How much does she weigh? That’s not a question that you will often hear in polite society. However, when discussing boats, it can lead to some interesting answers, depending entirely on who is asking. In this article we are going to see if we can provide an answer to the question of how heavy is a canal boat?
So, how heavy are they?
Well that depends on a number of factors. Some obvious, some not so much. First it should be pretty straightforward to assume that the more things you have on board, the heavier it will be. The lightest a boat will ever be is when it is brand new, from then on it will only get heavier as things are added,
On average, a moderately kitted out narrowboat will weigh somewhere in the region of 20 tonnes. If you are interested a tonne is exactly 1000kg. So, in this instance as a ballpark figure, a canal boat will weight around 20,000kg!
If you want a rough rule of thumb you can make a quite a close estimate using the following formula. For every metre of boat, count one tonne. So, for an 18-metre boat, you’ll be somewhere in the region of 18 tonnes. Simple enough?
If you want to get all technical, we can refer back to Archimedes… If you paid attention in school you will know the story of him jumping from his bath and shouting ‘Eureka’! His theory was all to do with calculating weight by using water displacement. This is handy as we are talking about boats, and as you’ll know, they sit on water.
One cubic metre of water weighs exactly 1000 kilograms. Therefore, if you can work out how much water has been displaced by your boat you could, in theory, work out how much it weighs. Provided you can make a rough estimate of how much boat is under the water, you will know how much your boat weighs.
Working entirely in metres… The draught of a boat is the distance from its lowest point under the water to the surface. It should be easy to work out if you know the total height of your boat. From there multiply this by the width (or beam) of your boat. Multiply this by the length of your boat to give you a volume. And from there multiply by 1000 to give you your answer in KG. Want an example? Here we go: –
- Boat draught: 0.5 metres
- Boat length: 17 metres
- Boat Beam: 2 metres
So, let’s plug our numbers into our formula… (Draught x Length x Beam = Water displaced in cubic metres)
0.5 x 17 x 2 = 17 cubic metres of water displaced. And as we know 17 cubic metres of water weighs 17,000kgs.
Hopefully from the above you will have seen that our rough rule of thumb with regards to boat length works perfectly with this example too. The boat is 17 metres and the weight is around 17,000kg!
Knowing the answer to the question “how heavy is a canal boat” might be important for several reasons. If you ever need it removed from the water to be blacked, you may need to organize a crane capable of lifting it. Another reason might be working out how much ballast you will need to trim your narrowboat. With the above information you will be able at least make a rough guess as to how much your canal boat weighs.