An Experiment

[Kern]

Academic exercises aside, the best way to test the process would be to plan such a multi-level dive, then actually dive it using a computer. Then the theoretical could be compared to the actual. This might sound like a waste of time but, you never know, it might come in handy for someone sometime.

It's too cold here to do it now, but maybe next summer I might try it. I think it's worth exploring.

I use an X1 with V-planer live. Assuming I was Mr. Perfect & hit my ascent/decent rates, maintained exact levels & times as planed on my desktop V-planer on these dives, I'd get exactly the same outcome. I'v done these sorts of dives many times ( except for the Mr. perfect part) on the X1, I never go into deco on a rec. dive. Oh, of course that's excepting that time with the anchor, or was that twice, or......

 

[Paladin]

Atom,
I checked that thread and it seems to me that the naysayers were merely repeating what they had been told without having any actual experience with using tables for ML dives. What we've been doing here shows, at least theoretically, that it is at least possible. Those old ex-Navy divers I used to dive with knew it and practiced it. Evidently, this is something that has become a lost art because someone, at sometime, decide that it should no longer be taught. They may have been afraid that rec divers might cut it too close and get into trouble. Personally, I think it could be a skill that might be useful under certain circumstances, if it is used correctly.

The profile I posted was just something I threw out off the top of my head with no consideration for SAC rate or air supply. Perhaps you could check in your logs for a past dive where all the numbers are known and we could use that dive for further experimentation. That is, if you think it worthwhile to continue this exercise.

 

[Blackwood]

Personally, I think it could be a skill that might be useful under certain circumstances, if it is used correctly.

You'd probably be interested in the way we (me and my group) dive. While we pre-plan, we also adjust our deco on-the-fly based on our actual profile. We compute a (conservative) average depth and use it along with either a NDL (we call it MDL) table or a direct ratio of bottom time to deco time (ratio being for deeper dives).

You can learn about it here: Ratio Deco - Unified Team Diving

 

[AfterDark]

You'd probably be interested in the way we (me and my group) dive. While we pre-plan, we also adjust our deco on-the-fly based on our actual profile. We compute a (conservative) average depth and use it along with either a NDL (we call it MDL) table or a direct ratio of bottom time to deco time (ratio being for deeper dives).

You can learn about it here: Ratio Deco - Unified Team Diving

That does sound interesting. All this discussion was getting me thinking that that's the type of thing that a PDC is really good for on the fly. I was telling some else that the introduction of the SPG (I predate SPG's) enable me to change my dive on the fly by knowing how much gas I had left. I'm not a PDC denier I just like redundancy and a low budget. If I get a PDC it'll probably be a top of the line model and be BIG $$$ I'm not buying two:shocked2: So for me the tables are the backup. As Palidan454 has shown all the table deniers they can be used for mulit-level dive. so there:mooner:

 

[The Chairman]

MV-Plan 1.5.1
Settings: GF=30-80
ft Time Run Gas SP
==============================
v 100 01:30 002 21 0.0
- 100 08:29 010 21 0.0
^ 070 00:54 011 21 0.0
- 070 10:00 021 21 0.0
^ 040 00:54 022 21 0.0
- 040 25:00 047 21 0.0
^ 020 00:36 047 21 0.0
~ 020 00:34 048 100 0.0

Gas estimate based on Dive RMV =0.7, deco RMV =0.5cuft/min
Air : 91.9cuft
Oxygen : 0.5cuft
Oxygen Toxicity - OTUs: 11 CNS: 5%

WARNING: This software is experimental
and should not be relied upon for actual dives.
It probably contains errors and may get you bent.

 

[SailNaked]

I have always assumed you could use the tables that way. I did a few comparisons with the wheel and the new Erdpml and it seems to follow exactly that method (0 surface time multi dive).
The tables are designed to limit the total surface N2 load that is the total amount of N2 your body contains at the surface with an acceptable rate of off gassing. now that I think about it, since they were not really assuming you would be multilevel diving it may be possible for you to mess it up by having more slow compartments and fast compartments maxed out at the same time, I think that would occur at some point if you managed a deep dive then worked it all the way to a W or more (lots of gas). however if you throw in a 3-5 min S-stop I would think there was absolutely no way you could have a problem with a single 80 multi level diving in this way.

My father was diving in the early 60s and he stopped using the tables and assumed he could not get into trouble with one tank, I dived this way for a few years until I got a computer and discovered he was wrong, it was possible to enter deco with one tank.

 

[AfterDark]

SailNaked, Your father was probably using a 72 and may have had a little higher CSA then you. It is very hard to get into decon with a 72, it can be done but you'd have to work at it. I dove that way too for years above 100'.

 

[boulderjohn]

I use an X1 with V-planer live.

In the past, I have only used V-Planner for decompression dives. Not long ago I fed a number of square profiles that would be within NDLs on any dive table into the program. In each one, V-Planner required surprisingly substantial deco stops.

I find that puzzling.

I do not believe a computer like the X-1 that uses V-Planner is representative of the PDCs that are used by 95% of the divers who use computers (Suunto, Uwatec, Aeris, Oceanic, Sherwood, etc.)

 

[NCadiver]

Padi has the wheel and the eRDPML Multilevel Electronic Recreational Dive Planner for what you are trying to do but remember today table are more conservative then the 60 and 70's

 

[ucfdiver]

In the past, I have only used V-Planner for decompression dives. Not long ago I fed a number of square profiles that would be within NDLs on any dive table into the program. In each one, V-Planner required surprisingly substantial deco stops.

I find that puzzling.

I do not believe a computer like the X-1 that uses V-Planner is representative of the PDCs that are used by 95% of the divers who use computers (Suunto, Uwatec, Aeris, Oceanic, Sherwood, etc.)

vpm vs Buhlmann aka mend and bend algorithms....why do you think everyone is so tired when they dive air to the edge of NDL, and feel so much less tired when they switch to nitrox for the same dives

Answer: They're as bent as you can get without going beyond sub-clinical symptoms.