Re-Evaluating My GF

[Pavao]

Who wants to start a poll and see how many more times the same joke will be repeated?

 

[CWK]

My understanding is that GF Lo was introduced to generate deeper initial stops in Buhlmann so that it resembles a deep stop/bubble model. The NEDU study suggests that a deep stop/bubble model will bend divers more than a gas content model. Perhaps it is time to get away from GF Lo (or set it to the same value as GF Hi).

 

[dmaziuk]

On the serious note, the base math will account for on-gassing in slower tissues at deeper stops generated by lower GF Lo values. It will pad the shallow stops accordingly. So in terms of the math, it only adds conservatism to the original M-values, you need to push your GF over 100 to make it do otherwise. I.e. if there's any problem in the model, I'd suspect the gas switch and the pure O2 part rather than gradient factors per se... but if that wasn't modeled right we'd've heard about that by now. I think.

You'd have to dive something like 10/150 to get the NEDU study profiles. There's no math reason you couldn't, but there's this study thing.

 

[Miyaru]

...
A recent study showed GF Low needs to be set between 55 & 70 while GF HI needs to be set below 70 for the algorithm to remain inside of Navy safe diving limits.
...

Which study is that? Can you provide a link to it?

...

My suggestions:

Get rid of the air. Replace with trimix.
Consider your thermal protection.
Consider your hydration.
Consider your post dive exertion.
Consider your exertion level on the dive.

And consider your pre dive exertion!
___________________

I'm interested in why you chose 50/80.
A recommended starting point would be 30/70, now also the factory default for SW. But then again, that is a starting point. Personal experience leads to other GFs.

 

[PfcAJ]

Which study is that? Can you provide a link to it?

And consider your pre dive exertion!
___________________

I'm interested in why you chose 50/80.
A recommended starting point would be 30/70, now also the factory default for SW. But then again, that is a starting point. Personal experience leads to other GFs.

Gf low of 30 is still very much a deep stops profile.

60/85 for me.

 

[rjack321]

Gf low of 30 is still very much a deep stops profile.

60/85 for me.

50/75 seems to be optimal for me. I can do a high of 80 but im clearly more tired

 

[Kensei]

Who else checked out this thread thinking GF= Girlfriend?

add me to the list. People really need to think a bit more when putting acronyms in the title of a new thread.

 

[JohnnyC]

I pretty much settled on 55/75 and have been happy so far. This is for technical dives, even shallow cave dives within NDL’s, as the potential to need to do some unintended decompression is more likely. Not an excuse to not dive your plan, but stuff happens in the overhead and you need to pad your safety margin.

I’m happy to run a high of 95 when doing typical shallow recreational profiles. There just isn’t enough tissue loading for me to be concerned, and I stay well enough away from NDL’s. Throw in a live aboard type of schedule and it changes, slow tissue loading becomes more of a concern over many days of repetitive diving. Cue increased level of conservatism due to a different set of variables.

Doesn’t mean you can’t get bent doing a shallow drift dive in Coz, but in theory it’s less likely to be an issue than day 5 of an aggressive liveaboard schedule....

@PfcAJ how are your ratios working out 60/85? Significant setpoint changes?

 

[PfcAJ]

I pretty much settled on 55/75 and have been happy so far. This is for technical dives, even shallow cave dives within NDL’s, as the potential to need to do some unintended decompression is more likely. Not an excuse to not dive your plan, but stuff happens in the overhead and you need to pad your safety margin.

I’m happy to run a high of 95 when doing typical shallow recreational profiles. There just isn’t enough tissue loading for me to be concerned, and I stay well enough away from NDL’s. Throw in a live aboard type of schedule and it changes, slow tissue loading becomes more of a concern over many days of repetitive diving. Cue increased level of conservatism due to a different set of variables.

Doesn’t mean you can’t get bent doing a shallow drift dive in Coz, but in theory it’s less likely to be an issue than day 5 of an aggressive liveaboard schedule....

@PfcAJ how are your ratios working out 60/85? Significant setpoint changes?

Ratios just get ya close.

Really though, if you 30fpm up to the 1st gas switch, it’s not far off with the higher gf low.

I’m rockin tables for planning, computer for fine tuning, and ratio just for talking run times and coarse deco figurin’. Most of the stuff I’m doin lately doesn’t jive too well with classic ratios anyways.

 

[happy-diver]

Not the old too tight gauges on the arms that let gas out when you take them off trick Chief!