Hypothetical question - building mast from common wood

Discussion in 'Boat Design' started by pironiero, Aug 7, 2021.

  1. pironiero
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    pironiero Senior Member

    Real dumb hypothetical,

    What if the only option of mast material would be wood for you-how will you build it and would you enforce it with something like FG or CF? it it actually worth it in a situation where is nothing else available?
     
  2. hoytedow
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    hoytedow Carbon Based Life Form

    Доброе утро.
    Building method would vary according to size of vessel and type of wood available. Some woods are excellent while some are not good for masts.
     
  3. pironiero
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    pironiero Senior Member

    lets say 32ft
    only most available, non exotic
     
  4. hoytedow
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    hoytedow Carbon Based Life Form

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  5. Rumars
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    Rumars Senior Member

    If it has to be round, birdsmouth, otherwise rectangular hollow box. No fiberglass or carbon at all, it's just added weight. Laminated out of close grained spruce if possible, if not, douglas fir or pine.
     
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  6. Ilan Voyager
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    Ilan Voyager Senior Member

    Yes it's worth, but that implies a lot of work. Also, that depends on the kind of sail boat.
    The choice of the wood is rather simple; a good light pine, with no knots and straight fibers. There are plenty in Russia.
    As it's pretty difficult to find, and far too heavy to use a complete pine tree, the best is to make a laminated one. The main advantage is that allows to use pieces (battens) shorter than the mast (length will be obtained by scarfing the individual battens).
    If correctly engineered fibers are not mandatory, although a layer of a light glass fiber will help to finish. But carbon fiber can help a lot to get a more rigid and "nervous" mast. Gluing with epoxy or polyurethane D4 (exterior quality) glue is mandatory, the epoxy is the easiest glue for the job as it need little pressure to obtain a good joint.
    Hoytedow gave you a pretty good link. The illustration is for round mast, but other shapes like elliptical can be done. It requires simple means of pressure (strings and belts) and a simple straight jig. The difficulty is the sawing at the good angles, and to have many hands for applying the glue, placing the pieces and squeezing before the glues sets as you have a big bowl of jelly before all is tightened and kept straight in its jig.
    You can simplify by making half sections on a jig. It's also preferable...
    Another method is to laminate strips by half section on a mold, add inside and outside glass and/or carbon, and join the half sections. A bit similar to making a strip canoe. The Gougeon Bros have on their site a complete description of the method, used mainly for small ice boats. We used this method very successfully for the "wing masts" of a cruising catamaran ( a cheap 14 m schooner) made in plywood and strip plank.
    A third method, used also by the Gougeon Bros, is ployed plywood. Look for it in their site.

    I repeat it's a lot of work, so you before going to this task look if you can't find a new or used aluminum mast. You're not very far from Finland.
     
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  7. pironiero
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    pironiero Senior Member

    Huh?
     
  8. clmanges
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    clmanges Senior Member

    What is that?
     
  9. Rumars
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    Rumars Senior Member

    Nervous mast = mast with better dynamic response / racing "bendy" mast

    Ployed plywood = bent/tortured plywood
     
  10. Ilan Voyager
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    Ilan Voyager Senior Member

    Thanks Rumars
     
  11. gonzo
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    gonzo Senior Member

    If you just need a mast that works, many wood species will do fine. All you need is a tree of the approximate height and diameter required. It doesn't need to be absolutely straight either. There are thousands of working sail craft with masts made of whatever local trees are available.
     
  12. Ilan Voyager
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    Ilan Voyager Senior Member

    Go to the Gougeon Brothers site and read the documentation. Wood/epoxy technic is a mature one, so there has been little evolution since 35 years, except a few refinements
    First, the book free PDF, and it's extremely valuable. It's a gold mine. https://www.westsystem.com/wp-content/uploads/GougeonBook-061205-1.pdf
    The Gougeon Bros made splendid masts in wood composite and superb giant wood epoxy blades for wind turbines which worked perfectly. That's for those who have a doubt about wood/epoxy/fibers composites.
    If the Stressform technique for masts is now obsolete for racing boats, it remains perfectly valuable for advanced amateurs, and it does not need all the tooling mandatory for composites. To give an idea, a mast for a 13 meters trimaran on 1985 was made in 5 mm plywood, 120 gr carbon UD and 160 gr glass cloth...
    But strips of light Nordic pine, glass and carbon make also excellent masts without the stresses of the neophyte builder discovering ployed plywood.
    Also, the simplest way is gluing planks of a good pine or spruce to get two full lengths half sections of the mast. You'll need hundreds of clamps (that can be home made). After grab the router and carve the mast, cutting away all the unneeded wood like you would have done on a classical mast. It's a lot of work, you'll need plenty of bits, pretty messy, but it's foolproof. Also pretty simple to calculate.
    The problem is not making it (that's simple and rather cheap if you do not pay the work) but engineering it in the rules of the art. No wild guessing but true calculations... It's now the same problem with all the special wood masts to find someone able to calculate them. The guys used to these calculations are now retired or dead.

    It's far simpler now to search in the catalog of aluminium profiles of a mast company, as for cruising boats the calculations of these masts are very simple, all the fine job of calculation have been already made.
     
    Last edited: Aug 8, 2021
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  13. wet feet
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    wet feet Senior Member

    Without knowing a bit more about the hull type for which the mast is intended its a bit difficult to be too specific.A Colin Archer of a Spray replica would be fine with a solid wooden mast because thats what they would originally have been intended for.A more recent design without the characteristics to accept the weight of a heavy mast would be OK with a well designed hollow wooden mast.The challenge is to arrive at a suitable design for the hull and then to build it well enough to work.There is guidance in the F S Kinney edition of Skene's Elements of Boat Design and there is a much better selection of glues these days than when built up masts were the norm.A birdsmouth style of construction doesn't actually have much to recommend it for a boat large enough to cruise on,although the American homebuilders seem keen on the technique.Its much better aerodynamically to have an elliptical or pear shaped mast and you would need to incorporate internal blocking at points where spreaders or shroud tangs are located.I don't think I would be tempted to add carbon or glass as the movement of the wood might be constricted by such a rigid material.
     
  14. kerosene
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    kerosene Senior Member

    the land sailing people use fiber reinforced wood masts.

    They tend to be less traditionalists than boat folks and as they compete I think pointless choices are weeded out. Thus I tend to think that fiber on wooden mast is not as bad as sometimes is suggested.

    I think north-european Spruce (or whatever it is called), the kind St Petersburg area should have plenty, should be pretty good spar wood.
    Even a small whole tree.
    Local spruce is the choice for flag posts too. We did on 30+ years ago and it still stands up pretty solid despite paint having been long gone and weather being pretty diverse here (Finland).
     

  15. pironiero
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    pironiero Senior Member

    and what about using veneer-fg(or carbon)-veneer-fg(or carbon)...etc?
     
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