Thinking about getting advanced/nitrox...

[stuartv]

In thirty or more posts on this topic in multiple threads you have never once recognized that diving right up to the NDL on any computer and especially on an aggressive one is riskier and much more likely to put you in the chamber (or worse).

Perhaps you didn't read (or comprehend) where, in the very post you quoted, I said:

In terms of allowed bottom time, of course.

I have an expectation that any diver with an OW certification understands that the longer you stay down, the higher the risk of DCS. At least, any diver who is reading/posting in the Advanced Scuba Discussions forum. Perhaps you are one of the Scubanati who acts on the basis that all other divers - or at least the ones with a lower number than yours set in their SB profile - are stupid and/or ignorant?

You can get all high and mighty about the dangers of using a liberal computer, if you want. But, at the end of the day, whether you pick a conservative computer, crank the Conservatism Factor up, and always start your ascent with at least 5 minutes of NDL left, or whether you pick a liberal computer and dive it to the limits, you are still making an arbitrary decision based on some "feeling" you have about what is "safe" and what isn't. We all know that staying under for less time reduces your chance of DCS, but when you make your choice about your conservative computer and how you use it, you don't have any idea whether you are reducing your chance of DCS by 50% or by 0.000001%.

You're making an arbitrary choice without any hard data to back it up. Then you're somehow transferring your anxiety about your decision onto me and my statements about computers. I am posting facts. Hard data. This place did a lab study and the results are here. In this particular case study, these data points were collected. Etc.. People can then make their own decisions about the significance of the data and how to incorporate it into their diving. I'm not telling anyone what computer to buy. I'm not telling anyone they should buy a liberal or conservative computer. I made the observation that a previous post was simply wrong - as in, refuted by data that I posted. Someone said that the computer (or algorithm - I don't remember exactly now) doesn't make any real difference in recreational diving. The available data indicates that that statement is wrong. That's all I said. I posted links to data to support my statement.

If you or anyone else disagrees, please feel free to post some citations of data that supports your position.

Please stop arguing with me just for the sake of hearing your keyboard click. And please stop putting words in my mouth and/or twisting what I said into some other statement that you can then enjoy yourself arguing against. The computer/algorithm CAN make a difference in recreational diving. At least, if your SAC is good enough. If you disagree, please cite some real evidence (not your useless personal anecdotes). Or save us all some reading and just say "I disagree, but I can cite no scientific evidence to support my disagreement."

 

[dmaziuk]

The garbage is the assumption you are making that somehow the aggressive computer is just as "safe" as the conservative one.

The garbage is also underlying assumption that when the computer shows 2 minutes NDL, YOUR GONNA DIE! What it really tells you is if you stay at this depth for more than 2 minutes, you will need to make a mandatory decompression stop on the way up. As opposed to optional safety stop. (But don't tell scuba police I said that.)

 

[Doby45]

The garbage is also underlying assumption that when the computer shows 2 minutes NDL, YOUR GONNA DIE! What it really tells you is if you stay at this depth for more than 2 minutes, you will need to make a mandatory decompression stop on the way up. As opposed to optional safety stop. (But don't tell scuba police I said that.)

 

[rjack321]

The garbage is also underlying assumption that when the computer shows 2 minutes NDL, YOUR GONNA DIE! What it really tells you is if you stay at this depth for more than 2 minutes, you will need to make a mandatory decompression stop on the way up. As opposed to optional safety stop. (But don't tell scuba police I said that.)

Also that any one of those computers is the benchmark, since no recreational computer is validated against anything. Most don't even match the underlying model exactly because they have various proprietary bits of code in them or conservatism settings that don't exist in the parent model.
Although Carl Huggins did make some mid 2000s era efforts to compare computers with profiles of known risk.
https://dornsife.usc.edu/assets/sites/222/docs/computer-tests.pdf
Its not exactly confidence inspiring.

 

[dmaziuk]

Also that any one of those computers is the benchmark, since no recreational computer is validated against anything.

Yup. I already wrote this in the other thread: spend an hour with a poplar dive planner, run those profiles through VPM-B and ZH-L16C with a few common GF settings and print those numbers as a baseline. At lest they'd get some semblance of legitimate methodology that way, with very little effort.

 

[urbaneve71]

HEY HIJACKERS -- TAKE YOUR CRAPPY FIGHT SOMEWHERE ELSE -- THIS HAS NOTHING TO DO WITH THE ORIGINAL THREAD -- LOL

when i started out -- i rented gear to find what fit me whether i liked a full chest inflate or a back inflate, a slime line reg, or full reg -- things like that... i think alot of these experienced divers are throwing alot at you. find what suits you. you may end up finding what fits you dry does not fit you well wet.

my very first bcd fit great dry and wet - but - my tank rode up and always banged me in the back of the head -- drove me nuts -- i had no choice but to upgrade my bcd. money NOT well spent. and the thing was, i had no problems what so ever with the bcd itself, it was the fact that it was single strap and not a double strap around the tank. see things like that ... things i would have never know until i got in the water and tried it. now had i rented gear first, i would have learned my lesson and not been 500.00.

talk to other people as you are doing here. go to other dive shops and talk to them about their gear. i say you would want your first set of gear to be with you at least 5+ years if not longer. computer wise, they are always coming out with better and better setups, you may want to upgrade in a few years, that is why i didnt go air integrated.

I do agree that those packages the LDS is offering is not good.... my little dive computer a mares puck pro was 149.00 but i got that as a steal of a deal - they run about 240.00 and every bit worth it and it dives air or nitrox. i prefer mares, but that is my opinion i was a dacor fan back in the day...

this is like a measure twice and cut once situation -- i would hold off buying before you did more research

 

[Rred]

hate to tell you, eve, but you were doing something wrong. My first BC, with over 30 years use on it, has just a single tap strap, as they ALL did at that time. And my tank never banged my head. If you have the tank positioned properly, and your regulator first stage attached properly, it doesn't bang your head, even upside down.

Now, it might also help that my BC has real shoulder straps that attach to the "backplate" (which is not what they were called then) so between the shoulder and waist straps, the tank is locked in position and the NC is left to float a bit around that. My second BC, with no shoulder straps, relies on the BC itself for shoulder support and THAT moves around way more.

With either one, a crotch strap also ensure the tank and BC can't ride up on you. People hate crotch straps, but you ask the USCG SAR guys about it some time. When you get in trouble and need the BC to keep your head above the surface? The crotch strap can save your life, because it keeps the buoyancy secured down low, where it counts.

One tank strap? I've got a big, tall, heavy tank, and it stays in place just fine that way. Two straps are nice, but another something totally unnecessary that the dive industry has foisted off in the need to make BC's into $600 purchases.

 

[urbaneve71]

thats a fine possibility -- however, it did.. im not sure what to say. i even took back to the shop, no one could figure out why it did that. we would set the tank lower, but by mid dive, the tank would be touching the bottom part of the back of my head. it was the strangest thing. lucky me i guess.

may i ask how tall you are@Rred?

and you are right on the button with that statement -- hate crotch straps (some women may find them fun, but im good without)

now my new BCD has 2 and I no longer have that issue at all -- I have also discovered that I can just as easily use a 63cu as an 80cu. I tend to conserve an extreme amount of air. (almost 3xs as much as the average diver) - wish i had discovered that before, i could have switched to a smaller tank...sigh the what ifs of life.

 

[scubadada]

...hate crotch straps (some women may find them fun, but im good without)

...I have also discovered that I can just as easily use a 63cu as an 80cu. I tend to conserve an extreme amount of air. (almost 3xs as much as the average diver)...

Fun?

Really, what's your SAC?

 

[Rred]

Height, sure, that could be part of the issue. I'm 5'11 and proportioned just like all the other runway models. (Not.(G)

Although, one of my dive buddies with identical gear was only 5'2" (I suspect a little less) and also had no problem.

Not to worry, I'm sure the folks at PADI will discover the huge marketing potentials for a "tank and regulator headrest" in your choice of exotic patterns and colors. Kinda like those fancy "mask strap pads" everyone keeps trying to sell me these days. (Thanks, no thanks, my head isn't quite THAT delicate.)

If you think a 63 Alu is nice, check out a HP 85 steel tank. Only about 20" long, and since it never goes buoyant when empty, you can skip carrying the extra lead an Alu tank requires. Damn sweet tanks! Alu is cheap, sure. For a 30-year investment...not such a priority.