Dive planner MG, TP and FC

Robert Helling helling at atdotde.de
Wed Oct 14 06:25:51 PDT 2015


Ivan,

> On 14.10.2015, at 15:13, Ivan Wagner <ivan.wagner at tecinvent.ch> wrote:
> 
> Minimum gas is for me the minimum gas pressure in your cylinders that
> you need in the event of an emergency such as an OOG diver making a safe
> ascent respecting ascent rates, deep-stops until the gas switch (for
> tech dives) or surface is reached (rec dives). Therefore we also need to
> take into consideration ascent rates, two divers breathing from the same
> unit (twins or whatever).
> 
> Turn pressure depends on the type of diving we are doing
> - All usable: direct ascent to the surface is not a problem at all (i.e.
> drift dives). With this you can reach minimum gas off from the entry point
> - Half usable: it's highly recommended to get back to the ascent line
> (wreck diving on a 100m long wreck). With this you should reach min gas
> back on the ascent line
> - Rule of thirds: overhead environment (wreck penetration).


thanks for more explanations but I am not sure I really understand what you want to do.

As I explained, in my understanding, we are already “minimum gas aware”, i.e. the planner let’s you know if your plan would violate minimum gas.

What exactly do you want to compute for “Half usable”? Do you want to compute the maximal time T you can stay at depth such that if you stay twice as long and then ascent (including all stops and gas changes etc) you are still within minimum gas requirements? If that understanding is correct, that would be almost trivial: Compute the maximal time for minimum gas (which would be like recreational mode but with stops and gas changes, only gas is the limiting factor) and then divide the bottom time by two.

And I guess rule of thirds would be: You double the bottom time for the computation of deco stops but triple it for gas consumption (where the scenario would be: You have to swim back your way through the wreck/cave with an OOG buddy, so you both breath your gas on the way back and during the ascent).

Is that what you mean?

Best
Robert

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Robert C. Helling     Elite Master Course Theoretical and Mathematical Physics
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                      Ludwig Maximilians Universitaet Muenchen, Dept. Physik
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