Film thickness Try and achieve a minimum dry film- thickness per coat of no less than 60 microns (approx. 120 to 150 microns wet). Use a Wet Film Thickness Gauge to measure by placing one edge flat on the wet antifoul. A natural-fibre roller should give roughly the right thickness.
APPLICATION Number of coats 1-3 layers (total film thickness for all layers max. 100 µm DFT) On places where growth of lichens is highest (water line) and on places exposed to damage (keel, prow etc.) is recommend to apply extra coat of antifouling paint.
Thinning your antifouling product can be useful in hot or cold temperatures if its flow properties are no longer as they were. Diluting antifouling can also be advantageous in extremely windy weather or when applying a top coat.
Removal Method 1: Sanding
Using 80-grit coarse abrasive paper, wet sand your boat to reach the desired level or when all of the antifouling has been removed.
The amount of antifoul paint that needs to be applied will depend on the condition of the hull. If your boat is antifouled every year, then it is likely it will only need 1 coat. However, it is has been a few years since the hull's last antifoul, then it may need 2 coats.
If the existing antifoul is not in good condition it will need to be scraped back. If you do not remove this antifoul you risk the new coat of paint peeling off. There might only be a few places that you need to scrape off.
Applying a primer is a must for bare surfaces and will also help the antifoul will properly stick to the hull. Many primers contain technology that enables multiple coats to be applied in just one day. Furthermore, primers including Hempel's Underwater Primer can also be used a sealing between old and new antifoul.
The clear coat should be wet-sanded with 400 grit sandpaper. This is to replace the orange peel with finer and finer scratches, which will eventually be filled in with polish. The sanding steps help diminish the clear coat until the entire surface is smooth.
Lightly wet-sanding the surface with 60 or 80 grit wet-and-dry paper wrapped over a sanding block will provide a key and help the antifoul to adhere well. Dry-sanding is not recommended because of the dust it puts in the air which can be inhaled, or get onto other boats' hulls and decks.
Complete a high pressure fresh water wash to remove loose antifouling. Ensure all residue and wash water is contained and disposed of according to local legislation.
Microfibre Roller 9 inch x 12mm. A roller that is suitable for use when applying antifouling and primers. The woven synthetic fibre is designed to provide superior paint loading and to release paint evenly to give a smooth delivery and consistent finish.
Here's how antifouling benefits your boat: Prevents Marine Growth: The biocides in antifouling paint actively repel marine organisms, stopping them from forming colonies on the hull. Without this layer of protection, marine growth can quickly accumulate, causing drag and slowing your boat down.
Typical coating thicknesses can range from a few nanometres to several centimetres. As an example, Titanium Zirconium (TiZr) coatings can be 1nm to 5nm thick, while anodic films can range from 0.5μm to 150μm, paint coatings can be up to a couple of millimetres in thickness.
For insurance purposes the minimum hull thickness must be 4mm.
Wet sand the clear coat in a back-and-forth motion. This replaces the orange peel with finer scratches. Start with ultra-fine 1,200-grit sandpaper for DIY painting or 3,000-grit paper if it's a factory paint job. Use light and steady pressure when wet-sanding.
Excessive product load per coat and too much distance between the spray gun and the workpiece will result in a less even coating, favouring the orange peel effect.
Typically, 2-3 coats are required for one season of use. However, if your existing antifouling is in good condition, a touch-up may be suffice. Also, some antifoulings, including Seajet Coastal 037 Antifoul and Hempel Tiger Xtra Antifoul only require one coat for a whole season.
3M's ScotchBlue Masking Tape has widely been regarded as the best masking tape for marine applications, thanks to its great balance between UV resistance and clean removability.
A good average rule of thumb is to expect $125-$150 per linear foot. For a 26-foot boat, this would mean the cost of bottom paint ranges from $3,250 to $3,900 for a quality job. And don't forget, you'll be paying to paint the bottom of your boat every few years.
The process of bottom painting can be messy and costly to do every year. It requires sanding down the boat's bottom and repainting with new antifouling paint to continue protection. But luckily if you use multi-season paint you can get away with a touch up for a year or two.