Layup schedule help

Discussion in 'Fiberglass and Composite Boat Building' started by Scuff, Sep 5, 2017.

  1. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    You're welcome. I could tell it was getting annoying so I was just going to carry on explaining, as I know it is right and makes a big difference as opposed to just eliminating the mat as an inconsequential part of the laminate. There were other people on to the difference, FallGuy and maybe others.

    It is very confusing mixing measuring systems such as metric and whatever it's called that we use here. It's also confusing with mat vs fabrics where (at least here) one is measured by sq yd and the other by sq ft. There seems to be no reason for that. I worked in Mexico for a short time and had to log things, including dates. In the USA, we number dates by month day year, in Mexico they do it day month year. So 7-4-1776 here is July fourth 1776, but there it would be the seventh of April 1776. So I just started spelling the month to eliminate possible confusion. (Cinco de Mayo works out fine either way, but it turns out that's not a big deal to them anyways.)

    A lot of big, bad, problems can be created by the confusion of mixing systems. That's why I like peer review. I want someone else to check and verify my numbers, verify measurements and the like, especially when it's important to be correct.
     
  2. rxcomposite
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    Location: Philippines

    rxcomposite Senior Member

    The manufacturer is also mixing units. On top of that, the decimal point was not explained.;)

    And no, you were not annoying. It helped me search the proper way the manufacturer define their product.
     
  3. rxcomposite
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    Location: Philippines

    rxcomposite Senior Member

    3 layers at the keel is good if it is a non cored, single skin. The rule of thumb is 1 1/2 X the laminate thickness. So 1 layer top + 1 layer bottom + 1 extra layer.

    Rather than change fabric, just add additional layer. Veil is 30- 50 gr/m2. Light CSM is 280 gr/m2. Mat is 300 gr/m2 and above.

    Previous build by members showed they can get by eliminating mat for a good bond if they use epoxy. But then, if you eliminate the mat which is a good 458 gr/m2, you might have to add another layer.
     
  4. rxcomposite
    Joined: Jan 2005
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    rxcomposite Senior Member

    It is not a good idea eliminating layers whether it is mat or fabric. Deflection of panel is dependent on thickness. As the analysis shows, positioning of fabric/mat is also important. Eliminating one layer and adding a different fabric type may cause the laminate to fail.
     
    TANSL likes this.
  5. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    How can a layup schedule be comparatively analyzed when the parameters are changed?
    The designer's layup is

    1.5 oz CSM
    DBM 1715
    o.625" foam (5/8")
    DBM 1715

    Basic Composite Structure - Bertram 31 http://www.bertram31.com/proj/tips/core.htm

    https://www.westsystem.com/wp-content/uploads/Fiberglass-Manual-2015.pdf

    I don't understand the last chart RX posted, but how can it be useful when the foam thickness is so different? It comes to 5/8" vs 1" (0.625" vs 0.984" or 15.875 mm vs 25mm) If the extra foam doesn't make a difference, what is actually being analyzed? A single skin?

    Mat does have structural properties, it does add 'strengths'. Stiffness is one. It also aids in waterproofing. The short, random fibers reduce water wicking, the resin rich layup does too. It also aids in bonding by molding and forming and carrying resin into the weave of fabrics and the surface of foams, previous layups etc. It is very hard to hand layup a thin fabric onto a hard surface without getting pits and bubbles, resin starvation and holes in the laminate.

    Anyway, the quotes show that thickness increases in materials result in exponential increases in various "strengths". Thickness has a definite function. I don't know if doubling the thickness of all materiel increases 'strength' 7-8 times, or just foam composites. I don't know what number would apply to pure fiberglass laminates.

    If you compare (using the chart in post #99) the thickness of DBM 1715 (.o58") and DB 170 (.029") Without the mat is only 1/2 the thickness. There goes something.

    In the designers schedule,

    1.5 oz CSM
    DBM 1715
    o.625" foam (5/8")
    DBM 1715

    the outside layer of mat is just mat by itself and is thicker than when combined with the DBM 1715. I guess the stitching or whatever compresses it somewhat. Most charts show the thickness of 1.5 mat as .040 to .045.
    The designers layup for the outside would be .040 + .058 = .098". Eliminating the mat or just using a veil and 1 layer of DB170, would give you a thickness of a bit more than .029". Quite drastic reduction in such a thin laminate. More than 60% or however that would work. One is two or three times thicker than the other maybe.

    Three layers of DB170 would give you a thickness of .087", still less than what the designer calls for thickness wise.
    Weight wise it would be 44.7 oz for the design schedule compared to 54 oz. for 3 layers of DB170.

    That's a difference of 9.4 ozs per square yard, which comes down to say 1 oz per square foot, so the estimate of 120 lbs added weight for each hull or whatever it was would probably be very,very wrong.

    There are other things also, but I'm done for now at least.
     
  6. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    It takes me so long to type and look up stuff that cross posting happens. Sorry.
     

  7. Scuff
    Joined: Nov 2016
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    Location: Richmond VA

    Scuff Junior Member

    Sorry for the use of 'strengths' i couldn't come up with a better word. Thank you all for providing your input I've a better understanding of the materials and what they contribute to the laminate as a whole.
     
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