91 replies to this topic

[PerroneFord]

What is the big deal about NDL? It's an arbitrary line in the sand. Best thing I ever did for my diving was to take that line in the sand and kick dirt in it's face.

[DandyDon]

What is the big deal about NDL? It's an arbitrary line in the sand. Best thing I ever did for my diving was to take that line in the sand and kick dirt in it's face.

Most of us dive the ocean, Perrone - with skippers who enforce safety standards. Violate your computer and your grounded for a day. Doesn't matter which brand, they have to keep it simple.

[PerroneFord]

the ocean, Perrone - with skippers who enforce safety standards. Violate your computer and your grounded for a day. Doesn't matter which brand, they have to keep it simple.

Whoa, just a sec. First, lets not assume that exceeding NDL is "unsafe". Many of us do it nearly every dive. Second, do they mandate you dive with a computer at all? And third, suppose your computer doesn't offer NDLs like some we dive with. Any skipper who was looking at my computer for NDLs would be sorely dissapointed. I've also been known to dive with a depth guage and a stop watch. And sometimes JUST the watch if I know the depths well.

[pir8]

the ocean, Perrone - with skippers who enforce safety standards. Violate your computer and your grounded for a day. Doesn't matter which brand, they have to keep it simple.

Whoa, just a sec. First, lets not assume that exceeding NDL is "unsafe". Many of us do it nearly every dive. Second, do they mandate you dive with a computer at all? And third, suppose your computer doesn't offer NDLs like some we dive with. Any skipper who was looking at my computer for NDLs would be sorely dissapointed. I've also been known to dive with a depth guage and a stop watch. And sometimes JUST the watch if I know the depths well.

I could be wrong, but I don't think many of us here subscribe to the DIR concept of no computers

[PerroneFord]

I wasn't a big fan of computers before I was DIR. And even though I am "mostly" DIR these days, I still often dive with computers. Depends on the dive I am doing. DIR divers usually dive with computers, they just don't use them for NDL information and turn those functions off.

But regardless, let's not make this an issue about DIR.

My concern in the matter is that the concept of NDL is hugely flexible and not a rigid fixed point. I would be doing REAL deco on some of the dives that most recreational computers say are well within NDL limits, and I would absolutely ignore some of the NDL information on some computers based on my dive profiles.

To wit, I did 2 dives last Sunday. One was a 30 minute dive with a max depth of 98ft. Did a 15 minute surface interval, then did a 40 minute dive to a max depth of 90ft. Upon reaching 60ft after the second dive, my dive computer said I needed almost 30 minutes of deco. Utterly ridiculous, but I know why it wanted it and I knew it was perfectly safe to ignore it. I did a safety stop, got out of the water, and went and had a nice lunch with my dive buddies.

People, like captains, who want to jump your case for violating NDL are not people I want to deal with. They are often clueless as to what is safe, and what is not. So to the original poster, take Nitrox, learn it's advantages, and work within it's constraints. You'll be the better for it.

I could be wrong, but I don't think many of us here subscribe to the DIR concept of no computers

[NJBerserker]

I'd also have to agree that you should take the course if it interests you. It opens up many doors in many aspects of diving. I don't know what your interests or aspirations are, but I'm sure you could find a benefit nitrox can bring to the table for you.

Perrone, I've got your back on the whole NDL thing. I cannot wait until I have the experience required to kick some dirt in its face myself. With all of the training currently available it is widely accepted among the diving community that the world doesn't end when the NDL reads 0:00. I would also like to say that I agree with the Tech mindset of working out all of your bottom times etc. with tables and math. Even with a computer one should still work it all out. It may just be that I live in an area that stresses militant self reliance and redundancy when it comes to diving, yet i find it truly amazing that people would put their LIFE in the hands of something that can malfunction. Computers fail, plain and simple. One must be ready.

I do not agree though, with your violation of your computer. Not that you did anything unsafe, it just defeats the point of having it. With a lot of the conservative algorithms out there it is common for people to violate their computers in such a way. I can't say from experience, but I've been lead to believe many divers do this regularly with no problems. This is why I feel one of the best pieces of advice I ever got from another diver is to put your computer on the liberal side of the coin if you can change this. It is built to not bend you. I'm not saying make it as liberal as it will go, but it can help you avoid a violation if for instance you're running low on gas and may not be able to make that longer hang without draining your tank. Just my .02. Thanks for reading.

[PerroneFord]

I do not agree though, with your violation of your computer.

Sounds like a good safe attitude you have there. If you get into deco training, you'll begin to understand why bending a recreational computer is sometimes the most safe way to dive. And you'll learn that recreational computers and what they tell you to do, are inherently unsafe if you are going to be doing planned deco.

Not that you did anything unsafe, it just defeats the point of having it.

Depends on what you think my point of having it is. Frankly, I use a computer do do three tasks.

1. Tell me my depth
2. Tell me my runtime
3. Store a graph of my dive for later downloading and scrutiny. Whether it bends or not is essentially immaterial to me. It does make a heck of a racket with all that beeping though.

I can't say from experience, but I've been lead to believe many divers do this regularly with no problems.

The question is, do they plan on bending it, and do they understand how to do it safely. If people are actually relying on the computer's data, and violating what it tells them, that that is foolhardy and dangerous. I generally leave my computer in my pocket on cave dives. I actually forget the thing half the time until I exit the cave and get back to daylight and am interested in what it's saying.

but it can help you avoid a violation if for instance you're running low on gas and may not be able to make that longer hang without draining your tank.

If you're running low on gas on a deco dive, you messed up BIG TIME somewhere. In fact, if nothing goes wrong on a deco dive, you should have enough gas to turn around and do the dive again without another fill (if we take safety margins out of the equation). With most of my dives now, I am surfacing with about half of my 80cuft stage (plus 200psi) and 1/3 of my doubles. I could generally do the dive again and still have a safety margin.

Edited by PerroneFord, 11 January 2008 - 06:34 PM.

[NJBerserker]

All good points. For clarification. Yes, my friends and instructors have told me stories of people who routinely plan to violate their computer and just lower it over the side during the surface interval to clear the error while they eat lunch and swap tanks. I have never seen it, but it sounds believable. As for the running out of gas thing, that was just an example to make my point. However I don't feel it is a stretch that an inexperienced diver on a non deco recreational dive could get themselves into a similar situation. After your explanation I definitely can appreciate why you bend the computer. Just having the downloadable graph available makes sense.

[ScubaDrew]

I agree, violating the NDL is not dangerous. Like many other aspects in diving it CAN be, but it is not automatically so. It is a no decompression limit, not a break this and die limit. Lots of divers violate conservative computers and may not actually violate the real NDL for them on that day, like the example Perrone offers us. And of course lots of divers violate NDL for serious and decompress. And before nitrox and helium they did it on air alone and survived.

I can see dive ops having a no deco policy if they don't want to sit on a site for the extra time those dives require and most others are NDL profiles. However unless you have to hang for 20 minutes or more longer than everyone else I see no reason to force that diver to sit out any dives if the SI says that they can get back in. Hell, for that matter you can violate your computer, hang, and still be out of the water before some other divers on the boat who don't trigger their computers.

If you are a repeat offender and are always inconvieniencing others than I can see banning that diver, but saying that if you hit the NDL you HAVE to sit out 24 hours is a little extreme if you have the experience and training to dive that way. If you are a new OW diver, well, thats a different can of worms.

[scubafanatic]

the ocean, Perrone - with skippers who enforce safety standards. Violate your computer and your grounded for a day. Doesn't matter which brand, they have to keep it simple.

Whoa, just a sec. First, lets not assume that exceeding NDL is "unsafe". Many of us do it nearly every dive. Second, do they mandate you dive with a computer at all? And third, suppose your computer doesn't offer NDLs like some we dive with. Any skipper who was looking at my computer for NDLs would be sorely dissapointed. I've also been known to dive with a depth guage and a stop watch. And sometimes JUST the watch if I know the depths well.

Hi Perrone, ......sometimes I think you need to get out more.... " do they mandate you dive with a computer at all? " ...um, not just 'yes'..but "H*LL YES !!!' ....someday we're gonna have to get you on an SD trip and dive as us mere mortals do.......the only two saltwater trips I've been on where computers weren't an issue was Bonaire/shore diving (where nobody could care less when/where/how you dive) and the Sea Of Cortez "DON JOSE" liveaboard, where all the divers used computers, but I don't remember it being a requirement, nor do I remember anyone EVER looking at our computers......in Cozumel, computers are required, but nobody has ever checked my computer there either. Sometimes on liveaboards the DM/crew will watch you at first, maybe even check your computer the first couple of dives, and if they see you're an accomplished diver, going forward they will leave you alone (don't ask, don't tell, as it were ) ...however, other liveaboards check your computer every dive, no matter what....and I'll admit the 'anal probes' do get tiresome....however, you are forced to accept these conditions because either it's a place you want to dive, and you are at their mercy......or you go on a dive trip and have no idea about the exact 'computer checking' requirement until you're on location and it's too late to do anything about it.

Karl

[DandyDon]

in Cozumel, computers are required

Huh? Nah, I don't think so.

[scubafanatic]

in Cozumel, computers are required

Huh? Nah, I don't think so.

Hi Don,
...I've dove with 3 different operators in Cozumel...ALL required computers...some even provide FREE computers to divers lacking them.......but perhaps it's because I 'do' 6-packs' with the upper tier of operators catering to advanced divers and diving the advanced (deep/high current/overhead) sites........maybe it's the cattle-boats hitting the 'kiddie' sites that don't really care about computers...ie 60 ft. for 30 min and then send the group up.

Karl

[diverdeb]

[quote name='PerroneFord' date='Jan 11 2008, 06:33 PM' post='204950']
[/quote]


The question is, do they plan on bending it, and do they understand how to do it safely. If people are actually relying on the computer's data, and violating what it tells them, that that is foolhardy and dangerous. I generally leave my computer in my pocket on cave dives. I actually forget the thing half the time until I exit the cave and get back to daylight and am interested in what it's saying.


[quote name='NJBerserker' post='204947' date='Jan 11 2008, 07:07 PM']
but it can help you avoid a violation if for instance you're running low on gas and may not be able to make that longer hang without draining your tank.
[/quote]

If you're running low on gas on a deco dive, you messed up BIG TIME somewhere. In fact, if nothing goes wrong on a deco dive, you should have enough gas to turn around and do the dive again without another fill (if we take safety margins out of the equation). With most of my dives now, I am surfacing with about half of my 80cuft stage (plus 200psi) and 1/3 of my doubles. I could generally do the dive again and still have a safety margin.
[/quote]

Perrone,

What you're not taking into consideration here is that in the grand scheme of things, the percentage of divers that are trained in decompression diving is very small (and please don't tell me that all dives are deco dives, you know what I mean). Personally, I think it's a little dangerous to be making general posts that it is not only "OK" to break no decompression limits, but to sound like it is something you are encouraging, especially without emphasizing the extensive training that is required to do so.

I am trained in technical diving (and just started my cave training ) and I love it, but most people are not and most people either don't want to take that risk or don't want to invest the time and/or money in the training required.

And back to the original post, Nitrox is great if it is used properly, but it not the gas of choice so you can dive deeper - it actually limits your depth, which you will learn in your class. In my opinion, it is worth the investment and will provide you with more options in your diving.

[PerroneFord]

Hi Perrone, ......sometimes I think you need to get out more.... " do they mandate you dive with a computer at all? " ...um, not just 'yes'..but "H*LL YES !!!'

Get "out more" eh? I did nearly 100 dives in 2007. I don't think I can get out much more than that!

however, you are forced to accept these conditions because either it's a place you want to dive, and you are at their mercy......

Do you think this sounds like something I would enjoy? Especially spending $1k-$2k for?

[PerroneFord]

Perrone,


What you're not taking into consideration here is that in the grand scheme of things, the percentage of divers that are trained in decompression diving is very small (and please don't tell me that all dives are deco dives, you know what I mean). Personally, I think it's a little dangerous to be making general posts that it is not only "OK" to break no decompression limits, but to sound like it is something you are encouraging, especially without emphasizing the extensive training that is required to do so.

Of course I am taking it into consideration. And I am most certainly NOT encouraging people to break NDL. I am merely encouraging people to examine what NDL actually is. And frankly NDL does not always align what the "computer" says. There is nothing wrong with strictly recreational divers actually THINKING about their dives. And to be quite honest, if we throw some basic gas management into the mix, a single tank, recreational diver would never approach either real or computer based NDL.

I am trained in technical diving (and just started my cave training ) and I love it, but most people are not and most people either don't want to take that risk or don't want to invest the time and/or money in the training required.

Congrats on starting your cave training. However, I tend to consider my technical diving as FAR less risky than liveaboard diving. You have technical training, so I'll leave the why's out of this discussion. Not wanting to invest the time or money in that type of training is perfectly understandable. Believe me, I wish I didn't have to either!

And back to the original post, Nitrox is great if it is used properly, but it not the gas of choice so you can dive deeper - it actually limits your depth, which you will learn in your class. In my opinion, it is worth the investment and will provide you with more options in your diving.

And I completely agree with these comments for the original poster. Take the class and learn.