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A short fat well off crap cave diver. Likes wrecks
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Discussion Starter · #1 · (Edited)
This profile raised questions comments about how long it was etc etc. I found this odd as I did the ratio in my head for the dive and the ascent time was about the same as the computer was asking for.

So I thought id put up this comparison between what my computer spat out and what DOTF works out (by my understanding).



The actual profile asked for by the computer was as follows:

2 @ 27
2 @ 24
2 @ 21
2 @ 18
4 @ 15
6 @ 12
9 @ 9
[email protected] 6

Including ascent times total deco running 10/85GF was 62mins


I ran it through Deco on the fly and came up with: 47mins @ 47m

1 @ 36
1 @ 33
1 @ 30
1 @ 27
1 @ 24
5 @ 21
[email protected] 18
3 @ 15
3 @ 12
10 @ 9
26 @ 6

I make this a total 62min ascent


If you ignore the decent time then it was a 42min bottom time avg depth 47m

1:1 ratio based on 45m so add 5mins = 47mins deco

so

1 @ 36
1 @ 33
1 @ 30
1 @ 27
1 @ 24
5 @ 21
4 @ 18
3 @ 15
3 @ 12
9 @ 9
24 @ 6

Total 59mins deco ascent.

As it was we did an extra 10mins deco to clear the VR3. Now i beleive the reasion for this was Howards VR3 would have been running something like 1.25 fixed set point and would asume Helium in the mix all the way to the surface. My computer was plumbed into the unit so it took my actual PP02 inot account including the Helium free time spent on 100% at 6m

If we look at Vplanner for a 1.25 setpoint profile with He in the mix it comes out at this:


Decompression model: VPM - B

DIVE PLAN
Surface interval = 5 day 0 hr 0 min.
Elevation = 0m
Conservatism = + 2

Dec to 47m (3:08) Diluent 21/50 1.25 SetPoint, 15m/min descent.
Level 47m 43:52 (47:00) Diluent 21/50 1.25 SetPoint, 11m ead, 19m end
Asc to 27m (51:00) Diluent 21/50 1.25 SetPoint, -5m/min ascent.
Stop at 24m 1:00 (52:00) Diluent 21/50 1.25 SetPoint, 0m ead, 10m end
Stop at 21m 1:00 (53:00) Diluent 21/50 1.25 SetPoint, 0m ead, 9m end
Stop at 18m 3:00 (56:00) Diluent 21/50 1.25 SetPoint, 0m ead, 8m end
Stop at 15m 4:30 (60:30) Diluent 21/50 1.25 SetPoint, 0m ead, 7m end
Stop at 12m 5:00 (65:30) Diluent 21/50 1.25 SetPoint, 0m ead, 6m end
Stop at 9m 7:30 (73:00) Diluent 21/50 1.25 SetPoint, 0m ead, 5m end
Stop at 6m 30:30 (103:30) Diluent 21/50 1.25 SetPoint, 0m ead, 4m end
Surface (105:30) Diluent 21/50 -3m/min ascent.



If we asume 100% 02 at the 6m stop it looks like this:

Decompression model: VPM - B

DIVE PLAN
Surface interval = 5 day 0 hr 0 min.
Elevation = 0m
Conservatism = + 2

Dec to 47m (3:08) Diluent 21/50 1.25 SetPoint, 15m/min descent.
Level 47m 43:52 (47:00) Diluent 21/50 1.25 SetPoint, 11m ead, 19m end
Asc to 27m (51:00) Diluent 21/50 1.25 SetPoint, -5m/min ascent.
Stop at 24m 1:00 (52:00) Diluent 21/50 1.25 SetPoint, 0m ead, 10m end
Stop at 21m 1:00 (53:00) Diluent 21/50 1.25 SetPoint, 0m ead, 9m end
Stop at 18m 3:00 (56:00) Diluent 21/50 1.25 SetPoint, 0m ead, 8m end
Stop at 15m 4:00 (60:00) Diluent 21/50 1.25 SetPoint, 0m ead, 7m end
Stop at 12m 5:30 (65:30) Diluent 21/50 1.25 SetPoint, 0m ead, 6m end
Stop at 9m 7:00 (72:30) Diluent 21/50 1.25 SetPoint, 0m ead, 5m end
Stop at 6m 9:30 (82:00) Oxygen 1.60 ppO2, 0m ead
Stop at 3m 15:00 (97:00) Oxygen 1.30 ppO2, 0m ead
Surface (98:00) Oxygen -3m/min ascent.


Whilst the Vplanner profiles are nothing like the VR3 profiles this demontrates how much diference it makes leaving He in the mix. It adds 7mins to the dive. Howards VR3 added 8.

I am interested to see what others make of the actual profile? WOuld you do something diferent with the DOTF? i know that at set point and just above the DPTF 1:1 ratio is very conservitave but do you taylor the deco with this in mind or do yo do the same adjustments on all DOTF profiles?

ATB

Mark Chase
 

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Mark - the standard response has to be "don't learn deco on the internet" - but then you know that ;)

Deco on the Fly is not a way of working out deco - it is merely compleing your stops whilst you travel rather than halting the team. Ratio deco is about looking for patterns in decompression profiles which is what you are referring to.

There are some errors in your suggested 'out of the box' Ratio Deco profile - we would certainly not, as standard, do the stops that you have set out as there is simply not enough time at 21 and far too much at 9.

The other problem is that you are using set point 1 ratio deco (worked out for one deco gas) yet your rebreather allows you the equivalent of two (or multiple ) gases. As such, the straight 1:1 profile is not really relevant.

The longer bottom time also skews the relationship slightly. Once we move beyond 40 minutes bottom time the stops have to start shifting.

There is no magic in Ratio Deco - it is just another way of working out profiles. The two or three set points which are often quoted on the internet are just two or three of the ratios that we can look at. As dives get longer we can shift these to take into account different loadings.

I'm definately not going to get in to a 'I'd do less that you' contest. Do what you believe is right for you and for the people you are diving with. The last thing I would ever want is for someone to feel that they have been peer pressured into doing too little deco.

Not what you are looking for I guess, but others will no doubt post that.
 

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I am interested to see what others make of the actual profile? WOuld you do something diferent with the DOTF? i know that at set point and just above the DPTF 1:1 ratio is very conservitave but do you taylor the deco with this in mind or do yo do the same adjustments on all DOTF profiles?
Mark - this looks like a typical Moldavia profile to me? One that you must have done dozens of times before? Therefore, if it were me, I would just do the same deco as I did last time, and the time before that....etc. assuming that you felt ok after these dives and that your deco wasn't overly protracted (i.e. you hit the surface and find everybody else has been on the boat drinking tea for the past 30mins..!)

I certainly wouldn't get involved in the sort of number crunching you have here. It's not exactly breaking new ground is it?

If it's *about* 47m for *about* 40 mins, I'd probably be on the surface in less than *about* 90mins.

However, it's not a race - just do what you are comfortable with.

Bob
 

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I'm definately not going to get in to a 'I'd do less that you' contest. Do what you believe is right for you and for the people you are diving with. The last thing I would ever want is for someone to feel that they have been peer pressured into doing too little deco.
.
But isn't the root of this thread from comments made on the trip report thread....ones along the lines of "I'm glad I wasn't with you for that deco"? As far as I can see Mark has just moved that discussion - opened by you amongst others - to a different thread. I certainly read the direction of the posts directed at Mark over that profile to read as "why on earth did you do so much?". I am sure it wasn't meant so bluntly, but as easy as it is to say "don't learn deco off the 'net" now, folk really should avoid this habit of criticism over excessive length, however light, of profiles that are posted. It does seem to be getting more and more prevalent on YD of late. i don't know why.

Equally Mark should be big enough and bad enough to take it on the chin, trust his own profiles and ignore such comments :D
 

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Actually Lou - I read Marks' tale about keeping down bile :eek: and the problems that they faced on the surface getting back on the boat...on this occasion. But your point is fairly made.
 

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A short fat well off crap cave diver. Likes wrecks
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Discussion Starter · #9 ·
Bob Clare et all,

The point I am genuinly interested from a point of view of OC bailout. Bailout is by nature sometimes pushing deco harder than i would normaly like to do.

The above ratio profiles are what I would do. The 50% of deco at 6 then spit the remainder between the 21-9m stops. Rather than the new KISS idea of 5,5,5,5,5 I still prefer to extend the shalow section by nicking time off the 18-12m stops. Hesce my mucking arround with the times.

I am interested to see how you would manipulate these numbers to make it more agresive in an emergancy. I was wondering is there a formula or is it just a case of shaving.

No ruck desired. I wouldent use it unless i had to I am too unfit.

ATB

Mark Chase
 

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Darren of the Deep
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Bob Clare et all,

The point I am genuinly interested from a point of view of OC bailout. Bailout is by nature sometimes pushing deco harder than i would normaly like to do.

The above ratio profiles are what I would do. The 50% of deco at 6 then spit the remainder between the 21-9m stops. Rather than the new KISS idea of 5,5,5,5,5 I still prefer to extend the shalow section by nicking time off the 18-12m stops. Hesce my mucking arround with the times.

I am interested to see how you would manipulate these numbers to make it more agresive in an emergancy. I was wondering is there a formula or is it just a case of shaving.

No ruck desired. I wouldent use it unless i had to I am too unfit.

ATB

Mark Chase
Mark
 

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If bailout is pushing deco harder than you would normally like to do, then why not carry more bailout? I had a discussion with a mate on Friday that largely revolved around don't make a dive plan fit the gear you have, make the gear you have fit the dive plan. This was for a dive with a set bottom time and set depth. That for me would include bailout (or obviously in this case cutting bottom time or depth). I'm not very comfortable with the idea of bailing out and knowing I was about to run an agressive profile when I did it.

The numbers don't look all that bad to me. I'd probably tweak here and there, but it's not more than a few minutes from one stop and onto another. But then you and I don't have to worry about adding in a few extra minutes anywhere really, the units save that hassle.

I run the plan using setpoint then run O2 RB as a safety factor. Makes a lot of sense. In this case I'd be in the water an extra 8 minutes, which is fine by me. Or I could go for the Juz standard do whatever plan you were going to do, then add 10 minutes at 6. Works for him, works for me. Unless I really need a wee. :)

Digs.
 

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vr

with the vr3 if you set it on to a mix, then alter the set point to 1.5 at 5m does it still plan on a % of helium in the mix? or have i missed the plot as usual? i tend to run at 1.25 for the bottom and ascent, then flush as much as poss when up at 6m
 

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For 47mins at 47m I'd be looking at a total run time of 110 minutes. The Shearwater would probably give me a few minutes more than this as I'm happy to let the ppO2 drop as I ascend which obviously extends the deco.

Worst case bailout (on 18/45 and 50%) would be 100 minutes but I'd be asking to be put on O2 as soon as I hit the surface.

Janos
 

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A short fat well off crap cave diver. Likes wrecks
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Discussion Starter · #14 ·
Actually Lou - I read Marks' tale about keeping down bile :eek: and the problems that they faced on the surface getting back on the boat...on this occasion. But your point is fairly made.

Hey you have two sausage & egg Mc muffins on the trip out and you have to pay the price :D. Indigestion is something I live with on a lot of dives so it wasent a biggy just going head down is a no no.

I would of folowed the Shearwater out 10mins earlier. I am perfictly happy running 10/85. However for the reasions i have explained already we had to wait for the VR3 to clear. When i ran two VR3s one plumbed in and one on a fixed set point, it was a problem i had all the time.

ATB

Mark Chase
 

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A short fat well off crap cave diver. Likes wrecks
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Discussion Starter · #15 ·
with the vr3 if you set it on to a mix, then alter the set point to 1.5 at 5m does it still plan on a % of helium in the mix? or have i missed the plot as usual? i tend to run at 1.25 for the bottom and ascent, then flush as much as poss when up at 6m

No it should work, but I dont know many people who bother to change the set point on the VR3.

I generaly found the VR3 to be arround a 20/80GF profile + a couple of pyle stops. The main diference therefor between howards profile and my profile was that at 6m I was on 1.6 02 and he was on 1.25 trimix 77/7/16.

ATB

Mark Chase
 

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DUE CEO, Booking agent, Coffee maker & Dogsbody...
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Just be glad you were not sticking with me on my Vytec ;) :)
 
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I'd be looking at at about 55 mins of deco with this profile. However, the curve I would run would be nothing like you planned Mark. I would do my first deep stop at 33 metres, not 36. I would also maybe do 30 second stops through the deeper stops rather than one minute and maybe do a 1 minute stop at 24 just to get the ascent slowed down before the gas switch. This would be at about 65% of the ATAS anyway so I'd be happy. I'd do linear stops through the intermediate part of the ascent, and would certainly not do all that time at 9. I wouldn't make the last 5 mins part of the deco, but would complete the final stop at 6m and then do a 5 minute ascent. Off the top of my head I'd probably end up with about 55 mins.
 

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Bob Clare et all,

The point I am genuinly interested from a point of view of OC bailout. Bailout is by nature sometimes pushing deco harder than i would normaly like to do.

The above ratio profiles are what I would do. The 50% of deco at 6 then spit the remainder between the 21-9m stops. Rather than the new KISS idea of 5,5,5,5,5 I still prefer to extend the shalow section by nicking time off the 18-12m stops. Hesce my mucking arround with the times.

I am interested to see how you would manipulate these numbers to make it more agresive in an emergancy. I was wondering is there a formula or is it just a case of shaving.

No ruck desired. I wouldent use it unless i had to I am too unfit.

ATB

Mark Chase
Hi

From looking at it, the runtime I worked out was 96 mins with RD and then checked on HLplanner and got 97 mins :), but I see it as 40 mins at 47, not 47 mins, as it took at least 5 mins for you to get to that depth, and I don't usually count that time. There are 2 spare minutes, so I guess another couple of mins at 6 polishes it all off at 100 mins.

The issue of having to cut short the deco is to cut the shallow stops rather than the deep stops, so I would stick to the deco as long as I possibly could, and then cut short the 6 mtr stop for example. To be perfectly honest, it really depends on the emergency and whether this emergency means I need to get out of the water, or whether I am able to go back down and continue the deco after sorting out whatever needed sorting out.

As an aside, doing 45 mins (40 mins BT at 48mtrs so 45 mins deco) on the 50% bottle is really maxing out the available gas, and this is where I would start thinking about taking along an AL40 of o2, which would take off another 10 mins and bring my time down to 90 mins.

So in answer to your question about being aggressive, you could forget the descent time and then do the deep stops, cutting short the 6 mtr stop if you have to. In terms of your runtime, I wouldn't be so bothered about doing more deco, although staring at Bob for an extra 20 mins might require a stiff drink when I get back on the boat.

Andy
 

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A short fat well off crap cave diver. Likes wrecks
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Discussion Starter · #19 ·
I'd be looking at at about 55 mins of deco with this profile. However, the curve I would run would be nothing like you planned Mark. I would do my first deep stop at 33 metres, not 36. I would also maybe do 30 second stops through the deeper stops rather than one minute and maybe do a 1 minute stop at 24 just to get the ascent slowed down before the gas switch. This would be at about 65% of the ATAS anyway so I'd be happy. I'd do linear stops through the intermediate part of the ascent, and would certainly not do all that time at 9. I wouldn't make the last 5 mins part of the deco, but would complete the final stop at 6m and then do a 5 minute ascent. Off the top of my head I'd probably end up with about 55 mins.


OK I can see what your doing but:

75% of 47m is 35.25 I rounded up to 36 by adding 0,75m you rounded down to 33 by taking away 2.25m

The 1min stops from 33 to 21 are not stops as you know they are 3m/min ascent rate with a pause. The run time remains the same I didnt add any run time for the ascent between these stops as they are not real stops.

Linnea stops = what i said

5 @ 21
5 @ 18
5 @ 15
5 @ 12
5 @ 9

I beleive this idea was brought in to avoid having to memorize the six standard intermediate profiles. I also beleive the use of linnea stops in no way improves the performance of the deco schedual, It makes it worse, doesent it?


These were the old stile intermediate stops for 5 -30mins

1,1,1,1,1
3,3,1,1,2
5,5,1,1,3
5,5,3,3,4
7,7,3,3,5
7,7,5,5,6

So apart from doing away with a 1min 36m stop your total run time should be the same as my profile. Spending the 5 ascending to the surface doesn't alter the in water time and I think most of us are doing this if the conditions allow. Howard and I ascended and cleared at 3 then went straight up because it was a big swell on the day and anything else just wasn't practical.

However with the intermediate stops I prefer the old school deco where they paused at 21 to Open the "02 window" (sorry Howard) then skipped through the 15 and 12m stops quickly to then push the off gassing gradient right up on the 9m stop.

The official GUE profile for 25mins of stops is/was

7 @ 21
7 @ 18 These two stops on a high PP02
3 @ 15
3 @ 12
5 @ 9 Extended 9m stop to max the off gassing gradient


Again I have looked at deco from several angles and one thing remains constant. Getting shallow fast speeds up deco. There is a irony to this concept that is missed by some divers, in that by running over 100GF they are getting shallow faster by getting out of the water and off gassing back on the boat at ambient rather than in the water at 0.6atm. And they are decoing on air :D

So if i wanted to make my deco faster, would i not redistribute the stop time to the 9m stop to maximize this off gassing effect?

It seems logical but not in line with thinking on ratio deco


So it seems as an outsider looking in that the main areas for reducing the deco on a standard ratio deco profile are:

  • Ignore the decent time
  • err on the shallow side of average depth
  • Round up the deep stop to the stop above never the stop below.

I am assuming then that after this its just up to the individual diver to shave off deco where they think its appropriate and use this experimentation to form schedules for the future?

This is a perfectly valid approach in my mind but the question is, does the alteration of the profile remain a constant? IE i always reduce the 6m stop by 10% 10mins what ever or does it vary across the depth run time range on an ad hock basis?

Personally i tend to run 10/85 GFs or 20/80 GFs for everything. Doesn't matter the run time or the depth. I am starting to consider changing that concept.

ATB

Mark Chase
 

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Mark, don't get too tied up in "official GUE line", becuase the only "official" line I have hjeard is "do the right deco for you". The standrad gases are only recommendations and may get changed for a specific project. The "standard" deco is only a starting position, not the official line on whjat you mudt do, hence my comments are for what I would do, noty anyone else.

With regards to 33 or 36 metres, why are you rounding deeper. We round shallower becuase there's little point rounding down so you are still ongassing. We round up to the nearest number divisble by 3 with the intention of being shallower than 80% of the ATAS.

You are talking about 1 minute stops (3 metres per minute). This is not what I said. I would do 30 second stops up to 65% of the ATAS - 6 metres per miniute ascent rate. Then slow it down to 3 metres per minute at 24 metres.

As For linear, non linear, in the intermediate stops, I haven't really noticed any difference, I think you could get away with murder in the tech1 ratio deco level. If anything I would padd the 21 sop a couple of minutes, but I wouldn't extend the 9 necessarily.
 
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