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Ingeborg, Arne's Marieholm IF

  • 14 Dec 2014 18:11
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    Reply # 3170005 on 3032430
    Anonymous member (Administrator)

    Dennis,
    the question is, what would that flagpole weigh after being cut down to max 10m? I have found that as long as the masts are not very tall and do not add more than 3% (better 2.5%) to the boat's displacement (sloop JR), you will be OK. The problem with heavier masts ( I once used one that was 5% of the boat's disp.) is mainly the added inertia in the pitch plane which will make the boat ride poorly over head sea. 

    Arne

    Last modified: 16 Dec 2014 10:30 | Anonymous member (Administrator)
  • 14 Dec 2014 18:07
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    Reply # 3170003 on 3032430
    Deleted user

    OOPS! that is another way of saying 3/16"

    Problem solved. 
  • 14 Dec 2014 17:45
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    Reply # 3169998 on 3032430
    Deleted user

    David,

    so far my choices are either that or 4.77mm.  A Goldilocks dilemma.
  • 14 Dec 2014 16:35
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    Reply # 3169991 on 3169983
    Anonymous member
    dennis gibbons wrote:

    Thanks David for the feedback.  Google searching has led me to a source of flagpole with a  6.35 mm wall thickness. While heavier, it may give me more of a safety factor.  Or am I overdoing it a bit?

    Overdoing it a bit. 5mm/3/16" is the right thickness to aim for.
  • 14 Dec 2014 16:17
    Quote
    Reply # 3169983 on 3032430
    Deleted user

    Thanks David for the feedback.  Google searching has led me to a source of flagpole with a  6.35 mm wall thickness. While heavier, it may give me more of a safety factor.  Or am i overdoing it a bit?
  • 14 Dec 2014 16:06
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    Reply # 3169980 on 3032430
    Anonymous member

    Dennis,

    6063T6 is fine. I have a 6063T6 tapered tubular mast, and after 80,000 miles, it shows no signs of weakness. Arne is using a 6"/150mm tube with wooden topmast on Ingeborg, so did Annie on Fantail, and I would say that this size is strong enough and just as importantly, stiff enough for a 26ft boat, whether it's 6061, 6082 or 6063.

    Arne's right about the hybrid mast-  it's the pragmatic way to get a mast, with no sacrifice of properties. Each part of the hybrid mast is easier to buy/transport/make than either a one piece alloy or wooden mast, and assembly on site is not difficult.

    Frances 26 - yes, a very sweet design, and would convert well, I think.
  • 14 Dec 2014 15:32
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    Reply # 3169978 on 3032430
    Deleted user

    That makes sense.

    Do you think the 6063-t6 may be too weak?

    If so, I will continue my mast search.

    BTW, while the IF is my number one choice, I have stumbled upon a Frances 26 which may be cheap enough for my budget. I think it would make a marvelous JR.
  • 14 Dec 2014 12:19
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    Reply # 3169935 on 3032430
    Anonymous member (Administrator)

    Dennis, my choice is based on what I can get  -  my motto is

    "Cheap, available and good enough"

    The fine thing with the 6m aluminium tubes is partly that I get them in the strong 6082-T6 alloy (250MPa versus 180MPa of the 6063-T6 alloy), and partly that it lets me transport that tube on the roof rack of my car, right to the harbour. The wooden top section can be made separately and mated with the lower section in the harbour.  If I find another, thinner aluminium tube to add as a top section, I may well go for that.

    Arne
  • 13 Dec 2014 15:06
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    Reply # 3169697 on 3032430
    Deleted user

    Arne,

     I wonder why you are going with the hybrid mast rather than all alloy?  I have found a source to a 4.77mm x 152 mm x 9.8m flagpole made of 6063-t6. 

    Is there an advantage to have the top 1/3rd wood?

    regards,

    Dennis ( Connecticut, USA)
  • 12 Dec 2014 04:11
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    Reply # 3168883 on 3168590
    Anonymous member

     

    Arne

    The mast on Mariposa is 9.9m from memory, but I think a 9.7m mast would be fine.

    Peter
       " ...there is nothing - absolutely nothing - half so much worth doing as simply messing about in junk-rigged boats" 
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