Double diamond spreader conversion

Discussion in 'Multihulls' started by aussiebushman, Jan 30, 2011.

  1. aussiebushman
    Joined: Oct 2009
    Posts: 283
    Likes: 33, Points: 28, Legacy Rep: 132
    Location: Taralga NSW

    aussiebushman Innovator

    G'Day from Oz

    I'm now more than half way to building a (modified) Trinardo 6.2 metre trimaran with a new main hull and where the ama volumes have been increased by a factor of 5 - more on this later. For now, I'd like input from you experts on beefing up the existing A Class mast into something more suited to the tri.

    No. I can't afford a new mast - Being semi retired, labour is readily available, cash is not.

    The existing A Class mast is only a 150 X 75 mm 1.5 mm thick section and is relatively unstayed (see picture) and being over 9 metres long with only a single set of spreaders one-third of the way up, it is hard to know why it never broke.

    What is proposed is more like the attached picture, with double diamond spreaders and associated stays. The radar dome in the picture will be replaced by a tri-lens radar reflector) Also attached is a MS Word file showing the modifications and dimensions applied to the existing mast. I shall also add an epoxy/glass sleeve (as suggested by Richard Woods in a former thread).

    Comments please - especially on my suggested positioning of the new top tang and new upper diamond spreaders



    Attached Files:

  2. gonzo
    Joined: Aug 2002
    Posts: 15,960
    Likes: 1,296, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    I find those diamond rigs complicated and expensive. They are great selling tools though. On a trimaran you have a very large beam. It is cheaper and simpler to add shrouds.
  3. michael pierzga
    Joined: Dec 2008
    Posts: 4,862
    Likes: 115, Points: 0, Legacy Rep: 1180
    Location: spain

    michael pierzga Senior Member

    Why two diamonds ?

    When the mast is loaded in compression , the diamond keeps the mast in column. Since you are changing the head stay geometry by raising and thus increasing compression why not simply relocate...raise and lengthen.... the existing spreader to achieve the correct shroud angle then add a diamond stay attachment near the new headstay ?
    Perhaps use the the new rigging attachment hounds compression tube to double as the new halyard sheave axle or make the new shroud tang double as the new headstay attachment.

    Two panels, diamonds, will work ... one panel should also work and with less gear aloft.
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