BC lift question

sealskin98

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• Aug 27, 2002

• #1

I have a Dacor Extreme BC that I bought about '96 or '97 and didn't look at the lift rating when I bought it new for Caribbean diving. The tag that came on it doesn't have the lift printed on it where it says "Surface Bouyance: lb/ Kg
When Fully Inflated in Fresh Water at Sea Level"

Is it in the 22-28 lb. range? I've e-mailed Dacor with no response.

Thanks

 

Iguana Don

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• Aug 27, 2002

• #2

I have & I'll git back 2ya.

 

FredT

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• Aug 27, 2002

• #3

1. weigh BC "empty."
2. Fill BC bladder with water.
3. Weigh BC "full."
4. Subtract weight empty from weight full.
5. Result is buoyancy in fresh water.
6. Result x 64.2\62.4 is buoyancy in salt water.

For a more exact buoyancy measurement you also need to weigh the "full" BC submerged in water to null the natural Buoyancy of the BC. That should only be a few ounces and can be considered "noise" for most commercial plastic BCs. This "it's down in the noise" deal does not hold for weight integrated BCs or backplate rigs though.

FT

 

G

GrantCarr

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• Aug 28, 2002

• #4

How come it doesn't hold for weight integrated BCs (with the weights removed)?

 

FredT

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• Aug 28, 2002

• #5

We are talking about buoyancyof the unit. The normal "plastics" used to make diving gear all have a specific gravity near 1 to about 1.8, so out of water weight doesn't figure into the calculation much.

Any BC will have the net buoyancy of the unit decreased by the amount of negative buoyancy the unit provides empty. On a BP or integrated weight BC while the "swing" compensation is there up to the weight of water added to the bladder the net lift is reduced by the negative buoyancy of the unit.

FT

 

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sealskin98

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• Aug 28, 2002

• #6

"I didn't know that."

That will be a quick way of getting a general idea the next time I rinse it (hope I don't ruin the extremely accurate, down to the gram, bathroom scales I have.)

This is scary, I actually understand what Fred is talking about.