How you write deco plan on your slate?

[doctormike]

Alas the ultimate response is to never go diving. Never drive. Always wear a helmet. Never fold paper without gloves... the infantilisation of the world. We go diving to get away from those ****ing ***kers.

Diving is the ultimate responsibility to oneself.

Thankfully the rest of the world doesn't have the plethora of ****ing **it-for-brains ambulance chasing lawyers that seem to infest the US of A. Had a hospital procedure: the last person to sign you off is a ****ing lawyer, then the accountant hands you the bill/check for 10x the cost of elsewhere on the planet.


Maybe this is why there's so few dive lifts on US dive boats!

Not sure where all that is coming from. What's infantalizing about surface support? The bigger the dive, the more important that it is.

I know that there is a lot of bravado among technical divers, but I never heard of anyone turning down a coast guard chopper ride to a chamber, or any other rescue, on general principals of rugged individuality.

 

[johndiver999]

I mean, it's sort of like what you said you were doing. You did something that isn't accounted for by the algorithm (exercise), so you do longer stops. Padding. While it's possible to adjust the algorithm in the DC itself during the dive, it's also possible to just do longer stops an guesstimate, which is what I thought you were saying that you did.

The problem with just guesstimating is that you may actually be increasing your decompression stress if you overdo it. See the controversy about "deep stops".

And as mentioned above, you can actually change GF hi, or just watch GF99 and SurfGF to get an idea what your leading compartment overpressure would be at any point in the dive or on surfacing, and use that to guide you to an ascent that you are comfortable with.

Wouldn't the computer give you feedback on your padded stop by, for example, start to increase your ascent time. I would assume that if the ascent time is staying the same as you continue to hang, then you are not moving in a negative direction with regard to the decompression process, but rather just approaching that goal slower than optimum? Even if it does, start to add a little to the ascent time, as long as you don't end up violating the computer, can you assume your guesstimate isn't too much of a problem?

 

[Celt]

Not sure where all that is coming from. What's infantalizing about surface support? The bigger the dive, the more important that it is.

I know that there is a lot of bravado among technical divers, but I never heard of anyone turning down a coast guard chopper ride to a chamber, or any other rescue, on general principals of rugged individuality.

the people on the surface are part of the dive and everyone must be on the same page. You need a supervisor to run the diving operations. A loose cannon is not a good thing.

 

[Wibble]

here's is a paper that has looked at Ratio versus compartment models

https://www.dhmjournal.com/images/47/DHM-Vol47.1.pdf

page 9

Their study was a single "experiment" testing two decompression curves, one using ratio deco which has deep stops and the other using Buhlmann 30:85 (again with a much lower GF-Lo than the ~50 which is more commonly used nowadays). I believe that this study was subsequently repeated in the UK at the (now defunct) National Diving and Activity Centre.

Overall, our findings contradict the idea that adding longer and/or deeper stops is useful to achieve a more effective decompression.

Does bring to mind how technical diving has changed in the past 10 years.

• Reliable equipment and the cost of helium has increased the prevalence of rebreathers; they dominate deeper diving nowadays to the extent that it's rare to see open circuit used
• Deep stops and bubble models are not popular
• Buhlmann with Gradient Factors has settled around 50:80 to 50:70; few dive GFs wildly outside of that range.
• Reliable, usable and effective dive computers have driven out the need for ratio deco meaning more consistent application of decompression algorithms as computers will recalculate on the fly.
• Training is more consistent; little variation between the syllabuses of the larger agencies (ignoring the small 'team-oriented' agencies)
• Rebreathers make multi-day deep diving possible as the marginal cost of diving is low.
• Rebreathers enable CNS and POT (pulmonary oxygen toxicity) to be controlled by adjusting setpoints. Warm and moist gas breathing may/should/is kinder to the lungs. Long decompression schedules are easier to manage as gas volumes are tiny in comparison with OC.

 

[Wibble]

the people on the surface are part of the dive and everyone must be on the same page. You need a supervisor to run the diving operations. A loose cannon is not a good thing.

Depends what you're doing and where you're diving.

Most of the diving I've ever done has no such person on board. If you need a buddy, bring one, else you dive alone. You agree with the skipper the dive runtime and that's about it.

If you want a drop bottle, you must explicitly agree the protocol (e.g. yellow bag comes up, throw my drop-bottle over attached to the 7m line and marker buoy/float at the other end).

Some clubs have a person with a clipboard.

If doing much deeper dives, say 100m+, you may put in a lot more planning and support. Is this what you're talking about?

 

[Celt]

Depends what you're doing and where you're diving.

Most of the diving I've ever done has no such person on board. If you need a buddy, bring one, else you dive alone. You agree with the skipper the dive runtime and that's about it.

If you want a drop bottle, you must explicitly agree the protocol (e.g. yellow bag comes up, throw my drop-bottle over attached to the 7m line and marker buoy/float at the other end).

Some clubs have a person with a clipboard.

If doing much deeper dives, say 100m+, you may put in a lot more planning and support. Is this what you're talking about?

For a solo dive you can run the entire dive on your own. But for a dive needing multiple divers and surface crew you need a supervisor to coordinate the diving. For example anything that would involve exchanging gear or materials between the surface and the site. Another example would be where a job would take longer than any one diver could complete, A large survey or ongoing work. All diving really should have standby divers especially complex deep dives. The standby is fresh and doesn’t have a deco obligation, he can also coordinate between people in the water and the surface. All of this is organised and run by the supervisor.

 

[Wibble]

For a solo dive you can run the entire dive on your own. But for a dive needing multiple divers and surface crew you need a supervisor to coordinate the diving. For example anything that would involve exchanging gear or materials between the surface and the site. Another example would be where a job would take longer than any one diver could complete, A large survey or ongoing work. All diving really should have standby divers especially complex deep dives. The standby is fresh and doesn’t have a deco obligation, he can also coordinate between people in the water and the surface. All of this is organised and run by the supervisor.

That's very much the commercial diving ethos. The surface supervisor is the overall controller; the divers are under his orders and generally diving as work.

Recreational diving (including tech diving) is very much about the individual choosing to dive. Whether in a team or solo is largely immaterial as the individual's mainly responsible for their actions.

 

[Celt]

That's very much the commercial diving ethos. The surface supervisor is the overall controller; the divers are under his orders and generally diving as work.

Recreational diving (including tech diving) is very much about the individual choosing to dive. Whether in a team or solo is largely immaterial as the individual's mainly responsible for their actions.

I was talking about scuba, I deliberately left out commercial surface supplied gas and coms. No dive is about an individual diver, unless solo. The actions of all divers affects everyone in the water and topside. You need a solid system and someone in charge. We always worried about a diver asking to dive with us outside our procedures.

 

[doctormike]

Wouldn't the computer give you feedback on your padded stop by, for example, start to increase your ascent time. I would assume that if the ascent time is staying the same as you continue to hang, then you are not moving in a negative direction with regard to the decompression process, but rather just approaching that goal slower than optimum? Even if it does, start to add a little to the ascent time, as long as you don't end up violating the computer, can you assume your guesstimate isn't too much of a problem?

Right, if you actually follow the computer as it follows your new padded schedule instead of just adding deep time to compensate for extra work. But the recalculations would be using the same GFs, so if you really wanted to change your ascent curve to compensate for something (like work) that's not accounted for by the model (whose only inputs are depth, time and mix/PO2), I would think that you would be better off actually changing the GFs.

And as mentioned above, precision and accuracy are two different things, and even if you do change the GFs, even that's a guess, since the computer can't measure work numerically. Or age, conditioning, underlying medical stuff, etc...

 

[johndiver999]

Right, if you actually follow the computer as it follows your new padded schedule instead of just adding deep time to compensate for extra work. But the recalculations would be using the same GFs, so if you really wanted to change your ascent curve to compensate for something (like work) that's not accounted for by the model (whose only inputs are depth, time and mix/PO2), I would think that you would be better off actually changing the GFs.

And as mentioned above, precision and accuracy are two different things, and even if you do change the GFs, even that's a guess, since the computer can't measure work numerically. Or age, conditioning, underlying medical stuff, etc...

My old computers don't allow that sort of thing. Last week I had maybe 5-6 minutes of deco when leaving the bottom at around 100 and an ascent time of a couple more minutes. I had been working hard so I wanted to be careful.

I stopped around 50 feet and very slowly came up to 40 for a little over a minute. I think my deco and ascent time went up another minute or so due to the delay, but that is not something that really surprised me or caused me to hurry my ascent. I generally move very slowly from 50 to 30 and just did my hang around 15-20 feet (with a 10-ft ceiling) and added another minute or so at 10 feet once it was clear. I figure any extra time at 25 feet or less on nitrox is not going to be a problem.