homebuilt wing mast

Discussion in 'Multihulls' started by village idiot, Dec 12, 2009.

  1. village idiot
    Joined: Dec 2009
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    village idiot Junior Member

    Anyone got plans / ideas on building a wing mast for 7m tri ? need to build a mast 10.5-11m with aprox 250-300mm cord .I'm thinking gaboon ply/foam composite with carbon reinforcing.? any suggestions.
    thanks. :)
     
  2. Gary Baigent
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    Gary Baigent Senior Member

    wing masts

    The first jpeg is Flash Harry's that is 9.1 metres x 0.450 length to chord, has a curved above hounds trailing edge/luff - but if you want a straight version, just reverse leading and trailing edges. This is a larger chord than what you listed and also a metre or so shorter - but you get the idea. Second image shows a comparison with Groucho Marx's cross section. Harry's mast is now over 20 years old, 4mm ply I beam, frames of same, skinned with 3 mm with carbon at hounds and other high load places, weighs less than 20 kgs with all rigging.
    Third image is David Knaggs wing mast for his foiler - which still survives but moulders away at the bottom of his garden.
     

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  3. CTMD
    Joined: Dec 2007
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    CTMD Naval Architect

    Build methodology for a carbon mast of my design here then
    here
    send me an email if you want help with laminates.

    can also be done with foam instead of ply.
     
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  4. jpquattro
    Joined: Oct 2009
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    Location: Pisa Italy

    jpquattro Junior Member

    Hi all.
    I am a new member, I write from Italy. I am building one 8 meter catamaran based on a Paul Fisher design.
    The project call for a 10 meters mast with a single shrouds order and diamond.
    The mast in this thread is almost of the correct size...
    But it appear really light, with thin skin...
    Some rough calculations suggests that it is close to the limit for me, then the question is: can you detail something about the number of shrouds and spreaders used?

    Paolo
     
  5. Gary Baigent
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    Gary Baigent Senior Member

    You talking to me, jpquattro? Guess you are since Flash Harry's mast is thin skinned. Three shrouds, no spreaders - but there are a number of layers of carbon run and spread over the halfway point area between hounds and base. FH is a light boat, around A Class weight, and the mast is actually 25 years old and has never broken, yet has been in some horrible sailing conditions, when my heart was in my mouth.
     

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  6. jpquattro
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    jpquattro Junior Member

    Yes Gary, Tank you for your fast replay.
    Three shrouds means that the longest free mast section is in the 2 meter range right?
    My cat will be trailerable then the mast weight is a major concern... I think if I can pass from one to two diamonds, to reduce the unsupported lenght...
    another problem is to trailer the mast it would be useful to split it in two sections...
    But I don't see any reliable and light joint for that type of mast...
    Do you have any suggestion?

    Paolo
     
  7. Gary Baigent
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    Gary Baigent Senior Member

    Paolo, Forget about breaking the mast down into two sections; the joint will be tricky to engineer and to build - and also heavy. A 10 metre mast is not difficult to transport, leave it complete. Also being only 10 m, if you build a reasonably thick section wing, like Harry's at .450 x 140mm or 150mm, you won't need spreaders - that also will make it easily trailered. Use carbon instead of wire.
    cheers Gary
     
  8. Boston

    Boston Previous Member

    nice boat Gary
     
  9. jpquattro
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    jpquattro Junior Member

    mmmhh I know...
    I can have a joint light, simple, reliable: pick any two...:) :)
    About the single piece stick we, here, have strange laws.
    The one related to this problem is: the trailer's load cannot extend over the car... This means that the mast must ang after the boat a couple of meter with a plate with red and yellow stripes... dangerous for road users and for the mast...

    about the carbon reinforcement I have a theory... maybe is better to open a separate thread on this...

    Paolo
     
  10. jamez
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    jamez Senior Member

    Hi Paolo, glad to hear your SF 26 is nearing completion. possible alternative.. a 9 metre mast with a big square top main and a high forestay attachment?? Or maybe a long drawbar on the trailer to accomodate the mast length. Most Ts's seem to cope with a bit of mast overhang but I can understand your apprehension about it.
     
  11. jpquattro
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    jpquattro Junior Member

    Hi Jaimez, maybe that You tink to another Paolo, I am building one heavily altered cat 254 from Paul Fisher
    http://www.selway-fisher.com/YachtCats.htm
    But the original has been altered so heavily that Fisher would deny the paternity :D
    I was also thinking to the use of a wharram main, but I don't have any definite replay to the main question: how it performs windward?

    Paolo
     
  12. village idiot
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    village idiot Junior Member

    Looks good ,can you explain the steps and materials needed to build a mast such as this? I starting to realise there are dozons of ways to build wing mast ,I'm trying to work out the easiest way with the best results possible(strength / weight /cost.)
     
  13. Gary Baigent
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    Gary Baigent Senior Member

    Strip planking in 5 or 6mm paulownia, cedar, balsa, or dense foams using half female moulds is one way, and although it is a picky, sticky time consuming method, the results, once faired, look very good. Laminate in combinations of box weave glass inside and outside with uni directional carbon at bending and high load areas also on the outside. Have an I beam of foam and glass or diagonally cut 4m ply running up the thick section of the mast - but this is not always necessary, depends on weight of boat. Glue the two halves together against the I beam then glass the seam joints. I like uni carbon for extra stiffness in the below hounds area - and also lower stays attached halfway between hounds and mast base (similar to the main hounds shroud attachment) that is, to the leading edge of the mast. That means you don't need diamonds, mast is clean. The trailing edge for the main luff on Flash Harry is 10mm alloy tube, base roughened and glued to squared off trailing edge of mast - then lay glass tape over the glue join.
    The other way for the non professional unable to pay a fortune to boat builders is to use tension ply. And this is a quicker method - and the results can be excellent IMO. Get the Gougeons' book. Explaining it all here is a very boring read. In short: Mast length I beam glassed both sides - cut frames in 4mm ply or glassed foam, cut out areas for halyards to run, also cuts weight, now cut frames at thickest section, glue these to I beam, there's your skeleton. Glue two lengths of thin wood to trailing and leading edges of skeleton, that's the bases for 3 mm ply attachment (leading edge) and alloy bolt rope tube for sail (trailing edge). Skin with 3 mm ply, or lighter aircraft ply if you can afford it. You can do this in the 2.4m ply length sections by carefully lining up the scarphs, glue and staple. Staple gun and lots of clamps are essential. Was that a bloody boring description or not?
     
  14. jamez
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    jamez Senior Member

    Confusion is certainly possible :) :confused: :)

    The Paolo I'm thinking of used to post as 'Zini' on another site building the same boat as you.

    cheers
     

  15. jpquattro
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    jpquattro Junior Member

    I am Paolo Zini.
    Now I have realized where I have read your posts...:)

    Just retired, but I have less spare time than before :(
    I am a slow builder, but I hope to finish now or then...

    Paolo
     
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