Frequently Asked Questions About Narrow Boat Hulls Answered.
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Tue Jan 26, 2016 at 10:22am

At Whilton Marina we frequently get asked questions about steel narrowboat hulls. So in this article we will share these popular questions and give you the answers.

How Do I Know What Condition a Narrowboat Hull is in?

Generally speaking we don't know what the hull is like on the used boats we have for sale, unless the boat has had a recent hull survey carried out. This is why as a company we always recommend a prospective used narrow boat purchaser to commission a survey to be carried out on the boat before proceeding with the sale. 

How Thick Should the Steel be on The Hull?

For insurance purposes the minimum hull thickness must be 4mm.

The majority of modern narrowboats are built using 10/6/4mm plating or steel thickness specification, 10mm is the steel thickness on the hull base, 6mm the sides and 4mm the roof.

Why Do You Black The Hull?

Blacking the hull is a way of maintaining the condition of the boat and protecting it from rusting and should be carried out every 2-3 years. If Two Pack Epoxy paint is used then you are able to go 5-6 years before reapplying.

Can I do the Blacking Job Myself?

Yes if you want, but once you realise the time and effort that is required to complete the task you will appreciate that paying for this service is well worth every penny!

How is The Boat Taken Out the Water to Work on The Hull?

There are three different ways for getting the boat out of the water so that the whole hull can be inspected and treated if necessary.

  • Dry dock: where the boat is floated into a chamber and then the water is removed.
  • Cranin: but this can be an expensive option.
  • Slipway trailer: the boat is floated onto a trailer in the water and a tractor pulls the boat out. This is the most cost effective and popular choice.

What is used to black the hull?

There are two types of coatings which can be used to protect the hull, Bituminous and Two Pack Epoxy.

Epoxy paint is more expensive but it will last 5 – 6 years once applied and a Bitumen finished coating will last around 2 – 3 years.

When opting to use Epoxy the boat has to be grit-blasted to produce a perfectly clean surface before it is applied, this is why it is a more expensive option. However it will save you money in the future saving on the amount of dry docks needed.  

NOTE: You cannot apply two pack to a boat that has been blacked with bitumen previously. All east west narrowboats were blacked with two pack from new.

How Long Does It Take To Black a Hull?

It’s basically a long, messy and hard three day process.

Day 1; The boat is taken out of the water and pressure washed to remove muck and grime, the old blacking and debris like weeds, mud, and rust. The hull is now ready for the new application of paint. If the water line needs more attention, a machine can be used to work on this area. This machine is called a “scrubbler” if it is used during the blacking process it will usually incur an additional charge.

Day 2; Now the hull is cleaned it is ready for painting. The application has to be done manually with a small roller. The paint has a similar consistency as tar so has to be applied in small sections as the paint goes hard very quickly, therefore no machines are used and it is a timely messy job.

Day 3; Repeat day 2! The second coat gets applied and if required you can ask for an additional coat around the waterline (this may incur an additional cost). The boat is then left for 48 hours to dry before it is returned to the water.

How Much Does It Cost to Black a Hull?

We have supplied some estimated price examples using Bituminous paint on 3 different sized boats, each marina or contractor will have their own individual prices so please only use these costs as a rough guide;

Bituminous paint;
57 foot - £820
70 foot - £1000

Epoxy paint;
57 foot - £1,130
70 foot - £ 1,400

What Should I Do to Keep the Hull Well Maintained?

Unless you suspect a problem with your hull, or if you've just had a recent hull survey, then your boat does not need to be taken out of the water every year, but it should be preferably be taken out every two to three years.

Careful cruising will go a long way in protecting your hull! Crashing through ice will damage the paint protecting the hull, as will crashing into banks and locks, so responsible cruising will lessen the chances of the hull being damaged.

When the narrow boat is out of the water you can get the hull pressure washed to enable you to check the hull and stern gear. It is important to check for rust or pitting, particularly round the waterline.

The sacrificial anodes should never be painted over when painting the lower part of the hull as this would prevent them from working.

What Are Anodes?

The correct name for these important lumps of metal is a ‘Sacrificial Anode’ and they form a key part in the boat’s battle against corrosion. Put simply, they have a higher electrochemical value than steel, which means they corrode away faster. They are basically blocks of magnesium which are bolted to the hull at the bow or stern.

Why are the Anodes on a Steel Hulled Narrowboat Important?

The “sacrificial anodes” corrode in place of the metal of the hull and prop, thereby giving protection. So it is important to check the anodes, as their purpose is to prevent electolytic corrosion of the steel plate and the bronze stern gear. If the anodes are half wasted it is vital to replace them to prevent pitting and corrosion of the steel hull. If you do not do this then it can be a very costly mistake.

If the hull is corroded because the anodes are not doing their job properly it can be one of the most expensive things to put right, as it may mean that some re-plating needs to be done to the hull.

What is over plating/re-plating?

Over plating and re-plating are actually the same thing and a boats hull may need a full over plate, side plating, bottom plating or just patching. Quotes for over plating work can vary enormously due to the various degrees of work that may need to be carried out. Watch our video for more information...

Who Decides a Narrowboat Needs Over-plating/Re-plating?

A qualified marine surveyor is the ONLY person that can survey a boat AND then issue it with passed certificates.

Does the Condition of The Hull Affect my Insurance?

Yes! As mentioned above the hull should meet the minimum thickness of 4mm plating or steel thickness specification.

You will need to have a hull survey carried out by a qualified marine surveyor. During the survey the surveyor will inspect the hull (and other areas of the boat if you have a full survey) he will measure the thickness of the steel and check for damage and pitting.

If any overplating work needs doing to meet the 4mm minimum requirement he will recommend this in his report. Once the work has been completed the surveyor will return, check the work and if he agrees it meets the correct standards he will present you with a certificate.

We hope we have answered all your questions regarding narrowboat hulls but if there is anything we have missed, please give us a call or leave us a comment below and we will get back to you!