Unlike continuous fibres, Chopped Strand Mat is literally short chopped strands sometimes described as random discontinuous fibres (about 1½” – 37mm long) and held together with a soluble resinous binder.  CSM is available in varying types and weights from ¾ ounce per square foot [225 grams per square metre] upwards however, 1½ oz. [450 g/m 2] and 2 oz. [600 g/m 2] are the weights you will most often see expressed by designers and manufacturers of boats.   In our own material lists we simply say 1½ oz. Mat [450 g/m 2] and so forth.

    CSM can be used as a “bulk builder” in a laminate where build-up is required but without great strength.  In a laminate, layers of CSM should be used between layers of woven roving as a cushion to promote a good bond and where the strength (or lack of) in the CSM, is complimented by the strength of the roving.  

The amount of resin required to impregnate CSM is approximately 2 ½ times the weight of the mat.