Noob questions about various weight(s) topics .....

[xanaphyst]

My very first post !!!

I'm brand new certified OW and only have 2 real post training dives. (Holy cow Kyalami Divers in West Palm Beach was crazy awesome)

I have a few questions about weight(s).

1. It seems to be a hot topic to have the least amount of weight on you as possible. Even a bunch of advertising has how light such and such part is. What's all the lead hate about? Is it really going to kill you to have one extra puff of air in your BCD ?

2. When am I ever going to "drop weights"? I hear all the talk about not ascending too fast. That seems counter to my lessons. What is a real world example where you had to drop weights? Wouldn't it possibly be a problem if you accidently dropped weight out of a quick release pocket? It seems more logical to have permanent weights with only a very small amount of releasable weight. Even then I cant think of a real need.

3. Why do I care if my 1st stage is light and compact? Wouldn't that make it less durable?

 

[rongoodman]

A little extra weight is no big deal, but the more you're overweighted, the more air in your BC required to compensate, and the more sensitive it will be to changes in depth, especially if you're shallow. If I can feel more than a fistful or so of air in the bottom of my wing on my safety stop I'll think about dropping a couple of pounds, but I don't want to have to struggle to get the last bit out in order to stay down.

The only reason I can think of to drop weights under water would be a BC which failed to the point that I couldn't get to the surface by finning or perhaps being adrift and wanting to ride higher out of the water. Losing weights inadvertently is a more common problem.

I can't see any reason to worry about "light and compact" for a 1st stage. Reliability and hose routing are more important concerns. (I'm a big fan of Deep 6 for that reason.)

 

[johndiver999]

If you can't think of a reason why you might have to drop lead when you are underwater, then I suspect your training was weak.

Knowing exactly (or approximately) how much weight you would need to drop is very situational dependent, primarily upon how deep you are and how thick your wetsuit is and if your air supply is not compromised or severely limited.

But other ancillary factors might include the weight of air in your tank at the time of the problem, your overall fitness (including strength, endurance and quality of your fins), also your ability to calmly access redundant means of buoyancy (like an smb) and perhaps access to an ascent line where you could just "climb a rope" up.

However, the OP is correct that there seems to be a strong culture and competition toward minimizing the amount of lead a diver carries - and this is a fool's errand in my mind.

As for the other question, There are very secure, comfortable and safe means to carry lead that does not risk "lead falling out of a pocket"; the solution I use is almost always a rubber freedive belt- something the OP has probably never heard about.

 

[inquis]

Buoyancy changes happen faster when your BC has more air in it. New divers' kinesthetic sense isn't as developed, but it will also degrade if an experienced diver goes awhile between dives. This combo can result in someone trying to vent (slowing the expansion and ascent rate), but not enough room to stop before surfacing. Also common is to overshoot the venting (dropping quickly), then overshoot the addition, and get into a yo-yo cycle. Poor visibility is also conducive to falling into the yo-yo cycle.

Minimizing your degree of overweighting helps deal with all the above. Yes, being a pound or two over the ideal is much better than under.

 

[gmerick]

1. Diving with an AL80, I have no air in my BC. I purge all air on descent, and use lung volume for buoyancy control throughout the dive. Extra weight would require air in the BC, and all the buoyancy issues that come with changing depth while managing a BC air bubble.

2. I may drop weight for managing an emergency at the surface such as a panicked or unresponsive dive. If properly weighted, there should be no issues with returning to the surface on a dive from a "normal" recreational dive.

3. For a "normal" recreational dive, not a consideration.

Rethink these issues when using multiple cylinders or thermal protection with harder to manage buoyancy characteristics.

 

[boulderjohn]

If you can't think of a reason why you might have to drop lead when you are underwater, then I suspect your training was weak.

In my 21 years on ScubaBoard, this is one of the most common thread topics. Instructors always talk about the need to drop weights, but they rarely talk about the circumstances that would lead to it, possibly because the need is so rare it would contradict their message about dropping weights. The question does not in any way reflect upon the quality of the training.

As for the actual questions, Ron Goodman gave a good response.

 

[xanaphyst]

1. Diving with an AL80, I have no air in my BC. I purge all air on descent, and use lung volume for buoyancy control throughout the dive. Extra weight would require air in the BC, and all the buoyancy issues that come with changing depth while managing a BC air bubble.

2. I may drop weight for managing an emergency at the surface such as a panicked or unresponsive dive. If properly weighted, there should be no issues with returning to the surface on a dive from a "normal" recreational dive.

3. For a "normal" recreational dive, not a consideration.

Rethink these issues when using multiple cylinders or thermal protection with harder to manage buoyancy characteristics.

For your answer on question 1 wouldn't that mean you are too light after you use up most of your air on the dive? Safety stop would be difficult ?

 

[inquis]

When am I ever going to "drop weights"?

You've hit upon the concept of "a balanced rig". When neutral at safety stop depth with minimal air in the wing and reserve cylinder pressure, you would then be negatively buoyant with a full tank by the amount of the gas weight. Thus, you add air to the BC, and all is well. When you descend wearing a wetsuit, compression will reduce suit buoyancy, so you add air to the BC, and all is well. However, if the BC fails at depth (e.g., the inflator hose comes off the elbow), you have to get up somehow. Kicking can generate 10-18 lbs of "up". Fullish lungs can generate 5-8ish lbs (depending on your size) of "up". If that's not enough, you're screwed. (Sidenote: it's a good idea to test your kicking thrust in a pool, as fins and strength obviously play a role.)

An AL80 has about 5 lbs of non-reserve gas. A single-layer 7 mm wetsuit could lose about 8 lbs in my experience, so 12 lbs negative. Ascending until your suit regains some of its lift should be doable by most without dropping weight. This is considered "balanced". However, if you're fairly overweighted (e.g., another 5 lbs), you may not be able to kick up from the bottom in this scenario. Also, larger cylinders could have more non-reserve gas (~9 lbs in an HP120), and combined with losing the buoyancy of a thicker double-layer wetsuit, it might not be enough to get off the bottom. Dropping all the weight would be bad, though, as when you do regain suit buoyancy, you cannot control your ascent. Dropping lead equaling the gas you still have (9 lbs in this case), would make you neutral at the safety stop as per normal and would be a reasonable response.

Yes, a buddy should be able to drag you up, but being self-reliant is never a bad thing.

Once into this territory, a drysuit is going to be the better choice of exposure protection and conveniently provides redundant buoyancy compensation. While not very likely, another case where dropping weight is a good idea is if you're in a drysuit and both the BC and suit are severely compromised (e.g., a large gash during a wreck swim through). Obviously, thermal is going to be another big concern.

 

[inquis]

Losing weights inadvertently is a more common problem.

Far more common! Problem for both for the diver and anyone below them.

 

[xanaphyst]

You've hit upon the concept of "a balanced rig". When neutral at safety stop depth with minimal air in the wing and reserve cylinder pressure, you would then be negatively buoyant with a full tank by the amount of the gas weight. Thus, you add air to the BC, and all is well. When you descend wearing a wetsuit, compression will reduce suit buoyancy, so you add air to the BC, and all is well. However, if the BC fails at depth (e.g., the inflator hose comes off the elbow), you have to get up somehow. Kicking can generate 10-18 lbs of "up". Fullish lungs can generate 5-8ish lbs (depending on your size) of "up". If that's not enough, you're screwed. (Sidenote: it's a good idea to test your kicking thrust in a pool, as fins and strength obviously play a role.)

An AL80 has about 5 lbs of non-reserve gas. A single-layer 7 mm wetsuit could lose about 8 lbs in my experience, so 12 lbs negative. Ascending until your suit regains some of its lift should be doable by most without dropping weight. This is considered "balanced". However, if you're fairly overweighted (e.g., another 5 lbs), you may not be able to kick up from the bottom in this scenario. Also, larger cylinders could have more non-reserve gas (~9 lbs in an HP120), and combined with losing the buoyancy of a thick double-layer wetsuit, it might not be enough to get off the bottom. Dropping all the weight would be bad, as when you do regain suit buoyancy, you cannot control your ascent. Dropping lead equaling the gas you still have (9 lbs in this case), would make you neutral at the safety stop as per normal and would be a reasonable response.

Yes, a buddy should be able to drag you up, but being self-reliant is never a bad thing.

Once into this territory, a drysuit is going to be the better choice of exposure protection and conveniently provides redundant buoyancy compensation. While not very likely, another case where dropping weight is a good idea is if you're in a drysuit and both the BC and suit are severely compromised (e.g., a large gash during a wreck swim through). Obviously, thermal is going to be another big concern.

That was an awesome answer and very clear.

Thank You !!