REMOVING-->Boom-Mast Trawler

Discussion in 'Stability' started by oldsalt1, Dec 6, 2007.

  1. oldsalt1
    Joined: Dec 2007
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    oldsalt1 Junior Member

    I have a 1981 steel trawler.

    I wanted to remove the existing steel mast and boom that are on top of my upper structure/pilot house.

    I never use the mast/boom and the former owner never used it. It would free up some room. I am not sure that it is has a positive effect since the boat weighs about 77,000. I also thought it may have a negative effect since it is so very high on the vessel and rather than aluminum or composite, it is quite heavy being constructed of steel.

    ANY helpful advice would be appreciated.

    Regards,
    oldsalt1
     
  2. Eric Sponberg
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    Eric Sponberg Senior Member

    If you don't use it, take it off. Stability will improve, if anything. If the base extends down into the interior, make sure that the surrounding structure is not relying on it for support.

    Eric
     
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  3. oldsalt1
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    oldsalt1 Junior Member

    Thank You

    Eric, thanks for the advice. Although I am in Boston, my trawler is in Ft. Pierce being updated. The mast does not go into the interior and serves no structural purpose. I believe the original intent of the builder-designer was to attach a stability sail. I am not sure whether sufficient sail area could be accomplished nor would I use steel for the mast and boom. I am a believer of low weight up high. I am a common sense thinker, so I just did not want to do something stupid that I'd later regret.
     
  4. Ekaiztea
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    Ekaiztea Seagoing Ships Master.

    Increase Stability

    Before anything else I'll introduce myself. My name is Txon, I live at Madrid, Spain. So, I beg your pardon for any mistake writting in English.

    OK, lets go to the topic. Removing high weights usually improves the ship's stability but it also decreases the rolling motion. A very short rolling period results in a very uncorfortable boat and in an overload of the structure due to dinamic forces. Before removing any structural weight, two calculations are compulsory. The VCG (Vertical center of gravity coodinate) movement and the reduction in the rolling period.

    Nothing else by now. Best regards
     
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  5. Kay9
    Joined: Oct 2006
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    Kay9 1600T Master

    Ekaiztea is correct. Trawlers have a big roll as is, but with the mast and steady sail it is generally a slow roll. Remove that and you might find yourself in wiplash territory. What was a nice gentile ride might now be a guarentee sea sic roller coaster. If you can contact the firm that designed her or built her and talk to them.

    My $0.02
     
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  6. Guillermo
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    Guillermo Ingeniero Naval

    Not only GMo will increase and so the rolling period will be reduced: Removing weights aloft also reduces gyradius. If the weight of the mast is relatively important and actual stability and motion are adequate, then the effect of taking it off should be previously evaluated working out some numbers.

    Ongi etorri, Cptn. Txon Aguirre!

    Cheers.
     
  7. alan white
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    alan white Senior Member

    If maintaining roll characteristics and freeing up room are desired, consider reconfiguring or moving the mast/boom instead of removal, since it is so useful for other purposes such as attaching lighting, radar, antennas, providing a lookout, hoisting cargo, and carrying a small sail.
     
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  8. Ekaiztea
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    Ekaiztea Seagoing Ships Master.

    Ha ha ha

    Ekerrikasko Ingeniero Guillermo ¡¡¡¡
     
  9. Guillermo
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    Guillermo Ingeniero Naval

  10. FAST FRED
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    FAST FRED Senior Member

    Perhaps it could serve as a strong point to set Flopper stoppers?

    OR do you have a hyd stability system?

    FF
     
  11. expedition
    Joined: Jun 2007
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    expedition Thorwald Westmaas

    removing boom and effect on stability

    I have a very similar issue. On our North Sea trawler we plan to remove the winches (on the maindeck) which weight about 22 tons and the front mast (about 13 tons) which will be replaced by something lighter.

    So, we also expect the roll period to decrease beyond what's comfortable but like I wrote in another post today, will this increased stability actually help us if we were to employ stabilizers?

    Or, do we better start running some numbers and use a lot of concrete on our new floor on the main deck :)

    Thorwald
     
  12. Guillermo
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    Guillermo Ingeniero Naval

    I'm totally atonished you have not runned numbers yet!
     
  13. expedition
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    expedition Thorwald Westmaas

    Don't!

    The designers in Holland simply have a lot of work. And my question remains, will increased stability lower the size-requirements of stabilizer systems?

    Thorwald
     
  14. Guillermo
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    Guillermo Ingeniero Naval

    I refuse to believe that. There's something very strange in all this.
     

  15. expedition
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    expedition Thorwald Westmaas

    "Something very strange ? " Maybe a conspiracy you mean? PLease elaborate. This could be interesting.

    Well, mine is very busy and yes, I'm considering getting another one but they happen to be the designers of this vessel so it made sense to use them.

    Thorwald
     
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