Modify mold

Discussion in 'Boat Design' started by Jayz, Dec 26, 2020.

  1. Jayz
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    Jayz New Member

    Hi, I am new at doing this and this maybe a silly question but we build a plug and made a mold for an outrigger canoe. We want to modify the nose of the canoe but will need to re-do a whole new mold, is it possible to change just a certain section of the mold without building a whole new one?
     
  2. Mr Efficiency
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    Mr Efficiency Senior Member

    What modification ?
     
  3. Jayz
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    Jayz New Member

    Its an outrigger mold and we want to change the sharp of the nose. We have a more sharp angle shape at the moment and we want to curve it a bit more.
     

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  4. rxcomposite
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    rxcomposite Senior Member

    It depends on the quality of finish you want. Some molds are made of several pieces with bolt on flanges. Several variations can be made by just changing the pieces. Unless made of steel, the part line shows.
     
  5. ondarvr
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    ondarvr Senior Member

    A skilled person can cut and change anything made from fiberglass into the desired shape.

    That's the nice thing about fiberglass, anything can be fixed or modified.

    The question is, do you have the skills to do it.

    On a one piece mold that change is complicated by it being very narrow on the finished mold. Not much room for tools and hands. But it can be done.
     
  6. wet feet
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    wet feet Senior Member

    I have to wonder why you would want to make such a change.It can certainly be done,and in more than one way,but the altered mould is likely to need a lot of finishing to give a good quality surface.In exchange you will get a hull with less buoyancy and less waterline length.The blunter entry will probably push the drag up by a bit as well.
     
  7. kapnD
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    kapnD Senior Member

    I’d be inclined to make the proposed changes to an actual boat first, before altering the mold.
    Is bow steering the issue here?
     
  8. Jayz
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    Jayz New Member

    Thanks, everyone this is very helpful. Some info on the design these are racing canoes, more drag harder for the paddler. The current design of the nose is very exposed to crosswind and makes it harder on sidewind course and on the turns. With the moderations, we hope to make it easier on the turn and easier to manoeuvre on a downwind surf.
     
  9. Jayz
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    Jayz New Member

    Thank you this is helpful.
     
  10. rxcomposite
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    rxcomposite Senior Member

    What you can do is just cut the part of the mold where you are going to modify. Modify the plug, plop the mold back in and add the new mold piece.

    If you plan two models of the basic part, make the new part mold with flanges otherwise just taper off the cut part of the old mold and laminate over the modified plug.

    Just make sure you strap tight the old mold to the plug. Zero clearance fit, otherwise the tooling gelcoat will seep in the crevice.
     
  11. wet feet
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    wet feet Senior Member

    With this extra information ,it's possible to suggest an alternative. By altering the bow in accordance with the original sketch you are giving the hull a less sharp entry as the waterline further aft has to get to the centre of the bow in a shorter distance-which leads to not only a blunter entry,but also leaves you with an overhang that can still catch the cross wind. This overhang will have greater leverage on the shorter waterline and may add to the problem you already have with keeping the boat going where you want it to.

    The advice about modifying a hull before changing the mould is something to try. I would also suggest that you might get a similar result by mounting the outrigger a bit further aft and possibly shortening the stern.
     
    bajansailor likes this.
  12. JRD
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    JRD Senior Member

    I'm curious if it would be feasible to flange the existing mold and then lay up a new bow mold section over a partial plug to the desired shape?
     

  13. rxcomposite
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    rxcomposite Senior Member

    "The advice about modifying a hull before changing the mould is something to try"

    That is a good advice. Make a prototype first, maybe a little penalty on weight. If it works, make a mould.

    There was an article on PBb magazine about racing kayaks. See if I can dig it up.
     
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