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

[lowviz]

Yes.

 

[BRT]

Yes.

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.

Talking about this

 

[MargaritaMike]

Many wouldn’t consider the descent.

I'm confused. Doesn't bottom start when you leave the surface? I have always started then which may have added some conservatism to my dives... I DUNNO.

1) Diving deeper than my tank
2) Staying at planned depth longer than the 120 rule
3) Starting my ascent (following the buddy system) with less than Depth in ft x 10 + 300 psi

These are good rules of Thumb. But doesn't everyone know that George Thumb (the inventor of Rules of Thumb) is a total pessimist, thus his Rules of Thumb may not fit everyone, if anyone. Seriously, having never heard of the deeper than my tank rule or the ascent rule, I haven't considered them before. #1: Not so sure of. #2: Not a bad "plan" #3: Has some merit.

This thread would be better served in Advanced. [/OPINION]

I agree. A lot of somewhat, if not very, advanced theories, facts, and opinions have been expressed in this thread.

Cheers -

 

[lowviz]

Talking about this

Now you weren't. That is just a weenie pullback.

Defend your post in basics as to how you stated that you dive.

 

[BRT]

Wow! You escalate fast. I was simply saying that if you leave the bottom with a reasonable amount of air it cuts into the apparent bottom time available with an AL80. I am not a particulariy conservative diver but I don't like to be at 100' with less than 700# in an AL80. That makes it hard for someone without great breathing to get bent on the first dive with an AL80 at 100'.

 

[rossh]

• A sequence of consecutive dive days with multiple-dives-per-day further loading those intermediate/slow tissues with residual inert gas;

That's not correct. This multi-day tissue residual gas stress accumulation, is simply not significant or even noticeable. It's grossly over hyped. Some simple checking with math reveals little or no valid difference pressures across several days. Take a look.

First one below is an NDL dive on nitrox32, 3 dives a day, at the NDL limit. Shown (left) is after day 1 and (right) after day 3. No significant change surface supersaturation values at all.

This one below is a CCR diver, on a 2 a day deco dives at 60m for 40 mins, for 4 days in a row. There is even less difference here.

Now experience shows there clearly is some lingering side effects of multi-day exposures, and a rest or extra care is always needed.

But it does not involve a build up of excess tissue stress. I think the real cause of multi-day injury, is some other tissue stress or fatigue is at play, still yet to be explained.

.

 

[lowviz]

Wow! You escalate fast. I was simply saying that if you leave the bottom with a reasonable amount of air it cuts into the apparent bottom time available with an AL80. ...//...

Sorry, yeah sometimes I do.

But we are amongst the newbies. It is all about the buddy system. The real one, not the BS that two paired clueless divers remove the liability from the instructor.

There exists a buddy system that works.

 

[BRT]

I guess I don't understand what the possibilities of getting bent on a single AL80 has to do with the buddy system. Pretty much no newbie would be able to get bent on a single AL80.

 

[lowviz]

"BRT, post: 8222638, member: 399950"...//... Pretty much no newbie would be able to get bent on a single AL80.

Don't go there my friend, I already did.

If you keep your buddy's reserve gas safe and obey the 'rules'. Well, pretty unlikely.

However, if you bomb into it on your own with a vengeance, yeah. Not only possible, but a matter of time.

 

[Eric Sedletzky]

....for those of you that don’t believe a diver can’t get into trouble with an aluminum 80, ha ha.

I gotta tell you guys this story...
(Kids, don’t try this OK, this is really BAD to do and goes against everything safe and sane in recreational diving....

...I know a guy who was a champion freediver/spear fisherman back in the early 70’s thru the late 80’s. He scuba dives also but could really care less about it, he just uses the gear for certain hunting needs.
He told me his buddy certified him privately thru NAUI on a one day course back in 1971, and the only reason he needed to be scuba certified was to enter a certain spearfishing competition that required it.
For his reg, he scored a used MK3/108 that he got dirt cheap with one single 2nd stage (for him only) and an SPG of some sort. He also used a plain simple plastic backpack, no BC. This was pretty typical of that era.

He told me the following story a few years back which left me with my mouth agape and speechless.

Sometime in the early 90’s he went to Florida to dive for the big groupers with a group of buddies he knew there. They went way offshore somewhere to spear on a wreck IIRC.
He used a “single” aluminum 80 and proceeds to go to 200’ (only for a minute or two he told me) with his big long gun on a certain wreck or reef (still unclear). He doesn’t see any groupers and searches around. Bottom time unspecified. He told me he was so narced out of his scull with tunnel vision and all of it that all he could do was just try to maintain and not freak out, or pass out. Mind you, this is a deep air dive, no computer, no real dive plan (except to shoot something big), all he had was a watch and depth gauge and not much else, no BC, no SMB, nothing.
His noticed his reg starts to breathe a little hard at depth (MK3/108 is a completely unbalanced 1st and 2nd so expected), so he starts up. He makes it to 60’, he stops, and by this time his reg is breathing really hard, so he continues up. Somewhere between 60’ and the surface he completely runs out of air and does a ESA, basically a “blow and go”.
When he gets to the surface their boat is right there so he jumps on board. A minute later he notices his shoulder is bothering him so he looks down and noticed his entire shoulder is inflating! All the fat tissue right under the skin was beginning to tear apart and inflate with gas. He could hear it crackling and tearing he said. By the time they made it back to the harbor (a few hours away) he was in really bad shape. He couldn’t move his arm, he was sick to his stomach and all sorts of other bad stuff. Don’t know if he ever made it to a chamber, he never said.
But he ended up having five surgeries over the years on that shoulder because of that accident.
I was just speechless when he told this story...and it was almost like he was bragging about it!!!
And BTW, just to sprinkle some more salt on this story, he told me he had NEVER had that reg serviced the entire time he owned it! So 20 years?
That dive was the last time he used that reg, then he gave it to me. I restored it and sold it.

Pure genius!
WOW! ..JUST WOW!!!
Yeah, ride um cowboy.

So yeah, stuff can happen if you give a single 80 to the wrong person.
And we’re freaking out over taking one past 80’, lol!