Planned deco on a recreational dive?

[MXGratefulDiver]

What method do you use to prevent yourself from getting distracted and forgetting to monitor your air and time? At that level, I haven't seen anything different in your planning from anybody else's. If either of you get distracted and forget to monitor whatever data it is that you use to turn the dive, it's a problem.

... because if you have an end point in mind ... knowledge beforehand of what your gas consumption is likely to be at a given point in the dive ... you're more likely to not only catch yourself during moments of distraction, but more likely to be able to formulate a response once you do. You're less likely to put yourself into a situation where you need to react to a mistake ... and if you do need to react, it'll be with more knowledge (because you put forethought into it) of how to do so without turning it into an emergency ...

... Bob (Grateful Diver)

 

[tursiops]

Bob, tell me what method will work for a person who doesn't pay attention to their gauges and gets preoccupied or distracted during a dive? You can have the greatest plan in the world and if you don't pay attention it won't matter. Will it?

This is exactly my point. Turn Pressures (for example) always take precedence over Objectives, or over Photography, but if you just zone out, the dive plan is quite irrelevant. I'm a little surprised that it seems to have been suggested that if you don't calculate your step-by-step dive using your SAC, you can't possibly dive safely.

 

[RainPilot]

Plan your dive: do gas calculations like Bob does beforehand so you know what to expect at various key points in the dive (turn around, navigation decisions etc.)

Dive your plan: compare the actual with the expected. If there are discrepancies then check for leaks etc and readjust your plan. When you get to your turn pressure or key point, decision making becomes so simple. X amount or more? Carry on. Less? Go to plan B.

Just because you planned doesn't mean you don't have to check and vice versa. It's not rocket surgery.

 

[MXGratefulDiver]

This is exactly my point. Turn Pressures (for example) always take precedence over Objectives, or over Photography, but if you just zone out, the dive plan is quite irrelevant. I'm a little surprised that it seems to have been suggested that if you don't calculate your step-by-step dive using your SAC, you can't possibly dive safely.

I'm a little bit surprised you've read that into what I've been saying ... nor did I say anything about "zoning out". Distractions happen during a dive ... particularly on deeper dives. That doesn't mean someone's going to go through the whole dive that way. Diving's a situational thing, and sometimes you need to or want to change the profile. It's useful to understand how that may impact the gas supply you have with you.

Or you can just ride your gauge, and hope for the best, I suppose ... I'd like to see one of you explain how you arrive at your turn pressure ...

... Bob (Grateful Diver)

 

[tursiops]

I'm a little bit surprised you've read that into what I've been saying ... nor did I say anything about "zoning out". Distractions happen during a dive ... particularly on deeper dives. That doesn't mean someone's going to go through the whole dive that way. Diving's a situational thing, and sometimes you need to or want to change the profile. It's useful to understand how that may impact the gas supply you have with you.

Or you can just ride your gauge, and hope for the best, I suppose ... I'd like to see one of you explain how you arrive at your turn pressure ...

... Bob (Grateful Diver)

You keep assuming that the alternative to your kind of planning is to "ride the gauge." I would suggest that having to pay attention to one BIG thing (SPG) is often better than having to pay attention to many things, and possibly getting confused or undertain.

How do I arrive at thirds for a no-flow cave dive? Seriously? I need to explain that?

 

[MXGratefulDiver]

You keep assuming that the alternative to your kind of planning is to "ride the gauge." I would suggest that having to pay attention to one BIG thing (SPG) is often better than having to pay attention to many things, and possibly getting confused or undertain.

How do I arrive at thirds for a no-flow cave dive? Seriously? I need to explain that?

I know how and why people plan for thirds in caves ... but that wasn't really the context of the question ... it's been suggested by some in here that 700 psi is sufficient for a safe ascent from 110 feet. I'd like to understand how they arrive at a specific number like that ... particularly without any mention of consumption rate, or any consideration of conditions (which affect consumption rate), or targeted reserves ... I'd like to know where that number came from ...

... Bob (Grateful Diver)

 

[BRT]

Depends on the dive profile and circumstances. As an example, I recently did a dive on a wall that's known for current. The reality of the current that day bore little resemblance to the prediction, and we found ourselves kicking against it on the return. Had I relied strictly on turn pressure I would not have made it back to the exit point without running out of air.

Turn pressure's just one of several criteria that needs to be applied to a gas plan. One must also factor in the exit strategy if things don't go as expected ... and "up" isn't always the best option, even on open-water, no-deco dives ...

... Bob (Grateful Diver)

Bob, what did you rely besides turn pressure? I'm assuming that you are going to say that when you noticed that the current was going to be against you coming back you turned sooner? That is not preplannable but it seems obvious. We always go against current out if possible and if I found myself going with current on the way out and had to get back to the entry point I would cut the swim short and stay close to the exit.

 

[scubadada]

I need just over 200 psi from an AL80 to ascend from 110 ft at 30 ft/min with a 3 minute safety stop at a little over my avg RMV of 0.37 cf/min. I usually dive solo, so starting at 700 psi would work for me. For two people, it would be cutting it close, particularly if the other diver had a higher consumption rate. For contingency gas calculations, i.e. my pony size, I use twice my average RMV in the calculations. Of course, I do watch my guage, I still can't quite figure out how divers can go OOA short of an emergent event

 

[BRT]

Reacting works just fine, as long as you remember when to react.

In my experience, people who go OOA/LOA usually are so focused on other things (like taking pictures or catching lobsters) that they neglect to monitor their gauge. When that happens, turn pressure doesn't mean much.

Having a dive plan always works better than relying on a data point to manage your dive. It gives you much more information to work with, and comes with better feedback to help you manage what you're doing.

... Bob (Grateful Diver)

So it someone is out lobstering and not watching their gauges what plan would save them?

 

[BRT]

I know how and why people plan for thirds in caves ... but that wasn't really the context of the question ... it's been suggested by some in here that 700 psi is sufficient for a safe ascent from 110 feet. I'd like to understand how they arrive at a specific number like that ... particularly without any mention of consumption rate, or any consideration of conditions (which affect consumption rate), or targeted reserves ... I'd like to know where that number came from ...

... Bob (Grateful Diver)

You get that number by leaving 110 feet with 1200 lb and finding yourself back on the boat with 800 after doing your safety stop. I don't want to leave the bottom at 110 high on nitrogen with 700 lb but I have.