I have always used airbags in my boats as they prevent part of the boat filling with water during a capsize. After a recent forced swim I was interested in how heavy my boat was when it was filled with water.
I currently have a couple of liquid logic boats – a Stomper 90 and a Biscuit 65. The Stomper has a volume of 90 gallons or approximately 341 litres. The Biscuit has a volume of 65 gallons or approximately 246 litres.
Here’s the maths –
1 Litre – The space occupied by 1 kg of pure water at the temperature of its maximum density (3.98 °C) under a pressure of 1 atmosphere.
Assuming that my Stomper (all fittings removed) is filled with pure water at 3.98 °C at 1 atmosphere then the mass of the water would be 341 kg! The fittings within the Stomper will of course reduce the volume of water able to occupy the space.
My current set of airbags within the Stomper have a total volume of 60 litres. Therefore they would prevent 60 litres or 60 kg of water to occupy an area within the boat.
So lets assume I have taken a swim and that my Stomper has filled with water (no air pockets left), and as an over estimate lets assume that all of the fittings and the airbags prevent half of the 341 litre volume being filled with water. Therefore the 170.5 litres of water in the boat has a mass of 170.5 kg. This gives a total mass including the actual boat (21 kg) of 191.5 kg. This by any measure is heavy and puts the importance of using airbags into perspective. It also explains why the boat was so heavy when I was hauling it out of the River Tees a few weeks ago!
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