Rock bottom gas calculation in planner

[Willem Ferguson]

On 08/01/2017 12:27, Robert Helling wrote:
> Hi,
>
>> On 07 Jan 2017, at 22:43, Rick Walsh <rickmwalsh at gmail.com> wrote:
>>
>> I'm interested in hearing Robert's feedback on your suggestion, but 
>> would be happy to implement it when I get a chance (and that's been 
>> far too rarely lately) after 4.6 is out.
>
> my concerns are pretty much the same: The planner already has almost 
> too many parameters to configure. Not concentrating on the essentials 
> has a real price in usability.
>
> So adding two more parameters (problem solving time and emergency SAC 
> or whatever you might call those) needs to be justified by the 
> benefit. I am not going to add those for everybody just to please a 
> single user. But if one can make the case that it benefits most users 
> (in the sense of they care about the resulting information) then we 
> should have those. I have done some googling on „Rock bottom gas“ and 
> almost everybody has their own idea how to exactly calculate that. But 
> indeed, the two parameter model fits many. So it might be something 
> for 4.7. But I would love to have some more user input.
>
> Best
> Robert
The rock-bottom approach is sensible in a recreational environment 
because it provides an explicit framework to think seriously about gas 
planning which few recreational divers do. I am not sure which training 
agency(s) uses this concept. In a technical/cave environment, most 
training agencies have their own ways of teaching explicit gas planning, 
with most using rule of thirds or rule of quarters. As indicated in the 
previous discussion, the situation becomes very complex when using deco 
gases and one wishes to use the rock-bottom concept (as well as 
additional planning for regulator failure of a deco cylinder) and the 
example calculation for a 60m dive in previous correspondence shows that 
this approach soon becomes unproductive within the technical diving 
context. I have been involved as a donor in two recreational OOG events 
and, fortunately, the gas consumption did not skyrocket. So rock-bottom 
pressure level is interesting to me, but I myself use the proven rules 
of the training agency where I got certified.
Kind regards,
willem

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