Repetitive diving on CCR

[Clare Gledhill]

Sorry - as Darren rightly points out I don't dive CCR. (can't personally see how this affects the deco but then YMMV and if I does, I shouldn;t have posted here)

We aim for bottom gas around 1 - 1.2 PPO2. Bottom times vary between 30 and 40 minutes on a wreck dive OC when doing two dives back to back. Cave can obviously go longer. Deco is personal preference and I've been burnt enough times on here not to post that

[DannyB]

Originally Posted by Clare Gledhill

Sorry - as Darren rightly points out I don't dive CCR. (can't personally see how this affects the deco but then YMMV and if I does, I shouldn;t have posted here)

We aim for bottom gas around 1 - 1.2 PPO2. Bottom times vary between 30 and 40 minutes on a wreck dive OC when doing two dives back to back. Cave can obviously go longer. Deco is personal preference and I've been burnt enough times on here not to post that

So constant PPO2 and Constant F02 Don't affect deco then? I need some new tables apparently.

[Clare Gledhill]

Originally Posted by DannyB

So constant PPO2 and Constant F02 Don't affect deco then? I need some new tables apparently.

I meant if it affects it by way of a penalty which I have never heard hypothesised.

[DannyB]

Originally Posted by Clare Gledhill

Sorry - as Darren rightly points out I don't dive CCR. (can't personally see how this affects the deco but then YMMV and if I does, I shouldn;t have posted here)

We aim for bottom gas around 1 - 1.2 PPO2. Bottom times vary between 30 and 40 minutes on a wreck dive OC when doing two dives back to back. Cave can obviously go longer. Deco is personal preference and I've been burnt enough times on here not to post that

Well for info as apparently I haven't been burnt enough yet, here is the deco I would run for 2 60M dives for 35 mins with 90 mins surface interval (actually I wouldn't, these are what the software gave me but I am not willing to run this aggressive a profile without a chamber on board the boat, only one sub 50M dive a day for me).

Dive profile for default:
Step Depth SegT RunT Gas ppO2 END
================================================== =============
1 0.0-> 60.0 2:37 2:37 Trimix 10/44 0.70 31
2 60.0-> 60.0 35:23 38:00 Trimix 19/40 1.30 27
Deepest effective stop: 45m
Buhlmann + Gradient Factor decompression schedule:
Step Depth SegT RunT %MV Gas ppO2 END
================================================== =============
3 60.0-> 36.0 3:00 41:00 69.6 Trimix 28/35 1.30 11
4 36.0-> 33.0 2:00 43:00 72.2 Trimix 30/34 1.30 9
5 33.0-> 30.0 2:00 45:00 73.0 Trimix 32/33 1.30 8
6 30.0-> 27.0 2:00 47:00 75.0 Trimix 35/32 1.30 6
7 27.0-> 24.0 2:00 49:00 77.4 Trimix 38/30 1.30 4
8 24.0-> 21.0 3:00 52:00 80.5 Trimix 42/28 1.30 2
9 21.0-> 18.0 5:00 57:00 83.4 Trimix 46/26 1.30 0
10 18.0-> 15.0 5:00 62:00 83.7 Trimix 52/23 1.30 0
11 15.0-> 12.0 7:00 69:00 86.8 Trimix 59/20 1.30 0
12 12.0-> 9.0 11:00 80:00 88.3 Trimix 68/15 1.30 0
13 9.0-> 6.0 14:00 94:00 89.0 Trimix 81/ 9 1.30 0
14 6.0-> 3.0 24:00 118:00 90.9 Oxygen 1.30 0
15 3.0-> 0.0 0:18 118:18 92.6
================================================== =============
Dive time: 0:38:00 Gradient Factors were used:
Ascent & Deco time: 1:20:18 Low factor: 20%
======== High factor: 80%
Total run time: 1:58:18
Ascent rate: 10, Descent rate: 23 (m/min) Total CNS: 65% OTUs: 172
CC Setpoints used:
Depth Setpoint CNS
==========================
* 64.7 CC CNS Total: 65%


Dive profile for default:
Step Depth SegT RunT Gas ppO2 END
================================================== =============
1 0.0-> 60.0 2:37 2:37 Trimix 10/44 0.70 31
2 60.0-> 60.0 35:23 38:00 Trimix 19/40 1.30 27
Deepest effective stop: 45m
Buhlmann + Gradient Factor decompression schedule:
Step Depth SegT RunT %MV Gas ppO2 END
================================================== =============
3 60.0-> 36.0 3:00 41:00 69.5 Trimix 28/35 1.30 11
4 36.0-> 33.0 2:00 43:00 72.2 Trimix 30/34 1.30 9
5 33.0-> 30.0 2:00 45:00 73.0 Trimix 32/33 1.30 8
6 30.0-> 27.0 2:00 47:00 74.8 Trimix 35/32 1.30 6
7 27.0-> 24.0 2:00 49:00 77.2 Trimix 38/30 1.30 4
8 24.0-> 21.0 3:00 52:00 80.2 Trimix 42/28 1.30 2
9 21.0-> 18.0 5:00 57:00 83.1 Trimix 46/26 1.30 0
10 18.0-> 15.0 5:00 62:00 83.7 Trimix 52/23 1.30 0
11 15.0-> 12.0 8:00 70:00 86.8 Trimix 59/20 1.30 0
12 12.0-> 9.0 11:00 81:00 88.4 Trimix 68/15 1.30 0
13 9.0-> 6.0 20:00 101:00 90.4 Trimix 81/ 9 1.30 0
14 6.0-> 3.0 42:00 143:00 92.3 Oxygen 1.30 0
15 3.0-> 0.0 0:18 143:18 93.6
================================================== =============
Dive time: 0:38:00 Gradient Factors were used:
Ascent & Deco time: 1:45:18 Low factor: 20%
======== High factor: 80%
Total run time: 2:23:18
Ascent rate: 10, Descent rate: 23 (m/min) Total CNS: 79% OTUs: 209
CC Setpoints used:
Depth Setpoint CNS
==========================
* 78.6 CC CNS Total: 79%

[DannyB]

Originally Posted by Clare Gledhill

I meant if it affects it by way of a penalty which I have never heard hypothesised.

No but constant FO2 runtimes and stops are vastly (sp?) different to constant PO2 runtimes and stops. Unless there is some black magic that we all need to be aware of it's simple(ish) maths to work out stops.

Some will believe they can run more aggressive than others, at the end of the day I believe that if we dive enough every single one of us, now matter how perfect CCR or DIR or DSAT or anything else is (yeah, even BSAC, although without the 88's). Someday your number is going to be up, that needs to be taught from day one of tech training in any system. It's about learning your personal limits, perhaps by sometimes getting that I feel like shit feeling and having the knowledge to understand how to tweak the runtimes/tables/DOTF/whatever to your own body/day of the week/phase of the moon/etc that allow you to plan and execute a dive that is safe for you.

There are no easy answers.

Danny

[PW1664]

Originally Posted by daveb0000

We have run a fair few plans and looked at the CNS side of it and the % drops a fair bit after a 2 hour SI. also..

The bigger issue here is repetative diving over a number of days with a high ppO2. Wspecially if you're doing two to four dives a day over a full week. The long term CNS exposure becomes quite critical.

You may need ot consider reducing your ppO2 set point if you're doing multiple dives over a number of days.... this ofcourse affects The short term on/off gassing and effect of your stated SI.





By the way, this might be bollx as I don't dive CCR either.....

[gobfish1]

More Tables ,,,,,

i ant going to print out loads of tables , and say two dive a day to 50m is ok

Cns are going to be at the top end , or out s are gonig to be this ,
I just save 650 out s for the pot, but thats just me ,,,,,

i had the same talk on a dive boat out in singapore with 11 divers i had just meet for a week s diving on a few well known wrecks

all said they were only going to dive one dive a day cos that's how thay do gas diving back in the uk ,

when i pointed out that one dive a day in the uk had sfa to do with deco / cns ,

had more to do with the tides and the boat skipper not wanting to do a 12H day,

they all said i was talking ballox . but after the first days diving , me doing two dive.s the rest only doing one , ( ps i was doing 20mis more bottom time than them as well )

they all had a re think on what i had said , next day all divers were diving two dives a day . we all had a good weeks diving ,

put all the tables you like out dont matter ,
cns can be sorted with a good SI, use the 90min half life

otu s ant going to kill you, and when it kicks in ,,You will know .

ps
some days i did, 3 58m dives, all my dives were oc 21/35 64% nitrox and o2 at 6m run times 120Mins not bad on oc but i did take 3 bottom gas s with me ( no pading out on my vr3 set on 0 safety)

we all have are ways of doing and seeing things ,
tables are ok . but its best to have maybe done some of the bollox your talking about .

I can'nt see the dif OC or CCr cns or deco wise
i know some one will want to tell me all about it ,

one thing i would never do, is go do my 2nd or 3rd dive after only 90mis si .
you need two 90mis to get you cns back down to some place nice
welllllllllll that's only if you worry about cns, ,,, some of us do and some of us dont

if you feel happy with one dive a day then thats ok with me , Girls ....

I dont know shite about deco or diving , all i can say is,
been there done that and i was aok,,,,, both in cold water and warm water ,,,,,

hope that helps ,, some what ,,,,,


More tables or black magic then ,,,,,

[deepbull]

Originally Posted by onthetrain

On my trip to Norway earlier this year I did a couple of 50 - 70M dives a day for several days in a row with no ill effects. That was of course in cold water too.


That said the profiles were still fairly conservative as many of the wrecks were so huge that you could do say 15 mins at 70M and then decompress slowly coming up the wreck so that the average depth over the course of the dive is only 30 - 40M and not square profiles like most UK wrecks

I would be quite happy to dive these sorts of profiles, especially on CCR

snap! 90+m in the morning 50m afternoon 5h in water time a day over the 2 dives

[Mark Chase]

Originally Posted by Clare Gledhill

Sorry - as Darren rightly points out I don't dive CCR. (can't personally see how this affects the deco but then YMMV and if I does, I shouldn;t have posted here)

We aim for bottom gas around 1 - 1.2 PPO2. Bottom times vary between 30 and 40 minutes on a wreck dive OC when doing two dives back to back. Cave can obviously go longer. Deco is personal preference and I've been burnt enough times on here not to post that

A dive to 60m for 45mins on OC using 18/45 50% and 100% will (using my deco settings not yours) take 131min

A dive to 60m using 16/45 diluent and running 1.3 set point and ending with an 02 flush will take 123mins.

So only about 8mins (6%) less deco for the same level of agresion.

Which is why I am happy to use DOTF as a bailout plan. The efficiency of the CCR does the padding for me.

Basicly it makes no odds. Any one getting a CCR to make big savings on deco in the 60+ range will be disapointed. It realy does its thing shalow 0-50
m but frankly you dont need a CCR there.

Totaly off topic realy, but as you say it makes no odds OC or CCR the issues are the same on deco just the CNS is higher on the CCR

ATB

Mark

[Clare Gledhill]

which is why I thought my own experience was somewhat helpful to the thread - OC/CCR makes little diference.

Good post gobfish. Always feel slightly nervous when I agree with you but can't and won't fault anything you said.

First time I tried to book a boat to do 2 mix dives a day the skipper declared it suicide and wouldn't take the booking yet it is relatively common practice abroad. Like you say, it has much more to do with tides here than deco or anything else.