[PATCH 2/2] Ticket #831 Fix

[Joakim Bygdell]

> On 10 Mar 2015, at 0:54, Davide DB <dbdavide at gmail.com> wrote:
> 
> No problem at all, I can live with them.
> 
> In the last few weeks I read so many times that usually people get
> everything right (mixes, tanks, gas changes) from their dive computers
> that I'm becoming feeling a bit outlier. Hence I'm trying to
> understand if, regardless of each his own convictions, there is still
> room for DIR/GUE/UTD Subsurface users :)
> 
> Regarding the gas change 0 at 0 it's a common scenario in advanced dives
> or dive locations having to switch to a particular mix on the surface:
> 
> * I dive with a pscr rebreather and a hypoxic back gas so I have to
> reach a safe depth prior to change to back gas.
> * I dive oc/pscr with a hypoxic mix and my dive location (cave or even
> reef) doesn't permit to reach immediately a safe depth.
> * I dive in a cave where gas mixes are chosen on the cave profile:
> first part on mix1 then mix2 and again mix2...
> 
>> The question to ask the bug submitter is "why do you want to add a gas
>> change at 0'/0:00? -- is this to correct the first gas used?"
>> Why? Enter your first gas as first tank. Voila.
> 
> What is the main gas and the main tank in the above examples?
> By default we tend to consider our main gas the back gas and I set it
> as default tank into Subsurface preference dialog then I describe my
> dive through the gas change events.

The default cylinder setup is more suited to people that do not dive the way you do, since the way you describe it you rarely start a dive on backgas.
It’s just a way to make it convenient for people that doesn’t have as complex setup. 

> In my above example:
> 
> I made a formal gas change at the surface switching to a 35/25
> At 30m I switched to my bottom mix: 16/60 on a AL80 [**]
> Deco was performed on 35/25, 50/20 and 100%
> My backgas was a D8,5L on 16/60 (that is set as default tank in
> Subsurface). It's my bailout reserve, my main tank.
> 
> [**] I could have more f this.
> 
> Should I remove the default cylinder to be able to switch at 0 at 0?
> If I had a proper DC managing all of this and I forget to press a
> button, could I fix all of this later? Hummm….

When you set up the cylinders for that dive make sure that the one you start with are the first gas in the list, the order of the other mixes is not as important.

At the start of the dive subsurface will implicit start you on 35/25 as that is the first gas in the list.
You can then do gas switches at the appropriate time points during the dive.

If you do this, is it something that is wrong in the way the dive is presented to you?

> 
> PS
> My crappy XDeep BT adds its own oddity: it exports via UDDF an unknown
> cylinder with real air...
> 
> Thank you in advance
> 
> -- 
> Davide
> https://vimeo.com/bocio/videos
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/Jocke