Post curing full hull

Discussion in 'Fiberglass and Composite Boat Building' started by fallguy, Apr 12, 2018.

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  1. gonzo
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    gonzo Senior Member

    A common method is to wrap the hull with insulation and use electric heaters with fans. You will have to modify the thermostats because the max at about 85F.
     
  2. fallguy
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    fallguy Senior Member

    Interesting idea Gonzo. There would need to be airspace, but using the hull as a tent frame would save some work. Thanks!
     
  3. PAR
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    PAR Yacht Designer/Builder

    I've tented small projects (up to about 20') with tarps, covered with blankets and using electric heaters, got about 130 degrees, continuous. Some of my heaters have modified thermostats, others zip. Most will hold 120 easy enough if the space is tight. Use small pancake fans to move air, but not a lot.
     
  4. rxcomposite
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    rxcomposite Senior Member

    You need air space between the heaters and laminate. You are basically removing all volatiles during curing so need vents.
     
  5. PAR
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    PAR Yacht Designer/Builder

    Heated air always finds a way out, unless you're really anal about sealing things up. Build a temporary PVC pipe or 1x2 frame to place the tarp over.
     
  6. fallguy
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    fallguy Senior Member

    I did a heat calc and it says I need 10000 btuh for the space if I insulate to R10 for an 80F t-delta. Actually says 4500 for the heat and 1500 for the air losses.

    We’ll plastic over a frame; perhaps with 2x6s. Then wrap in fiberglass. The glass can go up into an attic space on completion. I have one that is a bit low.

    I might buy a used electric furnace and take the limit out of it and run the heat in from outside the space. Another guy told me strip heaters in the space, but I like the heater out better.

    Thought about wood, but too hot...

    The plastic ... I’ll need to see if that can take that much heat or even say 170F. Maybe plastic is a horrible idea on further.

    I’ll check deformation temps on polystyrene.
     
    Last edited: Apr 16, 2018
  7. rxcomposite
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    rxcomposite Senior Member

    Fallguy- You are almost describing the prepreg walk in 250 F curing oven we built before. Since it is of a permanent construction, the frame was 4" x 4", inner liner of metal sheet, insulation of fiberglass wool, and outer skin by plywood. We used two gas fired home heater with the thermostat removed. gas is controlled (on off) by an electronic temperature control with a temp probe. Hot air is forced thru the top, dispersed by ductings. Cold air is drawn from the bottom heated by the furnace and fed back to the system thru a constant rpm centrifugal fan. Excess hot air is bled out.

    For the smaller electric version, the quartz heater is fed at the bottom by a blower, hot air rises to the top, is collected, and fed back to the bottom. Temperature is controlled by firing the quartz (via the controller) on and off via relays. A timer integrated in the controller controls the cycle for 3 hours.
     

  8. fallguy
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    fallguy Senior Member

    I am going to need to move the air to avoid overheat at the top. Thanks RX.
     
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