Thermoforming core to the mold?

Discussion in 'Fiberglass and Composite Boat Building' started by mrybas, May 12, 2020.

  1. mrybas
    Joined: Jun 2017
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    mrybas Junior Member

    Hi,
    I have built a Ripple Tender 13’ catamaran dinghy. I really like the boat and have a lot of people asking about the boat when I’m out cruising. I’m thinking about making a plug then a mold of a similar design and offering them for sale.

    I’d like to make the construction process as efficient as possible. Cutting out all of the foam pieces and tacking them in place is quite time consuming.
    Is it possible to thermoform the core in one or a couple of pieces on the mold?
     

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  2. mrybas
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    mrybas Junior Member

    http://www.fiberglasssupply.com/pdf/core/ThermoformDiab.pdf

    Well I guess I answered my own question.
    Well since it’s possible, is it a practical method to save time and make the build process more efficient? I think it would make for a better/lighter boat by elimination a lot of thickened epoxy joints.
     
  3. ondarvr
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    ondarvr Senior Member

    Most builders don't do it due to time and cost.
     
  4. Chris Rogers
    Joined: Apr 2020
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    Chris Rogers Junior Member

    Unless weight is a huge issue it is probably easier to use "double cut" or "contour cut core with scrim" if you have a mold and are doing production to a price target. Thermoforming is great for using foam with pre-pregs where the cook really makes the foam fit perfectly - or for very weight sensitive bagged layups where you take the time to fit it perfectly. It is hard with thicker foam and you have to re-drill the perforations.

    What core thickness did you use and how weight-sensitive is the design?
     
  5. ondarvr
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    ondarvr Senior Member

    It's not much different than making pre forms with the glass prior to using it in production closed molding.

    The production volume needs to be high enough, or the dollar value does, for the cost to be worth it.

    Building a pre former for foam wouldn't be hard, but it would time consuming and pricey to get it right for production purposes.
     
  6. mrybas
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    mrybas Junior Member

    The current boat used 8mm divinycel.
    The idea behind the boats is to keep them light enough that a couple can move the boat around easily (ie drag it up the beach, move it around on the deck of a bigger boat etc)
     
  7. mrybas
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    mrybas Junior Member

    I have not built a plug or mold yet. Would it be possible to build the mold so that it could also withstand the heat of thermoforming?

    For example: Use the mold to thermoform the core, use resin infusion to laminate fiber to the core in the same mold, remove from the mold and laminate the other side of the hull (with resin infusion)?
     
  8. ondarvr
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    ondarvr Senior Member

    Yes, as long as you build the mold so it is capable of surviving the temperature required for the core you plan to use.

    But you wouldn't use a 2 stage infusion.

    You would shape the core, then do the entire infusion in one step.
     
  9. mrybas
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    mrybas Junior Member

    Awesome. It’s good to know that it’s possible. Now I just have to figure out how to do it!
     
  10. Blueknarr
    Joined: Aug 2017
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    Blueknarr Senior Member

    Mrybas

    Before you get to far down this road.

    Have you checked that the designer is willing to have you commercially produce his design?

    Buying a set of plans many years ago doesn't automatically give you production rights today!
     
  11. mrybas
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    mrybas Junior Member

    Any suggestions
    IF I decide to try build boats for sale, I will change the design. I will make a plug then a mold, not pull a mold from the existing boat.
    I like the existing design, but there are changes I would like to make after using the boat.
     
  12. gonzo
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    gonzo Senior Member

    A flat or shallow vee bottom would make a lighter boat and have shallower draft. If you are looking for the minimum weight a catamaran is not the best design.
     
  13. mrybas
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    mrybas Junior Member

    I think it’s important to find the balance between light weight and a functional tender.
    A flat or shallow v would make it pound into the chop, no?
     

  14. gonzo
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    gonzo Senior Member

    A boat that size, even a catamaran will pound into a chop. The bridge clearance on that catamaran is almost nil with three people on board
     
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