Catamaran hull join

Discussion in 'Boat Design' started by gypsy28, May 18, 2017.

  1. gypsy28
    Joined: Mar 2010
    Posts: 218
    Likes: 26, Points: 28, Legacy Rep: 120
    Location: NSW Australia

    gypsy28 Senior Member

    I originally posted this in Fibreglass Building section but no replies, so thought I might try it here.

    Im currently extending/modernising a 16 ft beach cat hull to 18 ft with the intention of building a fibreglass mold so I can build 6 hulls for myself and 2 mates. We do a lot of camp cruising on our current 16 ft beach cats but could always do with a bit more space hence the 18ft cat. We could just buy 18 ft beach cats but they are designed/built for racing so we are designing/building ours with more camp cruising features (storage).
    Im a fibreglass mold maker myself so modifying the hull and building the mold is not an issue.

    I intend to split the mold on the centre line of the hull to do away with the hull/deck join flange. I have attached a picture of how I intend to do the hull join and am looking for opinions. The drawing isn't to scale or an accurate drawing but it gives the idea. The hull bottoms will have a join flange on the inside and a 2mm rebate on the outside. I intend to glue the flange together with epoxy and add a couple of layers of glass tape in the outer rebate followed by gelcoat over the top. The deck will also have a 2mm rebate on the outside for glass/gelcoat and a couple of layers of tape on the inside. Is this joining method adequate?

    The hull layup will be gelcoat, 450gsm biaxial, 6mm PVC foam, 330gsm biaxial with stringer from midships to bow on each side and extra glass layers on the hull bottom/bow. Does this sound adequate?

    Any other suggestions or tips are welcome.
  2. latestarter
    Joined: Jul 2010
    Posts: 401
    Likes: 50, Points: 28, Legacy Rep: 233
    Location: N.W. England

    latestarter Senior Member

    I am having difficulty visualising how you will get access to the inside for the layers of tape.
  3. garydierking
    Joined: Sep 2004
    Posts: 191
    Likes: 72, Points: 28, Legacy Rep: 174
    Location: New Zealand

    garydierking Senior Member

    I built a couple of 44' cats the same way, except I didn't have a flange at the keel. I had the outside rebates at the keel and deck centerline with just heavy taping on the inside. No problems and in commercial use.
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