WEEDKILLERS!

Using the most effective antifouling will save you money, but which of the many paints available really gives the best results? To find out once and for all, we decided to coat the hull of our own boat with a rainbow of 11 different biocides, and leave them to battle the barnacles for a whole season. Here’s how they coped.

Report by Mark Turley

Antifouling your hull is a thankless task. It needs doing every year, and it invariably seems to cost more money than you had budgeted for. Worst of all, all your hard work literally disappears from view as soon as you put your boat back in the water!

However, try to skip a season, or eke out the periods between fresh applications, and you will soon regret it. You’re asking for a noticeable drop in the bat’s performance and fuel efficiency once living organisms start to colonise the hull, and you’re giving yourself a harder job of cleaning and repainting the bottom when you do eventually bite te bullet.

The fact that antifouling is a chore is all the more reason to make sure you get good results from it. And the fact that there are massive disparities in the price of these paints (with some products costing almost three times the price of others) makes it all the more necessary to understand what you are getting for your money.

So which products are most effective at keeping weed and barnacles at bay, and which offer the best value for money?

In an attempt to find out, we gave our Sealine F37 a very fetching striped underwater colour scheme…..

SIX MONTH TEST

At the beginning of last season we gathered a selection of antifoulings which should be suitable for our boats and its usage. These numbered 11 in all from eight different manufacturers. We then decorated the underside of Calm Voyager amidships with a stripe of each paint running from the waterline down to the hull bottom (with an inch gap between samples), plus a ‘control’ panel coated with nothing more than the base coat primer.

Each of the antifoulings was applied in early May, and in accordance with the manufacturers’ instructions, with two coats giving a ‘dry-coat’ thickness in the order of 80-100 microns.

During the make-over we took careful note of how easy each paint was to apply; where the paint goes on quite thinly, it is less easy to obtain a suitable thickness than it is with those which are more viscous.

In a separate test to compare how our test samples would fare in different water conditions, we also painted bands of them on pieces of primed Perspex sheet, and left them immersed at Brixham Marina in Devon and at Lymington Yacht Haven in the Solent (we also riged one in the muddier waters of the Essex Estuaries, but sadly this did not survive the season).

Over the season Calm Voyager clocked up some 200 engine miles), which is four times the average for a motor cruiser. The panels were also immersed for a season, but in a static state with limited movement of water around them.

In November, the boat was lifted and the Perspex panels were retrieved for inspection. Each individual band of paint was inspected for the amount and type of fouling that had adhered to it over the previous six months.

MBM RECOMMENDED: FLAG FLAGship

Type Conventional antifouling from a low-cost, one-product brand.

Application A good thick consistency, and it slaps on easily.

Time between coats Minimum 6 hours

Time before launch Maximum 2 months

Hull performance A thick coating of slime around the waterline but only a light one underneath.

Panel performance A build-up of a fur-type weed in Brixham, but only light slime in the Solent.

Enquiries Tel: 01621 785173
www.flagfinishes.co.uk

MBM ratings
Performance * * *
Value for money * * * *
OVERALL * * * *

Verdict

Overall, we were impressed by what our test samples achieved over a six-month period. There was limited fouling across the board, while our unpainted control strips were heavily colonized. There was little disparity between the brands, but we can pick out some star performers. Blakes Ocean Performer gave marginally the best result but then you pay a premium for it. Jotun’s Mare Nostrum did almost as good a job for a rather cheaper price. And if your budget is really tight, FLAG’s FLAGship does an adequate job at a bargain-basement price.

MBM March 2004