User:Savvyboatermarine

The term boat cover refers to any covering that is placed over a boat to protect it and its content from the elements, typically during storage or transport. This differs from a Boat Top that usually refers to a cover or enclosure that is used to protect the boat, passengers or cargo while the boat is in operation.

Boat cover styles & terms
There are a number of styles and terms used in describing boat covers.

 Universal boat covers have a very general fit, typically designed for a general hull floor plan in very rough size increments, often 2’ in length and 1’ in beam. They are usually used when the boat is in either wet or dry storage to protect the boat from the elements. 

Semi-custom boat covers are a refinement in fit from the Universal Boat Cover. A Semi-Custom boat cover will fit a more detailed style of boat and the size increments are typically 1’ in length by 6” in beam. These covers will typically provide a better fit than a universal. Custom boat covers are designed for a specific make and model of boat. They may be mass produced in a factory to fit a popular model and configuration of boat, or they may be measured and sewn individually at a canvas shop for a specific vessel. Custom boat covers usually provide the most precise fit.

Mooring covers refer to a boat covers that can be placed on a boat while it is in the water, either anchored or docked. Typically these will have a forgiving fit and they need to be able to be installed while the boat is in the water.

Sailboat covers pose some unique fit issues to accomodate the mast. Because of this, sailboat covers are typically designed one of two =ways. If the mast is to be left in place the cover must have a way to fit around the mast, then close. If the boat is to be stored with the mast un-stepped, a standard cover shaped for the sailboat’s hull outline will work. Note that some sailboat covers will accommodate the mast stored on deck under the cover. Other covers will not accommodate the mast, requiring it to be stored elsewhere.

Storage covers can refer to any boat cover, but is most typically used to describe a universal boat cover that is used only while the boat is in storage.

Trailerable Boat Covers can be used when a boat is in transit, a poorly fit boat cover can flap in the wind, damaging the cover or the boats finish. When a boat cover is referred to as trailerable, it implies that the cover, when fit properly and tied down appropriately will provide a close enough fit to eliminate flapping material. Typically semi-custom boat covers and custom boat covers will be trailerable, while universal covers will not. 

Boat cover considerations
A boat cover is designed to withstand the forces of the elements, protecting the boat from damage. Because boats are kept in such a wide variety of environments, a number of different materials have been developed to deal with prevailing conditions.1 There are a few common factors boat covers need to contend with.

Strength and weight:
Boat covers are often pulled on and off a boat, stressing the fabric. Pressure points along windshields, trolling motors or other fixtures can wear and fatigue the cover. The fabric may be stressed by loads of moisture from snow or pooled water or by accumulations of dirt and debris. To withstand this, boat covers are often made from highly durable polymers like Polyester, which provide strength even at light fabric weights.

Moisture
A boat cover needs to keep moisture out of the boat (water resistance), but at the same time it must allow moisture trapped under the cover to dissipate (breathability). A truly waterproof material will keep most moisture out of the boat, but will trap existing moisture (damp seats or carpet etc.) beneath the cover. A water resistant cover may allow some moisture to enter the boat, but will typically allow moisture under the cover to escape. Breathability is most important in humid climates, or any time a boat is liable to be covered before it is completely dry. Trapped moisture can enable the growth of mold and mildew. Boats that are stored where they are subject to lots of rain or snow may benefit from a more waterproof cover. Some covers opt for a waterproof material but add protected vents to allow trapped water vapor to escape.

Note that even a cover made from waterproof material will allow some moisture to enter through stitch holes.

UV resistance
UV radiation from the sun will degrade most material over time. In areas with lot of sun, the UV resistance of the cover material is increasingly important

Typical boat cover materials
Boat covers are made from a wide variety of materials to meet different needs. The most common material is currently Polyester fabric, often with an additional coating of acrylic, urethane, PVC or other plastic polymer to enhance certain characteristics. Polyester is fairly strong, light weight and provides a good balance of water resistance and breathability. Addition of acrylic or urethane coatings will increase the polyester’s resistance to UV radiation, extending the life of the cover.

Older covers were often made from cotton canvas or duck, but these covers were susceptible to rotting in humid areas, molding when wet and degrading in the sun. New versions have been improved by going to a polyester-cotton blend. Most cover manufacturers will provide a comparative chart outlining the strength and applicability of the available materials for given environmental circumstances.

Boat cover sizes
Boats are usually measured for a cover by taking the centerline length (from the point of the bow to the center of the transom) in a straight line (not up and over the windshield etc.)2. The beam (width) is taken from the outside edges of the gunwale at the widest point of the boat.

Outside Links
1. Boat Cover & Top Articles articles covering various aspects of selecting and maintaining a boat cover.