Freshening up your anti-fouling at the start of each season is a tedious necessity, but necessity it certainly is. Chris Beeson explains why

What difference does fouling make?

Even light fouling, like slime, can reduce your speed by 5-10 per cent. YM technical editor Graham Snook noted his usual upwind speed of 5.5 knots reduced by half a knot with moderate fouling, ‘Like it’s got ’flu,’ says Graham.


This amount of fouling will make a notable difference to both speed and handling

Fouling, like that seen here on a Contessa 32 will provide significantly greater drag and could affect close-quarters handling, and you’ll notice it instantly. Fouling rarely grows evenly, as one side of the hull is often more exposed to the sun, slowing speed on one tack.


The owner of this yacht could only make one knot under power

It’s not just speed through the water that’s affected. Growth on propellers can also significantly reduce power output.

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Nigel Calder noted that ‘with just a handful of barnacles, fuel consumption increases almost 50 per cent’.

The owner of this yacht, with its heavily barnacled prop, found she could only motor at one knot.

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