Oceanic VTX too conservative

[sc00bad1v3r]

Not sure if this is the right place for this question but here goes.

Backstory.. Recently did a big dive trip totaling 17 dives in 3 days and the average depth being 90'. Now ive done a lot of dives 500+ and I had been using the Galileo Luna and had done the same exact trip 4 times with the Luna. My Luna unfortunately was in the shop so I could not use it on this trip. I had the opportunity to try out the VTX and I had done a 4-dive trip weeks prior with no issues. I also had a backup computer on the 17 dive trip which was an old Aeris Puck. We were diving nitrox obviously.

Now here is the issue. With my VTX on the 5th dive it maxed me out Where as the Aeris said 7 mins left. I ascended to 40 feet and the VTX said 5 mins NCD and the Aeris Said I had 3:30 hours. Now Knowing how my luna would have acted I know that it would have given me more bottom time than the VTX. The luna just kicks butt when it comes to bottom time. The VTX, not so much! Also the VTX battery lasts about 20 dives and the Luna lasts about 250.

The issue could have been dive profiles shallow deep deep.... but everyone else on the trip had the same drops and bottom with no issues. I just wish I had my luna on this trip to see how it would have handled the situation. Ok this is more of a rant now than a question but any feedback is welcome.

 

[scubadada]

Was the VTX running DSAT or PZ+, with or without the conservative setting? DSAT is certainly more liberal than the Scubapro decompression algorithm. I don't know how PZ+ compares to Scubapro but would imagine they are reasonably similar. Your old Aeris was probably running DSAT

Nearly 6 dives/day for 3 days is a lot of relatively deep dives on nitrox. Unless they were all short, I am surprised to didn't come up on your O2 limit. O2 limit for a ppO2 of 1.2 (32%, 90 ft) is 210 minutes, 35 minutes a dive for 6 dives. Oceanic uses a rolling 24 hour window, you may have had more than 6 dives in your 24 hour window for a couple of those days.

This might have been better in the equipment forum/dive computers

 

[Hickdive]

AFAIK, if you put the VTX into PZ+ it will be running Buhlmann ZHL16 and if you turn off the MB setting on the Luna it runs Buhlmann ZHL8.

So in theory, set up that way they should be pretty close if you also turn off all conservatism settings.

 

[scubadada]

Scubapro ZHL-8 may be slightly more conservative than Oceanic ZHL-16C but is very similar, certainly more conservative than DSAT
Innovation » Computers
http://ads.bonniercorp.com/scuba/PDF/ScubaLab-Computer-Test-September-2014-data.pdf

 

[KeithG]

Ok this is more of a rant now than a question but any feedback is welcome.

Why are you riding your computer? This IS a serious question. So far the only answer I have ever gotten is "because I can".

I fail to understand why some divers seem to be fixated on maximal depth as opposed to maximum bottom time. I pay the same for each dive, so I try to make every dive last as long as possible. This means i dive shallow-ish. And long. So NDLs are never an issue. My favourite Bonaire profile is 90 feet for 90 minutes.

When people start discussing 5 or 7 minute of remaining bottom time I look at them like they have 3 heads. Maybe if people were taught that they "would catch fire and explode" (there be dragons!) if they violated NDLs as opposed to believing that they are perfectly totally completely safe right to the very edge of the NDLs, we would see different behaviour?

I personally do not believe that any commercial dive computer is too conservative (well except the goofy spanking you get from Suuntos if you violate them!).

</rant>

 

[Bob DBF]

When people start discussing 5 or 7 minute of remaining bottom time I look at them like they have 3 heads. Maybe if people were taught that they "would catch fire and explode" (there be dragons!) if they violated NDLs as opposed to believing that they are perfectly totally completely safe right to the very edge of the NDLs, we would see different behaviour?
</rant>

I doubt that they are taught, or to be charitable learned, that NDL is a wide grey area and that being just under NDL is not a guarantee of safety, especially for multiple days of multiple dives. When they do "catch fire and explode" I hope there is a nearby chamber.

Of course it could be that we are just getting old and grumpy, however when I was young and pushing the limits I understood that I was poking the bear.



Bob
------------------------------------

That's my point, people, by and large, are not taught that diving can be deadly, they are taught how safe it is, and they are not equipped with the skills, taught and trained to the level required to be useful in an emergency.

 

[scubadada]

Diving within NDLs, with an established decompression algorithm, with a proper ascent and SS, is reasonably safe. That is my philosophy. Does anyone think differently? The SS is still optional, just in case.

 

[ronscuba]

Why are you riding your computer? This IS a serious question. So far the only answer I have ever gotten is "because I can".

I fail to understand why some divers seem to be fixated on maximal depth as opposed to maximum bottom time. I pay the same for each dive, so I try to make every dive last as long as possible. This means i dive shallow-ish. And long. So NDLs are never an issue. My favourite Bonaire profile is 90 feet for 90 minutes.

When people start discussing 5 or 7 minute of remaining bottom time I look at them like they have 3 heads. Maybe if people were taught that they "would catch fire and explode" (there be dragons!) if they violated NDLs as opposed to believing that they are perfectly totally completely safe right to the very edge of the NDLs, we would see different behaviour?

I personally do not believe that any commercial dive computer is too conservative (well except the goofy spanking you get from Suuntos if you violate them!).

</rant>

For me, it's not a competition about how deep I can go or my bottom time. It's about diving at depths where there are things to see and staying down as long as the dive is interesting. I've ended dives out of boredom. I use a dive computer to keep me safe. It's not a guarantee, but that is it's purpose.

Some algorithms are more conservative than others and many computers allow you to make them even more conservative if desired.

I guess some divers are fixated or in a competition for depths, SAC rates, bottom times, etc., but that does not describe everyone. I consider my Suunto conservative. Not so much a problem if doing 2 dives a day. On a liveaboard, it starts to act funny on dive #3 or #4.

 

[victorzamora]

Diving within NDLs, with an established decompression algorithm, with a proper ascent and SS, is reasonably safe. That is my philosophy. Does anyone think differently? The SS is still optional, just in case.

Reasonably safe and guaranteed safe aren't the same thing, right? Don't get me wrong, I agree with you completely....I'm just stating that there are good reasons to stay off the ragged-edge of a deco algorithm.

If I ever feel sub-100%, haven't been drinking as much water as I had been, expect a rapid ascent (or am afraid of one), expect post-dive exertion, or I'm doing a bunch of repetitive dives over a week....I stay farther inside the NDLs. First dive off of the plane? Very conservative and preceded and followed by gatorade and/or water. A friend of mine is a very experienced diver, cave and trimix diver, diving a well-established, fairly conservative algorithm. One dive, little post-dive exertion, extended the O2 stop after the dive, and was well within computer's limits of safety....he ended up taking a few rides in a chamber.


OP: Be aware that just because the luna gives you more bottom time doesn't mean you're guaranteed safe. I'm not saying the Luna is unsafe, simply that a computer telling you your safe doesn't make you safe. As for Shallow-Deep-Deep, Pelagic Z+ shouldn't punish you for doing reverse profiles. My computer on PZ+ (and my wife's, now that I think about it) gave us better bottom-times than another group diving Scubapros. I feel like Conservatism+0 is a little aggressive, even, just comparing to Buhlmann+GF (what PZ+ is based on) that I'm more used to in the Tech world.

 

[scubadada]

Reasonably safe and guaranteed safe aren't the same thing, right? Don't get me wrong, I agree with you completely....I'm just stating that there are good reasons to stay off the ragged-edge of a deco algorithm.

If I ever feel sub-100%, haven't been drinking as much water as I had been, expect a rapid ascent (or am afraid of one), expect post-dive exertion, or I'm doing a bunch of repetitive dives over a week....I stay farther inside the NDLs. First dive off of the plane? Very conservative and preceded and followed by gatorade and/or water. A friend of mine is a very experienced diver, cave and trimix diver, diving a well-established, fairly conservative algorithm. One dive, little post-dive exertion, extended the O2 stop after the dive, and was well within computer's limits of safety....he ended up taking a few rides in a chamber.


OP: Be aware that just because the luna gives you more bottom time doesn't mean you're guaranteed safe. I'm not saying the Luna is unsafe, simply that a computer telling you your safe doesn't make you safe. As for Shallow-Deep-Deep, Pelagic Z+ shouldn't punish you for doing reverse profiles. My computer on PZ+ (and my wife's, now that I think about it) gave us better bottom-times than another group diving Scubapros. I feel like Conservatism+0 is a little aggressive, even, just comparing to Buhlmann+GF (what PZ+ is based on) that I'm more used to in the Tech world.

Nothing is guaranteed, reasonably safe is good enough for me. No dive algorithm guarantees safe.