Speed, drag, fouling. These words are quick off the tongue whenever a competitive racing boat owner considers maintaining the condition of their boat and more importantly, the speed they can achieve in order to cross that finish line in the best time possible.
There are places to be gained and lost on every corner of the race course. And that’s why it’s so important to tick every box before you set sail; Keel & rudder fairing, recessing skin fittings and pristine foil condition. Just as important as these factors is the smoothness of your hull surface for low friction.
Whether fresh off a triumphant victory, striving to improve your position from that last difficult race or simply just aiming to climb up the knot ladder, ensuring you have optimal fouling defence is of paramount importance.
There are two camps with how to do this effectively. Some prefer antifouling paint that is applied in a super-smooth fashion. Others are beginning to utilise the benefits of foul release paints instead.
What’s the issue with drag and fouling with boat speed?
Ultimately, poor frictional resistance due to surface roughness is detrimental to your boat’s racing speed. Enhanced drag resistance can allow your boat to combat this issue and increase speed. And what is the main culprit for causing excessive surface roughness? You guessed it… fouling.
Alarmingly, a modest amount of fouling in the form of slime or minor macro-fouling species can lead to a loss of 0.2 knots. And whilst losing 0.2 knots won’t matter much to a cruising yacht, for a racing boat it can make a half hour difference on a 100-mile race and be the difference between you gain 30 seconds or losing it. So, you can imagine the excessive snail-like effect an accumulation of fouling from your boat being left unprotected in the bay for a few weeks can have on your race winning time.
In addition, even a small amount of growth will increase the amount of power used to get on the plane which in turn significantly increases friction and as a result, increases fuel consumption.
In a nutshell, the way to fulfil your boats top speed potential in relation to its surface is to have a polished, ultra-smooth hull along with immaculate propellers for optimum drag resistance.
What have people done about fouling on racing yachts in the past?
No different to all other boat types, the standard method of combating fouling over the years is the application of antifoul paint coatings. Most eroding antifouling paints are not recommended for speeds above 17 knots, so this factor has likely limited boat racers to hard racing types.
The idea with hard-antifouling coatings is that the copper biocide leaches out slowly over time when in contact with sea water, but it has enough durability to take a grounding without damaging the coating. In particular, if your boat needs to be burnished to a smooth finish before a race or you have a small cruiser that is kept on a drying or semi-drying mooring, hard-antifouling paint has been considered the go to choice.
Eventually however, after a few seasons and the biocides have been exhausted, you are left with a build-up of hard paint film that requires removal. The product becomes unsound and does not retain sufficient internal strength to be able to hold together when new compatible antifouling paint is applied to it. This results in a layer of unwanted ‘dead’ paint contributing to surface roughness, as well as the labouring task of applying the antifoul coating after you have stripped your boat down.
Why are the benefits of foul release coatings on yacht speed?
Foul release coatings rely upon a silicone based paint which offer a smooth surface finish meaning extremely low drag resistance. Studies have shown the positive effects of foul release paint on drag resistance and also how the surface roughness compares with antifoul.
In essence, foul release coatings offer a lower friction surface that has the additional benefit of self-cleaning on boat speeds exceeding approximately 20 knots. Together with optimizing all your other boat speed variables, incorporating an effective foul release coating can increase your boat speed with reduced drag whilst remaining eco-friendly, without having to endure the task of reapplying hard-antifoul coating year after year.