Beating a Dead Horse: BP/W Lift for Deep, Cold, Wet Dives

[decompression]

Balanced rig has to do with total weighting, not weight distribution. It can involve weight distribution, however.

For instance, if you're weighted in such a way that you can't swim up your kit with a full tank and empty wing, some of your weight needs to be ditchable or your
kit needs a major overhaul. The flip side os that if you dont need ditchable weight, thats ok too. You can still have a balanced rig without any ditchable weight. I do this all the time cave diving or single tank reef reef diving.

If you tried to add weight so you're neutral in just your dry suit and no tanks you'd be way overweighted when you put your tanks on. No thx.

---------- Post added June 6th, 2014 at 11:11 AM ----------

Balanced rig = able to swim up full tanks from depth with no gas in wing and able to hold a stop at 10ft with no gas in the tanks. Kit should be able to float at the surface without you in it.

If you can do all those things, you have a balanced rig.

Agreed AJ but not with ditchable weight, to the OP, this is critical especially if you dive deep/wet/cold and use ditchable weights. If you encounter a wing failure at depth and ditch say 5# to swim your gear up, as you ascend the buoyancy is restored to the wetsuit now making you say 10# positive and very challenging to hold your stops. As the OP mentioned dives to 130', ditching weights could pose a problem. With a balanced rig and drysuit you have redundancy and no need for ditchable weights.

To get back on track, the OP inquired about lift. The wing must compensate for the gas carried and float you at the surface. Once you know your gas and calc'd your balanced rig you'll see what you need for lift. I hope all this was helpful.


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[PfcAJ]

I'm not sure your example is valid.

If the suit has 10lbs of variable buoyancy, and you drop 5, you would be still be positive during the ascent if you hadn't dropped 5lbs. On a practical note, swimming up 5lbs or so shouldn't be a problem. It's easy to get wrapped up in unrealistic hypotheticals.

Thick wetsuits and heavy tanks are bad news bears, that's the moral of the story.

 

[decompression]

Ya I agree, you always make sure examples are applicable. How about this (more realistic), at 130' in thick wetsuit (25# pos), then wing failure drops 15# so is now -10 (tough) and swims to 10', suit is +25 but neg weight is now -10# and maybe used gas to get there, so roughly 15-18 # positive.


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[PfcAJ]

That would be not good.

 

[eelnoraa]

maybe thick wetsuits just don't belong parts of balanced rig for this kind of depth.

 

[decompression]

That's the thing, I try to illustrate that to anyone that maybe unfamiliar with the drawbacks. Of course there are alternatives for redundant buoyancy but they have their drawbacks as well. Deep, cold and wet don't really mix.


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[halocline]

Balanced rig = able to swim up full tanks from depth with no gas in wing and able to hold a stop at 10ft with no gas in the tanks. Kit should be able to float at the surface without you in it.

If you can do all those things, you have a balanced rig.

Exactly, but in very cold water with a thick wetsuit and a lot of ballast (what this thread is about, right?) this usually involves splitting weight in some way between the rig itself and the diver's body. All the weight on the rig could mean that A) it's very hard to float without the diver, and/or B) not enough would be ditchable to allow for a diver to swim up a very negative rig. So the best solution usually involves some ballast on the rig (like a steel plate) and some on a belt or harness.

 

[decompression]

Exactly, but in very cold water with a thick wetsuit and a lot of ballast (what this thread is about, right?) this usually involves splitting weight in some way between the rig itself and the diver's body. All the weight on the rig could mean that A) it's very hard to float without the diver, and/or B) not enough would be ditchable to allow for a diver to swim up a very negative rig. So the best solution usually involves some ballast on the rig (like a steel plate) and some on a belt or harness.

Ok, Halocline, if you've got a lot of "ballast" and it's difficult to float your rig then you need a bigger wing, that was mentioned previously. As AJ mentioned often we dive with no ditchable weight, I certainly prefer not to have a weight belt with my rigs and plan my gear accordingly. And b) if you can't swim up you are not balanced, regardless of where your weight is. Can you explain why you "usually" split your weight between yourself and your rig and what the advantage is?


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[ams511]

maybe thick wetsuits just don't belong parts of balanced rig for this kind of depth.

You can dis wetsuits but I get the impression that there are quite a few accidents because of dry suits, either because of a malfunction or poor diver training.

---------- Post added June 7th, 2014 at 01:46 AM ----------

Ok, Halocline, if you've got a lot of "ballast" and it's difficult to float your rig then you need a bigger wing, that was mentioned previously. As AJ mentioned often we dive with no ditchable weight, I certainly prefer not to have a weight belt with my rigs and plan my gear accordingly. And b) if you can't swim up you are not balanced, regardless of where your weight is. Can you explain why you "usually" split your weight between yourself and your rig and what the advantage is?

Why use a bigger wing? I agree with Halo on this. Assume your rig with a full tank is -15 negative and you dive a 2 piece 7 mil that needs - 25 lb to sink it. If you put all the weight on the rig you will need a 40 lb ( -15 + - 25) wing to float it. If you move 10 lbs to a belt or harness then you can get by with a 30 lb wing and if the diver needs to doff the rig on the surface neither he nor the rig will sink. As an added bonus in case the diver needs to doff at depth he will not go bolting to the surface because of his inherent buoyancy and the buoyancy of the wetsuit.

It has been a while since I read J.J.'s book but I remember him being very unambiguous on the need for ditchable weight, even if it is only a can light. I am pretty sure him and George mention the same thing in the video.

 

[dumpsterDiver]

It is amazing to me how the definition of "balanced rig" has (apparently) lost its meaning. As I recall, it used to have a very specific and easily defined definition, but now some people seen to re-define it so that it has lost its meaning.

Maybe I am wrong with the origination of the term, but I remember George Irvine going absolutely CRAZY about needless tech diver depths. What seemed to drive him batty was divers using wetsuit, big negative, double steel tanks (therefore no need for much or any lead) and then some of them even added steel stage bottles. He ranted and raved that this was an unsafe condition because of the potential for BC failure and no ballast to ditch.

In any regard, it made a lot of sense to me.

So a balanced rig was simply a scuba unit (and exposure suit combination) that, AFTER A COMPLETE BC FAILURE, the diver could ditch anywhere between 0 and XX lbs of ballast and be able to swim to the surface.


Or in other words, have enough ditchable ballast so that you won't die if the BC fails. Some rigs require ZERO ditchable lead/ballast.

So from this meaning, the actual lift capacity of the BC was irrelevant.

Is that correct?