Tips on Caring for Marine Canvas

A recent series of reports in Practical Sailor have focused on marine canvas, and after having spent more than I wanted on canvas upgrades for my own sloop, I thought it would be a good time to revisit ways to preserve my investment.

For subscribers who haven’t yet dug into the more recent issues, the September 2023 issue included a report on UV protection afforded by various marine fabrics. Our testing made the not-so-surprising discovery that loose-weave products like Phifertex, which provide shade but also allow in some breeze, do not provide as much UV protection as the maker leads us to believe. And in the July-August issue, writer John Stone offered a step-by-step guide to building your own compact dodger, one that provides protection but doesn’t make your classic plastic look like a horse carriage.

Canvas dodgers and Bimini tops are the hallmark of a cruising yacht, keeping the sun at bay and allowing the crew to dodge the worst of the weather. On board, canvas also protects sails, windows, and machinery. Collectively, these represent a substantial financial investment, and we wanted to find the best way to protect the investment and get the most life out of the canvas.

Sunbrella makers recommend that routine maintenance include frequent freshwater rinsing plus spot cleaning the fabric. After a more thorough cleaning, Sunbrella advises owners to apply a treatment (specifically Gold Eagle Products 303 High Tech Fabric Guard) to restore the fabrics repellency. In the February 2014 issue, we tested these and other treatments designed to keep on-board canvas water repellent and looking its best.

Waterproofing canvas is based on making the surface hydrophobic enough that water cannot wet the surface. Factory canvas comes with some pretty effective treatments, but after two to three years in the sun, they tend to wear off. Treatments containing waxes, PTFE (Teflon), and silicone promise to renew the repellency, if only for a month or so.

When we refer to canvas here, we mean acrylic marine fabrics like Sunbrella, not cotton duck, which some traditionalists still use. The chemistry of cotton and acrylic are quite different—cotton accepts treatments more readily, but acrylic is more naturally repellent-and we’ve previously tested water repellents for cotton duck (PS, June 2004).

For maximum water repellency, boat owners could use impervious waterproof fabric instead of canvas, but that typically isn’t a good idea. Waterproof sail covers hold moisture, mildewing sails more quickly. Waterproof dodgers sweat and hold condensation, drying slowly and mildewing. Waterproof machinery covers would trap salt and humidity, accelerating corrosion. For most on-deck equipment-protection tasks, water-repellent, breathable, durable acrylic fabrics are best. These include Top Gun, Weathermax, and Sunbrella.

If you are looking at making or buying new canvas for your boat, Sunbrella remains our favorite choice of material for the long haul, but some challengers like Stamoid and Weather Max have their converts (see PS December 2011, “Functional Fabrics”). Technical Editor Drew Frye’s dual-purpose awning is perfect for low-budget sailors (see PS June 2021 “Turn that Riding Sail into an Awning”). Sailrite (www. sailrite.com) also offers kits for the DIY stitcher, and our oldie-but-goodie from 1999 (search the PS website for “The Canvas Air Conditioner”) has step-bystep directions for making one.

If the basic, pup-tent style awning doesn’t suit you, Taylor Made, Crawford Marine and other companies offer domed designs that stow compactly (see PS October 2013, “A Reversible Awning”).Most recently, Stone, who has completely gutted and restored his Cape Dory 36, Far Reach, detailed his approach to canvas awnings for sailboats at sea and at anchor. Finally, if your biggest fabric foe is mildew, Tech Editor Drew Frye’s DIY formula for mildew prevention has saved countless boaters from paying $20 or more per bottle for a so-called miracle cure for mildew.

And if you are looking to upgrade — or protect — your entire canvas inventory, check out our updated eBook compilation of testing and reports on sail selection, care, and repair, A Look at Sails.