News article created on 3 March 2017

A hull lot of love

Keeping your boat afloat with regular hull maintenance.

Tooley’s Boatyard Location: Tooley’s Boatyard, Banbury, Oxford Canal

Whether your boat is made out of steel, wood or plastic there will be times it will need to come out of the water for essential maintenance. Steel boats are usually removed from the water for blacking every two to three years. As the owner of an older narrowboat, the regular chore of hull blacking is always combined with a slight anxiety about the condition of the hull. This is fuelled by most marine insurance companies paranoia of sinkings which leads to their demands for a hull condition survey when a boat reaches important milestone birthdays.

Time for a survey

This year was a milestone birthday for our girl and there was no escaping a hull condition survey  to keep our boat properly and comprehensively insured. For our own peace of mind too we wanted an ultrasound check to ensure that whatever electrical problems had plagued the hull in her very early life had not returned. For those of you who don’t know, steel hulled boats can turn into a fizzing electrical battery which corrodes the steel if there are stray electrical currents around. And one thing you don’t want your boat to be is a colander! This is why boats have anodes fitted as these fizz away instead of the hull’s steel.


We booked a week in dry dock at our local boatyard last year along with a surveyor. You often have to book a long time in advance, especially if you want a summer month or you moor in an area with a lot of boats. Into the dock we went on a Saturday morning in February and our surveyor arrived just as the water receded from the dock. Much to our relief the first sight of the hull below the waterline in four and half years was very good, despite having delayed blacking to coincide with the thirty-year survey. Even as the last of the water was pumped from the dock, pressure washing and the hull survey commenced. It’s amazing how much water weed and wildlife like mussels you find stuck to the hull and it takes some effort to get it off!

Pressure washing a narrowboat

Pressure washing the hull

Good preparation is the key

After pressure washing any loose paint and stubborn bits of marine growth need to be removed with a wire brush, either manually or with mechanical help. Finally, any areas of rust need treatment with a rust converter/anti-corrosion protection product before painting can commence. Much to our relief the ultrasound results of our hull survey were very good indeed and no new pitting was discovered. However, next time we dock, we’re going to have to bite the bullet and scrape the bottom, paint it, and fit extra anodes to the base plate to guarantee that it outlives our lives on the boat. There’s definitely two schools of thought regarding the painting of base plates with those for and those against. It’s a horrible job, often working in a very confined space.Removing loose paint from the hull with an angle grinder

Removing loose paint

Protecting the hull

The final stage of docking is the painting of the hull. In the distant past tar was used to paint boat hulls. More recently bitumen based paints or Two Pack Epoxy Paint systems are used for steel hulls. GRP or plastic boats use hull treatments that prevent osmosis. On this occasion we used a new bitumen water based paint instead of a traditional bitumen paint. We always try and get at least five coats on and below the waterline and at least two above the water line. The new paint allowed us to do eight coats below the water line and four above over four days before we had to stop painting and allow drying time. It will be interesting to see how it lasts the next time our boat is out of the water.

Letting the water back into a dry dock

Letting the water back in!

Floating the boat

Late on our final night at the yard it was time to flood the dock again so as to be ready to leave the following morning. It’s a relief when the hard work is over, but you do still worry if the paint is sufficiently dry, and whether or not you are going to scrape it off again once you leave the safety of the dock. As the water rises the boat’s running gear slowly disappears from view and she seems to come alive again on contact with the water. I am so looking forward to cruising again this summer.

About this blog

The boating team

Find out what the Canal & River Trust's boating team have been up to.

See more blogs from this author