Know-how: Maintaining the Canvas on a Sailboat

Maintaining canvas can be a daunting task. First there is the challenge of removing the canvas, then knowing exactly how to clean and inspect it, and finally properly reinstalling it. I’ve seen circumnavigators brought to their knees by a snap that wouldn’t snap, and cruisers who must apologize to their crew for things they said while trying to spray off mildew. I’ve listened to profanity, seen tears, and heard the sound of ripping fabric as boatowners do their best to care for their expensive new pet, only to walk away thinking, “This one bites.”

There is another way, though. A happier path that promises sundowners and smiles at the end of caring for your canvas rather than matches or blow torches. As many sailors will be removing canvas for the off season, or already have canvas removed from storage during the hurricane season, now is the perfect time to think about cleaning and maintenance.

Typically, your canvas worker will have met you on board and gone over the proper care of your canvas and upholstery. They may have inundated you with information, pamphlets, and how-to’s, and chances are when it’s time to clean and maintain, those instructions are long forgotten. So let’s go over the entire maintenance process from order of operations for removing, cleaning, maintaining, and reinstalling your canvas.

Assessment

There are a few things you can do to make maintenance easier and less time consuming, and it all starts with the initial assessment while your canvas is still on the boat.

Canvas on a boat should be tight. It prevents wind from grabbing loose ends and whipping them around until you have a tattered mess. Tight canvas allows for water diversion, preventing pools that stretch and change your canvas permanently. You want your canvas to make a drum-like sound when you tap the top with your finger—“drum tight.” Over time canvas may stretch and become less tight, but if you notice corners flapping or entire connector pieces inflating and deflating with wind gusts, it may be time for a repair. Take note and snap a few photos to show a canvas repair shop if there are areas that are especially egregious and will need modification.

In your walk around, also look for water intrusion. The first spots to fail in canvas are the seams. Some shops do not use PTFE (Polytetrafluoroethylene) synthetic thread. If they did not, the thread will fail faster than the waterproofing on the canvas; this means the hole that the needle created in the seam is compromised and will allow water to penetrate. Pour a cup of water over seams to see any problem areas. Be careful to note whether the seam is leaking, or the canvas itself is allowing water to permeate through. It may help to take a fabric marking pencil and circle seams that may need to be restitched or have a waterproofing compound added to seal the seam.

The scratch test is another way to test seams and their viability. Run your nail over the stitching in a scratching motion. If the thread holds, your seams are in good shape. If the thread breaks or comes loose, it may be time to restitch the canvas. Mark the areas needing attention with your fabric pencil to make it easier for your canvas repair shop to find. In some cases, your repair shop may deem it necessary to restitch the entire piece of canvas rather than the numerous spots you’ve marked.

Before removing your canvas completely for cleaning, label it. This helps you organize pieces in storage and make reinstallation a breeze. Some canvas shops will add red or green snaps or labels to enclosure panels, window covers, or other items whose orientation is hard to differentiate once they’re removed. You can take it one step further and add green or red pulls to zippers to ensure you have the canvas placed correctly. You can also use a graphite pencil to mark in a discreet location the name and location of a canvas item. Be sure the placement of this label is hidden, as graphite is very difficult to remove from canvas.

Zippers and Snaps

Now that you’ve assessed your canvas and labeled everything, it’s time to lubricate zippers and fasteners. Zippers can be frustrating at times, causing you to reach the point of ripping the car down the teeth causing damage. Zippy Cool, a cleaning and lubricating fluid, helps avoid this. It removes harmful dirt, sand, and salt and then uses a formula designed to make sliding the zipper pull easier. This will also prolong the life of your zipper, whether it’s plastic, metal, or a coil zipper, which is often found in your U-zip windows in dodgers. This product is also biodegradable.

Zippers are not the only items that need lubrication. Snaps have a small gasket that allows a positive fasten to the stud on deck. If you look inside the snap you’ll see it—a small ring around the perimeter of the inside cap. This needs to be lubricated so it doesn’t stick or seize. A good product to lubricate snaps—as well as zippers—is Iosso E-Z Snap. Zippy Cool and Iosso E-Z Snap are silicone-free, so they won’t damage or affect the adjoining canvas, which is likely acrylic-based and incompatible with silicone.

After your inspection, organization, and lubrication, it’s time to remove your canvas. If it’s the first time you’ve done this, take a short video or snap some photos before you take it down. This will help when it comes time to reinstall—especially important if you are having a dockmaster or friend remove the canvas and you or someone else is reinstalling.

Cleaning

A good rule of thumb when cleaning canvas is to be gentle. Sunbrella is the most common marine fabric used, and there’s good reason. Sunbrella is made using a process called “Color to the Core”—Sunbrella’s method of impregnating each fiber with UV-stabilized pigments and waterproofing, then spinning that into the yarn that is woven into the bolts of fabric your marine trimmer uses to make your canvas. Understanding this process should make it easy to see why you shouldn’t vigorously scrub or pressure wash canvas. Breaking up the fibers within the yarn strands can damage the UV resistance and waterproofing, deteriorating the canvas faster.

I often tell clients not to use a brush at all; instead fill a kiddie pool or bathtub with lukewarm water and OxiClean or Dawn dish soap. Place the canvas into the soapy water and agitate every 30 minutes for five hours. Do the same with clean water to rinse.

For tough stains or mildew you can use a prepared solution of one cup of bleach and one-quarter cup of mild soap per gallon of clean water. Allow the mixture to soak into the affected area for up to 15 minutes, then blot the area with a clean towel or sponge and rinse thoroughly until the soap and bleach mixture residue is gone. If you have Sunbrella Plus, Supreme, or Clarity, be sure to only do this process on the uncoated side of the fabric.

If you have an oil-base spill or have gotten some oil-based sunscreen onto your canvas, immediately apply cornstarch to the affected area and let it sit for 10 minutes. The cornstarch should absorb the oil. After 10 minutes, use a ruler to remove the cornstarch, scraping it off and preventing the oil from being pressed into the fibers.

Your exterior canvas is often not just constructed of fabric. You’ll also have clear vinyl glass, such as Strataglass or Makrolon. Be sure to adhere to each of their unique cleaning instructions. Strataglass, a common soft, clear vinyl that can be rolled up, calls for using the IMAR product line of glass cleaners and polishers. Makrolon, on the other hand, is the common product used for hard, inflexible clear vinyl. This vinyl cannot be rolled and is removed or swung up in windows or dodgers. For Makrolon you can use an ammonia-free glass cleaner.

It’s very important to know which type of glass vinyl you have on your boat, as some polishers will damage one type and polish another. When in doubt, turn to the canvas shop that constructed the canvas for guidance.

Once you have cleaned the canvas and glass, you’ll have the option to address the seams. If your canvas is older than two years and is out in harsh sunlight or stored for long periods of time without use, it may be time to add Iosso’s Premium Seam Sealer. This is a silicone-free invisible coverage that can be used on Sunbrella fabric to seal and prevent water intrusion in seams. It’s important to do it on both sides of the seam to have the desired effect.

Waterproofing in general can be useful when dealing with old canvas, however it should not be used on canvas that is less than three years old. It should only be considered once the waterproofing elements within the fabric begin to fail. At that point, a product such as 303 Fabric Guard, which is recommended by Sunbrella, can be helpful. It’s important to follow the directions carefully for this product to work properly. The cure time of 12-14 hours seems like a long time to wait, but if ignored, the waterproofing may not take effect. Once you feel the canvas has reached the point of using an additional waterproofing agent, it would be best to add the process into your annual maintenance, especially if your canvas is on for an entire season.

Storage

Now that your canvas is cleaned it’s time to take it to the canvas repair shop or put it in storage. Canvas shops are notorious for being booked out on both new projects and repairs, so giving them an adequate heads-up and being flexible with your schedule may help you find a shop to take on what you are looking for. Not all shops store canvas, but if they’re doing a repair for you, they may hold onto it while you are away or for the off season until you’re ready to reinstall.

If you’re storing your canvas, adhere to the most stringent of the various storage instructions you have on hand. You’ll be looking at your fabric, thread, and glass vinyl instructions, and they may seem completely different. It’s safest to follow the glass vinyl instructions, as they will be the most rigorous with temperature preferences for the glass and instructions on layouts so you don’t bend the glass or permanently alter it. It’s always safest to store panels with the glass vinyl flat in an area that does not get above 110°F. Any hotter and you risk the glass off-gassing chemicals. Under berths may be a good option, if your boat does not get too hot during storage.

Once you’ve inspected, cleaned, and properly stored your canvas, you’ll be ready come spring to reinstall it clean, fully functioning, and looking great.

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November/December 2024