How to antifoul your boat

Grandezza 26

Get your boat squeaky clean with this easy to follow guide on antifouling.

5 PsPreparations: Remember the 5 P’s, perfect preparation prevents poor performance!

The first step is to get your boat lifted and pressure washed thoroughly, which should remove some if not most of the existing growth and flaky paint. Don’t wait for the boat to dry before washing, as this will make it about 10x harder to remove that growth! For more stubborn patches, invest in a good scraper or pay to have UHP (ultra-high pressure) blasting if available.

An often missed step is to measure where the waterline is while it is still marked in the existing paint. Use a tape measure from a known location (deck fitting, porthole etc…) to the existing waterline and write it down! At least three measurements are needed to ensure a straight line, so I would suggest one at the stem, one at midships and one at the rudder stock.

If you have a lot of existing layers of paint, it will probably be necessary to remove them to get a good surface finish and let your new paint cover evenly. This will not be a pleasant job, but will be worth it later.

Sanding HullMake sure you wear safety kit such as goggles and facemasks

Don’t eat/drink anywhere near your boat while you’re doing it, as the paint is most likely highly toxic.

When stripping back the layers, look for a good base to start from. If all the layers are flaking, rough or worn-away, going back to bare hull might be the best bet. Again, a scraper is a good choice, or some coarse sandpaper, which will smooth any rough or uneven patches at the same time.

Some paints require a primer or barrier coat to work effectively, but you should think about using one anyway. Quite often they offer a little more protection for your hull than using antifoul alone, and if you use a primer or barrier coat, ensure you apply it to the whole hull.

Paint reactions can also be an issue, so do a small test patch and check, but if you have any doubts, make merry with the primer.

Before you think of painting though, it’s a good idea to invert the cans of paint the day before you plan on applying them, as it helps mix the solids back into the paint, making it easier to mix to a consistent mixture the following day.


Boat MaskingMasking off: how straight is straight?

Now you have done a lot of the dirty jobs, it’s time to re-draw the waterline.

Remember those measurements you took earlier? Well break out the tape and a (non-permanent!) felt tip pen, and mark small lines at the points you took measurements from. Don’t use regular width masking tape if you can, as a thick tape will allow you to be a little less careful when painting, speeding up the task. Aim for a 2” tape as a minimum.

Once complete, ask someone else to hold one end of the tape at the bow and walk slowly towards the stern. Keep the tape away from the hull to begin with, and when you have a few feet of tape between you, begin to offer the tape to the hull. Make sure you are holding the tape in line with the next measurement, and don’t press the tape down firmly until you stand back and check it hasn’t gone pear-shaped.

Also remember to mask off any anodes and through-hulls you don’t want painted, as well as your propeller. Anodes will only work if directly exposed to seawater, so make sure you can see zinc at the end.

Another thing to consider is not to use copper-based paint if you have outdrives or a saildrive, as using them could result in the drive disappearing quicker than anyone would like.

Boat Antifouling Painting: Probably the largest canvas any inner child could want.

Firstly, you’re going to need a nice day. Applying any paint wet conditions usually results in the paint flaking off at the first opportunity. Working indoors or under cover may be an option, but even high humidity can affect the paints effectiveness.

Small foam or short-hair rollers are quicker and easier than using brushes, but you will still need a selection of brushes to get to those hard to reach areas.

Make sure you have everything you could need before you think of opening a tin, most importantly;

  • Brushes/foam rollers,
  • Brush cleaning materials,
  • Extra masking tape,
  • Rags,
  • Decorator’s pots,
  • Protective clothing (full length sleeves/trousers, goggles, masks, disposable gloves)
  • Clean stirring sticks,
  • And lastly, enough paint!

Make sure you give any paint a good stir before use, as active ingredients have a habit of separating out and sinking to the bottom.

If you are using a primer or barrier coat, this will need to be applied first (basic advice I know!) and given a light sanding once fully dry to give the next layer a good surface to stick to.

If you are using a roller, try not to rush and flick paint everywhere, it’s a pain to have to clear up and remove it from your topsides. And the yard manager will thank you for not making a huge mess.

Use the manufacturer’s recommendations to calculate how much paint you will need to apply to your boat, and make sure you actually use this much, so don’t skimp. The paint it expensive, but less expensive than having to re-do it all because you didn’t use enough! Make sure you order a little extra paint, so you don’t run out halfway down the rudder!

Yachting and Boating World have a handy paint calculator that you can use if you can’t find the manufacturers guide, as well as some videos by SeaJet in their expert advice section.

If you have access to one, a paint thickness gauge will be a better indication of layer quality than quantity used.

Write down how much you use, preferably with photos of empty tins with your boat in the background and lots of photos of the steps of applying it, as if the paint doesn’t work, you can contact the manufacturer and ask nicely for a refund/replacement paint. (Yes, it does happen sometimes!)

Impress upon them the costs and effort you went to, and how disappointed you are. Maybe you’ll post the failure online to your blog/forum, they won’t want anything bad about their product online, so even a threat is a big deal for them. It’s a little extra insurance, and they will probably find an excuse for why it didn’t work, but if enough people do it, the manufacturers will soon learn that their products have to work as advertised.

Check how long your paint takes to dry, both to recoat and to harden fully ready for use, and allow for this when booking your lift in.

Now you’ve done the hard work, it’s time to enjoy the benefits.

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