Hard Vs Soft Antifouling

A common question we get asked is “How long will my antifoul last?”

While there is no one size fits all, I will help you gauge a timeframe as I see many different boats across Sydney.

The main factors you should consider are:

  • What type of antifoul are you using, in particular soft or hard? Soft is also referred to as ablative.
  • How often do you use the boat?
  • What area, and how far up the river do you keep the boat? For example, Sydney Harbour or Port Hacking?
  • Do you employ a diver to clean the boat periodically?
  • What is the hull material? For example, timber, fibreglass, alloy, steel etc.

You may be wondering, what is the difference between soft and hard antifoul?

Soft  (ablative) antifoul is self-eroding or “polishing”, which means when the boat is underway the antifoul is designed to wear a thin layer away, and with it, any growth that has started.

Hard antifoul is as the name suggests, a lot harder. This type you would need to scrub to remove the growth, but with scrubbing, the antifoul is less likely to lose its protective qualities when compared to soft.

One scenario where antifoul and prop speed coatings work best is through regular use of the boat. It is harder for growth to get a good hold onto your hull and running gear if it has water moving over the surfaces, cleaning away the growth. A simple solution to this is regularly taking the boat out, or running it in gear on the mooring/berth (if safe).

Why does location matter?

If you keep your boat further up the river, the water it lives in is called brackish (less salty water). As a result, marine life does not grow as quickly. The closer to the outlet or “heads”, where the water is salty and full of nutrients, you will likely get quicker and more damaging marine growth.

Employing a diver to regularly clean your hull is a good way to ensure that the hull is clean and all the running gear is in good order, but first you must make sure you have the correct antifoul to do so. Hard antifoul is best suited to this, and most soft antifoul brands will advise you not to scrub as it can take away too much of the antifoul.

How does hull material affect my growth?

The hull material is important when it comes to the brand and specific type of antifoul you choose. Different formulas are used for timber, fibreglass, aluminium and steel hulls.

Antifouling paint used for aluminium hulls/sterndrives should not contain cuprous oxide biocide as the high copper content can lead to corrosion problems. This is often found in paints used on fibreglass hulls, so it’s important to use a different type for the outdrives.

What about anodes?

It is important the correct anode is paired with your antifoul coating, as it can greatly increase the life span. There is a large number of factors to consider such as:

  • Is there a shore power lead connected?
  • Is there a galvanic isolator?
  • What type of water does the vessel live in?
  • What sort of metals are underwater?

Due to the complexity of all this, it’s definitely very specific to your boat and location. Generally your local slipway or yard will have a good idea of what has been working based on other similar vessels.

So, how long does my antifoul last?

In general, we see antifoul last anywhere from 6-15 months around the Sydney region. I typically witness less shell growth when a boat lives further up the river. The most common case we see is that owners get the antifoul done on a 12-month basis, to coincide with their engine, drive and anode maintenance to incur less cost and less down time for the vessel. It most cases, we recommend a 12-monthly schedule, unless the boat lives in an area of high growth and gets little use, where 6-9 month antifouling might be needed.

Below is a simple explanation of different water types

types of water

About The Author – Donald Nicholson

Growing up on the Isle of Barra on the West Coast of Scotland (population of around 1100), Don’s family owns and operates a fleet of fishing vessels that mainly fish for prawns and lobsters. At age 17, Don completed a degree in Marine and Mechanical Engineering, and has spent the last decade working in numerous engineering roles across the globe, before settling in Australia in 2017. Don specialised in diesel engines working on a diverse number of vessel and engines across Pittwater. Don has also completed his Diploma in Marine Surveying, and is a valued BoatBuy team member. Liked this article? Feel free to get in contact direct at don@boatbuy.com.au.


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