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measure the neutral buoyancy precisely?

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0m2p1dzw

New Member
Jun 6, 2019
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I just did some googling about how to set the neutral buoyancy but have some doubts want to clarify.
If I want to set the neutral buoyancy at 10 meters depth, then to precisely measure it, the steps would be:
(0. dive with qualified divers for your safety)
1. prepare yourself with the wetsuit and the approximate weight
2. dive to 10m depth and stop(with the help of diving line/dive computer)
3. stay upright w/o touching the rope
4. exhale completely
5. and then check whether you float, sink or remain still.
6. Back to surface and adjust the weight if you were floating up or sinking down at the 10 m depth, and then try the steps mentioned above again.

A freediving friend of mine once told me that the step 4 is considered important to measure a strict neutral buoyancy.
but this statement sounds weird.

can anyone clarify this?
 
There are a lot of opinions on this. Here's mine.
As a rule of thumb you should be neutral at 1/2 the depth that you expect to be diving. So setting yourself neutral at 10 meters would make sense for a 20 meter dive - but for a 40 meter dive you might be over weighted.
Your friend that told you to exhale for the neutral test is probably thinking that if you pass out and lose all your air then you still need to be neutral (or positive).
 
@J Campbell
I forgot to state the target depth for the 10m buoyancy and sorry about that. the neutral buoyancy should be set according to the maximum depth.

btw, is it acceptable to set the neutral buoyancy deeper, which is more close to the expected dive depth(more than 1/2)?
thanks in advance!
 
Yes, it is OK to set a deeper neutral point - you are more likely to float back up if you black out - which is good for safty. But the tradeoff is that you will be fighting the bouyancy for most of the dive, wasting energy to stay down, and your dive will be shorter.
 
Yes, it is OK to set a deeper neutral point - you are more likely to float back up if you black out - which is good for safty. But the tradeoff is that you will be fighting the bouyancy for most of the dive, wasting energy to stay down, and your dive will be shorter.
but in my opinion, setting neutral point deeper means it would be easier to ascend so the diver will be able to float up without kicking(after reaching the neytral)? therefore the overall energy waste will be balanced between descent and ascent?
 
I see your point. And if you weight yourself so you are neutral only at the deepest part of your dive (for example if you wanted to lurk while spearfishing) then resurfacing would take no energy - just relax and float back up. But doing a dive like that would take tons of energy to get down there, unless the dive were really shallow.I suppose it would take some sort of scientific study to find the perfect balance of weight versus energy expended.
 
Beat me to it, Nathan. Everybody ought to look at that one.

Excellent, somewhat counterintuitive and thought provoking article. It doesn't deal very well with dive reflex, the effect of which argues for a shallower neutral depth. A significant issue for FRC divers, less so for full lung.
 
Beat me to it, Nathan. Everybody ought to look at that one.

Excellent, somewhat counterintuitive and thought provoking article. It doesn't deal very well with dive reflex, the effect of which argues for a shallower neutral depth. A significant issue for FRC divers, less so for full lung.
Yup. It's a little 'misleading'.. might be the right way to put it.

Neutral at 1/2 max depth is the 'most efficient' from an energy expenditure point of view. But Jeez... it's not easy to dive that buoyant.. Doing 60m for example required finning to 45-50m, which doesn't feel very efficient.

On Inhale, I've had the best results with: enter a 1m/s Freefall at maximum 1/2 of target depth..

On FRC. I liked to enter a full 1m/s freefall at around 1/4 target depth

Interestingly, this takes about the exact same weight for me, w/3mm suit in red-sea.
 
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