Understanding lamination schedule wording ?

Discussion in 'Fiberglass and Composite Boat Building' started by gary1, Nov 10, 2006.

  1. gary1
    Joined: May 2006
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    Location: australia

    gary1 Senior Member

    Evening,
    I'm looking at a set preliminary drawings for a boat to be built out of plywood and Biaxial fabric (stitch/glue), and on the lamination schedule it has written "Tapering of laminates is not to be less than 20mm/600g or 1 in 20 thickness".
    I understand about staggering overlaps when laying fabric but the above mentioned statement has got me totally stuffed. Would someone please be able to explain to me in laymens terms what it actually means. As I'm the most amatuer of amatuer would be boat builder there is.
    Thank's
    Gary
     
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  2. yokebutt
    Joined: Aug 2004
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    yokebutt Boatbuilder

    Morning,
    That doesn't make any sense at all.
     
  3. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    20mm/600g doesn't make sense. If the g was supposed to be mm, it would still be 1 in 30 thickness. What I take the 1 in 20 to mean is the taper of any edge is supposed to be 20 times as wide as the thickness of the fabric. If you were making a scarf joint in plywood to join two pieces of plywood 1 centimeter thick, the width of the scarf would be 20 centimeters.
    1 in 20 seems like a lot. I don't think they do that much even in airplane repair and they are pretty extreme in that field, but the more you taper seams the less visible they will be on the finished product. Sam
     
  4. gary1
    Joined: May 2006
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    gary1 Senior Member

    Morning,
    The plans have apparently been drawn up to comply with the Australian Standard for boat and ship design and construction AS-4132-3. Which states Tapering of laminates " where laminates are required to be tapered,the changes in the thickness should be at a rate not greater than 1:20". So what you say Sam makes sense to me, don't know what the 20mm/600g part is supposed to mean.
    Thank's for the input Sam,Yokebutt I appreciate it, starting to think I should have bought an Alloy precut kit boat instead.
    Thank's
    Gary
     
  5. wet feet
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    wet feet Senior Member

    Having looked at the description the only thing that occurs to me is that it describes the rate at which successive laminates are supposed to overlap.For example if you were bonding a bulkhead in a conventional GRP hull you would use a number of plies and each successive laminate of 200gsm material is require to have an overlap of at least 20mm over the previous ply.Would this be the case in your application?
     
  6. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    What's required to conform to standards and what's required to actually work are usually different. If the structure comes from the ply and the glass is mainly to waterproof it, I wouldn't worry too much about making 20 to 1 tapers.

    Boatbuilding sort of has a reputation as being something that has to be done to NASA specifications. Materials have to be the best and workmanship something akin to what Michelangelo did. If everything is not just so, more than likely you will find yourself marooned in windswept desolation on a beach surrounded by the flotsam of your homebuilt folly, lamenting all the lives that were lost, pulling your hair and rending your clothes, cursing the Gods that they left you alive to suffer for eternity the pangs of sorrow and regret you have for even entertaining the notion that you could construct a boat.

    I don't think it's quite like that. Like most things, you can spend a lifetime around boats and still never learn all there is to learn, but that doesn't mean a person has to study for years just to build a servicable boat. Especially with all the knowledge and help there is on the net.

    The picture is one I took in the Dominican Republic in the late '70s and as far as I could tell the operation headquarters was everything under the tree. I didn't see more than 10 tools, what I remember was a common handsaw, a hammer, a handplane, a brace and bits. The stock of materials were a bunch of twisted limbs they sawed the frames out of. I think the guy in the boat was the brains of the outfit, the guy on the right was the skilled laborer who ran the saw and the other guy was a gopher and human clamp/vise.

    So don't get discouraged. If you can get the materials, you can build the boat and it will work. Sam
     

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  7. waikikin
    Joined: Jan 2006
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    waikikin Senior Member

    Gary, sounds like the increase in tape width per edge, say for chines or bulkhead tabbing as Wet feet mentioned, so you might lay a tape of 100 mm then a 140 mm one although its often neater to decrease tape widths from big to small for fairing (but thats a dicussion in itself). Look on the bottom of the plan & find the guy that drew it & strait out ask them for clarification, if they want to sell the paper & want the boat built right then they should be happy to fax a sketch. What design is it & where in Oz are you building Gary? Regards from Jeff.:)
     
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