A Reef of Barnacles

9 Jun

June 7, 2019

The Royal Nova Scotia Yacht Squadron
Halifax, Nova Scotia

I noticed barnacle growth before our first pass at Cape Horn, just one or two, spied going about their business in the eddies off Mo’s transom. And then, over the course of the Southern Ocean circuit, each time I hung myself over the stern to work on Monte, the numbers I could observe grew. Within a few months, were clearly hosting a colony.

A diverse colony of at least three species. The gorilla of the group was entirely purple, carried a long, thick stem at the end of which were two “ears,” and it grew anywhere reached by the bounding waves. I could see a few above the water line even at the bow. Next came the white, hard-shelled, teardrop-shaped barnacles. Then the smaller zebras.

A week from our second Cape Horn rounding, I put a camera over the side during a calm, and what it brought up was a shock–Mo’s underside had become a reef. The following three photos are from March 11, 2019. It’s day 158 of the Figure 8 Voyage and we’ve sailed 21,699 miles.

Starboard quarter above the waterline.
Starboard quarter and rudder (which is largely clean).
Starboard looking forward.

What was to be done about them?

During the previous year’s Figure 8 attempt, I’d hauled Mo in Hobart, Australia and, to save a few bucks, the yard boatswain had allowed me to blast away her goodly crop of barnacles myself. The pressure washer was so powerful, it nearly ripped my arms from their sockets, but still, the removal of barnacles took half a day. This suggested to me that diving the hull with a sharpened spatula would be a futile exercise.

So, I did nothing but lament the situation and press on.

Over the course of the next two months, Mo slowly climbed north into the Atlantic. As the water warmed and became clear, I noticed that the barnacles I could see from the transom begin to die off. First the long, “eared” barnacle bit the dust. Then the zebras. The barnacle with the teardrop shell seemed the most resilient.

In the Horse Latitudes of about 30N and 60W, Mo and I were again becalmed. Again I put a camera in the water and was shocked at the finding. The following three photographs are from May 18, 2019, 68 days after the above photographs. It’s day 225 of the Figure 8 Voyage, and we’ve sailed 30,106 miles. We are two weeks from Halifax.

Starboard quarter above water line.
Port side aft.
Starboard looking forward.

Elation hardly captures the feeling. The barnacles had nearly evaporated and Mo’s bum was remarkably clean. One element of relief for me in finding this was confirmation that our very poor mileage in the Atlantic was not entirely due to a dirty bottom.

On Friday, June 8, day 245 of the Figure 8 Voyage, I hauled Mo here at the Royal Nova Scotia Yacht Squadron. Given the above, my expectations were that the bum would be nearly spotless. Instead, we had a new crop of hitchhikers coming in at the base of those older barnacles that remained.

Coming onto the weighs at the Royal Nova Scotia Yacht Squadron.
Stands to support the bow.
Port side looking aft.
Starboard quarter.
The barnacle with “ears” and a few small zebras.

Lessons Learned:

  1. “There is no good bottom paint for aluminum boats,” says my friend, fellow cruiser, and aluminum boat builder, Gerd Marggraff. Prior to departure, I had applied three generous coats of a bottom paint known specifically to ward off hard growth, but barnacles are superior beings, able to penetrate even the best defenses.
  2. An early jump. I might have had an easier time of it if I’d dived the hull before the first Cape Horn rounding, when the barnacles were young and few.
  3. In hindsight, I think I could have dived the hull with some success, even when the barnacles had matured into a reef. I found here in the yard that the “hold fast” (the glue that holds the barnacle fast to the hull) was easier to remove with a sharpened spatula than I had thought. It would have been a big job, taking a full day or more–but not impossible.

This article was syndicated from The Figure 8 Voyage


  1. JB

    Two options I’ve heard that work are A) anchor in a freshwater river for a week or so and that will kill off the barnacles; and B) run a length of line (1/4″-3/8″) from the bow aft (no not far enough to reach the prop or rubber): while sailing as it will provide agitation to the hull and help ‘clean’ off whatever barnacles are starting to take take hold.

  2. Dean W

    I keep my boat in the water 12 months in the warm waters of Miami, FL. I get considerable barnacle growth, especially in the summer months. I use hard antifouling paint but it is pretty ineffective against barnacles. I dive on the boat every month to clean the bottom and my favorite tool for removing the barnacles is a plastic ice scraper for cars (unavailable in stores in Miami but can be purchased online from auto parts stores). I find that the best scrapers are the ones with the short handles and wide scraper blades. The plastic scrapers will eventually wear out, so buy more than one, but since they are plastic, they won’t remove the underlying paint.

  3. f. meyer

    I am more or less stationary on the East End of Long Island, New York and cannot often afford the hauling prices here . Also the eco-NAZIs have forced legislation in NY to take any effective biocide out of the paint so that only the flaking of the paint removes the growth. . I find that a garden hoe
    often with an extender pole taped on with duct tape does a fairly good job in the Spring & Summer . The cold water does it well in winter. Now that they have “saved” the barnacles on boat bottoms they should start on the thousands of miles of bulkheads in the area . FCM

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