"Gold Standard" weight check

[Smache]

I've been writing some blog posts about diving, and just wrote this one about correct weighting. I'd love to hear everyone's thoughts, either about the concept or the writing.

https://firstprinciplesdiving.com/the-gold-standard-weight-check/

(If self promoting blog posts isn't allowed here, please delete.)

 

[wetb4igetinthewater]

I won't repeat what I've written here: Teaching Neutrally Buoyant and Trimmed: How to weight properly, Part 3 - International Training - SDI | TDI | ERDI | PFI

But basically, the correct amount of weight is the amount needed to maintain a safety stop with an empty wing (and dry suit as empty while still maintaining comfort) with a nearly empty cylinder AND enough to control the ascent to the surface (as some neoprene dry suits / thick wetsuits may become dramatically more buoyant at the surface - you don't want to be so light that you cork.).

And the weight MUST be distributed so that the diver can hover effortlessly horizontally. Those weight checks at the surface fail in this case.

 

[johndiver999]

The primary function of a bc is NOT to address the reduction in mass of the tank when it is used - (at least in a lot/most diving). Also the required volumetric capacity of a BC is most definitely NOT defined by the buoyancy swing in the tank. You might want to address this fact more explicitly.

 

[Smache]

The primary function of a bc is NOT to address the reduction in mass of the tank when it is used - (at least in a lot/most diving). Also the required volumetric capacity of a BC is most definitely NOT defined by the buoyancy swing in the tank. You might want to address this fact more explicitly.

What is it for then?

 

[Cthippo]

What is it for then?

I believe it is for compensating for changes in suit buoyancy with depth.

There are dangerous positive feedback loops with changing depth and the BC allows you to mitigate those. For example, the deeper you go the less buoyant you are due to neoprene compression and so the faster you sink. Conversely, as you go up the increasing expansion makes your more buoyant and so you tend to accelerate ever more upwards.

 

[Smache]

I believe it is for compensating for changes in suit buoyancy with depth.

There are dangerous positive feedback loops with changing depth and the BC allows you to mitigate those. For example, the deeper you go the less buoyant you are due to neoprene compression and so the faster you sink. Conversely, as you go up the increasing expansion makes your more buoyant and so you tend to accelerate ever more upwards.

That's true.

Compensating for tank buoyancy swing is definitely one of the functions of a BC, though. Even an 80 has a buoyancy swing of 6 pounds from full to empty.

 

[Eric Sedletzky]

My idea of perfect weighting is when you can maintain your 15’ safety stop at the end of your dive with a near empty tank, no air in your BC, and control your stop with breathing alone.
This formula works with any configuration and/or any combination of exposure protection and the sum total/balance of all components.

 

[lostsheep]

“Center of air?” “Center of gas”?

Why make up terms?

 

[johndiver999]

That's true.

Compensating for tank buoyancy swing is definitely one of the functions of a BC, though. Even an 80 has a buoyancy swing of 6 pounds from full to empty.

LOL and what is the swing in some wetsuits? Perhaps your perspective has been constrained by exposure to only very warm water.

 

[Cthippo]

“Center of air?” “Center of gas”?

Why make up terms?

We used a similar measurement in kayak building...

Center of Ass