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Hydro-powered hull scrubber takes slime off but not barnacles.
Bottom-scrubbing is definitely one of our least favorite boat chores. And because the warm Florida waters are the perfect nursery for hull-fouling slime and barnacles, we’re always on the lookout for products that will make the never-ending hull cleaning more bearable. That quest recently led us to try the Subscrub, a device that allows users to clean their boat hulls without hauling out or going for a dive.
The Subscrub has a molded plastic body 15 inches long, 8¼ inches tall, and 11½ inches wide), two bristle heads (12 inches long, ¾ inch wide), a looped line for an attachment points, and two aluminum hydrofoils. It has no moving parts and uses hydrodynamics to scrub the hull, letting the water do the work.
Invented by an Irish sailor whose frigid homewaters weren’t conducive to regularly diving to clean his bottom, the Subscrub is designed to be used while the boat is underway, sailing or motoring at 2 to 5 knots. Users tie a working line and “anchor” line to the Subscrub’s looped attachment point. The anchor line is led through a bow roller or chock, then aft to a cockpit winch or cleat; the user holds onto the working line. As the 4.4-pound Subscrub is eased over the toerail and dunked in the water alongside the boat, its hydrofoils enable it to “grab” onto the hull and slide over the surface. The user directs the Subscrub’s speed and direction by working the control line.
The scrubber can be used on any type of sailboat hull, but it won’t clean flat surfaces, so it only scrubs the hull from just above the waterline to where the keel starts. This rules out scrubbing the rudder, centerboards, or swing keels as well.
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PS tested the Subscrub on our Sarasota, Fla.-based Cape Dory 25 test boat. The bottom hadn’t been cleaned in a few weeks, so the thin layer of slime and smattering of hard growth provided a good test platform. The Subscrub we tested came already assembled, so set up was extremely easy. We used two old, lightweight jib sheets for the anchor and control lines and followed the idiot-proof instructions for use. We dropped the Subscrub overboard, and it went to work as advertised—swooping and scrubbing all over the hull. We found that rather than leaving the Subscrub’s anchor line cleated, it was easier to have the helmsman control the line’s slack as another crew worked the control line.
While the Subscrub was easy to use, it took a few minutes to get used to its diving patterns and figure out how to guide it to clean a specific area. Since you can’t see beneath the water’s surface to know which areas have been cleaned, users would need to develop a customized cleaning method to ensure the hull really gets a good scrubbing.
The Subscrub’s stiff bristles took off a fair amount of the boat’s ablative antifouling as it worked, but no more than a scrubby pad would. It no doubt would be kinder to hard paints, and according to Subscrub Marine, the slower the boat’s moving, the less aggressive the scrubbing will be.
Examining the hull post-scrubbing, testers found that the Subscrub removed most of the slime from just above the waterline down to the keel (about a 5-foot wide swath), but it didn’t budge the barnacles. To clean the 25-foot Cape Dory’s entire hull well would take a first-timer about 35 minutes; we figure users would become faster with practice.
The Subscrub costs $75 and is sold through the Subscrub Marine website.
Bottom line: The Subscrub is easier to use and more effective than cleaning the hull with a deck brush from the dinghy or dock. It’s cheaper than hauling out or paying a diver regularly, but it won’t get your hull as clean. It likely would appeal to boat owners in cold-water areas and those performance sailors looking to eek every tenth of a knot out of boat speed with a quick pre-race scrub. However, the Subscrub’s limitations (can’t clean the keel and doesn’t remove hard growth) mean some human-powered bottom cleaning will still have to take place.
