Negatively buoyant divers vs. ditchable weights

[Bubbletrubble]

Another option is to dive an aluminum tank that will be positive when under about 1000 psi.

To clarify for some of the newbie divers out there, I just wanted to point out that just because a tank (containing whatever amount of gas) is positively buoyant, it doesn't necessarily make the diver + his rig (including the tank) positively buoyant overall.

Choice of tank, exposure protection, amount of weight, and how much of that weight should be ditchable are all factors which are considered in setting up a "balanced rig." I'm not a DIR diver, but the DIR crowd has put a lot of thought into this. There have also been many threads here on SB discussing this. Here's a link to one of them.

 

[ItsBruce]

I would need to be given a very good reason to ever enter the water while negative without ditchable weight or redundant buoyancy that if rapidly deployable. If that means going to aluminum tanks or not using a steel backplate, so be it.

 

[windapp]

I'm relatively new to diving, so perhaps it is my inexperience talking, but unless I was really far from a boat on rough seas with a busted BCD, I can't think of a reason why I would need to ditch my weights. It wasn't really covered in the e-learning or the classes.

Could someone clarify for me?

 

[Bubbletrubble]

I'm relatively new to diving, so perhaps it is my inexperience talking, but unless I was really far from a boat on rough seas with a busted BCD, I can't think of a reason why I would need to ditch my weights. It wasn't really covered in the e-learning or the classes.

Could someone clarify for me?

@windapp: You really can't think of a time when it would be best to establish positive buoyancy instantaneously?
I bet that if you just thought about it for a little while you could come up with lots of different situations.

Here's one...for whatever reason, on a boat dive entry, you forget to turn on your tank valve and inflate your BCD. Some divers would say that you should just reach back and turn on your tank valve, but this isn't a maneuver normally taught in a basic OW course and certain equipment choices (tank position low on BCD) or medical conditions (shoulder injury) might make it exceedingly difficult to perform. A vigilant buddy would be there with you...even if you entered the water first, but let's say he/she isn't around to help you.

Here's another...you're in a state of panic at the surface because you feel like you're sinking, you hit your power inflater but no BCD inflation occurs, and you're getting tired from all the kicking to remain on the surface. For whatever reason, you forgot to attach your LP inflater hose to your BCD power inflater or it became disconnected at some point. Rescuers attempting to help you at the surface would probably consider trying to ditch your weights to make you positively buoyant.

Also, take into consideration that, particularly if you're buddy diving, you might be called upon to assist another diver (your buddy?) in certain emergency scenarios. Ditching your own weight is an option if it helps during the rescue attempt.

 

[windapp]

I like the answers to my question. Not so fond of being talked down to.

 

[matt_w]

This is NOT a discussion about ditchable weights or not. This is a question about what to do about ditchable weights if you don't run any weights.


For whatever reason you plus your rig are negatively buoyant, and therefore you don't need to run any weights. Maybe you're diving in warm fresh water, so no exposure suit needed. Maybe you're diving doubles. Maybe you're 0% body fat and you'd sink even in the Dead Sea.

Whatever the reason, there's no extra weight you can jettison from your rig. Maybe it's by a little or maybe its by a lot, but at the surface you will sink without an inflated BC.
So there seems to be a conflict between divers who are negatively buoyant, and ditchable weights. I've never heard this discussed before. Does that mean these divers be carrying floats? It sounds absurd, but I don't know another solution.


Personally I am a sinker with a standard BC + single steel tank in fresh water. So far I've only dived cold waters so it's not an issue. Yet...

- Dack

I am a sinker with an al backplate, al tank, and 3/2. Actually nearly neutral, I can stay at the surface easy and hold a safety stop fine with no air in the wing. I can do all that without the wing at all. I really only I inflate to nap on Sunday afternoon...

Since I spend a lot of time as a victim in Rescue classes, I am fairly certain I can be brought up from the bottom . With a lot of students I still have to slow the ascent even with no air in my wing.

I have nothing against ditchable weight, I just don't need any. When I am wearing doubles it is tough not to be negative. Except double al80s and my 8/7, this is the only configuration were I need to kick (down) a bit to hold the safety stop. Even then it does not come up a lot since we don't normally breathe them down that far.

 

[Bubbletrubble]

I like the answers to my question. Not so fond of being talked down to.

@windapp: It wasn't my intention to "talk down" to you.
Sorry if that's how my words were interpreted.

I'm more than a little surprised that your e-learning modules and OW class sessions never discussed specific scenarios in which ditching weight was a good option. Perhaps something was skipped by you or omitted by PADI. As you know, there's a great deal to learn during OW class. My PADI instructor led a short discussion about ditching weight while we were discussing the remove and replace drills...and at several other points during the class. I can't be 100% certain (since it's been over 12 years ago) but I'm fairly sure that ditching weight was touched upon in the "What if...?" scenarios we discussed at the end of basic OW class. Feel free to click on the link in my sig to challenge yourself with some interesting and practical dive scenarios.

Dive safely out there...

 

[DaleC]

What does non-swimmers have to do with it? If you're unconscious or exhausted knowing how to swim doesn't help. Ditching weights does.

And personally, I'm not planning to dive any warm lakes...but I like to think about such things.

- Dack

Actually, being a non swimmer could quickly lead to panic when the feeling of exhaustion comes on. This will often blind the diver to the simple options available like
Inflating the BC
Dropping the weight belt
Dropping the rig
Breath off the reg
Many A&I reports of divers found on the bottom with functional gear who did not do any of those things.

If you're unconscious, best to have inflated a horsecollar BCD first. The only BC design that will reliably hold a divers head out of the water.

 

[Sat Diver]

I like the answers to my question. Not so fond of being talked down to.

This is the internet, so dont take it personally. This is great advice, and honestly anyone would be surprised that you dont understand why ditchable weights is important. Its a gaping hole in your dive education.

 

[Rich Keller]

In my opinion you need to do whatever it takes to at least be neutral at the surface with a full tank at the start of your dive. That could be a thicker suit or a non inflatable float of some sort attached to your rig. I did see a product that was meant to keep a tank afloat if you wanted to dive surface supplied and tow the tank behind you. That would probably be too much lift but it might be something you could modify and attach to your tank. You would be better off neutral with even a small amount of weight that could be dumped if needed so you have a fail proof way to stay afloat in an emergency. Another way to go would be with a composite tank system like the Interspiro Divator system that is buoyant even when filled to 4500psi.