Computer?

[lovles2274]

Do I need multiple gases for cave diving? Or is nitrox comparability enough?

First let me preface this with..."I'M NOT A CAVE DIVER"

With that being said I have seen a bunch and talked to a few cave divers. All the ones that I have talked to use at least a two gas computer so they can decompress on higher levels of O2. Most cave dives that I've heard of are longer than the NDL that you follow as a recreational diver. I've seen a lot of them going in the water with doubles on their backs, a stage bottle on their side and an oxygen bottle on the other side. I purchased a two gas computer strictly because no matter how I plan to dive this computer should get me all the way up until I need trimix. Let us know what you end up getting.

 

[tgsmith]

Oceanic's VEO 2.0 fits your desire, and it's not as conservative as others. I give it a two thumbs up!

Since this thread is active again, I figured I'd comment.

I was looking into the Veo 3.0, which is virtually the same as the Veo 2.0 except it can manage two gases. I currently have a Veo250 and a Shearwater Predator.

Anyone who's looking at using it for decompression dives, realize that it will enter into an error mode if you have deco stops as deep as 60 feet. That makes it outright unusable for me as a 2 gas deco computer, personally. A lot of my dives will have stops as deep as 90-100 feet. Now, if you use it with the Haldanean algo, you probably won't get stops as deep as 60 feet unless you're doing some crazy **** on air. But, the Haldanean algo isn't exactly viewed as the algo of choice for decompression dives today, which is great because the Veo 3.0/2.0/1.0 can all switch between Pelagic Z+(claimed to be a Buhlmann ZH-L16 derivative) or the traditional Haldanean model found on all Oceanic computers. So, if you use the Z+ algo, and it actually gives you a Buhlmann-esque deco profile, you'll most likely get stops as deep as 60 feet. That would relegate your 2 gas computer to duty as a bottom timer.

For anyone interested, to illustrate the differences between a Haldanean and Buhlmann profile, consider this: I took my Veo250 and Predator(GF's at 30/85) on an air dive to 180 feet max for a bottom time of 32 minutes. The Predator gave me my first stop at 70 feet..........the Veo250(Haldanean) gave my first stop at 30 feet. It's a "bend'n'mend" profile, not something that's very popular among divers these days for decompression profiles. If you're talking light deco, then I imagine the Veo 2.0/3.0 would be okay in the Z+ algo, but just be sure of what you're buying.

 

[TSandM]

I'd say if someone is looking for a trimix computer on a pauper's budget, they should get a bottom timer and run decompression tables. That's how many people doing staged decompression diving do things, and it's much cheaper than a trimix-capable diving computer.

The least expensive route for a novice diver who is contemplating future staged decompression diving is a Nitrox-capable computer with a gauge mode. You can use the computer until you are ready not to use it any more, then use it as a bottom timer. The Aladin is a good choice for this, if you can see the numbers, but the backlight function on it constantly irritated me ("Now, which button do I press, and for HOW long? Oh, shoot, just reset my average depth again . . .")

 

[Kern]

Since this thread is active again, I figured I'd comment.

I was looking into the Veo 3.0, which is virtually the same as the Veo 2.0 except it can manage two gases. I currently have a Veo250 and a Shearwater Predator.

Anyone who's looking at using it for decompression dives, realize that it will enter into an error mode if you have deco stops as deep as 60 feet. That makes it outright unusable for me as a 2 gas deco computer, personally. A lot of my dives will have stops as deep as 90-100 feet. Now, if you use it with the Haldanean algo, you probably won't get stops as deep as 60 feet unless you're doing some crazy **** on air. But, the Haldanean algo isn't exactly viewed as the algo of choice for decompression dives today, which is great because the Veo 3.0/2.0/1.0 can all switch between Pelagic Z+(claimed to be a Buhlmann ZH-L16 derivative) or the traditional Haldanean model found on all Oceanic computers. So, if you use the Z+ algo, and it actually gives you a Buhlmann-esque deco profile, you'll most likely get stops as deep as 60 feet. That would relegate your 2 gas computer to duty as a bottom timer.

For anyone interested, to illustrate the differences between a Haldanean and Buhlmann profile, consider this: I took my Veo250 and Predator(GF's at 30/85) on an air dive to 180 feet max for a bottom time of 32 minutes. The Predator gave me my first stop at 70 feet..........the Veo250(Haldanean) gave my first stop at 30 feet. It's a "bend'n'mend" profile, not something that's very popular among divers these days for decompression profiles. If you're talking light deco, then I imagine the Veo 2.0/3.0 would be okay in the Z+ algo, but just be sure of what you're buying.

Buhlmann is a single faze, Haldanian algo. Gradient factors alter the output, but most recreational computers that use Buhlmann don't have GF's, & so will give a bend & mend profile.

 

[tgsmith]

Buhlmann is a single faze, Haldanian algo. Gradient factors alter the output, but most recreational computers that use Buhlmann don't have GF's, & so will give a bend & mend profile.

Thanks for that. I didn't realize that.........the IANTD Buhlmann tables I have don't reflect that, but I'm not sure if IANTD modified them with GF's. I played around with jDeco using 98/99 GF's(about as pure Buhlmann I could simulate, I guess) and the deco profile for a given profile to 160ft still puts my first stop 20 feet deeper than the Oceanic would. Oceanic claims the algo in the Veo250 to be a modified Haldanean.

Do you have some tables to demonstrate? I'd much appreciate it.

 

[Kern]

Thanks for that. I didn't realize that.........the IANTD Buhlmann tables I have don't reflect that, but I'm not sure if IANTD modified them with GF's. I played around with jDeco using 98/99 GF's(about as pure Buhlmann I could simulate, I guess) and the deco profile for a given profile to 160ft still puts my first stop 20 feet deeper than the Oceanic would. Oceanic claims the algo in the Veo250 to be a modified Haldanean.

Do you have some tables to demonstrate? I'd much appreciate it.

DSAT, (which the Veo algo is based on), US Navy, Buhlmann etc, are all neo Haldanean, single gas faze algos. Most modern DC use some modification.

If you'd like to supply the bottom time, back & deco gas for your 160' dive, I'll post what I get for GF of 35/85, & 98/99.

Using air, 20 min bottom time, no accelerated deco; with 35/85 my 1st stop is at 70'; with 98/99 my 1st stop is 30'

PS. Just figured how to get output I could cut & paste from this software.

FreePlanner 1.0 by Colin Clark
GF code by Eric C. Baker

GF Decompression Model

Dive Plan

GF Low=35, High= 85, 2011-02-01 13:03:12
Units = FSW

--------------------------------------------
Dive #1
Descend to 160 for 3.3 (3.3) using 21/0/79
Level at 160 for 16.7 (20.0) using 21/0/79
Stop at 70 for 0.3 (23.0) using 21/0/79
Stop at 60 for 0.7 (24.0) using 21/0/79
Stop at 50 for 1.7 (26.0) using 21/0/79
Stop at 40 for 1.7 (28.0) using 21/0/79
Stop at 30 for 3.7 (32.0) using 21/0/79
Stop at 20 for 26.7 (59.0) using 21/0/79


GF code by Eric C. Baker

GF Decompression Model

Dive Plan

GF Low=98, High= 99, 2011-02-01 13:10:06
Units = FSW

--------------------------------------------
Dive #1
Descend to 160 for 3.3 (3.3) using 21/0/79
Level at 160 for 16.7 (20.0) using 21/0/79
Stop at 30 for 2.1 (26.0) using 21/0/79
Stop at 20 for 16.7 (43.0) using 21/0/79

 

[tgsmith]

I was asking for a conventional Buhlmann(no GF modifications) versus a common Haldane profile, since you had said they were essentially one in the same. I have multiple decompression programs to play around with using GF's. I understand the function of GF's on a profile and that 35/85 will start the stops deeper than pure-Buhlmann, or as close as we can come to it in our programs using 98/99. I'm not looking for GF-modified Buhlmann against pure Buhlmann.

I was looking for pure Buhlmann vs any of the other Haldanean profiles, such as DSAT, US Navy, ect, because with what I've observed pure Buhlmann would still give a deeper first stop than a US Navy table, even if it is a single phase Haldane algorithm. I'm basing this on looking at my IANTD Buhlmann tables versus the dive planner on my Oceanic.

I would think the reason IANTD sells separate US Navy tables(about as Haldane as you can get, no?) and Buhlmann tables is because the profiles would be different, and the understanding I've had is that they are.

EDIT: When playing with the software, I was looking at a 45 minute BT to a depth of 160 using air.

 

[tgsmith]

IANTD Open Circuit Flexible Dive Tables - Dive Gear Express

At this link you can view some samples of US Navy and Buhlmann ZH-L16 air tables. The Buhlmann ZH-L16 will give a deeper first stop than the US Navy table.

 

[myscubastory.com]

Ok check ebay for those watches. They usually have very competitive prices

 

[Kern]

I was asking for a conventional Buhlmann(no GF modifications) versus a common Haldane profile, since you had said they were essentially one in the same. I have multiple decompression programs to play around with using GF's. I understand the function of GF's on a profile and that 35/85 will start the stops deeper than pure-Buhlmann, or as close as we can come to it in our programs using 98/99. I'm not looking for GF-modified Buhlmann against pure Buhlmann.

I was looking for pure Buhlmann vs any of the other Haldanean profiles, such as DSAT, US Navy, ect, because with what I've observed pure Buhlmann would still give a deeper first stop than a US Navy table, even if it is a single phase Haldane algorithm. I'm basing this on looking at my IANTD Buhlmann tables versus the dive planner on my Oceanic.

I would think the reason IANTD sells separate US Navy tables(about as Haldane as you can get, no?) and Buhlmann tables is because the profiles would be different, and the understanding I've had is that they are.

EDIT: When playing with the software, I was looking at a 45 minute BT to a depth of 160 using air.

Yes, all the single faze algo's have different M values, compartment variations, & made different decisions during their validation process. Yes, they all show variations in their profiles due to these differences. No matter which one produce's the deeper 1st stop, they are still single faze algos, that produce, what most now consider unacceptable deco curves.

Yes, Buhlmann is probably the most conservative of the single faze algos. Yes, Buhlmann will probably give the deeper 1st stop.

Yes, according to my tables the US navy for a 48mt, on air, no accelerated deco, for 20min dive has its 1st stop at 6mt, & the Buhlmann at 9mt. No, I wouldn't use the profiles produced by either, or indeed any other single faze algo, to plan a deco dive.