Antifouling put to the test by PBO readers.

We gave a dozen readers a different brand of antifouling each and asked them how they performed over a season’s sailing. Andrew Simpson reports on the somewhat surprising results.

Which is the best antifouling? The answer, of course, is that there isn’t one. With so many variables, this is probably one of the most subjective questions in the boating world.

There’s simply no fair way of comparing the various products. But the experiences of a variety of yacht owners in a variety of locations, who use their boats in different ways makes interesting reading.

The majority of antifoulings fall into two general groups. The first, and most widely used, are often described as ‘self-polishing’ or ‘erodible’. These rely on ablation – the controlled wearing away of the coating thickness to (a) dislodge organisms clinging to it and (b) to expose fresh toxins to the front line. This approach has its advantages. Firstly, because a lot of what you apply is washed away as you sail, there’s much less build-up over the years. Secondly, since fouling organisms find it more difficult to get a foothold on the fragile surface, lesser amounts of biocide are needed.

The second group are ‘hard’ antifoulings, in which the toxins are leached from a semi-porous, non-ablative resin base. With these, successive coats will add to the coating thickness and, since the whole defence must rely on biocides, there must be rather more of them.

Testing, testing
We concentrated on erodibles, but there are some hybrid products, which blur the distinction between the two.
Traditional methods of testing involve mounting immersed test panels on rafts or dangling them from pontoons. On the face of it, this might seem a reasonable enough approach, but it won’t properly replicate conditions on a boat.

The problem with rafts is that they’re static, typically being moored in sheltered harbours or estuaries. Granted, they do have the tide washing over them, but the flow across their surfaces is nothing like as vigorous as that experienced by a hull under way.

It’s tempting to think that having the same conditions for all must yield valid comparisons, until you remember how the dual actions of ablation and biocide content are traded off. An antifouling that relies more on ablation than it does on biocide will be disadvantaged in a sluggish waterflow and vice-versa. Then there’s the matter of locality. Raft-mounted panels only face local fouling challenges – not at all like your typical cruising boat, which is likely to encounter many as it hops from port to port. Another testing method involves painting patches or strips of different antifoulings on the same boat. Problem gone? Not quite. The flow over a hull varies from place to place, both in its rate and characteristics. The water may be laminar in some parts, turbulent in others, and nearly static in a few places shielded from the main stream. The antifouling in the bow is not living in the same world as one towards the stern; the trailing edge of a keel will see far less erosion than the leading edge. Again, direct comparisons would be questionable.

A different tack
So we’ve taken another tack. The measure of a product often lies in the amount of satisfaction it brings, with many factors influencing opinions.

To find out what you think, we enlisted a small band of readers on your behalf and asked each to try out an antifouling that they hadn’t used before. This, then, is their story, for better or worse. Their boats varied in size and class and so did the way they were cruised. Let’s see how they got on.



Flag Flagship
Due to family bereavements, Martin Hayhow’s plans for last season were disrupted, restricting his sailing to short trips out into the Solent and Poole Bay. For the same reasons he admits to being behind with Grayling’s maintenance schedule.

Martin describes the application of the Flag as being ’straightforward’, and there appear to have been no conflicts with the Blakes Tiger beneath.

The boat is still afloat, but the water occasionally becomes clear enough to see much of the hull, and he can see no signs of significant fouling, though his log impeller (which was not antifouled) emerged encrusted with barnacles.

On the evidence so far, Martin feels encouraged enough to use the same product again.

FLAG
Antifouling tested: Flag
Type: Erodible
PPR:
Boat: Contessa 26ft
Keel type: Long
Mooring location: Port Solent
Type of mooring: Marina berth
Length of time afloat: Still afloat
Previous antifouling: Blakes Tiger Cruising

‘No signs of significant fouling. I’m encouraged to use the same again.

Contact:
Flag Paints Ltd
www.flagfinishes.co.uk
Tel: 01621 785173