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<font color='#0000FF'>I am doing this thread so maybe we can compare a profile with different deco programs. I am using prodive planner with 10% safetly and 20% microbubble formation. For this dive PpO2 at depth 1.4 and deco 1.6. I also would like to comapre gas choices such as deco gas and maybe even see your deep stops. Max depth 65m and 30min bottom time.


 Depth1=  40msw:   2mins 32%O2  0%He  Run Time=  2mins
 Depth2=  65msw:  30mins 19%O2 34%He  Run Time= 32mins

  DIVE 1 DECOMPRESSION REQUIREMENTS      
   Stop=  45msw:   1mins 19%O2 34%He  Run Time= 35mins
   Stop=  35msw:   1mins 32%O2  0%He  Run Time= 37mins
   Stop=  27msw:   1mins 32%O2  0%He  Run Time= 39mins
   Stop=  24msw:   1mins 32%O2  0%He  Run Time= 40mins
   Stop=  21msw:   1mins 32%O2  0%He  Run Time= 41mins
   Stop=  18msw:   4mins 32%O2  0%He  Run Time= 46mins
   Stop=  15msw:   4mins 60%O2  0%He  Run Time= 50mins
   Stop=  12msw:   7mins 60%O2  0%He  Run Time= 57mins
   Stop=   9msw:  10mins 60%O2  0%He  Run Time= 68mins
   Stop=   6msw:  56mins 60%O2  0%He  Run Time=124mins

     Total time to surface=93mins              
     Time to first stop=5mins                  
     CNS exposure: 60%peak, 60%dive end        
     CNS exposure= 60%                          
     Max PPO2=1.60bar  OTU=159units  OTUtotal=159
     Dive Start:   Day 1   Time 00:00        
     Dive Finish:  Day 1   Time 02:04        
     Flight Time:  Day 1   Time 11:30
     Surface gas=21%O2,  0%He
     Surface interval=   0mins
 

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<font color='#0000FF'>Hello Dominic,

Have I understood right,

1. are you using 15/55 as bottom mix , why use an 80m mix on a 65m dive?

2. are you using 4 deco mixes? 2 trimix and 2 nitrox, is this normal and divable in real life such as cylinders carried and cost? Also on what depths all these deo mixes are used except for the 50% and 100% and what are the benefits? Is it acceptable to use a CNS of 117.4% just to cut deco time?

3. Do you dive DIR, and even if not how you stage all that cylinders?

All above are not a provoking comments but sharing and understanding ideas as maybe I can benefit myself.

Regards

Pierre
 

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[b said:
Quote[/b] ]1. are you using 15/55 as bottom mix , why use an 80m mix on a 65m dive?
Yup - cos that's what DW defaults to for this dive

I didn't put in any personal touches on this one - just plugged in depth and time and asked DW what it thought I should do on it's default settings. I'm not a Mix diver, so there's a limit to how much I can explain it's logic..
However, these were all the standard GUE gases, so I daresay a DIR diver will be along shortly who can tell you why these ones in particular are used
 

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<font color='#0000FF'>Hello,

You are right I didn't add a lot of info, but I would like a profile in which you think you can dive. I didn't try to do the best possible profile with 4 mix deco. As to use that profile you need back gas, 30%, 50% , 100% and air for air brakes. Do you all dive this way or this is good only infront of a comp. as I will always take all gases with me but to use a twinset and 4 deco cylinders is too much considering a 65m deoth range?

Thanks

Pierre
 

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Both Dom and WL have posted profiles with over 100% cns post dive. 114% and 117%. Also they both use multiple stages for travel and deco I note that neither diver is a trimix diver.

Also Doms use of bottom gas is due to the GUE (DIR) philosophy of set gas mix so he has the choice of the folowing gas list:

Bottom Mix

3-30m

In real

THE REST OF THIS THREAD IS MISSING SO I RE DID IT ON THE NEXT PAGE
 

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Using V-Planner with conservatism set at +4 would give me this.  I used to use 50% and O2 for deco but for the dives I do it was adding about another 25% onto the CNS total and only cutting my deco down by a few minutes.  I also have a bit more leeway on the 6m stop using 80%.

Dec to  60m (4)  on  Trimix 18.0/40.0,    15m/min descent.
Dec to  65m (4)  on  Trimix 18.0/40.0,    18m/min descent.
Level    65m  25:43 (30)  on  Trimix 18.0/40.0,    1.34  ppO2,  30m  EAD
Asc to  48m (31)  on  Trimix 18.0/40.0,    -10m/min ascent.
Stop at  48m   0:18 (32)  on  Trimix 18.0/40.0,    1.04  ppO2,  21m  EAD
Stop at  42m   2:00 (34)  on  Trimix 18.0/40.0,    0.93  ppO2,  18m  EAD
Stop at  36m   4:00 (38)  on  Trimix 18.0/40.0,    0.82  ppO2,  14m  EAD
Stop at  30m   3:00 (41)  on  Trimix 18.0/40.0,    0.72  ppO2,  11m  EAD
Stop at  27m   3:00 (44)  on  Trimix 18.0/40.0,    0.66  ppO2,  10m  EAD
Stop at  24m   2:00 (46)  on  Nitrox 40.0,    1.35  ppO2,  16m  EAD
Stop at  21m   3:00 (49)  on  Nitrox 40.0,    1.23  ppO2,  14m  EAD
Stop at  18m   3:00 (52)  on  Nitrox 40.0,    1.11  ppO2,  11m  EAD
Stop at  15m   5:00 (57)  on  Nitrox 40.0,    1.00  ppO2,  9m  EAD
Stop at  12m   7:00 (64)  on  Nitrox 40.0,    0.88  ppO2,  7m  EAD
Stop at  9m   8:00 (72)  on  Nitrox 80.0,    1.51  ppO2,  0m  EAD
Stop at  6m   35:00 (107)  on  Nitrox 80.0,    1.28  ppO2,  0m  EAD
Asc to  sfc. (107)  on  Nitrox 80.0,    -10m/min ascent.

Off gassing starts at 50 m

OTU's this dive: 139
CNS Total: 53.2%

6626.9 ltr  Trimix 18.0/40.0
1038.5 ltr  Nitrox 40.0
1424.7 ltr  Nitrox 80.0
9090.1 ltr  TOTAL

Hope this helps

Cheers

Simon  
 

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<font color='#0000FF'>Hello,

You are right I wanted to compare prog. I didn't downloaded my self such programs as I want to know if possible from people who uses these prog and compare them with mine. I found Proplanner to be perfect for me and is 100% same as Suunto Vytec, the sort of sfely I need. Maybe Mark speaks from experience as a normal tech dive should be up to 80% of CNS clock and all deco gasses must be carried with you trough the dive as you are never sure to find shot line or if you had to abondon dive. If you read my post on Platti ship :0 there were about six guy bend because they didn't find shot and with it deco gasses.

Thanks

Pierre
 

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[b said:
Quote[/b] (Mark Chase @ Aug. 27 2003,15:38)]Both Dom and WL have posted profiles with over 100% cns post dive. 114% and 117%. Also they both use multiple stages for travel and deco I note that neither diver is a trimix diver.

Also Doms use of bottom gas is due to the GUE (DIR) philosophy of set gas mix so he has the choice of the folowing gas list:

Bottom Mix

3-30m

In real
Whoops, half of my reply is missing so it doesn’t make a lot of sense.

It was supposed to read

Available DIR bottom Mix

3 –30m 32% Nitrox
33 – 45m 21 / 35 Trimix
48 – 60m 18 / 45 Trimix
63 - 75m 15 / 55 Trimix
78 – 121m 10 / 70 Trimix

Available DIR Deco Mix

6m 100% 02
21m 50%   Nitrox
36m 35 /25 Trimix
58m 21 /35 Trimix

DIR divers are not suposed to use any other gas mix than these. This can and does result in high CNS profiles and missed deco for the He

As a result the dive plan is limited to and by the available gas mix. This results in extended deco unless (as WL suggested) you ignore the He in the mix. This is a new thing with DIR and it should be noted that ignoring the He in the deco mix reduces the deco on my profile by 10mins. So according to the dive soft where the DIR diver will have missed 10mins of stops. It is notable that DIR have not had the courage of their conviction to put this new theory into their planning soft where. The Americans are a litigatious bunch and I don’t think GI3’s arguments would stand up to scientific scrutiny at the moment .

The use of 100% for deco in 60m for 30min profiles is also going to push the CNS clock over 100% which is not advised by any other agency. Unfortunately DIR do not allow the use of 80% for deco so there is no option but to push the CNS over 100%

Whilst these arguments have been gone over before I think it is important to highlight them again for people reading these threads who might have a limited background knowledge. It also answers the question as to why Dom’s profile used such a strange choice of back gas.

Also 50 –90 is quite an aggressive profile and does not provide deep stops to alleviate Micro bubble formation. This level of dive is better dived on low GFs fro the deeper part of the deco to provide the deep stops or Pyle stops as they are popularly referred to.

So I  personally would opt for a 20-80GF using the ZHL16B model

Back gas would be 18 / 40 trimix P02 1.35 at 65m
Travel 32% Nitrox
Deco 80% 02



Stops in time and depth

1 @ 42m ascend and switch to 32%Nitrox @ 40m
1 @ 30
1 @ 27
2 @ 24
2 @ 21
3 @ 18
5 @ 15
6 @ 12 Switch to 80% on ascent passing 10m
7 @   9
[email protected]  6

Total run time 96mins
Total deco time 62mins
CNS post dive 52%
OUT 125.24  

The point of noting that WL and Dom don’t do Trimix diving was that they would perhaps not have experience of the problems associated with multiple stage bottles. Anything past two bottles is to be avoided if possible. That said I do use a pony of air attached to my twin set as a bail out to first stop depth. This idea is also used by some of the other deep trimix divers in my circle but the mix is redundant and not part of the deco plan.

5min stops for gas switch is also a bit odd as gas switching takes all of  10seconds. Also an additional 5mins at the first switch depth will add to the on gassing of the Nitrogen in the mix which would have to be planned fro in the deco. Prep in the from of unsheathing the reg and hose checking it is the correct mix and switched on and purging the reg is done on ascent. So it’s just a case of reg out reg in. I usually do this on ascent and switch the mix on the computer on the stop.

I am not having a go at any one. I am just looking at some of the practical considerations when planning deco.

ATB

Mark Chase
 

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Gradient factors

OK try to imagin two parallel lines in the horizontal plain.

the top line is 100% GF. The bottom line is 0 GF

If you run a 20  - 80 GF you will start your deco 20% of the way in between the top line and the bottom line. You develop an ever increasing curve runnig up to 80% throughout the deco so at the 6m stop you will be at 80% of the maximum off gassing envalope.

Theroeticly if you pass 100% you get bent

A 100 / 100 profile will have you running adjecent to the top line of the envalope throughout deco so no curve.

A 65m 20 / 80 profile looks like this

Stop depth / percentage of off gas limit

depth

42m           20%gf
30m           41%gf
27m           46%gf
24m           50%gf
21m           54%gf
18m           59%gf
15m           63%gf
12m           67%gf
9m             71%gf
6m             76%gf
0m             80%gf

If you plot the percentages on a bit of graph paper you can see the decompresion curve.

In the old days when people ran 100% Bulhman tables  less was known about the stress of deco. Now we understand that a slow gradual curve will get you out of the water safley and feeling better than a 'max the envalope' deco square profile. As a general rule of thumb the GF low bottom line for deco should be 10 -40% and the top line should be GF 80 -100. The more stress full the dive the lower I would go on the curve. There are people out there who dive 100/100 gf and they get out of the water very quickley. But they are a dieing breed  


ATB

Mark Chase
 

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Oh blimey, that's me in trouble then.
Turn VR3 on, turn brain off, jump in water.
Still having trouble with those smileys...

BTW ddplan's not bad - the user interface isn't especially friendly compared to Proplanner cos it's all in DOS. Does GFs and has a rather splendid table generating feature.
Free to download from http://www.drogon.net/ddplan/install.htm
 

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Thanks for the link Andy. An interesting read

Strange thing is I did a comparison on the dive profiles:

55m for 25mins on 18/45back
Gas 50% for deco at 20 – 80

1 @ 33m
1 @ 30
1 @ 27
2 @ 24
2 @ 21
1 @ 18
3 @ 15
4 @ 12
6 @   9
30 @ 6

Total run time 79mins  Total deco 51mins

The 20-80 profile gave them an additional 30mins of deco ??

I thought this was a bit excessive so I had a look at a 20-100 GF

20-100GF on Deco planner                                  Their 20-100profile

1 @ 33                                                                   0 @ 33
1 @ 30                                                                   1 @ 30
1 @ 27                                                                   1 @ 27
1 @ 24                                                                   1 @ 24
1 @ 21                                                                   1 @ 21
1 @ 18                                                                   1 @ 18
2 @ 15                                                                   1 @ 15
3 @ 12                                                                   1 @ 12
5 @   9                                                                   3 @   9  
21 @ 6                                                                   11 @ 6


According to Decoplanner they missed 16mins of stops on an already aggressive profile

I don’t know how this happened or how they set their version of decoplanner up but all in all it doesn’t make sense.

On the second dive they missed a staggering 19mins of stops on a 20 –100 profile

Decoplanner 20 –100                                 Their Profile

1 @ 27m                                                     1 @ 27
1 @ 24                                                       1 @ 24
1 @ 21                                                       5 @ 21
1 @ 18                                                       1 @ 18
2 @ 15                                                       1 @ 15
3 @ 12                                                       1 @ 12
5 @   9                                                       4 @   9
32 @ 6                                                       13 @ 6

I would be interested to know how they managed to get their profiles. It doesn’t seem to be based on Deco planner. On both dives compared to a 20 80 profile they missed a total of  71 mins of stops

That’s a lot

If only they had had a VR3 on them they would have realised they had made a mistake


Sorry couldn’t resist that

ATB

Mark Chase
 

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OK I have fafed about with Decoplanner and found the major diferance in our settings was the decent rate theirs is 30m/min my one is set to 20m /min

Having mirrored their settings i found that they missed 36mins of stops on a 20 -80 profile and 21mins of deco on a 20 -100 profile. allowing for their additional padding they missed 9mins of deco but how much of the padding was of benifit to deco can not be answered unless I can see a graph of their dive profile.

Also 30m /min is one hell of a decent rate, but it is possable so I will give them the benifit of the doubt.

What is without doubt is their deco plan is way off that of Decoplanner.

Any way what was a DIR diver doing diving non standard gas mix?

Confused of Maidstone

Mark Chase
 

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Hi,

Interesting thread this, I have not followed the link but I do know the guys at KPP (GUE) are now experimenting with gasses other than HE, O2 ans N2, namely hydrogen. The concept is that light gasses on and off gas quickly, so if the add them to there deco mixes they should off gas very quickly indeed. I don't know about you but I feel adding hydrogen to a rich O2 mix is a tad silly as all you end up with is a bomb. This could be one of the profiles they are playing with for these gasses.

As for the example, Mark knows me well enough to know that I have a thing about deep stops, I have had extensive discussions with people including a Professor of Physiology at UCL who happens to be an aggresive diver so has considerable knowledge.
The bottom line with deep stops is that they are intended to keep the bubble size to the minimum, and hence promote faster off gassing. Makes sense to me so I do deep stops.

If I run the profile using Decoplanner with GF of 10 / 80 (Mark has already explained what this is about) you get.

1 @ 45
1 @ 42
1 @ 39
1 @ 36 Switch to 32%
1 @ 33
1 @ 30
1 @ 27
2 @ 24
3 @ 21
3 @ 18
6 @ 15
7 @ 12
8 @ 9  Switch to 80%
[email protected] 6

Run time 105, deco time 72 mins, CNS is 53%

Bottom mix was 18 / 30

On the whole a nice safe profile, would rather have a longer bottom time, so personally would probably plan to do 40 mins

But there you go.

Andrew
 

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Hi

WL

GF, in practise will define the stop depths and thus how aggresive the profile is.

On decompression we are trying to avoid any bubbles the lunds require the gas to be in a solution in the blood. This being said it is virtually impossible to avoid the formation of some bubbles. Deep stops are about minimising the size and attempting to remove the so called micro bubbles early on before they become big enough to block something important  and cause us a problem. DAN are doing a lot of research into this at the moment, along with other research which is on the old favorite of bubble tolerence.

If we look at the rate of assent, when you start to do this type of diving you realise that you have to move fairly quickly to keep up your rate of assent, get to the stop and hang there for a bit before moving on. The VR3 and it's associated deco program assumes a very slow rate of assent, the idea is to avoid the necessity to actually stop, you just keep moving up, but very slowly until you reach a depth where you stop for greater than 1 min. All the other programs include the assent between depths in the 1 min stops. If you play with rate of assent you will find that a lot of the deep stops just vanish when you get to about 3 m/min, but the total deco time will remain roughly the same.

Since 90% of decompression theory is acquired empirically, the best way to judge whether or not deep stops work is to ask divers. All divers who have tried deep stops say they feel better when they get out of the water, i.e. less tired. This is sufficient evidence for me. There have also been a number of experiments where one diver tested has done deep stops and another has not and using a doppler test, they have been able to measure the number and size of the bubbles in the blood and the diver who has done the deep stops has fewer and smaller bubbles.

The reality is, you must decide what is good for you. Some divers I know charge off to each stop switch gas as quickly as possible etc, this has been described as bend and mend. I do not like it, but, some very good, very experienced divers I know regually do 90~100 M dives do this type of deco and have been fine for years so who am I to criticise them.

Mark crawls along, probably because of the weight of all the flipping crabs and lobsters he is carrying, he is a classic candidate for a VR3 and indeed now has one. I am more akin to this, I just make him do deep stops and he makes me go slow. I figure between us we dive a very safe profile.

Keep reading Andy, it is a facinating subject, as you can tell from these post both Mark and myself have read a lot and thought long and hard about this, not to mention a lot of conversations between ourselves and other divers / scientists. We are both at the begining of our TRIMIX diving and are just begining to push our limits. I continue to read just about anything I can lay my paws on about this.

Take care,

Andrew
 

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[b said:
Quote[/b] (wetlettuce @ Aug. 27 2003,23:20)] 
[b said:
Quote[/b] ]
Any way what was a DIR diver doing diving non standard gas mix?

Confused of Maidstone

Mark Chase
Hi

18/45 is a standard mix.
No I ment 50% for deco??

[b said:
Quote[/b] ]I don't have decoplanner so I don't know whether any other settings can be changed to mimic theirs. Things like alveolar pp02 etc.

I think they just got it wrong on the day for whatever reason, including not using the O2 they had.  Is it true that even with the gradient you can pick a safety grade like +1,+2 -1,-2 that kind of thing?
I had Decoplanner set to 0 safety and I still couldent get them out of the water as quick as they did. Conservitsum is usuley set through the Gradianet factors on Decoplanner.

[b said:
Quote[/b] ]30 m/min is excessive but all that would do is make the runtime more conservative if they descended slower. ie the software thinks they are down longer (thats as long as they adhered to the runsheet and not timed the bottom time when they got to the max depth which would mean they accrued more nitrogen than the computer has calculated) The ascent rate would be more critical in terms of run time and will impact the deco time at the stops. If you change ascent time from say 10m/min to 3 m/min it makes a difference to the total time but perhaps not so much on the timed stops.  
Errrr re read my thread. I only managed to get a time closer their profile by altering Decent from my setting of 20 to theirs of 30m / min so this REDUCED the amount of stop time and made the dive MORE agressive not more conservitave. This is because they have their computer set as decent in run time. so a fast decent will meen less on gasing on the way down but not a longer bottom time.



[b said:
Quote[/b] ] In terms of deep stops AndyP, from the research and reading I've done we use two methods to decompress. One is the gradient ie the speed of ascent to effectively create bubbles to pass into the lungs, and the other is the increased po2 of nitrox.
This is not correct there is only one method to decompress it can be accelorated but not altered. To explain will take a long time so I will leave that for later.

Deep stops are Vodo but they work and their is growing scientific backing for the idea.

Point is Andy, run their profiles through your computer and see what times you come up with? Does your computer think they missed any stops or dose it think it was a nice safe profile. What safety settings do you use to match their ascent run time?

Just curious.

ATB

Mark Chase
 

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[b said:
Quote[/b] (AndyP @ Aug. 27 2003,22:52)]Bottom mix was 18 / 30

On the whole a nice safe profile, would rather have a longer bottom time, so personally would probably plan to do 40 mins
Do you really think an END of 42.5 is a nice safe profile?  Not trolling - just interested.

For what it's worth, I planned this dive and would do it on 15/55 (END 23.7) and 50% and 100% Deco.  I would have to either borrow some twin 15s or reduce my bottom time to dive with twin 12s and leave myself and my team with sufficient gas reserves.

Incidentally, this is a similar profile to a dive I did on HMS PRINCE OF WALES earlier this year (68m/30min), and I can categorically state that all this stuff is a lot easier in nice warm water and a wetsuit!  Current and vis. were distinctly UK-ish at times, however.
 

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[b said:
Quote[/b] ]Do you really think an END of 42.5 is a nice safe profile?
Errr where did you get END of 42.5, I make it 39, as we know this is down to personal tolerence, and yes I think END of 39 is OK.

When I ran the profile I had a built in back up of 50 Bar

Andrew

WL, I was not having a go, I meant what I said, it is a fascinating subject.
 

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[b said:
Quote[/b] (andyp @ Aug. 28 2003,10:57)]Errr where did you get END of 42.5, I make it 39, as we know this is down to personal tolerence, and yes I think END of 39 is OK.
I put your profile through GAP, which counts O2 as narcotic (which it is).  Concur with 39 if you calculate it with the formula.
 
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