Catastrophic Failure - How much weight to drop? Theoretical Discussion
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New Scuba Guy
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My first thought was that if this guy weighs 160 pounds, 28 pounds of weight is way too much. Maybe I'm wrong, but at 180 pounds I dive with 12-14 pounds and I'm wearing a 7mm full wetsuit with hood, Aluminum 80 tank, 85-90 feet deep in fresh water, with bottom temp in the high 40's.
But that's secondary. Too often newer divers aren't taught about ditching weight or performing an effective emergency ascent from depth. As someone else mentioned, my idea of a "catastrophic failure" would be a medical emergency. And every year divers die because of panic when faced with a challenging situation where most of the time they put themselves into a situation that they are not trained to deal with and are literally "in over their heads".
I agree with the gentleman who mentioned about having a pony bottle along. I won't consider going 90-100 feet deep without having some sort of contingency or redunant safety measure. A 13 cuft. pony bottle with 1st and 2nd stage regs is part of my standard equipment.
Were proper equipment checks performed pre-dive? When was the last time the equipment was serviced? What kind of pre-dive plans were formulated and agreed upon. I know I'm spiltting hairs here, but if a dive is well planned, emergency procedures are agreed upon and reviewed.
I often wind up being the dive team leader at Dutch Springs with the guys I dive with. Before every dive, we agree that upon intial descent, usually to a platform, we all perform at least one or 2 basic skills; i.e.-mask removal and replacement, regulator recovery, buddy breathing, etc. just as a reminder that the basics could mean the difference between life and death.
I probably strayed from the original gist of the subject, and no I didn't take into consideration the compressionability of the wetsuit, saturation rates or any of the technical facets of scuba diving, but again, a well-trained and well practiced diver should be able to react in a rational manner even to a "catastrophic failure."
But that's secondary. Too often newer divers aren't taught about ditching weight or performing an effective emergency ascent from depth. As someone else mentioned, my idea of a "catastrophic failure" would be a medical emergency. And every year divers die because of panic when faced with a challenging situation where most of the time they put themselves into a situation that they are not trained to deal with and are literally "in over their heads".
I agree with the gentleman who mentioned about having a pony bottle along. I won't consider going 90-100 feet deep without having some sort of contingency or redunant safety measure. A 13 cuft. pony bottle with 1st and 2nd stage regs is part of my standard equipment.
Were proper equipment checks performed pre-dive? When was the last time the equipment was serviced? What kind of pre-dive plans were formulated and agreed upon. I know I'm spiltting hairs here, but if a dive is well planned, emergency procedures are agreed upon and reviewed.
I often wind up being the dive team leader at Dutch Springs with the guys I dive with. Before every dive, we agree that upon intial descent, usually to a platform, we all perform at least one or 2 basic skills; i.e.-mask removal and replacement, regulator recovery, buddy breathing, etc. just as a reminder that the basics could mean the difference between life and death.
I probably strayed from the original gist of the subject, and no I didn't take into consideration the compressionability of the wetsuit, saturation rates or any of the technical facets of scuba diving, but again, a well-trained and well practiced diver should be able to react in a rational manner even to a "catastrophic failure."
DevonDiver
N/A
Could you do it without air to breathe?
One scenario that must be accounted for is OOA. That'd be a primary cause for losing the ability to ascend by buoyancy alone. Swimming up 10+ lbs of weight on a CESA doesn't sound too clever..
And then.... all it takes is a leg cramp from the exertion....
We can justify just about anything if we only consider a single problem arising. As we know... problems tend to domino. To contemplate these scenarios from the (IMHO, more realistic) perspective of attributable secondary issues arising... we see a breakdown in potential resolutions...
Monterey divers wearing 2 piece 7mm rental suit diving Al80's can use a formula of 10% of their body weight plus 14 pounds. This is just a starting point. Slender people with low Bmi may/will find themselves a little overweighted, where as poi eating buoyant braddahs like me may need a tad more. So weight seems close for a nearly empty cylinder. Nice thread. I personally pray my streak of never needing to drop lead continues.
Malama pono
Malama pono
The above formula is what I've seen CA divers taught.
For all you out there flaming the OP for the amount of lead he used in his scenario... Out here on the central/northern CA coast the newbies and the occasional divers use 2 layer 7 mm wetsuits (that equals a lot of 14 mm area) and ballast often approaches 30#. The less fit often have much more (fat floats). Please don't forget that your shiny SS backplate and your steel tank ARE ballast - they just aren't made of lead.
I'm 66", 138#, have a 22% body fat, and currently use a membrane type drysuit with not enough air in my drysuit (as commented by at least 2 instructors) and my ballast is as below. Anything less (yes I have tried) makes holding a safety stop impossible without hanging onto the ever present kelp. Oh, and while my buoyancy control isn't as good as some of the cavers I've seen -- it is pretty darned good.
Steel LP 95, add 5# lead if using an Al 80
SS backplate (my best recollection is 8# neg)
Pony (3# neg when full)
6# ankle weights (divided) - would be less if my fins were negative, but they are neutral.
2# tank trim weight (becomes 2 + 3 if not using my pony, or 5 + 5 if Al 80 and no pony)
and 10# (5 each dumpable pouch) weight harness.
Summed up: 5# steel tank + 8# SS backplate + 3# pony + 2# lead trim + 6# ankle weights + 10# weight belt = 34 pounds
windapp
Contributor
My answer to the original question is "As little as is needed"
If I was OOA, and had to do and emergency buoyant ascent (from too deep to CESA), I would drop my weight pockets one at a time until I started to ascend.
If my BC lost buoyancy, I would only ditch weights as a last resort. In warm water, I can kick to get up. In cold, if the option was available for me to find somewhere to kneel or stand, I would use my SMB to create an up line, and climb it to the surface. If I was in cold water, and on a wall, and I couldn't climb the wall, and I was too heavy to swim up, and my buddy couldn't help me, I would drop just enough weight to enable me to swim up.
If I was OOA, and had to do and emergency buoyant ascent (from too deep to CESA), I would drop my weight pockets one at a time until I started to ascend.
If my BC lost buoyancy, I would only ditch weights as a last resort. In warm water, I can kick to get up. In cold, if the option was available for me to find somewhere to kneel or stand, I would use my SMB to create an up line, and climb it to the surface. If I was in cold water, and on a wall, and I couldn't climb the wall, and I was too heavy to swim up, and my buddy couldn't help me, I would drop just enough weight to enable me to swim up.
flots am
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That's an interesting point.
Without air, or a buddy to share with, or redundant air source, the only realistic option is an emergency ascent (swimming if neutral, buoyant if not).
Nobody is going to be swimming up any significant amount of weight without breathing.
flots.
There's the problem in why you think he is overweighted: the OP is diving in salt water, not fresh water.
His weight seems fine for cold salt water.
Whirling Girl
Contributor
Its a trick question because the answer is you should never, ever ditch weight at depth. Ever.
I'm sorry to come into the discussion so late, with a completely different perspective.
I'm sorry to come into the discussion so late, with a completely different perspective.
KD8NPB
Contributor
You can't breathe water.
If you need to dump, you need to dump.
A better investment would be O2 for the car. If you do experience a free ascent from 99 ft, you're probably going to come up a'bubblin'. Therefor, the faster you get on O2, the better.
If you need to dump, you need to dump.
A better investment would be O2 for the car. If you do experience a free ascent from 99 ft, you're probably going to come up a'bubblin'. Therefor, the faster you get on O2, the better.
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