Boom Jaws

Discussion in 'Wooden Boat Building and Restoration' started by lewisboats, May 16, 2012.

  1. lewisboats
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    lewisboats Obsessed Member

    To glue or not to glue...along with bolt...that is the question.

    [​IMG]
     
  2. alan white
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    alan white Senior Member

    Glue is unnecessary and if you've ever seen a broken jaw, you know that replacing one or both sides would be far easier if you didn't have to pare down the glue line with a plane in order to make ready for the new jaw.
    Since you want to keep water out of the joint, a low-adhesion polyurethane in the right color is enough.
    I think having a little give is a good thing to prevent the spar from breaking. Usually, jaws break because they are badly designed. Allow for a lot of twist so the jaw to spar joint never takes the torque, but I guess you know that.
     
  3. lewisboats
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    lewisboats Obsessed Member

    No, I didn't know that. The Sail is small...a 35 sf Opti, the Jaws are 3/4" thick Hickory and the boom is Doug Fir. I will bevel the inside of the jaws more so that there is plenty of twist room. My biggest concern is actually the end of the boom between the jaws. It got a little thinner than I wanted it to.
     
  4. PAR
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    PAR Yacht Designer/Builder

    The end of the jaws isn't the place they'll likely break. I generally do glue jaws, but also make a good fit between jaw and spar, so they become one homogenous piece. Heavily round over the inside of the jaws, as Alan has pointed out. You need all 3 axis of movement for them to work well and permit good sail set. A simpler arrangement is a big eye on the mast and a hook on the spar. It can move in all three directions without much restriction, doesn't weigh much and is easily unshipped.
     
  5. lewisboats
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    lewisboats Obsessed Member

    Thanks Paul...I forgot about that. I have seen it and never thought about it. I think I'll put the jaws aside, get a new stick and go that route. I'll work on setting up a nice boom with the jaws properly installed after Vacation when I have more time to play with it. I only have a couple of weeks left to get 2 boats finished enough to hit the water and the less time I spend fiddling the better they will be.
     

  6. alan white
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    alan white Senior Member

    I was thinking it was a gaff Steve. A boom jaws is a bit different. I perdonslly like a wood jaws but there are a million ways to do the same thing. It matters if you plan on a boom downhaul. Then a wood jaws is ideal. Otherwise, to have up and down positioning begins to get complicated with metal parts.
     
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