gcarter
Contributor
Carter Super Sausage with 25# lift.
Redundant Buoyancy
- Thread starter Michael Guerrero
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DogDiver
Contributor
Hollis SMS 100D... Dual bladder... 50lb lift bag.... Occasional Hollis Drysuit
DevonDiver
N/A
It depends on the parameters of the dive.
Simple balanced rig is my first preference, but only within known and tested parameters; where I can assuredly swim the rig up and complete necessary stops.
When that options becomes less assured, or impossible, (dictated by cylinders and extra equipment carried) I will switch to a dual-bladder wing. As I mostly now dive sidemount, I have two options; First, an supplementary MSR bag w/oral inflate (either worn or carried and donned as necessary). Second, if requirements are beyond the lift capacity of the MSR (5+ AL80s), I use a dedicated dual-bladder higher capacity wing set-up in a custom/DIY sidemount rig (see here).
I also tend to use the dual-bladder option when instructing, as I believe supervision requires preserving as much operating capacity as possible. As an instructor, I want to deal with problems swiftly, cleanly, with minimum fuss and to cause the least distraction. I also want to preserve effective positive buoyancy (comfortable surface flotation with 'hands free' and head above water) so that I could always perform rescue techniques on the surface. This is nothing more than accepting a need to plan/prepare for a near-unreasonable combination of failures; loss of my primary buoyancy in addition to my student having severe difficulties and requiring assistance on ascent or at the surface.
I'm not a fan of using drysuits in the tropics. I prefer to stay cool and hydrated. I've seen tropical drysuit users tempted to curtail pre-dive responsibilities due to discomfort/dehydration because of their choice of exposure protection. If an equipment choice puts negative pressures on a diver, then it's a bad choice IMHO.
I don't disagree in principle with lift-bags/DSMBs being touted as redundant buoyancy options. I do disagree with people using/relying on them as an option without having done specific training to accomplish that (in addition to the other demands of a 'worst case' technical deco ascent)... and/or without maintaining that skill familiarity through sufficient rehearsal and practice.
From what I've seen of the tech community, I don't have a high degree of confidence that many technical divers gain or retain the necessary skill-set and competency to rely upon DSMB/Lift-Bag as a form of buoyancy redundancy. It's as much a 'skills solution' as it is an 'equipment solution'... and half of that equation seems to be missing in many cases.
As I write this, some 51% of respondents have indicated they use DSMB/Lift-Bag for redundant buoyancy. I'd ask, honestly, how frequently they practice that skill. I just don't see 50% of the tech community practicing this frequently, or at all.
I suspect that DSMB/Lift-Bag is just a very convenient 'solution to a requirement', rather than a legitimate 'solution to an emergency'. We all carry lift-bags/DSMBs... so it's an easy option to dismiss a theoretical problem with. Staying alive on tech dives isn't about requirement tick-lists... it's about surviving emergencies.
Simple balanced rig is my first preference, but only within known and tested parameters; where I can assuredly swim the rig up and complete necessary stops.
When that options becomes less assured, or impossible, (dictated by cylinders and extra equipment carried) I will switch to a dual-bladder wing. As I mostly now dive sidemount, I have two options; First, an supplementary MSR bag w/oral inflate (either worn or carried and donned as necessary). Second, if requirements are beyond the lift capacity of the MSR (5+ AL80s), I use a dedicated dual-bladder higher capacity wing set-up in a custom/DIY sidemount rig (see here).
I also tend to use the dual-bladder option when instructing, as I believe supervision requires preserving as much operating capacity as possible. As an instructor, I want to deal with problems swiftly, cleanly, with minimum fuss and to cause the least distraction. I also want to preserve effective positive buoyancy (comfortable surface flotation with 'hands free' and head above water) so that I could always perform rescue techniques on the surface. This is nothing more than accepting a need to plan/prepare for a near-unreasonable combination of failures; loss of my primary buoyancy in addition to my student having severe difficulties and requiring assistance on ascent or at the surface.
I'm not a fan of using drysuits in the tropics. I prefer to stay cool and hydrated. I've seen tropical drysuit users tempted to curtail pre-dive responsibilities due to discomfort/dehydration because of their choice of exposure protection. If an equipment choice puts negative pressures on a diver, then it's a bad choice IMHO.
I don't disagree in principle with lift-bags/DSMBs being touted as redundant buoyancy options. I do disagree with people using/relying on them as an option without having done specific training to accomplish that (in addition to the other demands of a 'worst case' technical deco ascent)... and/or without maintaining that skill familiarity through sufficient rehearsal and practice.
From what I've seen of the tech community, I don't have a high degree of confidence that many technical divers gain or retain the necessary skill-set and competency to rely upon DSMB/Lift-Bag as a form of buoyancy redundancy. It's as much a 'skills solution' as it is an 'equipment solution'... and half of that equation seems to be missing in many cases.
As I write this, some 51% of respondents have indicated they use DSMB/Lift-Bag for redundant buoyancy. I'd ask, honestly, how frequently they practice that skill. I just don't see 50% of the tech community practicing this frequently, or at all.
I suspect that DSMB/Lift-Bag is just a very convenient 'solution to a requirement', rather than a legitimate 'solution to an emergency'. We all carry lift-bags/DSMBs... so it's an easy option to dismiss a theoretical problem with. Staying alive on tech dives isn't about requirement tick-lists... it's about surviving emergencies.
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gcarter
Contributor
Diving the St Lawrence, we shoot our DSMBs regularly. We also practice in the local quarry. At least 1/3 of my dives.
AS most have said, depends on the dive. I dive wet, so balanced rig if possible (double AL80s and a couple of half-full AL80 decos works quite well). If I'm sidemounting I like heavier cylinders, as they trim out better, so I use a Hollis SMS100D. For all other emergencies, there's a lift bag.
When I had to deploy a lift bag for real with a failed wing and too-heavy doubles (that's the last HOG wing I ever buy, and the last time I twin up Catalina C95s...), I was glad I'd given some thought to using a lift bag and run some practice ascents to work out the easiest method - deploy with a reel and climb the line, or use the bag as a BCD. It happened for real, I'd recently been playing with techniques, I had the bag out and was neutrally buoyant again in less time than it took me to work out that a large part of the seam of the bladder in my wing had unwelded itself...
When I had to deploy a lift bag for real with a failed wing and too-heavy doubles (that's the last HOG wing I ever buy, and the last time I twin up Catalina C95s...), I was glad I'd given some thought to using a lift bag and run some practice ascents to work out the easiest method - deploy with a reel and climb the line, or use the bag as a BCD. It happened for real, I'd recently been playing with techniques, I had the bag out and was neutrally buoyant again in less time than it took me to work out that a large part of the seam of the bladder in my wing had unwelded itself...
DevonDiver
N/A
"Shooting a DSMB" isn't the same as controlling a full decompression stop, gas-switching, stage-handling, ascent with a DSMB, simultaneously managing any one of the full spectrum of foreseeable emergencies/failures that we, technical divers, are expected to be able to deal with.
Or are you saying that on 1/3rd of your technical dives you abandon your primary buoyancy and complete the dive using only the DSMB... and, at the same time, practice other multiple failures?
gcarter
Contributor
Don't do technical dives (yes I know what forum I am in) but I am comfortable that I can handle buoyancy failures on my rec dives.
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