The Great Cover Up

Materials, Design Trends, and Maintenance Tips for Boat Canvas

Published: Monday, May 28, 2018
By: Zuzana Prochazka

If you’re seeking shelter on the water, or even just looking to make your boat look and feel new(er) again, a well-designed enclosure will make a difference. A canvas addition consists of many complementary parts: fabric or vinyl (both of which have improved in performance and aesthetics), window technology (also referred to as “the clear”), and advances in threads and fastening systems (to connect all the pieces).

Fabric & Vinyl

(Photo Credit: Castro Canvas Designs, Inc.)-->

The non-transparent materials of an enclosure are made of fabric or vinyl. Materials differ in aesthetics including colors and textures, and also in breathability, water and UV resistance, durability, longevity, suppleness, warranty length and dimensional stability, which is resistance to stretching and sagging. The choice of ideal material depends on the application and the objectives of the project.

The traditional option has been Sunbrella, which is a solution-dyed acrylic fabric that was developed as an alternative to cotton. It’s durable, water-resistant, and breathable and comes in over 30 colors.

An alternative to fabric is vinyl like Stamoid or Weblon. Vinyl is coated, woven polyester which has high dimensional stability, is fade-resistant, and is completely waterproof (rather than water-resistant like fabric) but that means it doesn’t breath much. It does, however, provide a very nice finish that is easy to clean and will not be permeable even where it rains — a lot.

The “Clear”

<--(Photo Credit: Castro Canvas Designs, Inc.)

Once you’ve decided on a body material, it’s time to choose the windows. There are two major types: clear flexible polyvinyl sheeting that is roll-able (think Isinglass) and semi-rigid polycarbonate or acrylic windows which will bend to varying degrees but will not roll.

Clear materials come in different thicknesses and, generally, the thicker the material, the more durable and expensive. Roll-vinyl comes in 20-60 mil gages (a mil = .0001”) and most shops will work only with 40-gage and thicker because thinner material will not yield good results. Flexible vinyl is susceptible to shrinkage and will change suppleness and fit depending on temperature. Semi-rigid windows come in 40-80-gage, have a glass-like clarity, and hold their shape extremely well — but they’re also more expensive.

Roll-able vinyl is used on side curtains that need to open to allow access or air flow. One brand, Strataglass, has a coating that blocks approximately 98% of UV rays, is scratch-resistant, adds dimensional stability, and protects against pollution and chemicals. (If you put Strataglass and Isinglass next to one another when they’re new, they look very similar. The difference is in the way they age. (singlass is less popular now.)

Semi-rigid windows come in polycarbonate or acrylic versions and are startlingly clear. They are somewhat flexible so you can bend them around corners but you cannot fold or roll them. Polycarbonate windows are coated with a UV-blocker, which makes them more scratch-resistant but, if you damage one, you can’t buff them out due to the coating. Under the polycarbonate options are Rainier Diamond, which must be bonded, and Makrolon that may be stitched to fabric and vinyl.

Rigid material comes in sheets rather than rolls. Like roll-able vinyl, longevity increases if the windows are covered when not in use, in some cases, doubling their lifespan.

Zippers, Tracks, Twisties & Thread

Now it’s time to bring it all together. Zippers are a clean way to connect sections and those you’ll see most often are #10 (size) heavy-duty zippers from YKK®, Lenzip®, and RiRi. Zippers do the grunt work in an enclosure by opening sections for ventilation and access, and they should be sewn with an outside flap, which not only looks cleaner, but also protects against UV damage, salt, dirt, and oxidation.

If you’ve ever had to stretch canvas while trying to get snaps or zipper sides to meet, you will appreciate twist lock fasteners that are more forgiving. Twisties are a surefire way to get two tight sections to meet especially when connecting the top and sides.

There is a way to connect those sparkling semi-rigid windows to the boat itself. Stainless steel or plastic slides are mounted to the boat while the body material is sewn onto the window and connected to a keder-welt, which slides into the track allowing windows to open just like at home.

Finally, there’s the thread, which has traditionally been very susceptible to UV damage and can be the weak link in the whole design. Depending on care and exposure, conventional polyester, nylon, and cotton thread used by canvas shops can last 4-6 years before it fails and pieces must be re-sewn. New technology includes polytetrafluoroethylene (PTFE) thread, which is the chemical name for Teflon. This type of thread resists stretching, fading, staining, chemical exposure, and sun damage. Some manufacturers warranty it for a lifetime and it comes in a variety of colors including clear. It also doesn’t absorb water, so it won’t swell and create larger holes in the stitching which, in turn, allow your enclosure top weep in the rain. This thread does have some tradeoffs, not the least of which is that it can be quite expensive and it doesn’t hold up to chafe well.

Design Trends

(Photo Credit: Mariner Canvas Company LLC)-->

Good canvas design means that you have a list of objectives that must be met in order to create a workable enclosure. Ask yourself what success will look like in the end.

Emerging design trends include lighter colors like beiges, greys, and medium blues. Despite the fact that a dark-colored top will get hotter in the sun due to the opacity of the dye, darker colors hold up better to UV rays while lighter colors break down faster. Lighter colors stay cooler and blend better with the boat, but they tend to mildew more so there are tradeoffs on both sides.

The lines of the enclosure should complement the lines of the boat. The addition should not be tall or boxy and the top should have a crown so that water channels away. The design should be void of wrinkles and should be tight but, because materials shrink over time, there’s a tradeoff between being initially drum-tight, and being reasonably easy to put back on if the enclosure is removed for washing.

Sight lines are important. Zippers and fabric connections should be discreet and windows should wrap around corners in a nice radius to prevent blind spots. The design should allow for good ventilation and easy access. The structure should channel and shed water easily, tolerate runs at high speeds, and shouldn’t squeak or flap because a noisy cover will stress your nerves.

A complicated design will be more expensive to create initially and harder to live with over time. A collaborative effort with your designer will produce the best outcomes. In many cases, a good enclosure provides nearly invisible functionality, and the cleaner and less obtrusive the design, the more thought went into it.

Extending the Life of Your Canvas

Canvas maintenance will define its longevity. Rinsing all parts with fresh water after a trip, polishing windows, cleaning and drying fabric and vinyl, lubricating zippers and snaps, and even turning the boat around in its slip to equalize UV exposure can add years to your enclosure materials.

Most manufacturers including Stamoid, Strataglass, Sunbrella, and Makrolon recommend approved cleaners to keep the material warranty in effect. Never use Windex, Rain-X, Simple Green, Fantastic, or citrus-based cleaners because these chemicals break down the plasticizers that keep your windows from cracking, peeling, and yellowing. Most material care will involve a soft cloth or mitt. Don’t use paper towels as their fibers are abrasive.

Don’t put canvas in a dryer and don’t dry clean it or you’ll disrupt some of its added properties such as UV inhibitors and waterproofing. For tough stains on acrylic, mix ¼ cup of non-chlorine bleach in a gallon of water and use a soft bristle brush.

Flush zippers with fresh water and work them back and forth. Lubricate both zippers and snaps every few months with a silicone spray, Shurhold’s Snap-Stick, or even ChapStick. Stay away from petroleum products such as Vaseline. Overlooking this hardware will absolutely result in frozen zippers and torn canvas around corroded snaps.

Enlightened Enclosure

An enclosure adds to boating pleasure because it protects you from the elements allowing you arrive less weather-beaten and fatigued, and rainy days won’t keep you in the slip. Now you’re armed with just enough knowledge to be dangerous, so get out there, ask questions, get referrals, collaborate, and eventually find your own bit of enclosed enlightenment.

6 Tips for Working with a Canvas Fabricator

1. Walk the docks. Check out label names on enclosures you like and then get feedback from the owners. Take pictures to start meaningful conversation with your fabricator.
2. Ask about a canvas shop’s turnover to make sure the people who created the projects in their portfolio are still there. Get specific referrals.
3. Get details on materials, upgrades, costs, delivery times, and an itemized estimate.
4. You may not save much by providing the old enclosure as a pattern for the new. The materials have either stretched or shrunk and it’s unlikely that a direct copy will fit well.
5. Most fabricators will take a deposit (up to 50%) and that’s a good time to ask about their warranty.
6. Remember that this project is a collaborative effort. Stay involved and open to new ideas and solutions.

About the author:
Zuzana is a freelance writer and photographer with regular contributions to over 18 sailing and power boating publications. A USCG 100 Ton Master, Zuzana is the founder of a flotilla charter company called Zescapes that takes guests adventure sailing at destinations around the world.

Zuzana serves as an international presenter on charter destinations, safety issues, and technical topics, and she's the Chair of the New Product Awards committee for innovative boats and new gear. She is a member of the American Society of Authors and Journalists and a board member of Boating Writers International.

This article first appeared in the Launch Issue (May/Jun) 2018 of Great Lakes Scuttlebutt magazine.

tags: Canvas & Upholstery, Do It Yourself (DIY)

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