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Old 29-09-2015, 15:36   #1
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Buoyancy question...

If a boat says (not that a boat can speak) that it has a positive buoyancy of 5000kg does that mean it would take 5000kg before it sunk or 5000kg for the boat to sink to the waterline??? Sorry if I didn't word this question right.

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Old 29-09-2015, 16:45   #2
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Re: Buoyancy question...

I would think that when it reaches that weight it will cease being buoyant !
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Old 29-09-2015, 17:35   #3
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Re: Buoyancy question...

Simple answer. The buoyancy force is equal to the water displaced by the boat.

If you boat weighs 5000kg, it will displace 5000kg of water when it floats, and that is the buoyancy force.
Now, make a hole underwater in the boat, it will start to fill with water rather than displace water, and will eventually sink, unless of course it has some sealed buoyancy tanks, in which case it will sink until the volume of water displaced by those tanks equals the weight of the boat, plus the weight of the water in the boat.
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Old 29-09-2015, 18:21   #4
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Re: Buoyancy question...

I suspect they might be talking about internal bouyancy foam. If so it's the total amount of buoyancy if the boat floods.

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Old 29-09-2015, 19:03   #5
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Re: Buoyancy question...

The meaning is most likely about 5 cubic meter of buoyancy built into the boat. Foam, sandwich, empty and sealed spaces, etc.

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Old 29-09-2015, 19:10   #6
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Re: Buoyancy question...

Positive buoyancy means that it weighs less than it displaces when the hull is fully flooded. i.e. it has sufficient internal sealed compartments (foam or air filled) to keep it afloat. 5000KG of positive buoyancy means that you would need to add that amount of weight to the flooded boat before it would sink.
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Old 29-09-2015, 19:29   #7
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Re: Buoyancy question...

Quote:
Originally Posted by Snowpetrel View Post
I suspect they might be talking about internal bouyancy foam. If so it's the total amount of buoyancy if the boat floods.

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That gets my vote just like life jackets,
and has nothing to do with whats attached to it just how much it can float. That said all weights that are heavier than water will have negative buoyancy all weights that are lighter than water will add buoyancy. both to varying degrees
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