I don't have it mounted that way now but you can mount a petrel onto a slate. It saves real estate on the forearm and avoids button bumping. Not my pics but you get the idea...
Inadvertent gas switch on Shearwater?
- Thread starter stuartv
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I can't take credit for it, Cave Adventurers did this for me when I bought the computer. They drilled four sets of two holes on the top sheet of a flip slate. Then used zip ties to run through the slots on the Petrel, through the holes on the slate and secure. Here is mine...
Last edited:
beester
Contributor
I'm not at home but I have a nice recent dive where my petrel was basically diving pure O² at 72m depth 
To be honest I'm normally diving it in pure gauge mode and use a table to plan and then align the ascend profile to make it easy to remember. Next I'll also have a ratio on which to fall back if really in the pickle. But these times a very experienced GUE diver asked me to experiment a bit and use it in OC/TECH mode (computer) as a fallback. Also to check if our planning and actual dive runtimes would match the computers expected values.
First dive very nice. However we ended up doing of course deco on 50 and O². Next dive was this 72m dive, and I forgot to switch back from O² to bottom gas (15/55). I only noticed when I arrived on the wreck with the team. Before you're too busy keeping everybody together, gas switch, etc, and with gauge you don't actually need any info at that time. So I noticed at the bottom where I normally take note of descend time, depth, to start calculating avg depht... BIG RED PPO² flashing (I wonder why... with O² at 8+ATA). I kept it flashing for a good 10 minutes just for the fun of it... CNS went through the roof and my deco obligation was a very gentle 3 min at 6m.
I switched to backgas after a while and continued the dive. I forgot what the repercussions where for this DEEP O² dive. I'll look them up on the profile when I get home.
What does happen to me from time to time (just because I'm not used to it in computer mode) is to forget switching to deco gas. This weekend on 2 North Sea wreck dives (50m range), I forgot to switch twice, only doing it after remembering some time into deco (once at 12m, the other at 6m). Funny tho, the total runtime/deco time was not that much off from our plan, even tho I had switched late and had done (in theory on the dc) sub optimal deco partially on backgas. Although probably only about 30% of total deco time.
Never seen it switch automatically but like I said, not that much experience using it as a DC.
To be honest I'm normally diving it in pure gauge mode and use a table to plan and then align the ascend profile to make it easy to remember. Next I'll also have a ratio on which to fall back if really in the pickle. But these times a very experienced GUE diver asked me to experiment a bit and use it in OC/TECH mode (computer) as a fallback. Also to check if our planning and actual dive runtimes would match the computers expected values.
First dive very nice. However we ended up doing of course deco on 50 and O². Next dive was this 72m dive, and I forgot to switch back from O² to bottom gas (15/55). I only noticed when I arrived on the wreck with the team. Before you're too busy keeping everybody together, gas switch, etc, and with gauge you don't actually need any info at that time. So I noticed at the bottom where I normally take note of descend time, depth, to start calculating avg depht... BIG RED PPO² flashing (I wonder why... with O² at 8+ATA). I kept it flashing for a good 10 minutes just for the fun of it... CNS went through the roof and my deco obligation was a very gentle 3 min at 6m.
I switched to backgas after a while and continued the dive. I forgot what the repercussions where for this DEEP O² dive. I'll look them up on the profile when I get home.
What does happen to me from time to time (just because I'm not used to it in computer mode) is to forget switching to deco gas. This weekend on 2 North Sea wreck dives (50m range), I forgot to switch twice, only doing it after remembering some time into deco (once at 12m, the other at 6m). Funny tho, the total runtime/deco time was not that much off from our plan, even tho I had switched late and had done (in theory on the dc) sub optimal deco partially on backgas. Although probably only about 30% of total deco time.
Never seen it switch automatically but like I said, not that much experience using it as a DC.
i use a Petrel and a Perdix. Never had either one switch unless i told it to. This is something that should be reported back to shearwater.
now, though slightly different, one thing i remind my students is to only turn "on" gases they will actually dive on the shearwaters. Otherwise the calculations will be off as they take into account ALL active gases. There is a recent article on the shearwater website on that topic.
now, though slightly different, one thing i remind my students is to only turn "on" gases they will actually dive on the shearwaters. Otherwise the calculations will be off as they take into account ALL active gases. There is a recent article on the shearwater website on that topic.
victorzamora
Contributor
The only inadvertent gas issues I've had with my Petrel have been me forgetting to switch back to EANx to start my next dive.
Stuart: Before you decide on an iX3M or OSTC4, just be aware that they're both at least as big as the Perdix. Though I don't have an issue with the form factor, I remember you disliking the size. The Ratio and OSTC4 aren't small computers by any stretch of the imagination.
Stuart: Before you decide on an iX3M or OSTC4, just be aware that they're both at least as big as the Perdix. Though I don't have an issue with the form factor, I remember you disliking the size. The Ratio and OSTC4 aren't small computers by any stretch of the imagination.
Mine were forgetting to switch during boom drills during my SF2 class. I'm over that now. I've learned to do a final check just before I splash, at 20 ft during my post splash sanity check and then at depth. Of course, I check it periodically as I continue the dive to check for alerts and to see my limits progress, etc. Learning to dive a CCR really forced me to check my PDCs more often. I just don't see a downside to that.
Shearwater advises turning off gases that won't be used on a dive, but for reasons other than an inadvertent gas switch.
Only Enable (Turn On) Gases That You Will Actually Use on a Dive - Shearwater Research
Only Enable (Turn On) Gases That You Will Actually Use on a Dive - Shearwater Research
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