Loss of human body volume vs depth (buoyancy)

[Akimbo]

Technical divers doing deep "bounce" dives (which is the term for all non-saturation dives) will descend as fast as possible in order to maximise bottom time. Don’t hear of this pain phenomenon from them.

Most tech divers aren't going to 600+ fsw.

I don't recall hearing anyone complain about compression arthralgia until the 450-500' or 140-150M range. There were quite a few deep bounce diving systems in the 1960s and 70s like this one:

The bell would be lowered to the working depth with the external hatches closed, meaning the inside of the bell was still at one ATA. The divers would observe the worksite to position the bell and evaluate the job. The diver would stand on the bottom external hatch fully geared up and blow the bell down as fast as possible. The external hatch would open when equalized with the bottom pressure and the diver would more or less fall out the bell. The bell would start being raised to the first stop as soon as the job was compete and the diver's head and elbows were back in the bell.

The bellman would usually complain more about compression pains than the diver, probably because he still felt the effects of gravity in a very cramped space — and was far less distracted. These bells were typically 66" or 1,676mm for two men, dive gear, umbilical's, and scrubbers. As described to me, compression pains were not debilitating but hurt rather than ached. Divers thought it was probably similar to their grandparents severe arthritis. My brother said it momentarily hurt like hell when he moved but not continuously. YMMV.

 

[sea_ledford]

I don't see how that follows since the wetsuit is the lion's share of what the BC should be compensating. (The other piece to compensate is the weight of the air you haven't yet breathed.) What happens when your 7 mm suit is compressed at 100 ft and you lose, say, 20 lbs of lift? That additional weight will be on you to raise if the wing totally fails. Anyone who has a 7mm suit should really measure its buoyancy as @johndiver999 described to ballpark the worst-case swimup. Even better is the bottom-line, actual swim up from depth with empty wing.

Yes, exactly my point. If the diver can maintain the weight mid water with zero buoyancy, they'll be fine. The will still have some buoyancy from the suit regardless of depth, so this would be a worst case scenario that is easy to do if you have access to the deep end of a pool. Of course there are better ways to ball park it, but probably not easier ways!

An alternate approach to estimate how much you can swim up can be done in a pool wearing a bathing suit and fins. Tread water while a buddy adds weight to a mesh bag until you have to drop it. Have the buddy also hold a line to the bag (to catch it when you drop it) or use coated weights to avoid damage to the pool bottom.

Which is effectively the same thing I said, but will now require measuring the buoyancy of all the non-compressible dive gear as well.

 

[tursiops]

Technical divers doing deep "bounce" dives (which is the term for all non-saturation dives)

A completely new and different definition of a bounce dive! I'll stick with the one that has been around for a while.

 

[Akimbo]

Technical divers doing deep "bounce" dives (which is the term for all non-saturation dives) will descend as fast as possible in order to maximise bottom time. Don’t hear of this pain phenomenon from them.

A completely new and different definition of a bounce dive! I'll stick with the one that has been around for a while.

The commercial diving industry has used "bounce dive" for non-saturation closed bell dives since the late 1960s, though they are very rare today. From my perspective, all recreational and technical dives are bounce dives.

 

[tursiops]

The commercial diving industry has used "bounce dive" for non-saturation closed bell dives since the late 1960s, though they are very rare today. From my perspective, all recreational and technical dives are bounce dives.

We are in Basic Scuba, not a Commercial diving forum.

 

[John C. Ratliff]

This is a interestong statement.

I don't see how that follows since the wetsuit is the lion's share of what the BC should be compensating. (The other piece to compensate is the weight of the air you haven't yet breathed.) What happens when your 7 mm suit is compressed at 100 ft and you lose, say, 20 lbs of lift? That additional weight will be on you to raise if the wing totally fails. Anyone who has a 7mm suit should really measure its buoyancy as @johndiver999 described to ballpark the worst-case swimup. Even better is the bottom-line, actual swim up from depth with empty wing.

An alternate approach to estimate how much you can swim up can be done in a pool wearing a bathing suit and fins. Tread water while a buddy adds weight to a mesh bag until you have to drop it. Have the buddy also hold a line to the bag (to catch it when you drop it) or use coated weights to avoid damage to the pool bottom.

Why use a wing for free diving? Usually, that is done without a BC.

SeaRat

 

[Akimbo]

We are in Basic Scuba, not a Commercial diving forum.

What defines a bounce dive to you? I have seen only noticed it used a few times on ScubaBoard but never could figure out exactly when a recreational dive becomes a bounce dive from the context of the thread.

 

[arew+4]

What defines a bounce dive to you? I have seen only noticed it used a few times on ScubaBoard but never could figure out exactly when a recreational dive becomes a bounce dive from the context of the thread.

An elevator ride, down and up, just for the sake of going deep.

 

[tursiops]

An elevator ride, down and up, just for the sake of going deep.

Exactly, like a ball bouncing off the "bottom." Down and up, no time at any level, hopefully avoiding deco.

 

[inquis]

This is a interestong statement.

Why use a wing for free diving? Usually, that is done without a BC.

SeaRat

The freediving aspect was introductory in nature. From the OP...

The question arises with respect to having non-ditchable weights on a scuba system without redundant buoyancy