Marine canvas

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Marine canvas refers to the field of work concerned with the design and fabrication of functional canvas products (usually custom) for sail and motor boats.

[edit] Purpose

Marine canvas is used as protection against harmful UV rays. UV damages varnish (causes degradation, loss of color and elasticity and finally cracking and peeling) and the materials with which sails are made (often Dacton). To avoid constant boat repair, covers are fabricated for all sails that are left outside, and all brightwork, or highly varnished wood. Hatches are covered for indoor sun protection and winches are covered to protect them from deterioration of airborne particles and rain.

Other marine canvas includes biminis and dodgers and similar enclosures that protect some part or section of a boat from the weather and/or to create a more comfortable environment for the boat owner.

In some instances, these covers are purely created to add to the aesthetics of the motor or sail boat.

The design of these covers requires the fabricator to either pattern the object being covered, by creating templates out of disposable paper or plastic that are laid directly onto the area or object, or by laying the fabric to be used directly onto the object and fitting it. Marks for seams, fasteners and chafe protection are then applied to the pattern, and then transferred to the fabric, or directly onto the fabric.

Many American marine canvas fabricators use Sunbrella acrylic fabric, and although there are many other brands of acrylic canvas, they apparently do not enjoy the market strength of Sunbrella Brand Fabrics, produced by Glen Raven, Inc. The light colors degrade more quickly in the sun and can, under certain conditions (usually full tropical sun), lose strength after the first five years. Darker colors (Pacific blue, darker greens, and black) may last up to 20 years in all but the the most tropical conditions.

The thread used to stitch marine canvas is often polyester due to the far greater resistance of polyester to ultraviolet radiation. Nylon is never used as it usually doesn't last longer than six months in direct sunlight. Polyester threads (in sufficient sizes, ie. 12 gauge or V138) can last many years.

Smaller thread sizes are not recommended for tropical or semi-tropical regions, due to the rapid loss of strength caused by exposure to extreme levels of ultraviolet radiation. Additionally, many authorities recommend keeping one of the usual two stitch lines from being exposed to the sun. This can be achieved by employing a stitch-turn-and topstitch technique, instead of stitching both lines simultaneously, as done on a double-needle machine where both stitch lines will be fully and continuously exposed on either side of the fabric.