PSA - Shearwater "Live" Deco & Bailout Plan

[lermontov]

• Dive execution (desired option)
  
  • Have 2 sets of GF (one for CC and one for BO) that are enabled automatically when switching between the 2 modes
  • Have a parameter that can be shown on screen that represents the current TTS if you would bailout and set the GF to the GF_BO

This last option is the most accurate and conveniente. Option 1 is quite convenient because TTS can be shown all the time and compared to TTS_BO. My only concern is that there may be profiles for which this estimation is not conservative (this is just a fear but have not proved it yet).

option 1 is pretty common id imagine however it doesn't allow for any further problems unless you calculate your gas consumption /TTS conservatively or have a second gas source ie staged or buddy

I cant see what your gaining by messing with GF when you may already be in stressful situation, unless your doing massive dives the differences will be minor and just increases your risk by pushing closer to the M value. the only justification I can see if you are in a situation where you are in medical emergency or your going to run out of gas in which case your going to surface anyway rather than drown

You'd need to produce some realistic dive profiles to see the parameters but if youve done hundreds of deco dives with no issues why start fiddling now

 

[J-Vo]

I agree, Changing GFs shouldn't be part of your bailout plan. I reserve this for when a second SHTF, like bailing out and losing a deco bottle.

I would like to be able to see a running bailout TTS throughout the dive. That would be extremely nice.

 

[oceance]

I would like to be able to see a running bailout TTS throughout the dive. That would be extremely nice.

+1

Please @Shearwater, @lynnpartridge , add a simple B/O-TTS display to the CC mode

 

[beldridg]

Yeah, I've been asking for BO TTS for 2-3 years now. Hopefully it will be implemented someday soon. Seems like an obvious feature to me.

- brett

 

[beldridg]

a BO countdown is already present in a way - TTS on CC mode assuming you know your SAC rate and gas quantities you can easily work out when to start an ascent -it doesnt however allow for a co2 hit which which inevitably mean carrying more gas - if im on a deep diver i carry a back up computer on GF 90 that gives me my "got to get out of here" times

Note that the CC TTS doesn't account for using open circuit gases since it assumes a constant PO2. Unless you cary a bunch of different O/C gasses, the TTS will change when you switch to BO.

My general rule of thumb is to assume 1.5x the TTS for O/C. For example, if my CC TTS is 40 minutes, I will assume I would have a 60 minute TTS on BO. It isn't really accurate of course, but I can calculate it on the fly and it is usually worse case depending upon the gases you cary for BO.

Obviously, having the actual BO TTS easily accessible would be beneficial.

The only downside I can see is that divers might start to push the limits of their BO TTS and not factor in all the other variables that go into gas consumption when you BO in earnest.

- brett

 

[LFMarm]

option 1 is pretty common id imagine however it doesn't allow for any further problems unless you calculate your gas consumption /TTS conservatively or have a second gas source ie staged or buddy

I cant see what your gaining by messing with GF when you may already be in stressful situation, unless your doing massive dives the differences will be minor and just increases your risk by pushing closer to the M value. the only justification I can see if you are in a situation where you are in medical emergency or your going to run out of gas in which case your going to surface anyway rather than drown

You'd need to produce some realistic dive profiles to see the parameters but if youve done hundreds of deco dives with no issues why start fiddling now

The difference in TTS between 50/60 and 70/85 can easily be 30 mins with dives to 180ft/60m

 

[LFMarm]

Note that the CC TTS doesn't account for using open circuit gases since it assumes a constant PO2. Unless you cary a bunch of different O/C gasses, the TTS will change when you switch to BO.

My general rule of thumb is to assume 1.5x the TTS for O/C. For example, if my CC TTS is 40 minutes, I will assume I would have a 60 minute TTS on BO. It isn't really accurate of course, but I can calculate it on the fly and it is usually worse case depending upon the gases you cary for BO.

Obviously, having the actual BO TTS easily accessible would be beneficial.

The only downside I can see is that divers might start to push the limits of their BO TTS and not factor in all the other variables that go into gas consumption when you BO in earnest.

- brett

If you calculate before the dive the TTS at the time of bailing out, you can compare it to your CC-TTS without need of additional math

 

[beldridg]

If you calculate before the dive the TTS at the time of bailing out, you can compare it to your CC-TTS without need of additional math

Yes, and I generally do that. The real driver for the feature is the situation where you are having a good dive, everything is going well and you want to stay longer.

Yes, I know you can/should also calculate the +5 minutes, +10 feet BO TTS, etc. but it would just be nice to know at an instant what your BO TTS during the actual dive.

- brett

 

[LFMarm]

Yes, and I generally do that. The real driver for the feature is the situation where you are having a good dive, everything is going well and you want to stay longer.

Yes, I know you can/should also calculate the +5 minutes, +10 feet BO TTS, etc. but it would just be nice to know at an instant what your BO TTS during the actual dive.

- brett

If the dive is going ok and you are doing multilevel, you can stay as long as your CC-TTS during the dive is at most equal to the CC-TTS at the end of the max bottom time for the square profile you calculated your bailout with. You if on average you stay shallower than the simulated square profile, it will take longer to reach that CC-TTS

 

[lermontov]

Note that the CC TTS doesn't account for using open circuit gases since it assumes a constant PO2. Unless you cary a bunch of different O/C gasses, the TTS will change when you switch to BO.

My general rule of thumb is to assume 1.5x the TTS for O/C. For example, if my CC TTS is 40 minutes, I will assume I would have a 60 minute TTS on BO. It isn't really accurate of course, but I can calculate it on the fly and it is usually worse case depending upon the gases you cary for BO.

Obviously, having the actual BO TTS easily accessible would be beneficial.

The only downside I can see is that divers might start to push the limits of their BO TTS and not factor in all the other variables that go into gas consumption when you BO in earnest.

- brett

1.5 as a factor is ok your carrying a 50% or better -im a lot more conservative than than that and use a factor of 3. Calculating BO and TTS is part and parcel of ccr diving, As you note ive found many ccr divers are optimistic in their OC calculations in stress situation