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Old 10-16-2012
peterchech peterchech is offline
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Still confused about water ballast

So water ballasted boats like the macgregor 26D (not the X and the other "power" sailors, let's exclude them from this conversation) obviously work, and its phrf rating isn't too bad either. It is a huge advantage that the entire hull weight is under 2000#, meaning a regular jeep can tow it when necessary. But I'm still confused.

The widely held idea that the water ballast in the bilge has to be lifted out of the water before it starts creating righting moment has been debunked on the internet at least, and frankly I don't see how the concept of water ballast could possibly work if it had to be above the waterline to work. Hey, our bodies are made of 90% water and a boat is more stable (theoretically) with a person lying in the bilge than without a person lying in the bilge, right? That's how you balance a very small dinghy no? I have heard the explanation that a pound of feathers is the same as a pound of lead if the cg of that pound is in the same place. This makes sense to me.

But if this were true, then wouldn't a bulb keel, full of water, also act as ballast? Weight is weight, right? Yet this is obviously not true. So how can water ballast work when inside a hull and below the waterline, but not when inside a bulb suspended below the boat, also below the waterline?

Could someone explain this concept to me, dumbed down enough that I understand ?
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