double tank weighting issue?

[nereas]

Wow, I actually agree with JeffG, for once, on one minor point. Miracle!

Ballast may need to be dropped at any time. Definitely. Good reason to have ditchable weight.

 

[cool_hardware52]

And there are many doubles circumstances that do not imply decompression, Tobin.

Are you suggesting that ditchable weight is a necessity for NDL dives in doubles, but maybe not if deco is part of the dive plan?

Is is smart to alter the rig for each circumstance?

I keep the "reaper" away by recognizing the risks I assume, and being adequately equipped to deal with them.

Redundant buoyancy in the form of a wing + Drysuit, and a proper weighting allows for controlled ascents even in the event of a buoyancy failure.

Tobin

 

[Flightlead]

I completely agree with the above.

There is a major flaw in DIR theory in their assumption that cave diving protocols are always appropriate to open water. They teach this, yet it is untrue. They believe it, yet it is false and misleading and dangerous.

It should be self evident that going into a fresh water cave is worlds apart from diving in the open seas. Yet to DIR it is no different at all. Funny thing. (Funny = sad.)

omg this pissing match is getting totally out of hand. my (I am the OP) original question was specifically about dives with an overhead (virtual or real), and mostly pointed towards dives with a deco obligation. any arguments based on being able to shoot to the surface like a bloody Poseidon missile are therefor null and void.

 

[JeffG]

omg this pissing match is getting totally out of hand. my (I am the OP) original question was specifically about dives with an overhead (virtual or real), and mostly pointed towards dives with a deco obligation. any arguments based on being able to shoot to the surface like a bloody Poseidon missile are therefor null and void.

whatever

 

[Thalassamania]

I disagree.

Ditching weight in an overhead is not a viable solution, however it's not much of plan in open water with virtual ceiling either.

If you ditch your ballast in order to become positive at depth, an uncontrolled ascent is almost a certainty.

This thread concerns weighting for double tanks. Doubles imply mandatory decompression.

Recognizing that ditching ballast with a deco obligation is unsound, the concepts of a "balanced rig" (which in practical application means avoiding being overweighted) and redundant buoyancy, i.e. wing + drysuit, or wing + lift bag is taught as a means to provide an acceptable level of safety without dropping any ballast.

In short one needs to weigh the consequences of an uncontrolled ascent against the "complexity" of redundant buoyancy. With a wing and drysuit the redundant buoyancy requirement is met with gear already necessary for many dives that require doubles.

Tobin

Your points are well taken. I find little to disagree with in terms of the question of ditchable weight, I was just trying to relate the early origins of the difference of opinion, not to advocate weightbelt dropping as some sort of super-self-rescue technique.

There are many times I dive doubles (in fact most of the time I dive doubles) that no decompression is intended or conducted.

omg this pissing match is getting totally out of hand. my (I am the OP) original question was specifically about dives with an overhead (virtual or real), and mostly pointed towards dives with a deco obligation. any arguments based on being able to shoot to the surface like a bloody Poseidon missile are therefor null and void.

Quite right, that was not part of the discussion at the onset. But that's the red herring that always comes in to derail rational conversation about weighting and weight systems.

 

[Thalassamania]

double post - sorry

 

[cool_hardware52]

Your points are well taken. I find little to disagree with in terms of the question of ditchable weight, I was just trying to relate the early origins of the difference of opinion, not to advocate weightbelt dropping as some sort of super-self-rescue technique. In fact, I made no mention of ditchable weight, I never broached the subject.

Another participant in this thread has apparently have missed this distinction, thanks for clarifying.

There are many times I dive doubles (in fact most of the time I dive doubles) that no decompression is intended or conducted.

I prefer to dive doubles, and often do so in "NDL" applications. I do "Minimum Deco" on every dive however, good practice, and it makes me happy.


Tobin

 

[Gilldiver]

Lot's of the same old arguments here, not much new mostly closed minds.

Here are a few things to think about:

1) What do you do if you have a nice balanced rig and when you get to the surface you are not near the boat?

I was on a boat when the fog came in while divers were in the water and the surface visibility went to less then 50 feet. A diver had been blown off the anchor line and was almost out of sound range of the boat – we could just barely hear his whistle. The zodiac was launched with two crew, a compass, and radar reflector and the captain guided them in a search pattern by the boats radar. It took them almost 2 hours to find this diver and by that time he was almost 2.5 nautical miles down current. When I saw that I figured that in a similar situation I would want to ditch whatever I could to get as light and buoyant as possible and swore never to dive in all black in the blue water, my suit is much closer to a Coast Guard Swimmers suit in colors – lots of orange. I want to be seen by the boat or aircraft if I need to be seen.

In a cave you never want to ditch weight as all it would do is glue you to the ceiling. In open water and on the surface you just might want to.

2) Every set of twins I have ever used from old 72's, 80's 100's, 125's, 130's etc. have always been negative with 300 PSI in them and fully rigged – back plate, regs, manifold, clips and lights, etc. At any PSI above 300 a set of doubles is always negative. I have practiced getting out of my rig on the bottom and at depth. It takes practice but you dump all the air out of your dry suit that you can, loosen up, adjust the BC to just balance the tanks, and swing out. You may still be a bit light in a dry suit, but you can dump a little air out of the BC and hang onto them, and now can swing around and grip them with your legs and put one arm through the straps. Now you have a hand free to clear a net, or my favorite, 90# test leader or, worse, Stainless Steel leader.

Try it, it is not all that hard to do and in a wet suit at depth you have almost no buoyancy anyway. The key is to move very very slow.

 

[Thalassamania]

Lot's of the same old arguments here, not much new mostly closed minds.

Here are a few things to think about:

1) What do you do if you have a nice balanced rig and when you get to the surface you are not near the boat?

I was on a boat when the fog came in while divers were in the water and the surface visibility went to less then 50 feet. A diver had been blown off the anchor line and was almost out of sound range of the boat – we could just barely hear his whistle. The zodiac was launched with two crew, a compass, and radar reflector and the captain guided them in a search pattern by the boats radar. It took them almost 2 hours to find this diver and by that time he was almost 2.5 nautical miles down current. When I saw that I figured that in a similar situation I would want to ditch whatever I could to get as light and buoyant as possible and swore never to dive in all black in the blue water, my suit is much closer to a Coast Guard Swimmers suit in colors – lots of orange. I want to be seen by the boat or aircraft if I need to be seen.

In a cave you never want to ditch weight as all it would do is glue you to the ceiling. In open water and on the surface you just might want to.

That's why I carry safety sausage, dye, smoke and flare.

2) Every set of twins I have ever used from old 72's, 80's 100's, 125's, 130's etc. have always been negative with 300 PSI in them and fully rigged – back plate, regs, manifold, clips and lights, etc. At any PSI above 300 a set of doubles is always negative. I have practiced getting out of my rig on the bottom and at depth. It takes practice but you dump all the air out of your dry suit that you can, loosen up, adjust the BC to just balance the tanks, and swing out. You may still be a bit light in a dry suit, but you can dump a little air out of the BC and hang onto them, and now can swing around and grip them with your legs and put one arm through the straps. Now you have a hand free to clear a net, or my favorite, 90# test leader or, worse, Stainless Steel leader.

Try it, it is not all that hard to do and in a wet suit at depth you have almost no buoyancy anyway. The key is to move very very slow.

If you can keep the buoyancy difference small, on the order of what you can swing on your lungs, that's fine ... very little is ever perfect. I prefer to have it small enough that I have two hands to comfortably work with with my feet well out of the way of the net ... but that's just me.

 

[texdiveguy]

omg this pissing match is getting totally out of hand. my (I am the OP) original question was specifically about dives with an overhead (virtual or real), and mostly pointed towards dives with a deco obligation. any arguments based on being able to shoot to the surface like a bloody Poseidon missile are therefor null and void.

Its just that SB has so many experts in these things....one keeps trying to top the other....then you get the dang GUE//DIR folks going and its a goal to see how many coverts they can get.....