powerboat mast

Discussion in 'Fiberglass and Composite Boat Building' started by pasty63, Apr 10, 2009.

  1. pasty63
    Joined: Oct 2007
    Posts: 58
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    Location: Lake Stevens, WA

    pasty63 Junior Member

    Our boat was fitted with an arch which is not quite in keeping with the lines of the boat. I'd like to replace it with a raked mast that would be roughly 60 inches high and hinge at the bottom for clearance in our slip. I'd like to try to build it in an epoxy/glass composite over a skeleton. Having it hollow would be an advantage for weight, and for running wire for the lights, radome and vhf antennas I'd like to mount on it. Has anyone seen such a design? The body of the mast would be essentially an eliptical cone with an obtuse shape (100 to 110 degrees?) at the base. What would work well for a skeleton?


    Thanks -.b
     
  2. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Rather then an internal armature or skeleton, a hollow composite of just a 'glass layup wouldn't need this internal frame work.

    I'd recommend two different approaches, one would be a hollow birdsmouth build, the other a pure laminate (fabrics and resin of choice).

    The birdsmouth method is an easy and light weight way of making a strong wooden mast of nearly any length. I build a few each year and they're surprisingly easy. They can be round oval or elliptical in section. They also can be sheathed in 'glass to protect them. The advantage if this method is the form serves as the mast, so you don't need a separate mold, it's easy and you can use inexpensive materials with good results.

    The other option, which seems the way you'd like to try is a real composite mast, constructed over a mandrel or other temporary frame. The finished materials could be regular 'glass fabrics (the least expensive) or as fancy as you'd like, including carbon and/or Kevlar (more costly).

    In the case of this composite mast, you need to construct a mandrel of the shape you desire, of course less the thickness of the composite materials. Most folks would build a wooden form, apply a release agent or even automotive wax, then "layup" the fabrics over this form to the desired thickness. When all is cured, you pop the composite mast off the mold and finish to your liking.

    In all honesty, most of use don't employ a "standard" mast, but design each per the desires and needs of each client/yacht.

    To answer your skeleton question, wood is a common material, because it's easily worked, but any material could be used if the internal frame work was to be removed after construction. If you elect to leave it in place, which to me doesn't make a lot of sense, then maybe more inert materials should be considered to prevent rot or other types of decay from haunting you years down the road.
     
  3. pasty63
    Joined: Oct 2007
    Posts: 58
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    Location: Lake Stevens, WA

    pasty63 Junior Member

    mast

    As always PAR, your insight is much appreciated. If I can get away without the skeleton, I would be happy to abandon it.

    -.b
     

  4. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 485, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    If you can carve foam fairly well, this would be an option. You'd carve the shape you like, then coat with wax or other release agent. Over this you apply a few layers of fabric set in resin. Fill the weave of the fabric and prep for paint. The internal foam could be pulled out, dissolved with thinner or just hollowed to satisfaction for wires etc. Real light, strong and not going to rot.

    Calculate how much stuff (total weight) you plan on hanging on this mast. This will determine how much fabric you'll need to apply to hold up a dome or whatever else you hang up there.
     
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