Perdix question
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Ryan Mcshane
Contributor
I recon it’s because the majority of divers struggle to hold a single 3 minute safety stop nevermind execute an ascent with multiple stops.
I’m sure 3mins at 5m or whatever else is taught was chosen simply because it’s easy to remember.
And then there's GUE's "Minimum Deco Ascent" (i.e., recreational ascent), which involves a 30-second stop every 10 feet to the surface.* The Perdix/Petrel doesn't have a specific feature to help with that, either. As AJ's comment suggests, I suppose there are various ascent strategies that people use on "no-stop" dives. I don't care for seeing my computer display a safety stop--I am content to watch the displayed dive time elapse and count the minutes myself--so I dive it in Tech mode even on dives that I know won't require any stops according to the computer.
* Let's put aside any debate over the merits of that versus the traditional 3-minute stop at 15 feet.
* Let's put aside any debate over the merits of that versus the traditional 3-minute stop at 15 feet.
AJ
Contributor
Nope, I have a better computer always with me that does these calculations for me. A thinking computer
GUE. The rationale is a controlled and safe ascent with the whole team according to a plan the whole team acknowledges. It gives the team plenty of time to check surroundings for safe surfacing, clean up, prepare for boat entry, etc. before surfacing. It takes quite a lot of skill though to do this right. One about 6 metre safety stop is much much easier to do.
AJ
Contributor
Totally agree, I don't want to imply one or the other is better. It's just a different strategy which is not supported by any computer I know of. If my buddy wants to do a 3 minute stop because his computers tells him to do so, that's fine with me. I'll wait until it has cleared.The slower the ascent, the better it is. It does not matter if it's done by computer of by brain.
Thanks. Seems like unnecessary overkill, but if that's the way you want to dive, fine. Won't work for me in cave diving, quite unnecessary and probably not possible in my rec diving.Nope, I have a better computer always with me that does these calculations for me. A thinking computer
GUE. The rationale is a controlled and safe ascent with the whole team according to a plan the whole team acknowledges. It gives the team plenty of time to check surroundings for safe surfacing, clean up, prepare for boat entry, etc. before surfacing. It takes quite a lot of skill though to do this right. One about 6 metre safety stop is much much easier to do.
The reason no computer does that ascent is for a reason that has been discussed frequently here. A computer has to choose an algorithm, and the manufacturer selects from a variety of well-researched algorithms based on more than 100 years of scientific studies. It will not use an ascent strategy that has no science behind it whatsoever.
In one of our more recent discussions in which the rationale for that kind of ascent was explained, we learned that the origin of it was a learning exercise to get students to practice a series of stops in preparation for learning to do decompression stops later on in their training.
In one of our more recent discussions in which the rationale for that kind of ascent was explained, we learned that the origin of it was a learning exercise to get students to practice a series of stops in preparation for learning to do decompression stops later on in their training.
PfcAJ
Contributor
Nope, I have a better computer always with me that does these calculations for me. A thinking computer
GUE. The rationale is a controlled and safe ascent with the whole team according to a plan the whole team acknowledges. It gives the team plenty of time to check surroundings for safe surfacing, clean up, prepare for boat entry, etc. before surfacing. It takes quite a lot of skill though to do this right. One about 6 metre safety stop is much much easier to do.
Oh boy.
The rationale for all the stops did not come from any of the reasons you state. It came from what DecoPlanner spits out at the maximum dive time you can do without getting a stop time longer than 1 min at any point in the ascent using gradient factors of 20/85. They picked the term "minimum deco" to describe that. It ALSO happens to tally up to 5mins from a 100ft dive, effectively redistributing a 5min "safety stop" significantly deeper.
"The slower the ascent the better" is certainly not the case. Refer to the various studies done about decompression efficiency of deep stops profiles.
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