How water ballast works

[Graham W]

What a hoot!  I wouldn't want to be a yacht in the next berth.  Or a tall person walking underneath the turbine blades.  And are those internal combustion exhaust gases that I can see coming out of the stern on the starboard side?

The video is quite old (2009) and I'd be prepared to wager half a pint of stout that Revelation II isn't with us in that form any more.

[David Hudson]

Why has my half full bottle of wine floated away on the tide?

[Peter Taylor]

Never thought of filling the ballast tanks with wine... good job I'm teetotal nowadays!
Peter

[David Hudson]

But my bottle is floating not sinking Peter.

[Andy Dingle]

Here's a thing. I have just had this bright idea that if I fill my ballast tanks this year with fresh tap water with a little disinfectant stuff chucked in. Keeping the 'bung' closed so not allow any sea water and little tiny creepy crawlies in that will die, rot and go slimy. I could change the water every month or so and therefore keep my tanks and pumps etc pristine.. I have a water supply on the pontoon.

But then, if I fill the tank with fresh water, which is less dense than sea water and as any diver will tell you, actually floats on sea water. How will this affect the buoyancy and stability of my boat compared to filling it with sea water? Will the boat float higher in the water?

Or am I just talking out of my transom..?


Andy

[Michael Rogers]

I think you're missing a trick here, Andy. I suggest some research into a species of fish which is a) edible, preferably delicious; b) loves to eat all the other forms of life inhabiting your ballast tank; c) thrives in the dark. Stock your tank, and at intervals (to be determined by more research) have inboard fishing parties through the 'bung', terminating in a fish and chips supper. (I find myself recalling the occasion when Thomas the Tank Engine got fish in his side tanks.) Voila! - a clean yet productive water ballast tank, and queues of people wanting to crew for you.

Can I come?

Michael

[Peter Taylor]

A few comments:

For David: that's 'cause you drank half the wine!

For Andy: density of seawater is about 1.027 times that of fresh water (depending on temperature and  salinity).  So if your BC23 has around 500kg water ballast the difference in weight is around 14kg.  Not insignificant, but how full or empty your drinking water tank happens to be can easily make that difference!

For Michael: if Andy used sea water he would presumably need an EC fisheries quota whereas with fresh water an Inland Waterways fishing licence should be sufficient (which is easier to obtain).  If the boat is on the trailer then Transport of Live Animals by Road regulations would apply....

Btw: the lower density of freshwater can be observed here on the River Itchen where the surface flow (being fresh water) is usually out even when the tide is coming in.  However the surface layer is very shallow so the current that the boat actually feels is different to what you see, for example by looking at a mooring buoy. If anyone wants to know more, look at "estuarine circulation" in Wikipedia, the Itchen is a partially stratified estuary!

[Michael Rogers]

Peter, at risk of becoming 'political' at this potentially sensitive time, do I detect someone who wouldn't mind being shot of some EC directives? The Fat Controller didn't/didn't have to bother himself with such red tapery...........sigh.