How to Antifoul a Fibreglass Boat

The fibreglass boat antifouling process is no different to the process of antifouling a boat with an aluminium or steel hull. The only variable is the antifouling that you use, as different products are suitable for different hulls. You will find this information either in the product description, in the product data sheet (attached to all our products) or on the back of the tin.

Preparing Your Fibreglass Boat For Antifouling

Preparation is key to any successful antifouling application.

Preparation begins before you even get to your boat. You must make sure you have the correct personal protective equipment – this includes:

•           Eye protection
•           Nitrile gloves
•           A mask that covers your nose and mouth
•           Overalls that do not leave any skin exposed.

To begin preparing your boat for antifouling, pressure wash your hull thoroughly, removing any grime, loose barnacles, and weeds on the bottom. If there is any existing antifouling in a poor condition or a build up of old antifoul, remove it by blasting the hull or using an antifoul stripper. If you do not do this, you can expect delamination, blistering or a decrease in antifouling performance.

Now your hull is clean, inspect it for any areas of damage, including peeling or separation. If there is damage, then fairing and filling many be necessary. We also recommend that you check for any signs of gelcoat damage and osmosis, then deal with them appropriately.

The next step is to mask up any areas, so you only paint the areas you want to paint. With masking tape, you get what you pay for. Purchasing good quality masking tape can save you a LOT of time.

Priming –
Primers are a must for bare surfaces and will help the antifouling properly stick to the hull. Some primers, including Hempel Underwater Primer can even be used as a sealing between old and new antifouling. Like with antifouling, it’s important to check that the primer you are going to purchase is suitable for fibreglass hulls.

The Fibreglass Boat Antifouling Process

Antifouling a fibreglass boat follows the same process as antifouling an aluminium boat, or any other vessel. Here’s a short step-by-step guide.

1. Ensure you are appropriately dressed, wearing the correct safety equipment. This includes eye protection, nitrile gloves, a mask and overalls.
2. Double check you are following any local regulations that may apply to the space you are working in.
3. Make sure you wash your hull thoroughly in order to remove any grime, loose barnacles, slime, etc. If there is a build up of old antifouling, remove it by blasting the hull or using an antifoul stripper.
4. Use masking tape to mask up any areas you do not want to paint.
5. Next, inspect the hull thoroughly for any damage. This may include peeling and separation. If there is damage of any kind, then filling and fairing may be necessary.
6. Using an antifoul primer, coat the hull. This is a vital part of the antifouling application process, as primers help antifouling adhere to the hull. We highly recommend checking that the primer you choose is compatible with fibreglass hulls.
7. Mix the antifouling thoroughly using a stirring stick as many ingredients sink to the bottom whilst the tin has been on the shelf.
8. Apply the recommended number of coats to achieve the required level of thickness.

If you’re looking for a more in depth look at the antifouling application process, we’ve written a detailed, see our step by step guide on how to apply antifoul.

Antifouling Paint For Fibreglass Boats

For fibreglass boats we recommend Seajet antifouling, Seajet Emperor 034 and Seajet Hard Racing 035. Lets take a closer look at both of these antifouling paints:

Seajet Emperor 034:

Seajet Emperor is a strong antifouling perfect for areas with high fouling. Like its counterpart Hard Racing, Emperor is great for racers thanks to its advanced biocides that put a fight up against fouling and even contain anti-slime qualities. As Seajet 034 contains no copper oxide, white antifouling will stay bright white and will not turn your hull green.

Seajet Hard Racing 035:

Hard Racing is the perfect antifouling for yachts and motorboats. The high-performance antifouling works quickly against fouling, ensuring your boat has a sleeker, faster journey through the water. It is worth noting that Hard Racing is designed for boats with speeds of over 70 knots.

We do stock other fibreglass antifouling paints – if you have any questions, feel free to contact us.

Applying Antifoul

Now you have found the right antifouling, you need to work out how much you will need. For this, we would recommend following manufacturer guidelines. Many people have made the mistake of not applying the recommended number of layers at the correct thickness in an effort to save costs, and then ended up spending more money than they would’ve done fixing the problem that they created. A paint thickness gauge will ensure that you have the right level of thickness.

Ensure the antifouling is thoroughly mixed before application as often, many of the ingredients sink to the bottom of the tin whilst it is sat on the shelf. If possible, apply the antifouling late morning or early afternoon as this will avoid dampness and overnight dew. Application is typically via brush, roller, airless spray – however this does vary from brand to brand.

Fibreglass Boat Antifoul Paint

In conclusion, the fibreglass antifouling process is the same as any other antifouling process, just remember to check that any antifouling and/or primers that you are going to purchase are suitable for fibreglass hulls.

Allow us to introduce ourselves. We’re Kent’s largest chandlery and have been selling antifouling paints for over 30 years – you can find out more about us here.

Our superb range of antifoul paint has been hand chosen by our highly experienced team (or crew, as we like to call them!). All our antifouling is from leading brands including Hempel,International and Seajet.

Since you’re here, why not check out other antifouling blog posts that we have written?
How To Apply Antifouling
How Often Should You Apply Antifouling?
Antifouling An Aluminium Boat