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Birdsmouth mast taper

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  • 11 Jul 2012 12:36
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    Reply # 1005642 on 975321
    Anonymous member

    I remember reading somewhere in cyberspace about Bertrand building his masts for his Tiki 30.  Low and behold I stumbled across it once more!  If you are building a mast this is a much less stressful method than 'bird mouth'. 

    Click here for Bertrands method.  As a bonus you get a good record of building a tiki 30.

    Peter

    ps don't follow the link if you are on an expensive internet connection.  Very picture heavy!

    Last modified: 11 Jul 2012 12:39 | Anonymous member
  • 18 Jun 2012 16:03
    Quote
    Reply # 975484 on 975321
    Anonymous member

    Paul

    You might want to look at this as well... http://www.junkrigassociation.org/Resources/Documents/Building%20of%20two%2016m%20wood%20masts%20V1-0.pdf

    Betrand had a slightly different approach to mast building, and it strikes me as considerably easier than the birsmouth method.

    Peter

     

     
  • 18 Jun 2012 13:26
    Quote
    Reply # 975356 on 975321
    Anonymous member
    Newsletter No 57 has an article I wrote on building my mast if you wish to read it.
  • 18 Jun 2012 13:01
    Quote
    Reply # 975345 on 975321
    Anonymous member
    Hi Paul, I think what you are looking at is a cut away view of a hollowed out mast not a birdsmouth. I built a 9 metre BM mast a couple of years ago. To get the taper on a BM mast you cut  you take off timber from the face opposite the BM.
    This site is invaluable for calculating your dimensions, I made great use of it.
    http://www.duckworksmagazine.com/04/s/articles/birdsmouth/index.cfm
  • 18 Jun 2012 12:01
    Quote
    Message # 975321
    Deleted user
    A friend and I are refurbishing a Hurley 22 and intend to put a junk rig on her. We intend to mount the mast in a tabernacle immediately in front of the coach-house.

    The sail will be 29.6 m2 on a 9 m mast which is 205 mm diameter at the top of
    the tabernacle and 84 mm at the mast head. The mast taper has been drawn as outlined in Skenes Elements of Yacht Design. I have been looking at Practical Junk
    Rig page 128 where the sugested section is shown. In the transition between
    staves and the "solid" sections of the mast, there is a gentle curve -
    presumeably to avoid high stress points.

    How is this achieved when building a birdsmouth mast. If the staves are cut to
    achieve this curve, then won't there be rapid twists in the staves?

    Also, is it worth reducing the wall thickness as the mast gets smaller towards the top? I have in mind using a jig which could be used for the initial taper but also for reducing the stave thickness.
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