Copper is on the way out

THE WRITING IS ON THE WALL for copper-based antifouling paint. Washington has become the first state in the U.S.A. to ban its use on boats, with effect from 2018.

Antifouling paint discourages the growth of barnacles and plant life on submersed hulls. If you have a wooden boat, it also discourages marine borers from eating your planks for lunch. Copper became the most favored biocide after 1988 when Congress banned the use of tin-based paint, which proved to be harmful to shellfish. But now there is growing concern that copper, too, is toxic to many forms of sea life.

It used to be easy to understand how copper worked. It was a poison, pure and simple, and the rule of thumb was that the more copper a paint contained, the more effective an antifoulant it was.

Now, new ecologically safe antifoulants are available, usually at much higher prices, but their modus operandi is not as obvious. There is vague talk of formulations with biopolymers and promises of photo-active technology, but the net result is a paint with a seemingly impossible mission—to discourage barnacles and slime without killing other forms of sea life.

Until 2018, however, unless new legislation changes things, there will still be four basic types of copper-based antifouling:

* Sloughing. This paint slowly dissolves over time, exposing fresh copper as it does so.

* Hard epoxy or vinyl. This is a scrubbable paint that allows the biocide to diffuse slowly through the skin.

* Ablative. This is usually a copolymer paint that acts by hydrolysis, or chemical reaction with water, and the scouring action of water flowing past the hull.

* Permanent coating. This is a coat of resin, polyester or epoxy in which millions of tiny pieces of copper metal are suspended, each one individually coated with a thin layer of resin and thus electrically insulated from its mates. New copper is exposed by scrubbing the hull every few months and it’s possible that this system could last the life of the boat. But application is a job best left to the professionals.

Today’s Thought

A ship is ever in need of repairing.

— John Taylor, A Navy of Landships

Tailpiece

There was an old lady of Worcester

Who was often annoyed by a rorcester.

She cut off his head

Until he was dead,

And now he don’t crow like he yorcester.

(Drop by every Monday, Wednesday, Friday for a new Mainly about Boats column.)

The rough's better than the smooth

THOSE OF YOU who roll your own antifouling paint on the bottoms of your boats will know how difficult it is to get a really good finish. Racing skippers who insist on finishes like glass spend many man-hours and many bags of money to achieve less underwater resistance this way. But they may be wrong.

I have mentioned this before but, sigh, nobody takes any notice of what I say:  Years ago golfers discovered that balls with dimples in them have better aerodynamics and travel farther than smooth round balls.  I have therefore always held that the dimpled (well, all right, rough) surface of my antifouling paint actually makes my boats go faster.

Now some high-powered scientists are finally, finally, agreeing with me. Here’s a fascinating piece from a very smart website at  www.sciencerecorder.com

“When it comes to moving rapidly through water, smooth is generally considered better. That’s why ships have smooth hulls and swimmers shave their legs. However, a new study published in the journal Physics of Fluids suggests that smooth might not be best and that some rough surfaces can reduce drag.

“’A properly designed rough surface, contrary to our intuition, can reduce skin-friction drag,’ said John Kim, a professor in the mechanical and aerospace engineering department at UCLA, in a statement obtained by EurekAlert.

“Scientists had previously tested the idea of using rough surfaces in water with limited success. More recently scientists have started working with rough surfaces that are very hard to wet, a property called superhydrophobicity, the National Monitor explains. In theory this implies that the surfaces can snare air bubbles, producing a hydrodynamic cushion, but in practice they frequently lose their air cushions in chaotic flows.

“The researchers modeled the fluid flow between two surfaces coated with small ridges. They used a superhydrophobic surface design that another UCLA team had already observed could keep air pockets entrapped, even in choppy conditions. The surface was blanketed with tiny ridges arranged in the direction of flow.

“The researchers tested the model in both laminar and turbulent flow. To their surprise, the drag-reduction was greater in choppy conditions.

“The irregular fluctuations and swirling vortices in turbulent flows on smooth surfaces generally increase drag, Kim noted. However, the air cushion generated by the superhydrophobic ridges changed the turbulent patterns near the surface, reducing their effect.

“Drag-reducing surfaces may one day cover the undersides of both cargo and passenger ships. ‘It could lead to significant energy savings and reduction of greenhouse gas emissions,’ Kim explained.”

Today’s Thought

The best scientist is open to experience and begins with romance — the idea that anything is possible.

— Ray Bradbury, LA Times 9 Aug 76

Tailpiece

“And you, madam, what’s your husband’s average income?”

“Well, on Friday nights, when he goes to the yacht club, it’s usually between 2 and 3 a.m.”

(Drop by every Monday, Wednesday, Friday for a new Mainly about Boats column.)

Haulout time again

THE TIME IS ALMOST RIPE for the boat to come out of the water and have its bottom painted. Every two years we go through this ritual, the boat and I. Every two years we humiliate ourselves in our pathetic attempts to back into the tiny slip at the boatyard, and every two years we argue with the man who works the big crane about where the slings should go.

I show him the architect’s drawing of the underwater profile and tell him the aft sling must pass under the full keel just ahead of the rudder, but not touching the rudder. He always says: “That’s tricky. Why don’t we put the sling underneath the counter? That’s the logical way.”

“Because that’s not the proper way,” I tell him. “It must go right under the keel. And you have to tie a line between the two slings, otherwise the forrard sling will slide up and the boat will fall out. And by the way, the forward sling must miss the knotmeter impeller, which is here.”

I stab a finger on the architect’s drawing and he looks at me as if I know nothing about boats, as if this is my first haulout. And I stare back at him eyeball to eyeball. People who work in boatyards are rarely properly informed about the customer always being right.

Eventually, after a little huffy fit and a full set of shoulder shrugs, he does it the way I want it, the right way, and I step aboard to remove the backstay and the topping lift so the big steel spreader bars on the crane can lie close to the mast.

This is the part of boat ownership I hate most, the hauling out and the putting back in. If it weren’t for the need to antifoul the bottom, I’d never go near a boatyard. In days gone past we used to lean our sailboats against jetties and wait for the tide to go out. As the water level dropped and the boat dried out on the sandbank, we’d scrub off the seaweed and barnacles, and by the time she was high and dry she was ready for painting, which meant a fine old race against the incoming tide.

We can’t do this any more. The gummint says we would pollute the ocean. Well, if a few stray spots of copper paint on a sandbank constitutes pollution, I hate to think what you’d call the stuff that factories spew into rivers and estuaries every day. I hate to think what finds its way into the water from boatyards where amateurs work unsupervised on their boats on weekends.

In any case, the sea bottom not far from my boatyard is already contaminated with mercury. It’s a declared clean-up site. But they’re not planning to clean it up. That would be too expensive. They’re planning to cover it with clean new sand. They’re going to hide it and pretend it doesn’t exist.

Anyway, all bitterness aside, the point is that the world would be a much nicer place for all of us if we didn’t have to paint our bottoms every couple of years. It has occurred to me more than once that fishes and some mammals, such as dolphins, never find themselves covered in weed and barnacles, as boat hulls do, even though they spend their whole lives in water.

Why can’t we make a bottom paint that acts like a fish’s scales or a dolphin’s skin? There must surely be a fortune waiting for someone who can invent a paint or some kind of skin like that, not only for yachts, of course, but also for large ships.

Give it some thought, will you? Find out why dolphins don’t get barnacles, and get back to me. I have a brother-in-law who’s an industrial chemist. He could probably formulate the paint accordingly. Maybe we could do some lucrative business together and save me a lot of pain every two years.

Today’s Thought
An idea can turn to dust or magic, depending on the talent that rubs against it.
—William Bernback, New York Times 6 Oct 82

Tailpiece
In spring a young man’s fancy lightly turns to thoughts of love
And in summer,
And in autumn,
And in winter —
See above.