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Writer's pictureGC Boat Antifouling

The Critical Role of Boat Antifoul Preparation

Updated: Jan 28

Preparation is the key to success in all facets of life! Your boats antifoul is no different. In this blog we will discuss why the preparation of your boat's antifoul is critical and why machine sanding with dust extraction is superior to wet sanding by hand.


Antifoul Coating Build Up

Improper sanding and preparation of your boats antifouling leads to a build up of antifoul coatings over the years. These extra layers of old antifoul add unnecessary weight to your boats hull. If you have ever picked up a tin of antifoul paint, you know it's heavy! Jotun's Seavictor 40 antifoul, which is a very popular product on the Gold Coast will add 1.6kg of weight to your boats hull per litre applied.

Based on a modest 30ft boat, applying approximately 10L of Antifoul per year, you have added up to 160kg to your boat over 10 years! Sure, maybe it's ablative and some will wear off, reducing the weight slightly, however the added weight can be the equivalent of two adult males!


Have you ever wondered why your boat isn't getting up on the plane as easily as it used to with fuel, water, and the same amount of people onboard? Scratching your head because the boat is serviced and has a "clean bum". The bottom might have minimal growth, but you can't see the extra weight of two people hanging off the bottom of your boat! No wonder it's not performing like it used to a few years ago! Time to think about a sand blast and starting fresh!


Why is Machine Sanding Superior?

Machine sanding with dust extraction provides more than just a "key" for your new antifoul coating, it actually removes layers of old / uneven antifoul and allows for a thorough inspection of the hull to identify any defects before they become costly repairs.


The picture below shows typical preparation of antifoul. It has been wet sanded with 80 grit sandpaper on the end of an extension pole. No care has been taken, just a quick once over to provide a "key" for the new coating. Copper within the antifoul coating has oxidised along the waterline and gone green with signs of crazing / cracking.


Poor preparation of old boat antifouling

If this level of care was taken along the waterline, you can only imagine how the bottom of the hull looks after a quick wet sand with 80 grit on the end of a 6ft pole. No thorough inspection for defects such as osmosis. Likely still marine growth around the chines that will be painted over. Unfortunately this is the reality for most boats on The Gold Coast.


The next photo shows how machine sanding can transform your boats hull. The waterline (and rest of the hull) has been thoroughly sanded with 80 grit on an orbital sander with dust extraction.


Oxidised copper along the waterline is removed, cratering of old coatings eliminated and a far superior key has been provided for the new antifoul coating. The blue colour coming through is a previous application of antifoul.


We are not suggesting that all antifoul must be removed every year back to the primer, however thinning out existing antifoul coatings will eliminate the build up of antifoul and the additional weight on your boats hull. Wet sanding with 80 grit sandpaper on a pole will simply not achieve these results.


Machine sanding boat antifouling with superior results

If you have a boat on the Gold Coast and want your antifouling, Propspeed and Anodes done the right way, why not give us a try? You won't be disappointed.


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