Wisdom of trusting one's dive computer?

[Fastmarc]

Wow I havent heard this for some time. Im no expert at all just lightly read. What I can gathered form the reading I have done which I can not cite. most computers if equally set up are about the same for the first dive. after that the numbers go crazy. due to how they use residual and from what compartment and the definitions of those conpartment groups.

It has me puzzled. I have been diving it for a while, but most of my recent dives has included more inexperienced divers that limit the dives due to poorer air consumption, so it wasn't noticeably. Having reconnected with some old buddies and doing more enjoyable longer dives with them, it just became more obvious.

 

[Lorenzoid]

I have a Shearwater Teric. I pay attention to the NDL reading and I ascend any time it gets too low. According to the computer I have never incurred a deco obligation and I also have never been bent over the course of 67 dives.

I recently dived with a buddy who is into the GUE approach, and he said that he only dives with his computer in gauge mode and always calculates his dive plan in advance to avoid deco or account for it or whatever.

What is the better approach? Trusting the computer or doing pre-dive planning?

The lame thing about the pre-planning is it doesn't really leave any freedom. With the computer, it feels like I am safe to dive without any plan whatsoever, other than making sure not to incur deco.

Asking out of curiosity, but by any chance is the buddy someone who is new-ish to the GUE system? I ask because in Fundies class GUE teaches you to pre-plan and then dive with the computer in gauge mode. They teach that because, as others have already mentioned, they want to wean you off the idea of "flying the NDL"--letting the ever-changing number on the screen dictate when you turn your dive. The strict use of gauge mode is more of a training tool than anything else. From what I have seen, there are some really experienced GUE-trained divers who keep their minds open to their computers' full capabilities--they just don't let the numbers on the screen override what they have already planned. Rather, the computer backs up or complements what they planned.

Planning shouldn't be onerous. A computer's planning mode can be used to pre-plan a dive. In advance of the dive, you should have at least a rough idea what you would like to see and the route to get there and back--it's not a great idea to go willy-nilly from one place to another and another on a whim, especially if these are cavern dives you're talking about. You should have at least a rough idea how deep the route and destination are. Based on the depth, you can go into your computer's planning mode and see how many minutes you can spend at that depth, or the average depth if you prefer. If you know that time limit in advance and plan to adhere to it rather than "fly the displayed NDL," there really isn't much point to restricting your computer to gauge mode on the dive.

 

[tursiops]

average depth if you prefer

Why would you want to do something incorrect like this? I understand its value for air consumption, but it is not correct for nitrogen uptake.

 

[Lorenzoid]

Why would you want to do something incorrect like this? I understand its value for air consumption, but it is not correct for nitrogen uptake.

You're right. Brain fart.

 

[ChuckP]

And I disagree, spinning the cylinder is when you compound one screwup (incurring a deco obligation on what should be a NDL dive) by using a very aggressive decompression profile.

I dive 45/85 and routinely dive small deco amount dives - something along the lines of allowing myself to get 10-15 minutes of deco (TTS 15min max). These are at rec depths with a source of some deco gas. My first stop has never been deeper than 20' per the computer.

With that being said and those type dive profiles - diving 85/85 or 45/85 is no different.

The dives I do are recreational dives, I'm right there with everyone else in the group other than I may stay a bit deeper longer than the others - it would be exactly like someone that accidently allowed themselves to slip past the NDL.

 

[PfcAJ]

Why would you want to do something incorrect like this? I understand its value for air consumption, but it is not correct for nitrogen uptake.

Its very close in practice.

 

[tursiops]

Its very close in practice.

A pure guess can be close, too.

 

[PfcAJ]

A pure guess can be close, too.

Except in this case, it isn’t a guess

fiddle with it using some deco software and see for yourself.

 

[NAM001]

Asking out of curiosity, but by any chance is the buddy someone who is new-ish to the GUE system? I ask because in Fundies class GUE teaches you to pre-plan and then dive with the computer in gauge mode. They teach that because, as others have already mentioned, they want to wean you off the idea of "flying the NDL"--letting the ever-changing number on the screen dictate when you turn your dive. The strict use of gauge mode is more of a training tool than anything else. From what I have seen, there are some really experienced GUE-trained divers who keep their minds open to their computers' full capabilities--they just don't let the numbers on the screen override what they have already planned. Rather, the computer backs up or complements what they planned.

Planning shouldn't be onerous. A computer's planning mode can be used to pre-plan a dive. In advance of the dive, you should have at least a rough idea what you would like to see and the route to get there and back--it's not a great idea to go willy-nilly from one place to another and another on a whim, especially if these are cavern dives you're talking about. You should have at least a rough idea how deep the route and destination are. Based on the depth, you can go into your computer's planning mode and see how many minutes you can spend at that depth, or the average depth if you prefer. If you know that time limit in advance and plan to adhere to it rather than "fly the displayed NDL," there really isn't much point to restricting your computer to gauge mode on the dive.

The only reason to not use teh puter that I can see is in a deco asccent where say ratio deco is used instead of teh puter and you end up locking up the puter for a missed stop. Again that is deco diving and not the rec environment.

 

[seeker242]

What is the better approach? Trusting the computer or doing pre-dive planning?

Plenty of GUE divers use the NDL on the computer, but they don't, or they're not trained, to rely on it exclusively. Every dive is planned as well as it can be regardless.