Boat Float Blog

Charles’ Law — Why your boat lift is sitting lower in the water

August 29, 2019

It’s cold and rainy in the Lowcountry today and we’ve had a couple of phone calls this morning with folks asking “Why is my boat lift sitting lower in the water today?  Is it losing air?”

If you own a Safe Haven or a DryDock (or any other type of lift that you add air to a tank to gain buoyancy) you may have noticed that the lift is sitting a little lower in the water each day (especially if you haven’t taken your boat out for a few days.)

Well, chances are your boat lift does NOT have a leak in the system anywhere.  Instead, you can cast blame towards a French mathemetician named Jacques-Alexandre-Cesar Charles who discovered that gas (air) changes volume with changes in temperature.  (Well, to be fair, Joseph Louis Gay-Lussac published this finding in 1802, but he gave the credit to Jacques Charles for the discovery.) 

Charles’ Law, as it’s called, states that “the volume of a gas is directly proportional to the absolute temperature.”  

In other words, as the water gets cold around your boat lift, the air in the tanks tends to lose volume (or shrink) and thus the boat lift rides a bit lower in the water.

Conversely, in the summertime, as the air gets warmer, you may notice your boat lift “burping” from time to time as the air in the tanks expands in the hotter water and the excess air bubbles out of the exhaust ports.

The Boat Float Company….we’re science geeks, too!

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