How and when to apply antifouling to a rib?

Data 21 June 2021
This question is the subject of discussion in every boating forum, and despite the title, the first aspect to consider is not how and when, but whether it is really necessary to use antifouling to protect your boat semi-rigid. Before tackling all the technical aspects, let's anticipate the answer: it depends.

Handle with care

Among the pros and cons to consider, there is certainly the commitment that this type of maintenance requires in terms of time and manpower. In addition, if you are doing the work yourself, you must ensure that you do it in a well-ventilated environment and with appropriate protective measures, as the substances you are handling can be potentially dangerous for you, for the environment. and, in some cases, for your boat. 

The Yes party

Antifoulings obviously have many advantages, to the point that their use is essential in many cases. The growth of algae and fouling increases friction with the water, which deteriorates performance and fuel consumption. Most importantly, failing to protect your hull if you plan to leave it in the water for long periods of time could result in irreversible damage. Any shell has in fact a certain degree of porosity and any agent which attacks it inevitably ends up compromising the integrity of the gelcoat and leaves the path free for the entry of water. Repairing this type of damage is neither easy nor inexpensive, and in some cases, it is simply not possible.

Antifouling, the unknown

But what is an antifouling? In general, this can be defined as paints intended to protect the hulls of boats which owe their effectiveness to the presence of biocides (the most common is copper oxide), released into the environment in a controlled manner, so as to only be effective near the boat. Generally speaking, they can be divided into two categories: the former also exploit the mechanical effect of water to keep the hull clean, and are generally easier to remove because the layer of paint gradually thins, while that the latter are based solely on chemical action. 

And the tubes?

Although there are various products marketed as being specific for this use, we absolutely do not recommend using these chemical compounds (like any other harsh detergent) on rubber parts. The reason for this is that you would risk exposing these parts, especially the joints between the different sections, to such a constant risk of deterioration that it would far outweigh the possible benefits.

When it is essential and when to do without it

This is obviously the central point. The key factor is time: are you the type of person who only launches your boat for the day? You can do without it. But if you plan to leave your boat in the water for three consecutive weeks or more, you are definitely in the case of those who cannot give up on protecting their hulls with antifouling paints.

Before getting to the heart of the matter, we would like to give you a very important piece of advice: antifouling, especially on a new hull, is a long and tiring job. We advise you to trust a shipyard to be sure to bring home an optimal result, whatever your level of expertise. But if you can't give up the pleasure of taking care of your boat, here are some suggestions.

Before you start: safety first

As we have already said, these are toxic chemical compounds that require all the necessary attention (ventilated environment, gloves, work glasses, mask with activated carbon filters).

Used hull, watch out for residues

In the case of a used hull, before starting to apply the paint to the hulls, make sure that the residues of the previous "layers" of antifouling paint or other impurities present on the structure have been removed: a pressure washer can be sufficient in many cases, but you can also use a nautical cleaner. The sander, on the other hand, is a tool suitable for expert hands: if you are in the condition of having to use it, you come back to point 1, that is to say, you must ask yourself if you should do call a professional.

New hull, grip problems

Here, things get complicated. A hull that has never been launched is in fact very smooth, so it will be necessary to mattify the surface to facilitate the adhesion of the paint. Obviously, you will need to use a very thin paper to avoid too much denting of the gelcoat (around 400 grains). For the same purpose, you will need the primer you need to use (we suggest two coats) before proceeding with the actual painting.


Cover the cart with a nylon cloth, put on a charcoal mask and gloves, sand and / or clean the shell, you are ready to begin. The use of rollers will make the work faster, but here there are no specific instructions: brush, roller or spray, the choice is personal. Remember the next morning to check for any uncovered spots and to move the boat around the cart lightly to cover the spots where it was resting when you did the heavy lifting.


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