Place of dive tables in modern diving (Split from the basic thread)

[Kevrumbo]

But, MOST DIVERS DON'T... That's the whole point of understanding the NDL and gas/time/depth....

Jim...

Citation needed.

Here's an interesting article and anecdotal case treated at the Catalina Hyperbaric Chamber:
What Happens When You Get an "Unexplained" DCS Hit?

". . .and most important, both of my computers — different models — showed no decompression obligation for either dive and cleared me. . ."

 

[boulderjohn]

I have on several occasions descended to 100 feet to look at something specific, ascended to shallower depths for the rest of the dive, and ended up with dive times in the 60-80 minute range--all within the NDL of the computer.

 

[The Chairman]

Here's an interesting article and anecdotal case treated at the Catalina Hyperbaric Chamber:

He obviously doesn't understand what happened to him but he seems to understand DCS. The citation I was asking for was that "Most don't" comment in regards to divers understanding the relationship between depth and time.

Back to the article. In a conversation with a DAN presenter in the Keys a dozen or so years ago, it became apparent to me that while getting bent is "noise" how you get bent isn't. If you suffer Type 1 DCS (muscular) then there's a %95 chance you're a commercial diver. If you suffer Type 2 DCS (neural) then there's a %95 chance that you're a recreational diver. DAN no longer makes this distinction, but when they did this was what they found. The best guess is that neural fluids have the same half-time as blood, which is about 5 minutes. That means that after only 25 minutes at depth, your neural fluid is essentially saturated with N2. Consequently, I ascend slower from half my depth (or from 40ft) and do a full 5+ minute safety stop and teach this to my students, no matter what class they take from me. On the surface, I again take my time before I board the boat. Five minutes there is ideal, but often the crew gets agitated. In any event, I usually get close to three minutes before I have to begin the climb. That has effectively eliminated the after-dive fog or sleepiness for me (subclinical DCS?) and I wonder how many unexplained hits could be avoided by doing this? If I get close to my NDL, the time I spend at my safety stop increases. If I'm tired or feel puny, I increase my time at my safety stop. If the boat ladder looks crowded, I increase my time at my safety stop. It's not unusual for me to have a ten-minute safety stop. I try to be the last one on the boat for just this reason. This is doubly true when I'm shore or cave diving. Everyone is quick to get out while I'm just chillaxing in that beautiful water.

 

[Eric Sedletzky]

One doesn't outsmart tables. (you know that) You either choose to follow them or just make stuff up.

Tables, if dived precisely, are very aggressive. But if you play by the rules in real life diving, they rapidly become very conservative as you don't get any credit for downtime spent above your deepest depth. The entire dive is one depth, period. Knowing tables makes this obvious. Worthless knowledge to some, useful for me.

Approximations are fun too. The 120 rule breaks right at the depth you picked. At 110' feet, it is massively conservative and you can't even go to 120' using that rule.

80 cuft tanks are the salvation of clueless divers. You just don't have enough gas to seriously bend yourself on a single dive unless you have a medical condition such as a PFO.

Oh no, I’m sure there are people out there that could bend themselves with an 80 no problem.

 

[tursiops]

80 cuft tanks are the salvation of clueless divers. You just don't have enough gas to seriously bend yourself on a single dive unless you have a medical condition such as a PFO.

This is a really dangerous myth, especially in the Basic Scuba section. Anybody except an air hog can easily stay too long at (say) 100 ft, then can easily come up too quickly. Work it out: 100 ft is 4 ATM, so a SAC of 0.7 cuft/min (not a great SAC, by the way) means 2.8 cu ft/min at 100 ft. So NDL is 20 mins on Navy tables, 12-16 on other tables, PDCs give 9-16 depending on brand and setting. But 2.8 goes into 77 (not 80) 27.5 times, so even if you spend a couple of minutes getting down, and don't even go too fast on the ascent, you can STILL have more gas than NDL. By a lot, depending on what table/computer you are using.

 

[lowviz]

OK, let me rephrase that. TOTALLY clueless divers could. An 80 isn't supposed to be seen below 80'.

 

[oldschoolto]

Pete... You saying that you... MAKE up your own safety stop times and your own way of off gassing without any specific table or computer model ?

Just playing around with you... I really think 98% of us are on the same page. It's very hard to "talk" sometimes on a thread like this.. Now if we where in Bonaire with a beer and shots of rum, We would be great..

Jim..

 

[oldschoolto]

OK, let me rephrase that. TOTALLY clueless divers could. An 80 isn't supposed to be seen below 80'.

I plead the 5th....

Jim...

 

[dmaziuk]

OK, let me rephrase that. TOTALLY clueless divers could. An 80 isn't supposed to be seen below 80'.

Oh, so that's why it's so hard to stay in horizontal trim: all that air in my head where clue is supposed to be! Whodathunk.

 

[tursiops]

An 80 isn't supposed to be seen below 80'.

Sorry, not familiar with this rule. Where does this come from?