Wood Physical Properties comparison between WRC and DF

Discussion in 'Materials' started by Martell, Jan 8, 2020.

  1. Rumars
    Joined: Mar 2013
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    Rumars Senior Member

    The cedar is just a core and it's strenght is not considered. Of course it contributes something and a cedar cored panel will be stronger then a foam cored one, but stiffness comes from thickness and you can't mess with that without redesigning the boats structure. Wood is cheap, the core will probably come out as the least expensive big item in your build. Woods to use beside WRC are Atlantic white cedar, Northern white cedar, paulownia. Get in touch with some big lumberyards and resellers and have them price your order + transport (remember to add the sawing waste plus some extra for sorting, breaks, etc.).

    A few tips for quick stripping:
    Have the strips cut by someone with big machines (or rent them). Powered in and outfeeds make a difference, as does a quality saw that can cut straight for hours. There is no need for bead and cove, square is good. It's not required to plane the strips, you will be fairing and sanding them smooth anyway. The glueing surfaces are fine just as they come from the saw, thickened epoxy likes some tooth. Wood is cheaper then epoxy, have the strips cut to 20mm and fair the wood.
    Use plastic nails (Raptor or other brand) for stripping. Expensive but worth every penny, no hundred clamps to use, no screws to install and holes to fill (ok maybe a few in stubborn areas) and they sand flush in fairing.
    Have a helper mixing epoxy for you and precoat the strips. If the epoxy keeps coming you can keep hanging strips. There is no need to scarf the strips beforehand to lenght, just butt them on the hull.
    Ask Waller if you can infuse the fiberglass skins on. If he is ok with it you just transformed a lenghty and messy operation into a leisurely, clean one.
    I wish you luck, and please open a thread here and post pictures.
     
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  2. DogCavalry
    Joined: Sep 2019
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    Location: Vancouver bc

    DogCavalry Senior Member

    Another factor where wood absolutely eclipses foam core is impact strength. Not big blunt impacts, but hard sharp impactors comparable to the claws of a hammer. I've seen thick foam core test panels that had extravagant amounts of strength and stiffness for the yacht they were designed for, that I could and did punch the claws of my 15 oz stilletto through with one good swing.
     
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  3. Martell
    Joined: Feb 2018
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    Location: Pittsburgh

    Martell Junior Member


    Thanks for the encouragement. I am going to hear Gimme Shelter many time before this baby is launched. Thanks for the helpful tips. I am sure I need many many more.

    I am setting up my tooling and learning how (learn by doing) vacuum infusion this weekend. Will be setting up the test table, systems, and working out the process.

    After I work out the process I will create test panels that represent different sections of the hull design lam schedule. We shall see how the test panels and material: epoxy, fiberglass, and core(ceder) fair against the temp chamber, shock, and vibe testing before subjecting them to destructive testing.
     
  4. fallguy
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    fallguy Senior Member

    Apples and oranges DC. The wood is 4 times heavier when weight matters; discounting seams completely..
     
  5. Rumars
    Joined: Mar 2013
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    Rumars Senior Member

    A preview of what awaits you (the good only):

     
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  6. DogCavalry
    Joined: Sep 2019
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    Location: Vancouver bc

    DogCavalry Senior Member

    Hardly. Boat hills occasionally hit things. If I design my hull for adequate strength in tension and compression, and flexural stiffness and let that be the only consideration, it could be thick foam core with thin skins. It will have no puncture resistance.
    If the op wants to switch to foam from wood core, extra material must be added to resist puncture. Unless he wants to desperately try to manage a leak, while trying to figure out if the hole was made by an apple or an orange.
     
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