DIR- GUE Balanced rig with a thick wetsuit - mathematically impossible?

[Celt]

That is misinformation. Your wetsuit loses buoyancy at depth: basic Boyle's Law calculation. Most of the buoyancy (and warmth) of neoprene comes from the gas bubbles permanently trapped inside the rubber. As the ambient pressure increases with depth, those bubbles are compressed and suffer a proportional loss of buoyancy. This is true regardless of the type of neoprene used.

If you don't believe me then put an empty wetsuit and some weights into a mesh bag and take it down to 100 ft (30m). Use a fish scale to see how much lift it loses at depth.

To answer the original question, yes it is pretty much impossible to have a fully balanced rig with a thick wetsuit. With a single tank most of us can probably swim it up if we have to, but it's safer and more comfortable to use a proper shell drysuit.

Not 22lbs it doesn’t, all neoprene is not the same, there are different densities and linings. I use 16lbs with my Elios 7mm long John + 7mm jacket with hood in cold water. No problem swimming up steel twins. Photo coming to the deco station in an O’Dare high density wetsuit 7mm long John + 7mm jacket and hood no wing and no weight belt , no problem swimming up the loss of buoyancy on the bottom at 57m. Perfect balance at 10 foot stop with 50bar.
I understand where the problem comes from with soft stretchy neoprene in xxxlarge sizes. It’s not a good idea to make divers helpless, they should be able to overcome a bit of weight or buoyancy. Neutral is nice but you shouldn’t drown or get bent if you’re not.

 

[jadairiii]

I am still convinced that balancing a rig according to the GUE definition is impossible but I guess you can bend the rules a bit for simpler dives.

it's not impossible, but GUE has tended to give the impression, as the agency has aged, of a very "rigid" system. It never was intended to be that way. And trust me, I know, my trimix instructor was like #2 instructor at GUE (I took his mix class as they were creating the courses for GUE in 1997) and one of my Cave instructors was a very early GUE cave instructor.

Think the problem through, but dont over-think the problem, dont use gear to solve a problem that skills can solve. Dont plan you whole dive and gear selections based on the .0001% possible bad outcome. Sure, I can get eaten by a shark, but that doesn't mean I dive in a chainmail suit, or a shark cage or carry a .357 mag powerhead on every dive.

You would be shocked at what was considered "DIR" in 1998.

 

[crofrog]

I think your concept of the balanced rig is incomplete, the fundies handout has limited information in it because it's the slides for the lectures. Your fundies instructor would better answer this question, but I'll provide my understanding of it.


The concept of the balanced rig has 2 goals:
1. Be light enough or have enough ditchable weight to allow you to swim the rig up in the event of a wing failure at the heaviest point of the dive when your tanks are full and you're at the max depth if diving wet.
2. Allow you to hold your shallowest stop when you're at the lightest point of your dive, i.e., the end when you've lost most of your gas weight.

In a wetsuit, "goal 1" is accomplished by having enough ditchable weight, e.g., removable lead weight, light canister, etc., that you can generate enough thrust with your legs to start swimming up, and as you get shallower, your wetsuit will start providing more buoyancy.

Goal 2 is accomplished by having sufficient weight so that you aren't fighting to stay down at 10ft, which is super annoying when it happens.


If you're diving wet with appropriate tanks and your wing fails towards the end of the dive, you should be able to swim up without ditching all of your weight (or potentially any), and you'd still be able to accomplish goal 2.

 

[crofrog]

or a shark cage or carry a .357 mag powerhead on every dive.

what is this the 70's... The DIR approved solution is a Glock 19 with Maritime spring cups

 

[Nick_Radov]

it's not impossible, but GUE has tended to give the impression, as the agency has aged, of a very "rigid" system. It never was intended to be that way. And trust me, I know, my trimix instructor was like #2 instructor at GUE (I took his mix class as they were creating the courses for GUE in 1997) and one of my Cave instructors was a very early GUE cave instructor.

The tension has always been between one approach of giving students a set of basic guiding principles and allowing them to deduce the details versus the other approach of having students memorize detailed protocols and standards that they can follow without having to think. The first approach produces flexible divers who can manage any situation but it tends to fall apart with those who don't already have enough variety of dive experience to understand what will work underwater. For example, much of the chirality in the DIR backmount gear configuration is due to fact that common DPV motors always spun clockwise which implies you have to drive the scooter with your right hand and stages naturally go on the left to stay out of the prop wash. But divers who lack experience with tow-behind scooters sometimes struggle to follow that logic.

The second, more prescriptive, approach produces divers who can safety and smoothly integrate into teams because everyone is interchangeable. You don't have to waste time getting them clear on the basics. But when faced with a novel situation they have to ask for help or sometimes go completely off the rails because they only know the "how" and not the "why". This is how we get divers with many years of experience and multiple GUE certifications coming up with wacky nonsense like claiming that double bladder wings are actually a smart idea or using sidemount rigs for regular ocean dives or whatever.

Most of us could benefit from a mix of both approaches. With online forums it's just really tough to explain anything from first principles as you never know what kind of background the reader has and even the clearest messages are often misinterpreted.

Think the problem through, but dont over-think the problem, dont use gear to solve a problem that skills can solve. Dont plan you whole dive and gear selections based on the .0001% possible bad outcome. Sure, I can get eaten by a shark, but that doesn't mean I dive in a chainmail suit, or a shark cage or carry a .357 mag powerhead on every dive.

I hear that .223 is the new DIR powerhead standard.

You would be shocked at what was considered "DIR" in 1998.

Indeed.

 

[johndiver999]

The concept of the balanced rig has 2 goals:
1. Be light enough or have enough ditchable weight to allow you to swim the rig up in the event of a wing failure at the heaviest point of the dive when your tanks are full and you're at the max depth if diving wet.
2. Allow you to hold your shallowest stop when you're at the lightest point of your dive, i.e., the end when you've lost most of your gas weight.

In a wetsuit, "goal 1" is accomplished by having enough ditchable weight, e.g., removable lead weight, light canister, etc., that you can generate enough thrust with your legs to start swimming up, and as you get shallower, your wetsuit will start providing more buoyancy.

Goal 2 is accomplished by having sufficient weight so that you aren't fighting to stay down at 10ft, which is super annoying when it happens.


If you're diving wet with appropriate tanks and your wing fails towards the end of the dive, you should be able to swim up without ditching all of your weight (or potentially any), and you'd still be able to accomplish goal 2.

So you are saying that the concept of a "balanced rig" includes having a ditchable weight belt for example? I think a lot of people seem to think the definition precludes the use of ditchable lead.

I think the distinction, or at least agreement upon, the definition of "balanced rig" is critical.

 

[Nick_Radov]

So you are saying that the concept of a "balanced rig" includes having a ditchable weight belt for example? I think a lot of people seem to think the definition precludes the use of ditchable lead.

Oh no, here we go again...

I think the distinction, or at least agreement upon, the definition of "balanced rig" is critical.

Before we get into the details of what does or doesn't constitute a balanced rig in particular circumstances let's go back to first principles. The point is to not drown and (hopefully) avoid decompression injury even if you have an equipment failure, without introducing convolutions that cause a cascading series of other problems. Now, what does that imply about ditchable weight or lack thereof? And does the answer change depending on what type of diving you're doing? Think things through from that perspective and you can probably answer your own question.

I'm not trying to be unhelpful here but the fact that this question keeps coming up indicates that divers are still not getting clear on the basics. And unfortunately the GUE training materials are still lacking on this topic (I have submitted a formal RFC asking them for a revision).

 

[johndiver999]

Oh no, here we go again...

Before we get into the details of what does it doesn't constitute a balanced rig in particular circumstances let's go back to first principles. The point is to not drown and (hopefully) avoid decompression injury even if you have an equipment failure, without introducing convolutions that cause a cascading series of other problems. Now, what does that imply about ditchable weight or lack thereof? And does the answer change depending on what type of diving you're doing? Think things through from that perspective and you can probably answer your own question.

I'm not trying to be unhelpful here but the fact that this question keeps coming up indicates that divers are still not getting clear on the basics. And unfortunately the GUE training materials are still lacking on this topic (I have submitted a formal RFC asking them for a revision).

I'm not DIR, I'm just asking a question.

One which seems to me to be absolutely primal and terribly important, yet it can't be answered in a straight forward manner? It is a term we always hear but you can't definite it, even with all your big words? (BTW I had to look up chiral) my organic teacher would probably be disappointed in me; at least that Cis Trans isomerism is peripherally related to today's society. LOL.

What is this a secret sect that won't define their most commonly used terms?

 

[JoeTPhilly]

 

[overthinking_diver]

I think your concept of the balanced rig is incomplete

I am using the exact same definition for a balanced rig that you gave in your post With one addition that if you need to ditch weights you should still be able to hold a stop at 10ft and not rocket to the surface.

I think the distinction, or at least agreement upon, the definition of "balanced rig" is critical.

We're all using the same definition for a balanced rig here. There's some argument about ditchable weights. But that argument is irrelevant to my point in the OP. I claim balancing a rig is impossible even with ditchable weights. Without them it is even more impossible.

it's not impossible

Can you give me an example using all assumptions I have in the OP? You need weight_we_can_swim_up + positive_buoyancy_at_10_feet_we_can_handle >= 22. So do you want to swim up 15 pounds and be 7 pounds positive at 10 feet, or swim up 12 pounds and be 10 pounds positive at 10 feet? Or do you want to drop different amounts depending on how much gas you have left?

dont use gear to solve a problem that skills can solve

I'm not doing this at all! I never mentioned skill anywhere in the OP. Clearly, the weight_we_can_swim_up and positive_buoyancy_at_10_feet_we_can_handle numbers will be different for different divers. But we need to have some default numbers for the average diver.

I honestly have no idea what would be a reasonable estimate for these numbers. It just feels impossible to have them add up to 22 pounds.

Dont plan you whole dive and gear selections based on the .0001% possible bad outcome

Which bad outcome am I over-planning for? Are you saying we shouldn't plan for a wing failure?