Ratio deco for ccr?

[hoffi]

Class posts IMO by Clare and Igor,
also Lizard and Ebt, their posts show nicely,
"manual deco" ( I'll use that term to differ from RD later ) is not so seldomly used by people who can't be recognized as brainless DIR-folks.

I'll try to add a little bit...in good hope this does not become just another RBW marketplace...I'll repeat some stuff, just for clarity.

Overheating the debate and abusing RD for witchhunts is irvinesque and anachronistic in my opinion...
or it's driven by business-interests.
George Irvine retired a decade ago, no sense to mimic the same social-media reflexes on and on...in 2013.

GUE as an example of a DIR-program teaches RD in a clearly defined corridor, gaschoice, depth and time,
which happens to cover well for the majority of the profiles being executed.
Its well mentioned to use it with caution and its NOT presented as the one and only tool.

T1 RD to about 50m is a little conservative compared to a TC in average settings, minor differences plusminus 10min max, roughly.
T2 RD to 75ish , one needs to be more careful, the road becomes narrower, tendency to be more aggressive, one needs to be more aware of individual physical deco-capabilities.

I think its quite narrow-minded ( or driven by politics ) to condemn RD in whole just because of individual mishaps with RD and DCS-cases.
Same as condemning a computer after one or two cases of DCS with regular settings.

I'm "hausmeister" for one of the oldest european DIR-lists, I've heard and seen a thing or two, not that my own horizont would mean too much, just to enhance perspectives, all fully anecdotal for sure.
DIR-GER has 360 members, a recent ( and ongoing ) poll TC vs. RD vs. precut tables shows two divers primarily using live-computers, I'm not aware anyone is in a wheelchair or permanently disabled due to DCS after RD.
In thirteen years since 2000 no member of the list has died while/after diving, we had one member die from cancer, thats it.
For sure people experienced dives going south and royal fu***ps including cases of DCS, bents and more.
Does this mean, the approach alltogether is flawed? I don't think so.
My feeling its the normal average, as it happens while using live-computers.
Quite a few computer-users may have had their niggles while fumbling with the settings.

IMHO, its 100% possible to do manual deco under mental pressure but its very helpful to be proficient with,
IMHO its not good as backuptool when not second nature...an it only becomes warm and familiar when used for years as primary decotool.

This hearsay popping up frequently, about DIR-folks getting bent ( like in the other thread for instance ), it should be connected to case-specififc details,
otherwise it has this certain taste of agenda-driven bashing.

I'm not aware that RD, used in proper manner and with confidence under teamperspectives
includes a greater risk to get bent under mental stress over live-computer.





Absolutely,
there is this narrow corridor of "manual/anecdotal/empirical deco" beyond teaching-level, also using ratio-calcs, long cave exposure, combos of multilevel & reverse profile, accelerated deco, other gases than standard, close-to-Heliox-mixes, setpoint-diving, shooting over the hills with a fast scooter....all possible,
within careful and 100% individual margins for sure...and more so with full acceptance of the high risks involved, it may work 10 times and end up with heavy spinal bends the 11th time.

There is no "model" for it I'm aware of and It should'nt be called RD IMHO as it gives the impression to be part of teaching-standards.


I'd strongly recommend to approach "manual-long-exposure-deco" with well established confidence on RD,
own practical experience with one's own body collected on more regular profiles,
it will take a while, for sure.

Get to know your body and how to influence physical preconditions, it should take years of careful approach.
It takes time, nothing to find on the internet, by far.

Strapping three live-computers on and follow the calculations,
its easier on the first glance and its done quite often on the more extreme dives,
but in my opinion its also a good road to the chamber,
anecdotes about chamber-rides after computer-record-dives float around in wide variety.

My opinion/observation is based on what I've witnessed, I'm not into longer runtimes beyond 180min to date,
hav'nt done the real long dives myself, there's only a handful of people with own practical experience about it.

FWIW & m2C & HTH,

hoffi

 

[lamont]

A small amount of mathematical analysis on various ratio deco algorithms would demonstrate the extent to which their results align with proven models and, better, indicate where deviations occur. I'm surprised that more has not been done here. Without this analysis, the process is best regarded as inductive inference, and mathematically unverified.

So can ratio deco work in the same way with CC as it does with OC? Of course... it's the same process of restriction and approximation. The be main area of concern would be the inductive nature of it's construction, coupled with lack of sensitivity analysis on deviations. It's the second of these which might prove interesting. I suspect the volatility might be very different from OC.
OC ratio deco at least has the benefit of being very widely known (if not dived). It may lack formal verification, but enough people like me prod and probe it to see what it does. Which is not the case for CC ratio deco.

More interesting would be to see what divers actually do in the water.

Typically it seems that RD divers think they're deeper for longer than they are. There's probably a built-in conservatism which allows for any sloppiness in how it matches the profiles a deco planner spits out.

Dealing with contingencies and going over time and adjusting profiles on-the-fly is also an area where I've heard of some very disconcerting choices taken by divers to deal with contingencies (i.e. adding waaaaay too much intermediate time and running out of deco gas shallow).

Also, to deal with human error you must have a team where when the deco captain has a brain fart, the other divers are willing and able to give them the middle finger. If you've got a weaker diver following a stronger divers lead then the stronger diver becomes a single point of failure.

 

[hoffi]

Also, to deal with human error you must have a team where when the deco captain has a brain fart, the other divers are willing and able to give them the middle finger. If you've got a weaker diver following a stronger divers lead then the stronger diver becomes a single point of failure.

Good point, it may influence Deco, it sure affects all aspects of the dive.
Cases when supposedly weaker teammates handled a tricky situation well and overruled the " alpha-diver " spring to my mind as much as examples for the situation you describe.

Its a social challenge for all teammates, to handle alpha-genes floating around in a team, this topic usually is mentioned during a teamoriented course..and its one reason among others why students usually have more to take home on teamdiving-courses with three students.
Social interaction in teamdiving is an important and challenging part, when the challenge is fresh and alive it may help to keep complacency away from the dive.

hoffi

 

[lamont]

Good point, it may influence Deco, it sure affects all aspects of the dive.
Cases when supposedly weaker teammates handled a tricky situation well and overruled the " alpha-diver " spring to my mind as much as examples for the situation you describe.

Hah, yes, and the stronger diver needs to be willing to see a middle finger and let themselves get 'voted out'.

 

[DSix36]

You can simplify that even more.

Background

RD for T1 splits the ascent up into three phases:

- the 20fpm "deep stops" phase
- the gas switch at 70 feet to 20 feet
- the time spent hanging at 20 feet.

The start of the 20fpm ascents is determined by 80% of ATA and just continues up to 70 feet. For a 150 foot dive this is 110 feet. For a 170 foot dive this is 130 feet. Taking depth minus 40 feet is a way to keep it simple for tech1 dives.

The time spent going from 70->20 is set to be equal to the time spent hanging at 20 feet. Or, alternatively, half your deco time is awarded to 70->20 and half to hanging at 20. You linearize all the stops from 70->20.

The total deco time at 150 feet is equal to the bottom time (20 mins @ 150 = 20 mins deco, 30 mins @ 150 = 30 mins deco). For every 10 feet deeper/shallower you add/subtract 5 mins of deco time.

Standard Profiles

You wind up with basically three profiles, 10 minute deco, 20 minute deco and 30 minute deco:

1-1-1-1-1-5 = 10 mins
2-2-2-2-2-10 = 20 mins
3-3-3-3-3-15 = 30 mins

Examples

So for 20@150 (20 min deco):

110->70: 20fpm
70->20 : 2 min stops
20: 10 mins

For 30@150 (30 min deco):

110->70: 20fpm
70->20: 3 min stops
20: 15 mins

for 10@170 (20 min deco):

130->70: 20fpm
70->20: 2 min stops
20: 10 mins

for 20@170 (30 min deco):

130->70: 20fpm
70->20: 3 min stops
20: 15 mins

for 30@130 (20 min deco):
90->70: 20 fpm
70->20: 2 min stops
20: 10 mins

for 40@130 (30 min deco):
90->70: 20 fpm
70->20: 3 min stops
20: 15 mins

Restrictions

T1 is a single 50% deco gas class, with a max depth of 180, and max planned deco of 30 mins. The ratios only work around 10-30 minutes of bottom time and 130-170 feet, as you get outside that window they work less well.

Interpolation

And if you need 25 minute of deco, interpolate something like:

2-2-2-3-3-13

But generally with RD you're doing "too much" deep deco anyway, so I'd also be fine doing this:

2-2-2-2-2-15

Planning

This makes it generally easy to plan a dive with someone else that knows ratio deco. Generally you do it backwards and you figure your deco time to be 20 or 30 minutes (which tells you if you're doing 2s and 10 or 3s and 15). Based on your max depth you adjust your runtime to hit your deco time (if you're doing a 30 minute deco you're typically doing 20@170 or 30@150). Based on actual runtime you'll have the deco captain call a bit more or less deco.

That last paragraph there is really how you go about doing ratio deco.

Theory

A lot of it is just due to playing around with deco planners and inserting deeper stops and noticing that it doesn't change the overall deco time much, which gives the divers leeway to move stops deeper in order to simplify things. The 50/50 split from 70->20 and 20 foot stops keeps it easy, but 60/40 and 40/60 will also work. What v-planner spits out works, linearized deco works, and just about anything else reasonable that approximates a curve and gets the total time right will work. *BUT* if you play around with edge conditions and find a profile that doesn't work in v-planner, then *DON'T* do that -- *DO* play around with v-planner to find the edges.

HTH

I just read this entire thread and this is really the only post that I found informative and understandable at the same time. Maybe it is just due to the small number of undamaged brain cells that I have left, But I still thank you for this post.

I am still not a big believer in RD and will still use my Shearwaters, but I will start to test this stuff when I dive now that I understand it enough to get started. I think it could be another tool if I can make it work for myself.

 

[Fldvr]

For me the real headache is trying to utilize Ratio deco from my Oc days to running quick profiles in my head while the Shearwater is giving me some strange stops and weighting towards the shallow end.
I miss my deep stops, usually 1's to my first deco bottle then take advantge of the controversial O2 window:square:
The Shearwater just runs me up shallow with minimal Po2 adjustments of the stops.

But as a tool, either running your entire dive on a constant set point using a computer or using Ratio deco in the end they are both just tools to accomplish your goals....having the proper tools and being able to use them effectively always makes for a safe team experience.

Now the big mind melt is TTS using the shearwater....yowza!

Henry

 

[hoffi]

Hah, yes, and the stronger diver needs to be willing to see a middle finger and let themselves get 'voted out'.

It takes two to tango ( or more )...I for one had my share of solo-career.

The majority of alpha's into teamdiving I know are keen about divepartners acting up to their eyelevel,
quite a few are capable to tone themselves down as needed.
I've experienced sensitive reaction from alphas in all aspects to enhance rich hobby-experience.

That said, it is a challenge for all parties involved, absolutely.

Sorry for the tangent.

hoffi

 

[dlk]

More interesting would be to see what divers actually do in the water.
..

What divers actually do in the water is very interesting.

My point was simply that it's even more interesting when we subject it to scientific analysis. All science is skeptical, and examination against hypothesis is what separates science from witchcraft.

What divers do is evidence. To draw useful conclusions from it we need theory.

If CCR RD in practice yields profiles outside the envelope of what might be predicted by accepted models then that is hugely interesting. If not, then where within the envelope do the profiles sit with respect to conservativeness? What small changes might cause big shifts? This might usefully inform on-going practice. It certainly something I'd want to understand if I was diving CCR RD.

DLK

 

[keri.lewis]

If CCR RD in practice yields profiles outside the envelope of what might be predicted by accepted models then that is hugely interesting. If not, then where within the envelope do the profiles sit with respect to conservativeness? What small changes might cause big shifts? This might usefully inform on-going practice.

Traditional OC RD profiles are an approximation of 30:85 to 20:80 GF Buhlmann.. it's just a rough calculation method within the bounds as outlined by Lamont.

Using RD on a CCR involves identifying bounds and patterns you are happy with. 25:80 seems like a reasonable set to me - but what do I know? Everyone can set their own parameters. if you wanted to move your High GF down - you could change the RD "set-point" (as previously noted - an unfortunate choice of name) shallower by 3 metres or the reverse if you wanted to change the High GF for a higher value..

I was just running sets of tables on GAP (free trail for this purpose) - using Buhlmann CC 25:80 - comes out pretty close to traditional OC RD except for the 6 metre stop (the Difference being the use of O2 vs the CC Setpoint at 6 metres) - when used within the limits I choose to set.

In-water deco reminds me of the engineer's maxim..

Calculate to 5 decimal places: Measure with a ruler: cut with an axe!​

The fudge factors be they VPM conservatism factors, Buhlmann GFs or whatever else we use mean that the deco is padded enough to take small differences in in-water PO2 or the differences in the depth sensor reading or the small differences in Helium composition etc. No sensible person is likely to run at the edge of the deco curve except in the worst sort of low-gas emergency... which in caves at least is a planning and gas-staging issue.

You pays your money and takes your choice...

As for "Voodoo" - well I always plan my dives first. Don't you? I am in transition from OC to mCCR - so I don't claim great expertise in CCR issues, but I have no desire to go away from planning my dives in advance. That taken as read, the use of RD as a planning tool then becomes a discussion in the team and changes in the water are flexing the deco rather than calculating it. Isn't this much like interpolating from a pre-printed table in your pocket?

This does work in caves - just as well as in Open Water. You just need a resettable average depth counter. Now I like computers, but having the ability to run a simple range-based calculation that checks it is a good safety factor. It's the equivalent of the printed set of tables as long as you are close to the ranges for the ratios.

EDIT for Clare... if you use resettable.. make sure it's a very positive control to reset...

 

[Clare]

Please don't use resettable average depth counters. I've seen people reset them by accident and then, as they were letting it do things for them, have no idea what the depth had been.

(I married him a few years later though so it can't have been that bad)

 

[DSix36]

I had a friend explain RD to me a bit, at least T1, and it seems to actually work. I am no where ready to rely upon it without my computers, but with the pc planners it is very easy to see the pattern and how it works. I only have about 4 hours in studying and figuring so far, but it is a very interesting thing to learn.

I can even see how it could work in a cave as long as you could either plan or figure an average depth for the dive.

Now it is time to step up to T2 and get a real headache.

 

[lamont]

What divers actually do in the water is very interesting.

My point was simply that it's even more interesting when we subject it to scientific analysis. All science is skeptical, and examination against hypothesis is what separates science from witchcraft.

What divers do is evidence. To draw useful conclusions from it we need theory.

If CCR RD in practice yields profiles outside the envelope of what might be predicted by accepted models then that is hugely interesting. If not, then where within the envelope do the profiles sit with respect to conservativeness? What small changes might cause big shifts? This might usefully inform on-going practice. It certainly something I'd want to understand if I was diving CCR RD.

DLK

The problem with decompression is that as long as you have one algorithm you are precisely certain of where you should do your stop and for how long. As soon as you introduce 3 of them (RGBM, VPM+2, GF 20/85) you no longer know exactly what decompression profile to run. RD leverages that so that you're still getting profiles "within the envelope" of what the algorithms produce, but manipulates the grey areas to make it easier for humans.

And, again, to study anything like this scientifically and with precision you can't ignore the human element, because that's your biggest source of error. Take the average RD practitioner who boasts in the bar afterwards that they routinely cut their deco 5 minutes short from what RD calls for and they're great offgassers -- but look at their profiles and they're all average depths that are 20 feet shallower and profiles that are 5 minutes shorter than they think/claim. Rounding up in this case makes you inherently more conservative and gives you a bigger dive to boast about later...

 

[Mark Chase]

Have there been any scientific studies done on Ratio Deco as even being remotely safe? Relative to the mountain of data we have on everything else?

I dont think you understand what ratio deco is.


Its not a fixed set pf peramiters, its a system that enables you to dive without a deco computer and it needs to be developed to the personal tolerance / preferance of the dive just like ANY other deco system.

I guarentee you that ratio deco can be far less agressive than the deco system you are using today if you chose to run it like that.


There is no great mystery to it. I use it all the time to back up my Sheerwater dive computer. I cant afford (nor do i reely want) two £1300 dive computers. I used to run two VR3s but they only cost £350 each


I have put up ratio deco profiles many many times with full details of the calculation so I dont see any evidance of partial information. Its all freely available on the web as well but whats not there is the way in which you adjust the profile.


At the most basic level: (Ignoring minimum deco)

There are three set points: 45m, 66m & 81m

The ratio between bottom time and deco for each of the set points are

1 TO 1

2 TO 1

3 TO 1


Personaly past 80m i havent done enough time to develop my own ratios so i stick to 1:1 and 2:1 ratios.


So if i were to do a dive for 60mins at 45m I know the ratio between bottom time and deco is 1:1 so I will need 60mins deco from 21m & up using ratio deco.


Using the system i also know Ill need haf of that time at 6m and the rest between 21m and 6m in 3m incraments so 5 stops.


I coud say my deco was

6 @ 21
6 @ 18
6 @ 15
6 @ 12
6 @ 9
30 @ 6


Two points. First off you have to get to 21m.

According to GUE you should ascend at 9m / min to 80% of ATAs so your first stop on a 45m dive would be 34m where you would pause and slow your ascent rate to 5m/min up to 21m pausing at 3m intervals.


I dont agree with this as it adds too many dep stops so i always do my first top on Ross's advice (VPlanner fame) and stop at 2 ATMs above max depth

QED id ascend to a first stop depth of 24m where id stop for 1min and then ascend to 21m.


So now we have a deco plan

1@24
6@21
6@18
6@15
6@12
6@9
30@6


But I dont like thiose block 6min stops so I am going to adjust them. I want it to be simple so Ill just do something like this.


1 @ 24
2 @ 21
4 @ 18
6 @ 15
8 @ 12
10 @ 9
30 @ 6


So now I have a finished plan for my 60min dive at 45m on 1.3 set point using ratio deco and 18/45 diluient (which i always use from 0m down to 55m)


So how agressive is it?

Lets look at VPlanner multi deco 35/80GF

MultiDeco 4.01 by Ross Hemingway,
ZHL code by Erik C. Baker.

Decompression model: ZHL16-C + GF

DIVE PLAN
Surface interval = 5 day 0 hr 0 min.
Elevation = 0m
Conservatism = GF 35/80

Dec to 45m (2:30) Diluent 18/45 0.70 SetPoint, 18m/min descent.
Level 45m 57:30 (60:00) Diluent 18/45 1.30 SetPoint, 14m ead, 22m end
Asc to 30m (61:40) Diluent 18/45 1.30 SetPoint, -9m/min ascent.
Asc to 24m (62:20) Diluent 18/45 1.30 SetPoint, -9m/min ascent.
Stop at 24m 0:10 (62:30) Diluent 18/45 1.30 SetPoint, 2m ead, 12m end
Stop at 21m 2:30 (65:00) Diluent 18/45 1.30 SetPoint, 0m ead, 11m end
Stop at 18m 4:00 (69:00) Diluent 18/45 1.30 SetPoint, 0m ead, 10m end
Stop at 15m 5:30 (74:30) Diluent 18/45 1.30 SetPoint, 0m ead, 8m end
Stop at 12m 7:00 (81:30) Diluent 18/45 1.30 SetPoint, 0m ead, 7m end
Stop at 9m 10:00 (91:30) Diluent 18/45 1.30 SetPoint, 0m ead, 6m end
Stop at 6m 14:30 (106:00) Diluent 18/45 1.30 SetPoint, 0m ead, 4m end
Stop at 3m 25:30 (131:30) Diluent 18/45 1.30 SetPoint, 0m ead
Surface (131:50) Diluent 18/45 -9m/min ascent.

OTU's this dive: 192
CNS Total: 72.6%



So as you can see the Ratio deco is more conservitive than 35/80 GF



But what if the dive is 60mins at 52m?

OK so past set point you have an additional 7m of depth.


Using Ratio deco for every + or - 3m of depth you should add 5mins so 7m devided by 3m = 3

3 X 5mins = 15 so you need to add 15mins.

So for a 60min dive to 52m you need bottom time + 15mins = 75mins deco. 1/2 at 6m so 38 @ 6m and 1/2 over 21m to 9m so 5 stops of 8mins (rounded up to 40mins) between 21m and 9m

Start deco at 2 ATMS above max so first stop depth = 32m


1 @ 32
1 @ 28
1 @ 25
8 @ 21
8 @ 18
8 @ 15
8 @ 12
8 @ 9
38 @ 6


And i dont like block stops so id do


1 @ 32
1 @ 28
1 @ 25
4 @ 21
6 @ 18
8 @ 15
10 @ 12
12 @ 9
38 @ 6



So what does V Planner say?

MultiDeco 4.01 by Ross Hemingway,
ZHL code by Erik C. Baker.

Decompression model: ZHL16-C + GF

DIVE PLAN
Surface interval = 5 day 0 hr 0 min.
Elevation = 0m
Conservatism = GF 35/80

Dec to 52m (2:53) Diluent 18/45 0.70 SetPoint, 18m/min descent.
Level 52m 57:07 (60:00) Diluent 18/45 1.30 SetPoint, 18m ead, 25m end
Asc to 30m (62:27) Diluent 18/45 1.30 SetPoint, -9m/min ascent.
Stop at 30m 0:03 (62:30) Diluent 18/45 1.30 SetPoint, 5m ead, 15m end
Stop at 27m 2:00 (64:30) Diluent 18/45 1.30 SetPoint, 4m ead, 14m end
Stop at 24m 3:30 (68:00) Diluent 18/45 1.30 SetPoint, 2m ead, 12m end
Stop at 21m 4:30 (72:30) Diluent 18/45 1.30 SetPoint, 0m ead, 11m end
Stop at 18m 6:00 (78:30) Diluent 18/45 1.30 SetPoint, 0m ead, 10m end
Stop at 15m 7:00 (85:30) Diluent 18/45 1.30 SetPoint, 0m ead, 8m end
Stop at 12m 10:00 (95:30) Diluent 18/45 1.30 SetPoint, 0m ead, 7m end
Stop at 9m 13:30 (109:00) Diluent 18/45 1.30 SetPoint, 0m ead, 6m end
Stop at 6m 19:30 (128:30) Diluent 18/45 1.30 SetPoint, 0m ead, 4m end
Stop at 3m 33:00 (161:30) Diluent 18/45 1.30 SetPoint, 0m ead
Surface (161:50) Diluent 18/45 -9m/min ascent.

OTU's this dive: 236
CNS Total: 89.2%




So how do i adjust it to make it more / less agressive?


Well i could lower my average depth by rounding it down instead of up

I could shorten my bottom time by ignoring the decent time

I could just decide to knock off some of the bottom time before doing the calculation.


And How do you know which way to go on the agressive scale?

You spend a lot of time comparing RD profiles to you personal prefered deco for that depth and you make adjustments accorningly.


Every dive i calculate the ratio deo. Then I compare my RD plan to the plan my Shearwater Preditor gives me.

Then i decend on a depth range and make a note on how i will adjust the deco,.


So for me in the 40 -55m range i know Ratio deco is soft so I can be a get more agressive on my calculations. So on a dive which is 50 to the sea bed and 42 to the top of the wreck ill probably calculate on 45m and knock off 3mins for the decent.

From 55m to 75m I find RD a little on the agressive side so i tend to be less agressive more padding on my calculations. So on a dive thats 68 to the sea bed and 58 to the top of the wreck. Ill calculate the whole dive at 68m and put decent in run time.


If this all souns too complicated? i cant realy aggree. Deco takes for ever and i have a shead load of time to calculate and re calculate my deco so i dont find it a problem and it passes the time.


ATB


Mark

 

[matt]

I think Mark, you ought to write it up as an article as you're the only person who explains this well.

Matt.

 

[DeepUnderground]

I dont think you understand what ratio deco is.





Its not a fixed set pf peramiters, its a system that enables you to dive without a deco computer and it needs to be developed to the personal tolerance / preferance of the dive just like ANY other deco system.



I guarentee you that ratio deco can be far less agressive than the deco system you are using today if you chose to run it like that.





There is no great mystery to it. I use it all the time to back up my Sheerwater dive computer. I cant afford (nor do i reely want) two ***163;1300 dive computers. I used to run two VR3s but they only cost ***163;350 each





I have put up ratio deco profiles many many times with full details of the calculation so I dont see any evidance of partial information. Its all freely available on the web as well but whats not there is the way in which you adjust the profile.





At the most basic level: (Ignoring minimum deco)



There are three set points: 45m, 66m & 81m



The ratio between bottom time and deco for each of the set points are



1 TO 1



2 TO 1



3 TO 1





Personaly past 80m i havent done enough time to develop my own ratios so i stick to 1:1 and 2:1 ratios.





So if i were to do a dive for 60mins at 45m I know the ratio between bottom time and deco is 1:1 so I will need 60mins deco from 21m & up using ratio deco.





Using the system i also know Ill need haf of that time at 6m and the rest between 21m and 6m in 3m incraments so 5 stops.





I coud say my deco was



6 @ 21

6 @ 18

6 @ 15

6 @ 12

6 @ 9

30 @ 6





Two points. First off you have to get to 21m.



According to GUE you should ascend at 9m / min to 80% of ATAs so your first stop on a 45m dive would be 34m where you would pause and slow your ascent rate to 5m/min up to 21m pausing at 3m intervals.





I dont agree with this as it adds too many dep stops so i always do my first top on Ross's advice (VPlanner fame) and stop at 2 ATMs above max depth



QED id ascend to a first stop depth of 24m where id stop for 1min and then ascend to 21m.





So now we have a deco plan



1@24

6@21

6@18

6@15

6@12

6@9

30@6





But I dont like thiose block 6min stops so I am going to adjust them. I want it to be simple so Ill just do something like this.





1 @ 24

2 @ 21

4 @ 18

6 @ 15

8 @ 12

10 @ 9

30 @ 6





So now I have a finished plan for my 60min dive at 45m on 1.3 set point using ratio deco and 18/45 diluient (which i always use from 0m down to 55m)





So how agressive is it?



Lets look at VPlanner multi deco 35/80GF



MultiDeco 4.01 by Ross Hemingway,

ZHL code by Erik C. Baker.



Decompression model: ZHL16-C + GF



DIVE PLAN

Surface interval = 5 day 0 hr 0 min.

Elevation = 0m

Conservatism = GF 35/80



Dec to45m(2:30)Diluent 18/450.70 SetPoint, 18m/min descent.

Level45m 57:30(60:00)Diluent 18/451.30 SetPoint, 14m ead, 22m end

Asc to30m(61:40)Diluent 18/451.30 SetPoint, -9m/min ascent.

Asc to24m(62:20)Diluent 18/451.30 SetPoint, -9m/min ascent.

Stop at24m 0:10(62:30)Diluent 18/451.30 SetPoint, 2m ead, 12m end

Stop at21m 2:30(65:00)Diluent 18/451.30 SetPoint, 0m ead, 11m end

Stop at18m 4:00(69:00)Diluent 18/451.30 SetPoint, 0m ead, 10m end

Stop at15m 5:30(74:30)Diluent 18/451.30 SetPoint, 0m ead, 8m end

Stop at12m 7:00(81:30)Diluent 18/451.30 SetPoint, 0m ead, 7m end

Stop at9m 10:00(91:30)Diluent 18/451.30 SetPoint, 0m ead, 6m end

Stop at6m 14:30(106:00)Diluent 18/451.30 SetPoint, 0m ead, 4m end

Stop at3m 25:30(131:30)Diluent 18/451.30 SetPoint, 0m ead

Surface(131:50)Diluent 18/45-9m/min ascent.



OTU's this dive: 192

CNS Total: 72.6%







So as you can see the Ratio deco is more conservitive than 35/80 GF







But what if the dive is 60mins at 52m?



OK so past set point you have an additional 7m of depth.





Using Ratio deco for every + or - 3m of depth you should add 5mins so 7m devided by 3m = 3



3 X 5mins = 15 so you need to add 15mins.



So for a 60min dive to 52m you need bottom time + 15mins = 75mins deco. 1/2 at 6m so 38 @ 6m and 1/2 over 21m to 9m so 5 stops of 8mins (rounded up to 40mins) between 21m and 9m



Start deco at 2 ATMS above max so first stop depth = 32m





1 @ 32

1 @ 28

1 @ 25

8 @ 21

8 @ 18

8 @ 15

8 @ 12

8 @ 9

38 @ 6





And i dont like block stops so id do





1 @ 32

1 @ 28

1 @ 25

4 @ 21

6 @ 18

8 @ 15

10 @ 12

12 @ 9

38 @ 6







So what does V Planner say?



MultiDeco 4.01 by Ross Hemingway,

ZHL code by Erik C. Baker.



Decompression model: ZHL16-C + GF



DIVE PLAN

Surface interval = 5 day 0 hr 0 min.

Elevation = 0m

Conservatism = GF 35/80



Dec to52m(2:53)Diluent 18/450.70 SetPoint, 18m/min descent.

Level52m 57:07(60:00)Diluent 18/451.30 SetPoint, 18m ead, 25m end

Asc to30m(62:27)Diluent 18/451.30 SetPoint, -9m/min ascent.

Stop at30m 0:03(62:30)Diluent 18/451.30 SetPoint, 5m ead, 15m end

Stop at27m 2:00(64:30)Diluent 18/451.30 SetPoint, 4m ead, 14m end

Stop at24m 3:30(68:00)Diluent 18/451.30 SetPoint, 2m ead, 12m end

Stop at21m 4:30(72:30)Diluent 18/451.30 SetPoint, 0m ead, 11m end

Stop at18m 6:00(78:30)Diluent 18/451.30 SetPoint, 0m ead, 10m end

Stop at15m 7:00(85:30)Diluent 18/451.30 SetPoint, 0m ead, 8m end

Stop at12m 10:00(95:30)Diluent 18/451.30 SetPoint, 0m ead, 7m end

Stop at9m 13:30(109:00)Diluent 18/451.30 SetPoint, 0m ead, 6m end

Stop at6m 19:30(128:30)Diluent 18/451.30 SetPoint, 0m ead, 4m end

Stop at3m 33:00(161:30)Diluent 18/451.30 SetPoint, 0m ead

Surface(161:50)Diluent 18/45-9m/min ascent.



OTU's this dive: 236

CNS Total: 89.2%









So how do i adjust it to make it more / less agressive?





Well i could lower my average depth by rounding it down instead of up



I could shorten my bottom time by ignoring the decent time



I could just decide to knock off some of the bottom time before doing the calculation.





And How do you know which way to go on the agressive scale?



You spend a lot of time comparing RD profiles to you personal prefered deco for that depth and you make adjustments accorningly.





Every dive i calculate the ratio deo. Then I compare my RD plan to the plan my Shearwater Preditor gives me.



Then i decend on a depth range and make a note on how i will adjust the deco,.





So for me in the 40 -55m range i know Ratio deco is soft so I can be a get more agressive on my calculations. So on a dive which is 50 to the sea bed and 42 to the top of the wreck ill probably calculate on 45m and knock off 3mins for the decent.



From 55m to 75m I find RD a little on the agressive side so i tend to be less agressive more padding on my calculations. So on a dive thats 68 to the sea bed and 58 to the top of the wreck. Ill calculate the whole dive at 68m and put decent in run time.





If this all souns too complicated? i cant realy aggree. Deco takes for ever and i have a shead load of time to calculate and re calculate my deco so i dont find it a problem and it passes the time.





ATB





Mark

You state that v planner is more aggresive in these examples however your last 6m stops are shorter by about 1/4 than the numbers you have given in v planner...

Meaning your rd is more aggresive in my eyes...

Sent from my BlackBerry 9900 using Tapatalk

 

[hoffi]

Mark,
what's your intitial source?
Is that based on the 5thD docs that were floating arround after AG had left GUE.

RD how it is taught has become more conservative over the years.

For instance, I'd suggest to try shorter bottomtimes for a start to build confidence, say not more than 30min, not deeper than 45-50m.

hoffi

 

[Mark Chase]

Mark,
what's your intitial source?
Is that based on the 5thD docs that were floating arround after AG had left GUE.

RD how it is taught has become more conservative over the years.

For instance, I'd suggest to try shorter bottomtimes for a start to build confidence, say not more than 30min, not deeper than 45-50m.

hoffi

My initial source was a GUE training paper headed Ratio Methodology which was used for Tec 1 level training in about 2004/5

I Lernt Tec 2 level ratios and adjustment from a GUE diver and later (again arround 2005) i finaly got hold of the 5th D X stuff but there wasent much new in there.

I now have a copy of the GUE Tec1 training manual from 2010 with the revised ascent rates and a copy of J Riba's paper of 2009 which you can upload here:

Publications of Jaume Riba Sagarra

My adopting the 2 ATM stop came from here

Decompression myths and mistakes


But thease are just building blocks for what i do now. What i do now used these and then i adapted them to suit my diveing. Which remember is on a 1.3 set point not on OC set gas lists and I typicly would do 60mins on the bottom on a 45-55m dive so thats where i aim my profiles.

I am running GF 30/90 on my Shearwater and my RD method is within + /- 5-10mins of the Shearwater on 30/90 and thats is plenty good enough for me should my computer pack up. I have blown 10mins of stops on a 180 min dive because i needed a piss let alone for a computer issue


ATB

Mark

 

[Mark Chase]

You state that v planner is more aggresive in these examples however your last 6m stops are shorter by about 1/4 than the numbers you have given in v planner...

Meaning your rd is more aggresive in my eyes...

Sent from my BlackBerry 9900 using Tapatalk

Sorry i didnt notice the last stop depth was set at 3m and i read off the 3m stop instead of the 6m stop

And thers a reasion i dont teech profesionaly and thats because unless you teach you miss out on stuff you just do and dont think abbout.

In this instance it was the fact I didn't explain the 3m/min ascent between stops so each 3m stop adds 1min to the deco ascent profile, nor did i mention that id do a 1m min ascent from 6m which adds 5mins TTS.


Ignore the split on stops and just look at the overall ascent time which in the less agressive profile (example 1) is 74mins total ascent time to surface and in the 30/80profile is 71mins


As an aside I personaly run 30/90 for deco but I wanted to show how conservitive RD can be without manipiulation.


The second RD example is a total TTS of 98mins and 30/80GF has a total TTS of 101.5mins so in total 3mins more than my personal RD settings and 30/90 would be closer still.


Remeber this is MY voodoo.

If you want to run RD for you and 30/90 is too aggressive than simply alter your personal buffering.

• Make the average dive depth deeper
  
• Include decent in run time
  
• Choose a lower set point.

Nothing stopping you riunning 40m & 60m as your set points


This is the whole point. I can easily make RD super safe or super agressive with a few simple tweeks on my personal peramiters. Just like all deco systems there is no single line in the sand for the deco.


If you read the GUE Tec1 training manual it specificly tells the divers in traiing to do RD comparisons with GFs and or VPMB and to modifie their profiles to a comfort zone.


HTH

ATB

Mark

 

[DeepUnderground]

Sorry i didnt notice the last stop depth was set at 3m and i read off the 3m stop instead of the 6m stop

And thers a reasion i dont teech profesionaly and thats because unless you teach you miss out on stuff you just do and dont think abbout.

In this instance it was the fact I didn't explain the 3m/min ascent between stops so each 3m stop adds 1min to the deco ascent profile, nor did i mention that id do a 1m min ascent from 6m which adds 5mins TTS.


Ignore the split on stops and just look at the overall ascent time which in the less agressive profile (example 1) is 74mins total ascent time to surface and in the 30/80profile is 71mins


As an aside I personaly run 30/90 for deco but I wanted to show how conservitive RD can be without manipiulation.


The second RD example is a total TTS of 98mins and 30/80GF has a total TTS of 101.5mins so in total 3mins more than my personal RD settings and 30/90 would be closer still.


Remeber this is MY voodoo.

If you want to run RD for you and 30/90 is too aggressive than simply alter your personal buffering.

• Make the average dive depth deeper
  
• Include decent in run time
  
• Choose a lower set point.

Nothing stopping you riunning 40m & 60m as your set points


This is the whole point. I can easily make RD super safe or super agressive with a few simple tweeks on my personal peramiters. Just like all deco systems there is no single line in the sand for the deco.


If you read the GUE Tec1 training manual it specificly tells the divers in traiing to do RD comparisons with GFs and or VPMB and to modifie their profiles to a comfort zone.


HTH

ATB

Mark

say you have 3 gue divers diving together

all have their prefered ratio settings

one likes to do deeper stops and reduce shallow time

one likes to get shallow quickly

and one does a bit of both


how do they happily dive & deco together to please all three ?

without spending all the extra time on deep stops and shallow stops ?

 

[Richard Lundgren]

Hi

The three musketeers would agree upon a deco strategy before going on the dance floor. If someone want to keep dancing, the cavaliers happily stay for another dance