Does a BC filled to capacity maintanin a constent amount of lift at different depth's

[GSmith]

I undertand that Boyle's law will represent the change in density/volume of gas with the change of pressure resulting from depth changes. (probably not exactly correct)
But, will a BC that is filled to it's maximum capacity have the same lift at say 100' FSW as it does at maximum capacity at 5' FSW?

And, at what pressure do BC's relief valve's typically burp off pressure?

Thanks in advance for any thoughts,
Greg

 

[Walter]

Yes.

I have no idea.

 

[Snowbear]

But, will a BC that is filled to it's maximum capacity have the same lift at say 100' FSW as it does at maximum capacity at 5' FSW?

Yes

And, at what pressure do BC's relief valve's typically burp off pressure?

Hopefully less than the burst pressure of the bladder

 

[pos-tech]

yes,

Higher than I can blow

 

[Bob3]

Technically, no. The gas in the BC at depth will be more dense & therefore weigh more, deducting from the BC's total overall effective lift.

In reality, the difference is so small as to be insignificant.

Next; how many pieces can you split a hair into?

 

[GSmith]

Bob3 has the context of my question...
This seems to make sense, and the difference I would expect be very small. Flipping through the old Physics book to Archimedes principles which states: When a body is completely or partially immersed in a fluid, the fluid exerts an upward force on the body equal to the weight of the fluid displaced by the body.
The source of my concern actually comes from a "Lessons For Life" feature in the July '03 Rodale's Scuba Diving Mag.(pg 69, #2). I states, "Extra weight is dangerous on a deep dive. The compression of wetsuits and BC's compounds negative buoyancy. At about 200 feet, negative buoyancy is self-propogating."
After rereading the related article, it appears that the context in which they are making this statement pertains to the rate at which a power inflator can supply air to your BC.
The reason for my question is that I just purchased an 18# wing for some diving in the Islands.
No tricks, honest!
That's the ticket!

Technically, no. The gas in the BC at depth will be more dense & therefore weigh more, deducting from the BC's total overall effective lift.

In reality, the difference is so small as to be insignificant.

Next; how many pieces can you split a hair into?

 

[GSmith]

relates to a theoretical (in my mind) point of no return. A x FSW your pressure relief valve my realease air before effectely increasing your buoyancy.

If you are at 200 FSW, your ATA is approx. 7x14.7=102.9 psi. It seems that your bladder must be capable of containning maybe 150 psi?

Is this correct?

 

[donacheson]

I undertand that Boyle's law will represent the change in density/volume of gas with the change of pressure resulting from depth changes. (probably not exactly correct)
But, will a BC that is filled to it's maximum capacity have the same lift at say 100' FSW as it does at maximum capacity at 5' FSW?
Greg

In short, yes if it's kept filled to it's maximum capacity.

 

[Scubaroo]

relates to a theoretical (in my mind) point of no return. A x FSW your pressure relief valve my realease air before effectely increasing your buoyancy.

If you are at 200 FSW, your ATA is approx. 7x14.7=102.9 psi. It seems that your bladder must be capable of containning maybe 150 psi?

Is this correct?

I think so, but don't test it on the surface by pumping your wing to 150psi! At depth, the water around the wing will be exerting the same pressure - "every force has an equal and opposite force" etc type stuff. On the surface, the atmosphere is only exerting 14.7psi of pressure on your wing - if the OPV dump valve sticks or something, you'll make Marvin the Martian very happy :bomb:

There's probably a delta pressure that the OPV is supposed to release at (ie difference between internal and external), but I've no idea what it is.

 

[ElectricZombie]

And, at what pressure do BC's relief valve's typically burp off pressure?

Depends on the strength of the spring used in the dump valve. The spring keeps the valve closed so, for the BC to burp off pressure, it must overcome the force of the spring. It's going to differ for each BC as I'll willing to bet that no two springs are exactly alike. You could probably calculate how much pressure it would take if you had some special measurement tools, but it seems like a waste of time.