Material weight comparisons

Discussion in 'Materials' started by jmolan, Jan 3, 2010.

  1. jmolan
    Joined: Dec 2008
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    Location: Mexico/Oregon/Alaska

    jmolan Junior Member

    :confused: I cannot find anywhere on the web so I will ask here. I want to look at all of the popular boat building materials, and compare them by weight. I am not interested in steel or Aluminum.
    I want to see what a Cubic Foot of plywood weighs, or a cubic foot of foam glass, or a cubic foot of ?
    Is this the way ask? I want to see what one 40 Tri, built of foam and glass would weigh compared to the same in ply and epoxy, or cold molded.


    Thanks ahead of time :)
     
  2. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    There are several reference volumes that could be helpful, but generally, you'll have to do a masses calculation anyway so looking them up isn't unreasonable.

    For example plywood suppliers will tell your the weights per sheet for different species (20 pounds per sheet for 1/4" Okoume as an example). Solid lumber weights are available, moisture content specific, resins, 'glass fabrics, even paints are all available. For example, my last build had about 10 pounds of paint on it, counting primer. Another issue would be how do you want this information? Plywood - lets say 1/4" marine grade 5 veneer, Douglas fir might weigh .7 pounds per square foot, which is much more helpful then a volumetric figure (32 sq. ft. per sheet or .66 a cu. ft. if 1/4 ply), when working with surface area, like a hull or deck. A plain old SPF 2x4 will be about 1.2 pounds per foot, Douglas fir about 7% heavier, SYP about 14% heavier.

    I'm not sure what you used for a search, but "weights of building materials" will yield thousands of hits and will likely offer the information you need. Then again you could by a book or two, like "Architectural Graphic Standards" or the "Boat Data Book".
     
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  3. Boston

    Boston Previous Member

    you might skip over to the "planking and Epoxy" thread were I went into this exact issue in detail
     
  4. jmolan
    Joined: Dec 2008
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    jmolan Junior Member

    Thanks to both of you, I have much to look fwd. to in the search....:)
     
  5. Steve W
    Joined: Jul 2004
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    Steve W Senior Member

    What you are looking for is not as easy as just knowing the comparative weights of the materials unless you have scantlings,ie,you know what your searunner weighs built out of plywood as designed but to calculate in foam you would need to know figure out the density and core thickness and layup schedule etc.It may be interesting to contact Ed horstman as he designed most of his tris to be built of either cold molded plywood or foam/glass so you would be able to directly compare a specific design,they would have been designed for wet lam in polyester so weight savings could be had by using epoxy and stitched fabrics with no mat involved and bagging for better resin to glass ratios.
    Steve.
     
  6. Autodafe
    Joined: Jun 2008
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    Location: Australia

    Autodafe Senior Member

    The aust ultralight federation has an excellent materials section on its website,
    http://www.auf.asn.au/scratchbuilder/contents.html most of which is applicable for composite boats.

    Be aware that the relative strength and density of the material does not directly affect the weight of the final boat. For example if local stiffness is required, then a lighter (less dense) material in a thicker layer would be best, while if abrasion resistance is needed, then a very dense material is your only option. For most global loads the important consideration is the specific strength or the specific modulus (stiffness), depending if deflection or breaking is the critical case.

    Also consider the fatigue resistance of the material in question. Glass fibre has good specific strength in a simple failure test, but actually has lower specific strength than clear wood if a 10million cycle life is required.
     
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  7. jmolan
    Joined: Dec 2008
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    jmolan Junior Member

    That is a good idea, I will check out Horstman boats. I was mostly interested in the foam/glass boat and a well built Ply boat. Tahnks Autodafe, I will check out the site also.
     
  8. Steve W
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    Steve W Senior Member

    Hey Jack, Im curious what design you are looking to build.
    Steve.:cool:
     
  9. jmolan
    Joined: Dec 2008
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    jmolan Junior Member

    http://www.ptwatercraft.com/ptwatercraft/Welcome.html

    This is the boat that initially caught my attention. Look close at the details of this boat. I spent a good amount of time looking at it at the Port Townsend Wooden Boat Show. Check out the "jigsaw scarfs" panels line up and lock with these joints. There are a few shots where you can see the tabs.
    The idea of a CNC cut kit is pretty wild. I talked with Trimaran Jim Brown about it. He showed me his son Russell's boat. The 18' Skiff is Russells baby. How everything is tabbed and goes together. No measuring or cutting. The idea really spun me out.
    So I got to thinking :eek: about all those good plywood designs Trimarans from days gone by. I have inquired on a number of boats. Something along the lines of this boat. Only modernized as far as using better plywood (saving weight) and a few other ideas.
    http://www.bajayachts.com/seaclipper-tri-41/images/images1.htm
    In reality, it will probably be a dinghy first of all to re-familiarize myself with the method. There are a number of them in CNC.
    Also these guys have a nice line up of boat kits. The cats they are doing caught my eye, and tell me the bigger boats cut out as a kit are possible. There is much to learn.
    http://www.ckdboats.com/proteus10.asp
    Russell Brown is working on a nesting Dink that will be CNC ply build kit. That is going to be project #1. After that, I am dreaming of a long lean 45' Trimaran. Know any good designers that has one sitting around in files that can be converted for CNC cut out?
     

  10. matowakan1
    Joined: Apr 2010
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    matowakan1 New Member

    I am new to the forum and need some information. Not sure where to go. We are restoringa 1973 74ft Aluminum hull Chris Craft Roamer. We are going to sound the hull as a first step. Does anuyone out there know if those hulls were 5086 or 5061 plate and what the original thickness specs are for these materials? I have several "speculations" but no hard facts?
    Matowakan1
     
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