Chopped Strand Mat

4 products

  • Chopped Strand Mat Tape 1.5oz6" Chopped Strand Mat Tape
    Boat Suppliers

    1.5oz Fiberglass Mat Tape

    Chopped strand mat, precut to tape widths, so you can tab a bulkhead or glass a chine without...
    $3.25 USD
    $3.25 USD
    $3.25 yd

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  • 3/4 oz Chopped Strand Mat.75oz Fiberglass Chopped Strand Mat
    Boat Suppliers

    0.75oz Fiberglass Chopped Strand Mat

    The thinnest chopped strand mat we carry, 0.75 oz per square foot of randomly oriented E-glass held with...
    $4.45 USD
    $4.45 USD $3.12 USD
    $4.45 yd

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    Length
  • Close-up of 1.5 oz fiberglass chopped strand mat showing random white glass fibers, with a US quarter on top for scale1 1/2 oz Chopped Strand Mat
    Boat Suppliers

    1.5oz Fiberglass Chopped Strand Mat

    1.5 oz per square foot chopped strand mat, the mat every boatyard runs. Random fiber means it has...
    $6.45 USD
    $6.45 USD
    $6.45 yd

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    Length
  • Black-gloved hand holding the corner of 2 oz fiberglass chopped strand mat, showing its random glass fiber strandsChoosing Your Fiberglass Chopped Strand Mat Size
    Boat Suppliers

    2oz Fiberglass Chopped Strand Mat

    Heavy chopped strand mat at 2 oz per square foot (18 oz per square yard), 50 in wide....
    $8.95 USD
    $8.95 USD
    $8.95 yd
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    Length

Chopped Strand Mat

Chopped strand mat in 0.75, 1.5 and 2 oz

Chopped strand mat is random fibre held together with a binder rather than a woven or stitched fabric. It has no directional strength to speak of, which is exactly why it is useful: it conforms to shape, it builds thickness fast and cheaply, and it creates the resin-rich layer that bonds a new laminate to an old hull.

Mat only works with polyester or vinyl ester

The binder holding the strands together dissolves in styrene. Polyester and vinyl ester contain styrene, so the mat breaks down, the fibres spread and wet out, and the layer merges into the laminate. Epoxy has no styrene, so the mat stays a stiff sheet that never fully wets out and drinks far more resin than it should. If you are building in epoxy, use cloth or biaxial without a mat backer instead.

Which weight

The number is ounces per square foot, not per square yard like cloth, which is the detail that trips up most first orders. 0.75 oz is the thin one for conforming to tight curves and for a first layer against a mold. 1.5 oz is the standard boatbuilding weight and covers most repairs. 2 oz builds thickness fastest where there is room for it.

Alternating with roving

The traditional hull schedule alternates mat and woven roving, and the reason is mechanical, not traditional: roving is coarse and will not bond well directly to another layer of roving, so a layer of mat goes between them to key the two together. Never lay roving straight onto roving.

Resin to mat

Mat drinks roughly twice its own weight in resin, considerably more than cloth. The resin calculator accounts for that by ply so you are not guessing halfway through a transom.

Chopped strand mat comes in three weights: 3/4 oz, 1.5 oz, and 2 oz per square foot. For most repair and layup work, 1.5 oz is the right call: it's the workhorse weight for building thickness and tying together layers of woven roving or cloth.

Drop to 3/4 oz when you need to conform to tight curves or lay a clean first layer behind gelcoat. Step up to 2 oz to build thickness fast on large, flat areas.

One ply of 1.5 oz mat lays up about 0.035 to 0.045 inch thick, so divide your target laminate thickness by that to get your ply count. It works with polyester, vinyl ester and epoxy, though it stays stiffer in epoxy.

Chopped strand mat (CSM) is a non-woven fiberglass reinforcement made from randomly distributed glass fibers held together with a binder. It’s commonly used in composite layups for its affordability, ease of use, and excellent bulk-building properties.

Yes. Our chopped strand mat works with epoxy for repairs, tabbing, and flat or gently curved panels. The binder that holds the strands together is made to dissolve in polyester and vinyl ester, so in epoxy it stays put: the mat stays stiffer, does not drape as easily into tight curves, and can cure cloudy instead of clear. Roll it firmly until no dry white fibers remain, and for complex shapes use polyester or vinyl ester resin, or a stitched fabric like 1708 biaxial with epoxy.

Plan on about 2.3 times the mat's weight in resin for hand layup. For 1.5 oz mat that is about 3.4 oz of resin per square foot, about 31 oz per square yard, or roughly 32 oz per yard of 38 inch mat and 42 oz per yard of 50 inch mat, per ply. Add about 15% for waste, or use the resin calculator.

Absolutely. It's commonly used between layers of fiberglass cloth or woven roving to add bulk and prevent print-through in gelcoats or top layers.

Yes, it's important to use a fiberglass roller to eliminate air bubbles and ensure proper wet-out during lay-up. This improves the strength and finish of the final part.

CSM can be easily cut with scissors or a utility knife. For complex curves or better blending of layers, it can be torn by hand to help it conform to the mold shape more easily.

CSM is ideal for hand lay-up and open-mold applications. It’s used in boat building, mold making, and general fiberglass repair to create strong laminates, fill voids, and provide a smooth finish when layered with polyester resin.

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