Feedback on recent two-tank and dive limits

[grantmac]

Correct, recreational divers should not be customizing their GF's.

What exactly do you think changing the conservativism on most computers does?

 

[Belzelbub]

Correct, recreational divers should not be customizing their GF's.

So, I partially agree with this. Recreational divers should not be customizing their GFs without understanding what it means. I don't have my Shearwater on me at the moment, but I did try altering my custom GF on my Garmin. Mainly I wanted to see what the max I could set (it's 100). My computer warned me that I shouldn't mess with these settings unless I have a good understanding of what I'm doing.

I'm a rec diver, but I took the time to read as much as I could about Buhlmann, GFs, etc. when I got my DC. Shearwater was nice enough to point me to some sources in the manual. I've gone to a custom GF based on that reading. It is in no way any more liberal than what is in the defaults.

 

[matt9122]

So, I partially agree with this. Recreational divers should not be customizing their GFs without understanding what it means. I don't have my Shearwater on me at the moment, but I did try altering my custom GF on my Garmin. Mainly I wanted to see what the max I could set (it's 100). My computer warned me that I shouldn't mess with these settings unless I have a good understanding of what I'm doing.

I'm a rec diver, but I took the time to read as much as I could about Buhlmann, GFs, etc. when I got my DC. Shearwater was nice enough to point me to some sources in the manual. I've gone to a custom GF based on that reading. It is in no way any more liberal than what is in the defaults.

There are always exceptions. When I think recreational diver, I think of the casual diver who does no research aside from the minimum standards of training. If you have an understanding of what you are doing and think there is a safer option for you, then go right ahead. I just think that we have had prety good safety in no-decompression diving for an awaful long time. If divers are just looking to extend bottom times and assume that a manufacturer will not allow changes that risk safety, decompression hits may increase. But again, I will always promote further research and understanding that leads to individual changes.

 

[lowwall]

I don't have my Shearwater on me at the moment, but I did try altering my custom GF on my Garmin. Mainly I wanted to see what the max I could set (it's 100).

Damn. There's goes my plan to mimic a true Haldanian computer for my multi-level standard dress dives.

 

[rongoodman]

After close review it appears that both of your ascents were significantly faster than descent and the opposite is optimal. Your safety stop will be longer if you ascend too fast.

Not if he's diving Buhlmann, that's an RGBM thing.That doesn't make it a good idea, of course.

 

[SuitableSkies]

Not if he's diving Buhlmann, that's an RGBM thing.That doesn't make it a good idea, of course.

am I misunderstanding? Isn't it always better to have a reasonably slow ascent regardless of the tissue model?

 

[rongoodman]

Of course, but it isn’t something the Buhlmann algorithm tries to model. RGBM does, but it’s unclear how since the various versions are all proprietary.

 

[SuitableSkies]

but that's only relevant to planning right? Where the algorithm will have to assume a certain ascent rate. In actual operation, won't the computer continuously monitor the ambient pressure (and thus implicitly the ascent rate) and use it in whatever calculations it performs?

 

[lowwall]

am I misunderstanding? Isn't it always better to have a reasonably slow ascent regardless of the tissue model?

If you are starting deep enough and are at the No Deco Limit, a slow enough ascent rate at the start of your ascent could theoretically cause you to exceed NDL.

It's definitely better to go slow down as you get shallower though. Taking it slow from 10m up and especially from the safety stop to the surface makes me feel a lot better later on the day compared to when I started diving and did all my ascents at the max rate my computer allowed.

 

[rongoodman]

but that's only relevant to planning right? Where the algorithm will have to assume a certain ascent rate. In actual operation, won't the computer continuously monitor the ambient pressure (and thus implicitly the ascent rate) and use it in whatever calculations it performs?

I meant that Buhlmann doesn’t use the ascent rate to alter the safety stop, which is just an add-on anyway. RGBM evidently does.