Boat Cover

The [Condensed Version]

Your Boat Cover is only a season or two old but it is already leaking. We have all been there and have the solution. Read on to learn how to revitalize your canvas.

Getting drenched in a surprise shower out on the lake is no fun, especially when your Bimini top is supposed to keep you dry. We have all been there and experienced the two-season leaky-top itis. So, let’s get that boat cover ship-shape and properly waterproofed with the right Waterproofer for your boat cover or Bimini

Boat Cover Waterproofing

Boat Cover Waterproofing Article Image

Boat Cover Waterproofing

Let’s start with the materials. The classic canvas covers that your parents used are made with cotton. Consider, cotton strands act like the wooden planks on your deck, they swell and seal between the gaps when wet. So, this keeps water from dripping between the gaps and forces rain to flow off the boat cover. Understandably, cotton canvas has fallen out of favor because mildew can take hold and it tends to stain and discolor over time. Hence, why the boating industry adapted vinyl-coated polyester and acrylic woven fabric as its mainstays. These materials require less treatment and cleaning because their polymers are hydrophobic (waterproof) and so, will not absorb water.

Unfortunately, water can still pass through the gaps in any woven fabric but we will get to that in a moment. Every material has its drawbacks, vinyl-coated fabric will stay waterproof for the life of the material but it will not allow moisture to escape, causing moisture to build up. This inevitably leads to mold and mildew. But remember, vinyl is inexpensive and an effective short-term solution for Bimini tops but should not be used to enclose something like a sail or boat cover. In the past two decades, acrylic fabrics have become the material of choice of seafarers because of it’s breath-ability and strength.

Acrylic fabric is impregnated with compounds that resist UV light from sun exposure and will inherently stop mildew growth. Like most synthetic materials, it will not permanently stain and keeps it factory-fresh look for longer. Consequently, all of the big marine manufacturers have switched to acrylic and so it’s the primary pick for most people. 


Boat Canvas Waterproofing

Traditional cotton canvas is waterproof in the same manner that traditional wooden boats are waterproof. The cotton fibers — like the wooden planks — swell when they get wet. This seals the weave.

But because cotton canvas loves mildew and hates bird droppings, it is not used aboard pleasure boats much anymore. It has been replaced in most applications with either a vinyl-coated polyester or woven acrylic.

The vinyl-coated fabric is waterproof for the life of the fabric, but unlike traditional canvas, it doesn’t breathe. Unless it is well ventilated, condensation wets the underside of the fabric, eventually leading to mildew. Vinyl-coated fabrics are a good choice for Bimini tops, but unsuitable for enclosures such as sail covers or boat covers.

Acrylic canvas, like cotton canvas, is a tight-weave fabric. It is waterproof yet breathes; it stands up to ultraviolet radiation (sun exposure) better than any other fabric; it snubs mildew; it resists staining; it is colorfast and comes in every color imaginable; and it looks marvelous. Not surprisingly, acrylic canvas — Sunbrella being the best known — is the most popular marine fabric by a wide margin.

Acrylic canvas does have one negative characteristic, other than high cost. It gets its water repellency from a chemical treatment, not from swelling fibers, and eventually that treatment loses some of its effectiveness. Generally speaking, acrylic canvas in continuous use may start to leak after about three years. Scrubbing or the use of detergents to clean the canvas may hasten the failure of the coating. Fortunately, reproofing the canvas is easy.

How to Waterproof a Bimini Top or Sunbrella

Before you start, it’s important to understand that most waterproofing agents can damage your Gelcoat and put off dangerous fumes. These VOCs (thinning agents) are flammable and do irreparable damage to the environment. Additionally, the active waterproofing ingredient in these mass-market proofers is PTFE which will release PFOA and PFOS into the air and water over time. These chemicals cause cancer in human reproductive organs and are toxic to the environment. We strongly suggest you choose a waterproofing agent that lasts for years and is not toxic to your health. Hawk Tools is the only manufacturer with a fabric waterproofer that meets these requirements.

Sunbrella Recommends the Following Method :

  • Brush off loose dirt.
  • Spray on a cleaning solution of water and mild soap.
  • Use a soft bristle brush to clean.
  • Allow cleaning solution to soak into the fabric.
  • Rinse thoroughly until all soap residue is removed.
  • Air dry.

How to Waterproof a Boat Cover

How To:

  • Pick up a gallon of quality fabric weatherproofer. Get a paint roller and 12v power port.
  • Thoroughly clean your boat cover with light detergent and water. Let it dry out in the sun.
  • Place the gallon of fabric weatherproofer on a non-heat sensitive surface and plug cord into power port.
  • After it becomes liquid, unplug and remove heater from the weatherproofer.
  • Dip your roller in the solution and apply even coats onto your boat cover.
  • Make sure to test in an inconspicuous area to make sure you like the look.
  • After the fabric is completely saturated, brush off any thick areas with a brush or scrape with a spatula.
  • That’s all folks!

Chemicals and Your Boat Cover

After a couple of seasons, your pristine-looking boat cover or Bimini top will start leaking. Like with all woven fabric, water will start seeping through the gaps between the strands. Acrylic fibers cannot absorb water and so will not swell to fill the gaps. 


For this reason, all acrylic marine fabrics are sprayed with chemical waterproofing agents from the factory. When your top starts leaking, it’s the treatment that has worn out and needs re-application. So, a popular fix is chemical waterproofing sprays that can be purchased from marine supply stores. Just remember, every time you clean your boat cover, the chemical waterproofing agent is removed.


Marine Fabric Weatherproofer With Brush

Ultra Durable

Boat Cover Waterproofer

Your Boat Cover deserves the most durable fabric weatherproofer available. Natural waxes and oils are reinforced with TYLOL, bonding the blend to synthetic and natural fibers for years of UV stable waterproofing performance.

Just warm the weatherproofer in a pot of simmering water and apply.

2 thoughts on “Boat Cover Waterproofing”

  1. Brenda Williams

    There is some duplicate content here from another article, you may want to clean some of it up before you post next time. Thanks for the great info though!

  2. Bart Amundson

    Will this waterproofer work on rubber or teak? Do you have any tutorials about how to waterproof sail materials?

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