DIY Topside Paint Test: Two-part Linear Polyurethanes Face Off

Practical Sailors amateur painters try their hand at painting a sailboat hull to see which paint is best suited for a DIY project


Is painting a boats hull a job for an amateur painter? Should a mono-urethane or two-part linear polyurethane (LPU) be used? Practical Sailor is often asked these questions. Our answer? That depends on the painter and the paint.

With the right tools, research, and enough time and patience, any boat project is a manageable do-it-yourself endeavor. However, most of us lack the tools, time, and know-how to tackle all of the repairs and maintenance our boats require. The key is to only take on those projects that most realistically match our skills, budget, and schedule. But the trick is accurately assessing ones own skill level and the difficulty of the task at hand.

Two-part Linear Polyurethanes

So when it came time to freshen up the topsides of our long-neglected Catalina 22, Jelly, we weighed the pros and cons of doing it ourselves versus paying a yard to spray on some Awlgrip.

Our duty to answer our readers oft-asked questions and our addiction to product testing-and perhaps an underlying masochistic tendency-won out, and we decided to mount an amateur encounter of the polyurethane kind. The mission was neither swift nor painless, but in the end, Jelly shined with a glossy new paint job, we tucked another project under our DIY toolbelts, and our readers (hopefully) will benefit from our hard-learned lessons.

The Jelly Adventure

While our panel test (Practical Sailor August 2008) seeks out the most durable topside paint, this Jelly test was to determine which two-part LPU is the most user-friendly for the amateur painter and whether the project is manageable for the average do-it-yourselfer.

That meant trusting Jellys paint job to Practical Sailor s “amateur” staff, rather than banking on the talent of editors like technical guru and former boatyard manager Ralph Naranjo (who can handle a spray gun as easily as the rest of us handle fingerpaints). That in turn meant settling for a less-than-perfect finish, but it also ensured a true test of the products and techniques user-friendliness.

What We Tested

We chose to use the roll-and-tip painting method. It is less hazardous and requires less skill than spraying on the paint, but it does call for more deftness than brushing alone.

Testers selected two-part polyurethanes from manufacturers that historically have done well in Practical Sailors topside paint durability tests: Interlux and Epifanes. While Interluxs Perfection was released after our last test, its predecessor, Interthane Plus, took top honors for two-part white polyurethanes, and Epifanes Poly-urethane was named the best red or blue LPU in our four-year test published in the May 2006 issue.

Two-part Linear Polyurethanes

On Jellys port side, we applied Epifanes Poly-urethane No. 800 white thinned with Epifanes poly-urethane thinner, and on her starboard side and transom, we painted Interluxs Perfection Mediterranean White and used 2333N brushing reducer. (Both paints can be sprayed on, but different thinners are required.)

We also tested several fairing compounds, natural-bristle brushes, high-density foam rollers, and two-part epoxy primers. See page 29 for more on primers and preparation techniques, and look for reports on our brush and fairing compounds test in upcoming issues.

How We Tested / Painted

Before getting started on any first-time boat project, its a good idea to do some homework. We searched for application tips on the Internet, surveyed boatyard “experts,” and consulted our library of how-to books, the most helpful of which were “Boat Maintenance” by William Burr Jr. and “Sailboat Refinishing” by Don Casey. We browsed paint manufacturers websites and marketing literature for instructions and any helpful advice. And we raided the Practical Sailor archives for past tests and how-tos. (April 1, 1996; Feb. 15, 2002; May 2006; and August 2008 issues.)

The 1974, never-painted Jelly was in pretty sad shape. Hull shine was long gone. Her gelcoat was crazed in places; bare fiberglass showed through in other spots, and others still had deep gauges, pin holes, and scratches.

To properly prepare the hull for painting, much sanding, filling, and fairing was required, as were multiple coats of primer. (See “A Primer on Prep” on page 29 for specifics.)

Two-part Linear Polyurethanes

We followed makers instructions for surface preparation, priming, and application. The starboard side was primed with two coats of two-part Interlux Epoxy Primekote, and on the port hull, we applied two coats of Epifanes Epoxy Primer.

After priming, testers used blue dye to find any areas that were uneven and then sanded the hull with 220-grit sandpaper and a pneumatic dual-action sander (DA). After wiping down the hull with maker-specified solvents and tack a rag, it was time to apply the LPU paints.

Three coats of each product were rolled on using high-density, closed-cell foam sausage rollers and tipped with 3-inch Wooster and Epifanes (Omega) natural-bristle brushes. Testers wet-sanded between coats with 320-grit sandpaper, and wiped down with Interlux 202 and Epifanes thinner.

For most, two coats would suffice, but Murphys Law, uncooperative Florida weather, and amateur mistakes led to Jelly getting a third coat on each side.

To determine which DIY topside makeover system was more amateur-friendly, testers rated the products on the following criteria: how easy the product was to lay on, how forgiving it was, maker-supplied instructions, finish hardness, and initial gloss.

What We Found

For select jobs, you may find that one coat of Epifanes Primer covers well enough, but in our opinion, two coats of the Interlux Epoxy Primekote will always be necessary. We ended up doing two coats of both for better coverage in areas like Jellys blue bootstripe and where pink and gray fillers were used.

When it came to hand-sanding between coats, the Epifanes primer, like its LPU, was much harder to sand than the Interlux, but it also left a harder finish-a bonus for durability but a drawback during application.

There was a noticeable difference in the workability of the LPU paints. The Epifanes Poly-urethane had a tendency to dry much quicker than the Interlux, making it hard to keep a wet edge and easy to leave holidays. Adding thinner dropped the viscosity too much. Perfections “open” time (time where it can be brushed without leaving marks) was significantly longer than Epifanes, a major bonus for the novice.

Two-part Linear Polyurethanes

Both paints pulled together well as they cured, but the Perfection seemed more forgiving, in our opinion. In some spots on the Epifanes side, the brush strokes never pulled together. (Admittedly, this may have been an application hiccup, but the goal here is to identify the most amateur-friendly coating.)

Both paints offered acceptable gloss, not exactly a slick, sprayed-on shine, but better than expected. Reflection tests showed Epifanes Poly-urethane to have the upper hand in gloss ratings. (See photos, page 30.) The difficulty testers had in sanding the Epifanes (primer and LPU) is a testament to its hardness.

Epifanes does offer detailed instructions, but we prefer Interluxs idiot-proof approach with spelled-out, step-by-step directions on the cans and downloadable information, including how-to videos, on its website. Epifanes offers limited application tips online.

Lessons Learned

The Jelly topside project was not without its stumbles, but rather than recount all the things that went wrong, we offer this brief rundown of knowledge gleaned from the experience.

The right tools and supplies make the job easier: Dont skimp on sandpaper or brush quality; use a soft, wide, full brush with natural bristles (expect to spend $30-$40 for a good brush); use maker-specified solvents.

Prep brushes and rollers by going over them with tape to remove lint, fuzz, and stray bristles. Clean brushes immediately after finishing a coat.

Paint a white hull white; a dark paint could result in print-through.

Be aware of the weather: Do not paint in the direct sun, and if you live south of the Mason-Dixon, buy plenty of thinner. As the humidity climbs, so will the paints thirst for thinner. (Youll also want to have enough for cleanup.)

Keep an extra clean brush and extra paint on hand in case one brush gets dropped or paint spills during application. Wet the ground around the boat to keep dust down.

Two-part Linear Polyurethanes

Try vertical and horizontal tipping. For Perfection, Interlux recommends rolling vertically and tipping vertically, but we had better success rolling vertically and tipping horizontally.

For more tips, check out the “DIY Notebook” from the August 2008 topside paint review. Also, look for it with the online version of this article at


For amateur do-it-yourself application of a two-part LPU, we recommend Interlux Perfection. Its more forgiving than its Epifanes counterpart, and idiot-proof instructions are easy to come by. Epifanes Poly-urethane, a harder, glossier finish, is worth considering for the more advanced painter or for those hiring a pro.

Is the super-slick look of a professional, sprayed-on Awlgrip job achievable for the beginner with a roller and paint brush? Not without a fair amount of practice at roll-and-tipping and experimenting with flow. If a mirror-reflection is the look you want, hire a pro.

If youll be happy with a finish thats not-too-far from perfect but perfect from afar, then try your hand at self application. DIY topside painting is a feasible project with the right product, but we do recommend practicing on a fiberglass dinghy, rudder, or piece of glass before touching your hull.

All told, the projects two testers spent about 60 hours prepping, priming, and painting. We estimate the supply cost to be about $450 for the whole project-a savings of $1,000 or more over having it professionally prepped and painted.

So was the Jelly test worth it? While were much happier now that Jelly has a fresh face, getting her there was a tough road. We learned a lot along the way, and take pride knowing that her clean look is a result of our hard work, which afterall, is the DIYers mantra, is it not?

Now that weve recovered from all that sanding and the white paint has finally come off our fingernails, were turning our attention to one-part topside paints. We plan to paint Jellys decks and the hull of our ODay Javelin test boat with Epifanes Monourethane and Interlux Toplac one-part paints. Stay tuned for more tales of topside fun, including our one-year update of the long-term panel test.



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