Rebreather Dive Planning

kiam

I'm curious about what people are doing and wondered if someone could explain in detail or not, how to plan a dive to 130 ft. on the SK using the following: Nitek HE, a bottom timer and Vplanner. I'm lookiing for the sequence from start to finish, including formulas, logging of CNS and OTU's.




"In life, there's things you know and things you don't know and things you don't know that you don't know."

zbskii

They should have taught you this in your rebreather training class. Don't try and E-Learn. I believe most people here use a constant ppo2 capible computer, see the poll/thread on "what computer do you use?"

wedivebc

I don't think the HE has constant PPO2 mode so it may not be the best choice. V-planner has CCR mode you plug in your set point but when diving the kiss I always use a lower setpoint in planning than actual diving in case I get distraced and my PPO2 goes low I don't want to throw my deco out. I use 1.0 for deco and 1.4 for O2 exposure. That should have been covered in basic nitrox training and actually I am wondering why you are asking here.
Please get proper training before diving your Rebreather.

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Cheers,

Dave....

Man is the only animal burdened with the knowledge he will eventually die

nigelh

130ft = 42meters?
While kitting up:
"What bailout did you bring?"
"Both. Bottom and 50"
"Skipper! What's max run time?"
"Over two hours and the tide will be running like a train so you'll miss lunch."
"Go for it?"
"Skip! Divers ready!"

This is the whole magic of a rebreather and computers. We can cut and stick the plan live - depth, duration, conservatism. The only consideration is bailout (and lunch). Sorry it's not a very useful reply but this is what I do down to my normoxic limits.

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nigelh

lizardland

As previously said, it's fairly basic stuff.

For myself it depends on the dive. For <30-35m with limited deco then I just follow my very old and very trusty Aladin Pro as an air dive and chuck in some extra stops, usually I cut back the last stop by a fair bit (the old Pros can be reset if you bend them). So I'm a bit longer in the water than I need, so what? I like the water, the decos are short and I've got the option of going deco on the fly if I get bored. I'd considered buying an OC nitrox computer but that involves spending cash.

For deeper/longer then I plug the figures into a deco program (I use one I wrote myself, again because it involves spending no money) and follow the plan it produces. I plan for 1.0bar for the bottom, 1.2 for the way up and 1.5 for 6m, as mentioned it accounts for lapses in concentration. I don't generally bother looking at %CNS unless the dive is starting to get quite long. I redo the plan for OC bailout with whatever gases I've got and then I do a "bollocks to it" plan for a shorter than planned bottom time.

I don't use a mixed gas/constant pO2 computer, I'm happy diving tables, there's nothing to go wrong and it doesn't involve spending £700+.

Cheers,

Stuart

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Terry

Kiam -

The question you ask is fundamental dive planning. You need to get with a an instructor to walk you through dive planning.

But if your going to dive w/o training, I would -

Calculate your RMV.
Calculate needed gas at the planned depth and choose your tanks
Identify your target PO2 if OC
Create a best mix if OC that is safe to the sand.
Run the dive in V Planner.
Create tables for target depth and time bracketing 5 minute increments up a down your planned dive time and 10 ft intervals in depth- based on available gas.
Create a BO plan for the last second of the dive, ensure you have enough gas to deco.
Create a deco plan - ensure you have enough gas - Planned amount X 1.5

Print tables, seal them with clear tape, and stick in your pocket.
If CCR - get a constant PO2 computer - learn how to use it.
The HE is an OC computer.

Call your wife, mom, children, and dog, them them your are going techincal diving with the knowlege you picked up from reading the internet.

We will be reading the papers looking out for you.

kiam

What if it wasn't taught in my class? As hard as it might be to believe, suspend your own heightened sense of knowledge and consider, if it wasn't taught should I still not try and learn it? Why not try and E-learn? I thought part of the idea for a forum of this type was to enhace, exchange and impart shared learning. I specifically asked people to share in detail or not. I wanted to compare what I've learned about dive planning with what divers of more experience are doing. I'm not trying to circumvent the system of rebreather training. I have received Rebreather training, I have my "C" card, I have my unit. I also have identified key areas that I'm not entirely comfortable with. It's those areas that I'm trying to clarify, so that I can enjoy my unit without hastening my slide toward the big dirt nap. Don't assume that this is a shady post, I have a valid reason for it and will continue asking questions until I'm satisfied with what I learn. You my friend can participate in my learning or not.

kiam

Terry, I'm not entirely sure of the rules on this board, but I'm pretty sure they prohibit me from using the "F" word. I can appreciate the caring attitude that you obviously have, yet not so much references to my demise. I don't know you but if our paths should cross and by chance your stomach was on fire, I would't piss down your throat to save you. You might want to call someone and tell them that!

nigelh

Easy easy....

He's an American and he doesn't even dive rebreathers according to his profile. He is just expressing too loudly what should be said gently.

Most MOD2 and above courses go into this in some detail with bailout planning et. al. MOD 1 (aka CCR 101) doesn't do that stuff because you can bailout onto the DIL and swim out if you are on a no stop schedule. A non-deco dive doesn't need a plan. Work out what your mix is on the bottom and set your OC computer to that. If you do slip into a bit of deco do the time but don't let it go to far unless you have bailout gas with you. Your real stop time will be less than indicated but, hey, we wouldn't be divers if we didn't enjoy being in the water.

Rebreathers, well I'm really talking my Inspiration here but it goes for most CCRs, make deco diving easy but you have more faults to plan for and, as always, you need a get-out-unbent bailout gas plan. Running 1.3bar ppO2 I know I have three hours before CNS becomes a question and that's the point where I start asking serious questions about the scrubber. I never have to worry about gas. Unless I'm doing several days on the trot I don't think about OTUs and then a day off solves the problem.

Chill guys.

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nigelh

Deepwreck

I will say that what has been said is a bit harsh, and need not be said to loudlly. When I started out CCR diving I had questions all the time, and I hate the way some divers will answer the question with "you need to get training". Yes we all know that training is usefull and necessary for the safety of our dive, but we also know that knowing everything about your dive is important. Before I started diving Mix I learned everything I could about he, and then got training. The training went smothly and I found that I only filled in some blanks instead of starting from scatch.

With that said, The only planning you need to a dive to 130' is gas, and some kind of timeing devise. I use the hs explorer, and a bottom timer with v-planner as backup. For a dive to 130' I dont' worry about much else as I always carry a bailout tank. for deeper dives I will carry more bailout and plan out my deco so I know what is happening to my deco if I go deeper, longer, have the wrong ppo2, or what ever else happens. The great thing about training is that you get the chance to practice things you may not want to do. For example in mod 2 or 3 you will do a full bailout at depth, and prove your bailout tank has enough air to get you back to the surface alive. This helps in planning your dives to deeper and darker places.

Dive long, dive happy.