accelerated deco

[addive]

hello you all
I am looking for a good book on accelerated deco
please can any body have or tell me which book would be best
thank you adrian

[Zubar]

What is it you want to learn? Deco for Divers explains what is going on very well. I can't advise on one for diving practices.

[addive]

hello
it is the practical parts the maths
the course notes mite be the best
thank you Adrian



What is it you want to learn? Deco for Divers explains what is going on very well. I can't advise on one for diving practices.

[gobfish1]

google ,

nitrox diving pdf , NOAA or DAN plus a years worth of reading , to keep you going ,


if your doing a course / nitrox , just turn up and do it , you would need to be a real half witt not to get a card .
feek edit that ,

ment to say even a half witt will pass as long a course fee is payed ,

[Zubar]

I have the iantd book for ART. you are welcome to it if you want. It's not 'good' though.

[addive]

hello
does it have all the info and the maths how to work it out the hard way
thank you Adrian


I have the iantd book for ART. you are welcome to it if you want. It's not 'good' though.

[Yellowduke]

'Deco For Divers' by Mark Powell is what I would recommend if you want to get into it. For an overview of the research that has been done into decompression theory you will be hard pressed to do better. Mark is a well known and highly regarded technical diving instructor as well so the book is written by a diver for divers.

[MikeF]

hello
does it have all the info and the maths how to work it out the hard way
thank you Adrian

what maths are you looking for? what do you want to work out?

[Zubar]

hello
does it have all the info and the maths how to work it out the hard way
thank you Adrian

Yes it has all the calc at the beginning by the looks of it. i think I had a work book to but lent that to someone else.

[Ian_6301]

hello
does it have all the info and the maths how to work it out the hard way
thank you Adrian

There's a hard way?

Standard gasses, ratio deco. Ends up as either 1 min deep stops and 5 mins at 6, or 2 with 10 or 3 with 15.

If you want to get real fancy and do O2 deco, you need to reduce the 6m stop by... some... But tbh 30 mins of deco should see you right.

Just get multi-deco and plug some numbers in, then get a feel for the way the deco stops stack up. As above, I wouldn't bother reading up too much, as it will be taught on the course.

If you're just planning on having a bash without doing the course... Well, put it this way. Figuring out which stops to do can be made very easy by using a computer. Being able to hold a stop is contingent on good / excellent buoyancy control and on having enough gas to do the stops. Gas planning can be made easy or difficult by your choices of gas and your deco model, but there are some shortcuts that you can learn pretty quickly.

Having the discipline and the skills to execute the dive safely and to deal with emergencies / failures is what you pay the money to have beaten into you. If you don't think you need it, fine. Just don't go diving somewhere where someone else will be expected to rescue you.

Equally, if we're talking about nitrox / air dives with nitrox/O2 deco, then what is the point? Use Multi-deco. Run the profiles. If you use EAN32 for back gas, max depth 30m, you have to try pretty hard to get past 20 mins of deco (my personal threshold for wanting to take a 40 of O2). For anything deeper, there's trimix. Some will argue to 40m on air / weak nitrox but tbh I'm off my tits past 30m and on somewhere around a 24% Nitrox, the difference between that and air is worth very little.

Advanced Nitrox or whatever it's called this week is an utterly pointless course in its own right. As a primer that gets you used to doing stops and using stages before you actually do dives that really need them, it's kinda handy as a stepping stone to a mix course, but tbh there are better ways to get there.

Short version of all of the above? Do Fundies. Then Tech 1. Should come in at £1500 odd quid in course fees, plus whatever kit you need to change, plus your soul. Oh, and then there's the probe...

[Garf]

if your doing a course / nitrox , just turn up and do it , you would need to be a real half witt not to get a card .
feek edit that ,

ment to say even a half witt will pass as long a course fee is payed ,

A fundies course is basically an open water course done neutrally buoyant ith a nitrox ticket.

I historically have about a 23% failure rate. Three people started fundies with me last weekend. One person passed today.

[Paulo]

A fundies course is basically an open water course done neutrally buoyant ith a nitrox ticket.

I historically have about a 23% failure rate. Three people started fundies with me last weekend. One person passed today.

Ya but you are reknowned for being a ☺☺☺☺ :D

[Garf]

Ya but you are reknowned for being a ☺☺☺☺ :D

For once I can't argue with you :)

[turnerjd]

If you're worried about calculating stop times for accelerated deco, you could also do it the French way..... 100% O2, and if 6m and 3m stops are less than 5 mins do the complete stop, 5 mins or more then remove 1/3 of your air stop time with a minimum of 5 minutes on the stop.

Jon

[gobfish1]

A fundies course is basically an open water course done neutrally buoyant ith a nitrox ticket.

I historically have about a 23% failure rate. Three people started fundies with me last weekend. One person passed today.

lol good man ,
tho i have to say i sent about 20 diver,s from my old dive club on a tdi or iantd and all passed , maybe i was just lucky and had 20 smart dives,

[Janos]

hello
does it have all the info and the maths how to work it out the hard way
thank you Adrian

Most people plan accelerated deco on tables, their dive computer, software, or on their phone. I use the Baltic Deco app on my phone. Plug in depths and times and it tells you what stops you need to do.

It's all very straightforward when everything goes well.

However, the real test is when it goes wrong - such as if you lose your deco gas or overstay your time? That's when a course really helps.

Janos

[matt]

hello
does it have all the info and the maths how to work it out the hard way
thank you Adrian

According to BJ you'll give up diving after reading about the sums: http://www.thediveforum.com/showthread.php?789-Diving-Sums

[Ian_6301]

According to BJ you'll give up diving after reading about the sums: http://www.thediveforum.com/showthread.php?789-Diving-Sums

erm, yeah... 8/10


Sumz for Deco:

1. How much gas do I need on the bottom?

Gas required (in bar) = Avg Depth (in Bar) x Consumption rate at Surface (in Bar/min) x Minutes of Bottom Time.

eg, in a 24L twinset, with an SAC of 18L/min, I chew through 3/4 of a bar per minute, so a 30 min bottom time at 40m looks like this:

Gar Required (in Bar) = 5bar x 3/4 x 30 = 5x22.5 = 112.5 bar.

2. How much Gas do I need to get me and a buddy to the switch?

Slightly more complex and will be different for each depth, but essentially, take the average depth between the bottom and the switch depth, figure out how long it will take you to get there and then do the calculation above, then multiply by 3 to allow for elevated breathing rates etc. Do this for a selection of the depths you'll be diving at and scribble the answers down somewhere, we'll come back to them in a minute. It helps if you use a standard deco gas and for a single standard gas for the 40-60m range, EAN50 is pretty optimal in terms of the trade off between total deco time required and being able to get on it deep (hence reducing min gas)

3. How much deco gas do I need?

This one is a doddle with a standard gas. You know the shape of the profile (because they're all similar at this range) and it'll look ROUGHLY like 50% of your time spread evenly(ish) over stops between 21m and 9m, then 50% at 6m. Ooh, handy. SO that's an average for the deep stops of 15m and 6m for the shallows. So an overall average of 10.5m Go to #1 above and figure out how much gas you need for 5, 10, 15, 20, 25, 30 mins of deco. Or actually, work it backwards. How big is your stage? Based on a deco SAC of 15l/min, My AL80 gets me 75 mins of deco, my 232bar 7L gets 53, a 207 bar 7L gets 47, an AL40 gets 38, a 300 bar 3L gets 29 mins and a 232 bar 3L gets 22 mins.


4. Deco Gas Reserves
STOP. That's the TOTAL amount of gas in the cylinder at the stamped fill pressure. You need to adjust down based on ACTUAL fill pressure and then you need to consider your buddy. Once we get to tech diving, there's a mantra: "If you need one, take 2.... Or maybe 3" This goes for deco gas. Yours, your buddy's and maybe a third team mate's gas. In a team of two, you need to be carrying enough deco gas for BOTH of you to deco out on one cylinder. Now it doesn't take the brains of an archbishop to figure out that that means that the times posted above get HALVED for diving as a buddy pair. AND then disregard the last 20 bar, just in case, so go re-calculate!

5. Min Gas Reserve It also doesn't take the brains of an archbishop to figure out that while diver A is hogging the deco gas, diver B needs to be on his back gas. SO whatever the deco gas requirement is, compare that to the min gas numbers we looked at above and pick the bigger amount as your min gas number. Once you get past about 30m, the dominant number is the deco one, not the ascent one.

If you dive in a team of 3, you get 2/3 of the times above and you only need 50% of the deco gas amount as extra back gas, because you take in turns to do 2 stops or 2/3 of the stop at 6m on deco gas and 1/3 on back gas... And then you pad the stops by 50%, so everyone gets the original amount of deco time on deco gas PLUS 50% again on back gas.

Now deco. OK, use the planning software. Or do voodoo deco. 45m, for example, I know I need 1 min deco per 1 min bottom time (out to 30 mins at least). Bit deeper? Bit more deco. There's a ratio between these two "bits" and that's the voodoo...

OK, so I know that sounds complex, but really it's not and you only have to do these sums ONCE if you use standard gasses. What you end up at the end of all of this is a series of tables that you can print off or copy into your wet notes.

6. So What Do I Need to Know?
Well, for example, I can go to mine and look up a "30 mins deco" dive using EAN50 for deco in a team of 3 for a max depth of 45m:

Min Gas (leave bottom with not less than) 100 bar
Deco Gas Needed 190 bar (in 232Bar 7L) or 120 bar (in AL80). This includes reserves.
How much bottom time? 30 mins
Back Gas needed for bottom time =30*5.5*3/4 = 22.5*5.5 = 124 bar
Minimum gas to start dive? =Min Gas + Back Gas Needed = 100+124 = 224bar


A Quick Word About Standard Gasses and Procedures

All of the above works because by using standard gasses and standard procedures, we end up fixing some of the variables and it allows us to do easy maths. It means that you are not necessarily breathing THE OPTIMUM gas for the dive every time, BUT it means that you can do the planning on the back of a fag packet. Or you could, but you'd have to scrounge a fag packet, 'cos smoking is banned...

Garf writes about this stuff a lot more eloquently than I can (and hence makes money out of it) and has a great website here, which explains a lot of stuff: http://www.divedir.com/Blog/i-heard-you-use-standard-gases.html Regrettably, I get no kick backs.

The Disclaimer

So these numbers work for me, based on my SAC, my agency bias, my training etc. They are shared here to give you a feel / flavour for the sort of thinking you need to put into this. They are NOT under any circumstances to be used as a substitute for proper training and I STRONGLY recommend that you challenge and verify any/all assumptions and/or statements made above.

Rule 3: Nothing underwater is worth dying for.

[JPTaylor]

deleted

[londonsean69]

erm, yeah... 8/10


Sumz for Deco:

1. How much gas do I need on the bottom?

Gas required (in bar) = Avg Depth (in Bar) x Consumption rate at Surface (in Bar/min) x Minutes of Bottom Time.

eg, in a 24L twinset, with an SAC of 28L/min, I chew through 2/3 of a bar per minute, so a 30 min bottom time at 40m looks like this:

Gar Required (in Bar) = 5bar x 2/3 x 30 = 5x20 = 100 bar.

Your maths is way out.

5bar (depth) x 30mins (time) x 28l/min (SAC) = 4200 litres of gas, which in your twin 12s is 175 bar.

PS - to be using 2/3rs of a bar per minute in twin 12s, your SAC would need to be 16 ;)

[Ian_6301]

Balls. Typo plus hypo-caffeination = Edit time

18l/min SAC. Which is 3/4 bar/min.

[Ian_6301]

Your maths is way out.

5bar (depth) x 30mins (time) x 28l/min (SAC) = 4200 litres of gas, which in your twin 12s is 175 bar.

PS - to be using 2/3rs of a bar per minute in twin 12s, your SAC would need to be 16 ;)

and THAT is why you don't try to learn this shit on the interwebz...

[notdeadyet]

and THAT is why you don't try to learn this shit on the interwebz...
Yep. It was much more fun when you just bought a twinset and taught yourself in the water. Even better is buying a rebreather and teaching yourself :)

Sent from my GT-I9300 using Tapatalk

[Iain Smith]

1. How much gas do I need on the bottom?

Gas required (in bar) = Avg Depth (in Bar) x Consumption rate at Surface (in Bar/min) x Minutes of Bottom Time.

eg, in a 24L twinset, with an SAC of 18L/min, I chew through 3/4 of a bar per minute, so a 30 min bottom time at 40m looks like this:

Gar Required (in Bar) = 5bar x 3/4 x 30 = 5x22.5 = 112.5 bar.

Or, to keep the numbers even simpler, 18L/min ≈ 4 bar per 5 minute "block". 30 min = 6 "blocks"

5ata x 4 x 6 = 120 bar.

[Digger]

and THAT is why you don't try to learn this shit on the interwebz...

Isn't that quite similar to calculating it in your head underwater?

I find that I get about 30% more stupid underwater. And I am pretty stupid on the surface already.

Digs.

[londonsean69]

Yep. It was much more fun when you just bought a twinset and taught yourself in the water. Even better is buying a rebreather and teaching yourself :)

I've never been as cautious when diving as when I had the EDO-04. No monitoring, and only a vague idea of what I was doing.
The vagueness remains, but the SCR is long gone :)

[AxeMan]

Yep. It was much more fun when you just bought a twinset and taught yourself in the water. Even better is buying a rebreather and teaching yourself :)

I went the first option. Well, it was independent twins for a bit.

Never did the second option. I have been on boats over the years with rebreather divers carrying quite a lot of bailout but still probably not enough to get them out of the water if they had to come off the loop. And for those who bought a rebreather because they were gas pigs, not a hope. I doubt they'd last long enough to get up to 21m for the drop tank.

[matt]

erm, yeah... 8/10

I use DDPlan for gas-calculations ;-)

Matt.

[JPTaylor]

deleted

[Ian_6301]

Or Multideco software, runs on Windows 10 unlike DDPlan (unless you've found away?)

Spin up a W7 VM...?

[JPTaylor]

deleted

[Ian_6301]

Tried compatibility settings for exe, but will not work on a 64bit machine, get

http://i1079.photobucket.com/albums/w504/jptaylor9/ddplan%20error_1.jpg

But MultiDeco software gives gas requirement for OC/CCR bailout plans....

hmm...

there's your problem - it's a 16 bit app.

least bad option is a shitty old pc with windows xp 32 bit. wont run as a vm, I don't think.

[Mark Chase]

hello you all
I am looking for a good book on accelerated deco
please can any body have or tell me which book would be best
thank you adrian


Hi Adrian

Mate the only math you need is SAC and gas planning stuff (PC is the answer to that)

Everything else you either use standard gas and tables or you use a computer.

For OC id calculate gas required, planned dive + 5mins and dive + 10mins

Then thers a lost deco gas calk

For multi deco gas dives id do a calk for decoing out on either one of my two deco gas.

So its all SAC and error margin calks best done on a PC

ATB

Mark

[AxeMan]

hmm...

there's your problem - it's a 16 bit app.

least bad option is a shitty old pc with windows xp 32 bit. wont run as a vm, I don't think.

Can't you download something like DosBox and run it in there?
That's what I've done linux and my phone.

[matt]

Or Multideco software, runs on Windows 10 unlike DDPlan (unless you've found away?)

Runs fine on Windows 10 in DOSBox. I can send you the settings at the weekend if you need them.

[matt]

Runs fine on Windows 10 in DOSBox. I can send you the settings at the weekend if you need them.

I have the settings with me if anyone wants them:

http://i1214.photobucket.com/albums/cc497/MatthewOutram/TDF/ddplan_zpsggyzfslh.png

[addive]

hello you all
thank you for all the help
I like the deco table on the computer
safe diving adrian