have the talent to work it out with a pencil.

  7. #27
    Join Date
    Jun 2011
    Location
    Berkshire, UK
    Posts
    2,777

    Default Re: Dismasted

    Quote Originally Posted by JumbleDuck View Post
    I'm an academic and have been fluent in pedantic gibberish so long that my English are rusty.
    In contrast with the tool kit thread that claims that cheap tools rust sooner, whereas the posh ones resist for longer?

    Mike.

  8. #28
    Join Date
    May 2001
    Location
    North Wales, sailing Aegean Sea or Menai Strait
    Posts
    22,130

    Default Re: Dismasted

    Quote Originally Posted by KellysEye View Post
    A list of the best bolt cutters: https://www.gearhungry.com/best-bolt-cutters/ What concerns me is the handles are much shorter that the one we carried.
    I agree. I initially bought a pair with handles about 18 inches long. I tested them on a length of 8 mm 1x19 wire and they came nowhere near cutting through. I replaced them with a pair almost twice as long that cope very well.
    Answers to some technical queries at new website http://coxeng.co.uk

  9. #29
    Join Date
    Nov 2001
    Location
    Me: Johannesburg South Africa Yacht: Richards Bay East Coast Africa
    Posts
    7,347

    Default Re: Dismasted

    Quote Originally Posted by JumbleDuck View Post
    I'm an academic and have been fluent in pedantic gibberish so long that my English are rusty.
    JD

    I simperise with you I have the same issues but I am not in an academic environment so most of the people I get involved with tend to ignore me as I think they don't understand my pedantic English. The additional factor is a lot of the people where I live don't have English as their first language and don;t understand Engineering. Computer systems design and the local Laws.
    Life is too short not to have a sea view
    Distantshaws tinyurl.com/yclt6l68

  10. #30
    Join Date
    Mar 2017
    Posts
    22

    Default Re: Dismasted

    We've got a set of hydraulic croppers. When we replaced the backstay I played around trying to chop it up with various bits of kit onboard. Manual croppers were as good as useless, even with the wire flat on the ground. Hydraulic ones went through the wire like a knife through butter. Horrendously expensive through.
    A handheld angle grinder might be equally good and cheaper, though obviously then you've got sparks and heat to contend with.

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