Fiberglass Weight

Discussion in 'Fiberglass and Composite Boat Building' started by Boat Man, Feb 11, 2008.

  1. Boat Man
    Joined: Feb 2008
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    Boat Man New Member

    Hi guys,

    I'm looking for information about types of fiberglass used on boat hulls. Thickness, composition and weight to be exact.

    Can anybody point me to a good site or tell me approximatley how heavey a square meter of Fiberglass would be?

    Something similar to what brands like Sunseeker or Fairline might use for their 40"+ Hulls.
  2. SamSam
    Joined: Feb 2005
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    SamSam Senior Member

  3. Dutch Peter
    Joined: Aug 2004
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    Dutch Peter Senior Member

    weight of a square meter of fiber glass depends on thickness, type of weave, and can be found on every website of suppliers of the stuff.

    check out:

    look for 'fiber glass matt and fabric' and you'll find all the details you want.
  4. Eric Sponberg
    Joined: Dec 2001
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    Eric Sponberg Senior Member

    Three books cover this topic:

    Fiberglass Boat Design and Construction, by Robert J. Scott, available from the Society of Naval Architects and Marine Engineers.

    Elements of Boat Strength, by Dave Gerr, Published by International Marine/McGraw-Hill.

    Marine Composites, published by Eric Greene Associates.

    Just Google those names and you'll get the links.

  5. Landlubber
    Joined: Jun 2007
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    Landlubber Senior Member

    Weights for fibreglass cloth are as you buy them, 900gsm, for instance is 900 grams per square metre.

    Fibreglass clothweights and resin ratios etc.
    The heavier the fabric, the more resin it will take to wet it out. A good hand laminate consists of about 50% fabric and 50% resin by weight. For example, if an application requires 3 sq yds of a 4 oz/sq yd fabric (total fabric weight = 12 ounces), 12 oz of resin will also be needed. However, if 3 yards of 10 oz/sq yd fabric is chosen (total fabric weight = 30 ounces), 30 oz. of resin will be needed.
    Glass mat requires a minimum of 2 ounces of resin for each ounce of mat. Therefore, it the application calls for 20 sq feet of 1-1/2 oz/sq ft mat, it will require a minimum of 60 ounces of resin. Remember that mat is specified in ounces per square foot, where fabrics are specified in ounces per square yard. 1-1/2 oz/ sq ft chopped mat actually weighs 13.5 oz/ sq yd!
    CSM is weight per square foot (0.0929 m^2) and all others fabrics are per square yard (0.8361 m^2).
    To convert ounces to grams x by 28.349523
    To convert feet to meters x by 0.3048
    To convert square feet to sq metres x by 0.0929
    To convert square yards to sq metres x by 0.8361
    To convert square meters to sq feet x by 10.76
    To convert square meters to sq yards x by 1.196
    To convert square yards to sq metres x by 0.8361
    To convert gallons (US) to litres x by 3.785
    To convert litres to gallons (U.S. liq.) x by 0.2642

    Chopped strand mat:
    The general rule for chopped stand mat is 1.5 to two times the weight in resin to the weight of mat. So one pound of chopped mat would take two pounds of resin. One square yard of 1.5 ounce chopped strand mat weight 13.5 ounces so it would take 1 pound 11 ounces by weight of resin to wet it out. Our mat is 50 inches wide. One linear yard of 1.5 ounce weighs 18 ounces so it would soak up 2 pounds 4 ounce of resin by weight.
    ¾ oz csm=228g (200)
    1 oz csm=284g (300)
    1 1/2 oz csm=457g (450)
    2 oz csm=610g (600)

  6. Landlubber
    Joined: Jun 2007
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    Landlubber Senior Member

    Fibreglass Product Guide

    Fibreglass Product Guide

    CSM Chopped Strand Mat
    The most common form of reinforcement used with polyester resin for hand lay up. Strands of glass fibre are held together by an emulsion binder to form a mat. Supplied on a roll usually 92 cm wide in grades of various thickness expressed in weight per metre. Three most used are 300gm, 450gm and 600gm per m². Polyester resin dissolves the binder allowing the fibres to follow the mould contours. A usual GRP structure would contain 2.5 kg resin to 1kg CSM. 1kg of 300g = 3.33m². 1kg of 450g = 2.22m². 1kg of 600g = 1.67m².

    Powder bound CSM
    The same style as emulsion bound CSM but held together with a powder binder. When using epoxy resins with CSM, powder bound must be used. 300gm and 450gm. Approx. 1 mtr wide.

    Surface Tissue
    A thin glass fibre mat in a form similar to tissue paper. Supplied on a roll 1m wide and only 25-30 grams per m². During moulding it is applied to the dried gel coat to cover up the coarse glass pattern produced by CSM. When sheathing It can be applied onto the CSM while the resin is still wet, again to cover the glass pattern and form a smooth surface for the flowcoat to be applied. Uses 750g of resin per m².

    Woven Rovings
    Supplied on roll usually 1m wide in grades of various thickness from 300g - 1000g per m². It is not twisted is easier to wet out and drapes fairly well. As it cost less than fabric it is often used for boat building in conjunction with CSM as a simple means of adding bulk to increase stiffness. Fabric laminates use approx. 1kg resin to 1kg fabric.

    Plain Weave cloth
    Cloth is made from "Yarn" (twisted glass filaments) generally to produce a lightweight laminate with uniform thickness from approx. 100g per m². Fabrics will flex more than CSM before breaking but are not as rigid. The best strength comes from the thinnest cloth with the tightest weave which tends to make them difficult to wet out and so for fabrics above 275g per m² woven roving is used. Adhesion between 2 layers of fabric is poor and should be avoided. Bonding is improved with thicker cloth and fewer layers or combining with CSM.
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