Feedback on recent two-tank and dive limits

[boulderjohn]

Who's complaining? Nothing wrong with GFs when used as they were intended to by its designer Erik Baker (that is technical diving).

So what is wrong with using them in NDL diving? The only reason you have provided so far (GF lo settings cause you to have to do deep decompression stops while still on a NDL dive) is simply not true. You have not responded to repeated questions asking how using GFs on NDL dives differs from conservative settings on every other algorithm

 

[boulderjohn]

Who's complaining? Nothing wrong with GFs when used as they were intended to by its designer Erik Baker (that is technical diving).

I don't know why this has not been mentioned before, but before this thread, I never encountered anyone claiming that GFs were created specifically to be used for decompression dives and not NDL dives. I have read Baker's work and don't see any hint of that. Could you show me where I missed it?

Even if he didn't make that restriction, can you explain why there would be any difference between using GFs on a decompression dive and a NDL dive?

 

[Eric Sedletzky]

GFs are simple, if someone is struggling with them they shouldn't be considering tech diving.

Maybe tech diving shouldn't be discussed in the basic forum?

 

[old frogman]

So what is wrong with using them in NDL diving? The only reason you have provided so far (GF lo settings cause you to have to do deep decompression stops while still on a NDL dive) is simply not true. You have not responded to repeated questions asking how using GFs on NDL dives differs from conservative settings on every other algorithm

I f you read the original statement made by the inquiring gentleman:

1. On the first dive there appears to be no reference to a stop by the dive computer.

2. On the second dive a 5 min stop appears on the computer, which the divers interprets as a safety stop however his perception is that it is mandatory and consequently is anxious about being forced to directly surface omitting the 5 min stop.

From this statement, it is quite clear to me that the that the distinction between the safety stop and a stage decompression stop are not being differentiated by the dive computer to the diver. Consequently the diver is confused and anxious. This is not a good outcome. Despite the fact that both dives may have been well within the no decompression limit (NDL) confusion and subsequent anxiety has occurred.

My point is, if the diver had been using a computer by OCEANIC with DSAT or straight Buhlmann (dual algorithms). When simply set on DSAT it would have given him a longer NDL bottom time for the first dive and automatically provided a predictable 3min safety stop at 15 ft. The NDL bottom time for the second dive would probably be shorter and again automatically provided a 3 min safety stop at 15 ft. It works for NDL recreational diving why convolute it with GFs.

This is the basic scuba section. My guess is that over 95% of recreational divers have no interest in technical diving or convoluted pseudo technical diving equipment. When it comes to dive computers, they just want to slap it on the wrist and jump into the water. They want a no fuss computer that gets them in, gets the job done and get out.

 

[Blackcrusader]

It works for NDL recreational diving why convolute it with GFs.

Having Gradient Factors on by Perdix has not convoluted my dives. As for the OP maybe you missed he was using the adaptive settings so got the 5 minute stop. It was not a deco stop as in anycase he never exceeded NDL. His DC gave him a vibration alarm when he had low NDL.

@lizzzzz I believe did not understand how being set on adaptive settings affected safety stops. 3 min for shallower dives and 5 minutes for deeper dives but within NDL on the Shearwaters. Also one needs to understand the DC they are using such at TTS Time to Surface. I've had non shearwater divers ask me what that means on my DC when they saw it on a dive.

There is a clear difference on the Shearwater when you clear a DECO obligation than clearing a safety stop and deing told the depth and stop time. This never happened for the OP.

 

[old frogman]

Having Gradient Factors on by Perdix has not convoluted my dives. As for the OP maybe you missed he was using the adaptive settings so got the 5 minute stop. It was not a deco stop as in anycase he never exceeded NDL. His DC gave him a vibration alarm when he had low NDL.

@lizzzzz I believe did not understand how being set on adaptive settings affected safety stops. 3 min for shallower dives and 5 minutes for deeper dives but within NDL on the Shearwaters. Also one needs to understand the DC they are using such at TTS Time to Surface. I've had non shearwater divers ask me what that means on my DC when they saw it on a dive.

There is a clear difference on the Shearwater when you clear a DECO obligation than clearing a safety stop and deing told the depth and stop time. This never happened for the OP.

View attachment 913612View attachment 913614

No disrespect to you. You are an experienced diver. However, you have confirmed that this dive computer is a convoluted apparatus for "new diver" to use. The risk on "new divers" programming it incorrectly for dives is real.

 

[old frogman]

Maybe tech diving shouldn't be discussed in the basic forum?

Agree.

 

[JMarc]

From this statement, it is quite clear to me that the that the distinction between the safety stop and a stage decompression stop are not being differentiated by the dive computer to the diver.

The manual of the Peregrine shows a clear difference.

and I still don't see how this is related to GF.

That feature of safety stop is not a tech feature (in tech mode, my perdix simply count the time since deco was cleared, but I admit that could be a setting I choose and not the default), it is a rec one which has similar one in more rec oriented computers I've used, and for some the display was more confusing.

 

[Blackcrusader]

No disrespect to you. You are an experienced diver. However, you have confirmed that this dive computer is a convoluted apparatus for "new diver" to use. The risk on "new divers" programming it incorrectly for dives is real.

Are you diving a DC with GF? Because you make claims about the shearwaters which are wrong. Such as being given a deep stop on an NDL dive ( it does not ) and that safety stops and Deco stops are not shown differently on. They are.

Any DC when slapped on the wrist of a new diver can be considered a convoluted apperatus when they do not understand how it works. I've seen new divers with their DC alarms going off not even knowing it was their own DC. So even for a diver using RGBM they can setup the DC incorrectly. I've seen it happen.

So the risk really is that divers buy a DC and just expect it to work, which it does. The issue is the diver now knowing what the DC is telling them or even what settings the DC is on. They never look just power it on an assume all is good. Also many new divers get told by guides to just do as the guide does and they lost the fact they should be diving independent of the guide. They should always pay attention to themselves not the guides.

Even as an experienced diver I went from Suunto RGBM to the Shearwater. When I got in on Firmware V65 did not have all the features it does now. I've spent a lot of time reading on things like GF GF99 Surf GF tissue readings and other things my Shearwater can tell me. I decided to not use the REC mode as use the TEC mode. I don't want my DC to be a babysitter. Anyway the OP is learning about the Peregrine and also about being more responsible for paying attention to not only the DC, but to looking at his Surface Intervals before joining a dive. The Peregrine like any DC one needs to read the user manual. The OP has also posted here so he is not so much of a "new diver" just a diver with a new DC.

It's great @lizzzzz made the post and uploaded his dive logs. Peregrine cannot be too convoluted if as a new diver he can do that.

 

[old frogman]

I don't know why this has not been mentioned before, but before this thread, I never encountered anyone claiming that GFs were created specifically to be used for decompression dives and not NDL dives. I have read Baker's work and don't see any hint of that. Could you show me where I missed it?

Even if he didn't make that restriction, can you explain why there would be any difference between using GFs on a decompression dive and a NDL dive?

I don't know how long you have been diving or how versed you are in diving related literature. If you research books written about 15 years ago you will note that Gradient Factors (GF) were discussed exclusively in technical diving books. No mention to the best of my knowledge of GF in recreational diving books.

"Deeper into diving", John Lipmann OAM and Dr Simon Mitchell circa 2011

"Mixed Gas Diving Encyclopedia (The Tao of Survival Underwater", Tom Mount circa early 2000s

Also, the first dive computer to use Buhlmann with GF was the Shearwater Predator circa 2009. The Predator was specifically designed for technical diving.

Conclusion, Erik Baker did not have recreational diving in mind when he developed gradient factors.