Painting a sailing catamaran

Catamaran Painting
Undercoat - INTERNAL

The undercoat of the yacht finally shows its true colour (so to speak).

Its here that the painting learning curve starts. The small things that you once payed no attention to like daily temperature, humidity and measuring to the gram, finally hit home. These three things are so important in doing the job once and correctly.

The frustration of runs, spray nozzle blocking are so easily overcome with some self-training on possibly the inside of the hulls, till you get confident with your own painting practices.

Spray nozzles, spray-guns, respirators and compressors are supplied in more detail in our Diaries.

Choosing the correct Inline Airflow Respirators and spray equipment saves your health and definitely minimises the spray painting time. The 'Two-Pack Paint Warning' and 'Dont kid yourself about Two Pack Carcinogens' articles will be information well worth consideration.

Fairing and
Two-pack Painting

In our case, the last of the external fairing was tackled. A little more effort in prior preparation, payed dividends down the line with the finish.

It was at this late stage that an indentation was found down one side and it was back to filling and fairing all over again. With the kind assistance of a few friends namely Andy (may he rest in peace) and John, this was completed to perfection.

Added to this was our late decision to add plinths to the whole yacht. They all had to be made, glassed and faired. This did add another two weeks of part-time boatbuilding. From here it was smooth sailing, the rest of the undercoat was sprayed on in two thick coats. The following day, this was very lightly sanded, ready for the topcoat.


Catamaran Painting
Undercoat -EXTERNAL

The ‘high-build’ undercoat was sprayed on with a large nozzle (around 2.5mm – 3mm).

Anything smaller tended to take too long with this type of undercoat and the undercoat needs to be further thinned prior to spraying.

They (the Wattyl paint technical advisors) are fairly particular with the thinners used too, as a stronger type is required with the resin based paints, a small blow as this now has doubled the thinners cost.

The initial undercoat took four full days to apply, which completed 95% of the internal fittings and what a magical difference.

All of a sudden the small imperfections had mysteriously gone and the white undercoat had done two things:
> Made the boat look larger internally, and
> Definitely lightened up the darker areas.

The second undercoat was then laid on thickly (using the 2.8mm spray nozzle).

The advantage with this was that all the blemishes were covered and small timber indentations / marks would be covered and when sanded back should come out reasonably smooth, which it did.

The disadvantage is the cost due to the increased amount of undercoat.

We have chosen to sand this initial coat back to a smooth surface (using 120 grit paper) even if it meant coming back to the timber in places.

This did take a very long time, in fact four days longer than planned and we are not after a car gloss finish either.

When they are all in place, the painting system seems to work OK and run smoothly.

"Dont kid yourself about Two Pack Carcinogens"

Stippled finish

Another challenge was the compatibility of paints (specifically the stippled paint, which we used on the under side and bow areas) and the two-pack final coat.

We needed the deck walking surface to resemble a reasonably smooth textured feel as opposed to the coarse sandpaper feel. This surface too had to be very easily washable with no small pin holes. The small holes would prove prefect breeding ground for algaepainting001 especially in the cooler spots of the boat.

While additives to paints were an option, none of the local hardware paint manufacturers provided a suitable textured easily washable finish (that we liked) with the exception of one manufacturer, which also happened to be compatible with our Wattyl two-pack top coat.

It is the same paint used in the car industry for the undersides of the wheel wells that prevents chipping and rust.

It too has a dampening effect with regard noise and best of all, is compatible with 2-pack paint. We trialled three brands and the best textured came from K & R products.

This has presented so well that we have now used this on the saloon ceiling as well as those internal patches where the finish was a little so so … (if you know what we mean).

Non-skid water-based Paint

Sailboat non-skid paint is a must as far as we are concerned.


The catamaran external deck areas were lightly prepared with 120 grit paper and the Tredgrip laid in 5 coats.


The first coat was very watery and the they slowly increased in texture thickness to the last coat, complying with manufacturer instructions.

This brand has proved very successful, with adhesion being brilliant over the last four years.


The rubber compound additionally provides thermal qualities internally, reducing rain noise and improving temperature ranges. We discuss these and more information in our Boatbuilding Books.

Antifouling and
Deck Tred (Tredgrip)