Engine box 98 lb

Discussion in 'Marine Electrical / Electronics' started by Thomas, Jan 5, 2019.

  1. Thomas

    Thomas Senior Member

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    Is it necessary for the engine box to be built so heavy I have a 28 Terry Jason engine box weighs 98 lb any thoughts do we need the weight or can I build one out of lighter material
     
  2. Bill

    Bill Administrator

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    I don’t think so.. nida core, balsa , or solvent proof foam from HD will be lighter..
     
    Bill,
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  3. skyeboat

    skyeboat Senior Member

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    Start with sheets of 3/4" balsa, Divinycell, Corecell, plastic honeycomb, or Urethane foam from HD or Lowes. Then add a couple of plies of mat and 1708, 1808 or woven roving on both sides. Cut to shape, and assemble, then create putty fillets on the inside corners, add strips of fabric "tape" to the corners inside and out, and done ! De-core where all hardware is going. The thicker the better for the panels as this is where the stiffness will come from. Use peel ply on all surfaces to reduce shading and smooth out the laminate. Nothing to it :)
     
  4. Thomas

    Thomas Senior Member

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    How many pounds do you think I can save by using honeycomb and will it be strong enough for a double seat I will post pics later
     
  5. skyeboat

    skyeboat Senior Member

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    The better the core shear properties of the foam , balsa or honeycomb you use, the lighter the glass (or carbon ! ) skins can be. Balsa has very high shear strength, (but has other obvious issues, but that are probably not an issue for an engine box), PVC and Corecell are both good, and the plastic honeycombs have the lowest shear props. All will work, but extra laminate will need to be added to increase the stiffness with the plastic honeycomb and light weight HD-type urethane. In general terms, I would think you could come up with a laminate that would come in at 1.75 to 2 lbs / sf. Do the math and see how that compares to your current structure. Like anything else, with more thought / planning and higher-quality materials used the better the project can come out.
     
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  6. fordy

    fordy Senior Member

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    What's the box dimension? It all depends on the widest or longest unsupported span.

    If its under 36"wide I bet you could get 1" carbon core and only need 3 layers of 1700 biaxial and epoxy resin. 2 layers on one side and 1 on the other.

    What material is it now?how hot does it need to tolerate
     
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  7. skyeboat

    skyeboat Senior Member

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    What exactly is 1” carbon core?
     
  8. fordy

    fordy Senior Member

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  9. Thomas

    Thomas Senior Member

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    The present it is 3/4 plywood when I can get to the boat I will take measurements thanks for all your help
     
  10. Saltaire

    Saltaire Member

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    Glad to find this discussion as I am also interested in building a new engine box to replace the existing heavy 3/4" plywood box. Just looked up weight of 3/4" plywood, it is 2.13 ppsf so finding a strong composite weighing half or two thirds of this would be great.
     

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