Rebreather Dive Planning

urho

And if you have a multigas OC computer, like Nitek HE is, you can work out more depth / mix pairs and set them to your computer.

--
Harri

robinfante

Yow, chilly atmosphere here. I know Charles, I've dove with him, and he's a very capable diver. OK, I agree the question came off really naive, but that was probably because he was looking for a detailed answer (as opposed to, say, a ration of "Die You f-ing newbie Die!") Telling him he's an ignorant hazard to himself and his family is not constructive. Its not even constructive criticism, its just scornful.

Ok, so let me try and answer you, since I did the first 45 hours on my sport kiss using an HE. What I would do is work out whatever the FO2s would be to match a PO2 of 1.2 at the various depths I anticipated being at. I would then dive at 1.3 for conservatism. With the HE you get 7 mixes, so it almost certainly will suffice for a 130' dive. If for some reason my bailout is not represented in those numbers then I reserve a slot for it as well. The other thing I would sometimes do is up the FO2/PO2 for the 20' stop to something higher, 1.4 typically. It takes a little more attention to dive with the HE, since everytime you change depths you need to fiddle with the computer. Its not too onerous though, and cultivating an increased time/depth awareness is a worthwhile pursuit.

That's plan A, the computer. For plan B, I'd just cut a bunch of tables on vplanner for 130 and stick them in my wetnotes. You'll be looking at your computer enough that if it did suddenly die on you, you'd also still have a pretty good idea of your deco obligation. The nitek algorithm is less than ideal (to me at least) but its helpful in that the deco time its going to show you will pretty much be 20', maybe a little at 30. You can cut your backup tables as precisely as you care to, but I wouldn't sweat every possible depth, so long as your tables are at least cut for deeper than you are. So your computer dies at 45 minutes at 120', but you've only got tables for 130'? Who cares, just do the extra deco. I just checked, and the difference is 20 minutes vs. 26, would it really help you to be able to shave those 6 minutes? Not likely, you'd probably pad them right back in anyways, I know I would. BTW I tend to cut my backup tables with less conservatism. I want to know what I NEED to do, I'll do the padding myself.

Plan C, both the computer and the loop go down. When you are in vplanner, add a one-minute OC line at the worst possible time/depth for your loop to go down. You don't need to figure it out at every minute of the dive, just find out what your worst-case deco obligation is, and how much OC gas you need to do it with. Presto! Now you have tables to get you home.

Re the OTUs and CNS, vplanner will show you that. As mentioned though, for the dives you are going to be doing off NJ neither will be a factor. Good to know, but ultimately you will be limited either by temperature, or how much bailout you feel like bringing with you.

That's pretty much it, its not hard. If you have any questions, and don't want to bring them up here, pmail me. Likewise I can walk you through it in person, come on up for dinner some time and we'll cut all the tables you'll need.

zbskii

I don't dive a rebreather, just researching. Get this book. It explains how to dive a CCR with a nitrox computer. The main issue is max depth at a give setpoint - given a certain F02 put into your computer at certain depth you'll be going over the computers estimate. Of course you'll be diving way more conservatively than if you used fixed pp02 tables.

See: http://www.tmishop.com/math1.htm for an excellent explaination of how to calculate F02 from pp02.
-Brett

Terry

To All

Allright - yes I was a bit harsh and insensitive...
Apologies to Kiam for my most negative reference, and to all of you who read it, and mostly to those who tried to understand my perspective.
(Also - I AM a brash American - I will tone it down.)
I respect this community and want to remain part of it.

Kaim - I am in the middle of Rebreather training now- and so am not a RB diver yet. Hopefully, I soon will be. Though I am an OC tech instructor (not active), and trimix certified, it pains me when I hear of diver who try to ask the questions to get them in water and diving in the shortest period of time possible. They just want to go diving... Iam fumbling with "how to say it quietly".

I have an Inspo with the Vision on the way, so I suppose I will be asking alot of newb q's too.

BTW - Kiam - the fellows here are offering good advise on planning. I learned a thing or two from Robins concise response.

Hat in hand,
Terry

Terry

Brett posted a great article - if you get through the whole thing it pretty much delivers all the physics and pysiology you'll need to know:


See: http://www.tmishop.com/math1.htm for an excellent explaination of how to calculate F02 from pp02.

also - Tom Mount's on Tec Rebreather book is pretty good too:
http://www.diveriteexpress.com/rebreathers/books.shtml


Seriously, try to understand the entire article. I am printing it out and am going to refresh on it a few time.

Thanks,

schford

Member self moderation its a wonderful thing....

Saves me making comments like I set up Rebreather World to share knowledge or indeed awarding out a red blob for sarcy comments that do not even answer the original quesion.... hell I asked a bunch of silly questions before doing all my training to ensure that I was as prepped as I could have been for the training!

I really see nothing wrong with people asking detailed questions before doing training, replies can always be politely caveated with this is how I would do it but you need to confirm this in a formally training enviroment and not rely on it...

On another note Rons excellent article is in our library - http://www.rebreatherworld.com/gener...explained.html as is a bunch of other really useful info so make sur eyou give the whole library a good going over!

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Mark Chase

130ft is a jump in an do it dive. Its a no brainer.

The CCR running a set point of 1.3 gives you three hours before you breach your CNS limits so forget CNS and just keep the dive under three hours. You can easily calculate your OTU's after the dive whilst looking at your profile on the PC. Multi dive days over multi days it needs a little more thought but not much. You just decide your set point and your in water time and calculate the accumulated 02 over the planned dive schedule.

In truth i have never seen any one actually do this on a livaboard and i have only done it as an exercise. Possibly I am mad for being so lax but its the truth,

I carry three computers. Two VR3s and a depth and bottom timer. A dive to 45m is a perfect 1:1 ratio dive so for every min of bottom time I need a min of deco using 50%. I know I can get 60min+ out of a 7 at 230 bar on deco so id take a 7 of 50% and a full dill tank.

If i know and trust the skipper of the boat I may opt for a 7 of 32/25 and a drop tank of 80 on the boat. This will allow me to do some penetration on the wreck.

For bigger dives the real planning is the bailout and obviously if your going over three hours the CNS. Drop the set point to 1.2 and thats the CNS sorted unless your doing masive cave dives.


ATB

Mark Chase

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magentaseas

The only silly question is the question thats not asked!

sharon

vid

a really great article - the only problem is that the tables don't appear???

any one able to access these and pm them to me ?


ta
vid

ROB DAVIE

Inventing a new verb form this morning are we, Boss?

To caveat:
He/she/we/they caveated. Sounds kinda kinky!! Yum!

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[SIZE=2]"CC Rebreathers will become a viable part of tech diving [U]WHEN PIGS FLY[/U]!!"--GI3[/SIZE]