Deco Dives With Liberal Computers

[Dr. Lecter]

yes of course i have extra gauge and a timer , and as i said we have an extra 15 l tank equipped with a regulator ready on the boat in case of free flow , we are descending according to a marked line attached to the boat and we are always returning to it , we also have an emergency parachute marker aside from the regular one in case of emergency. i don't think my computer profile is risky as long as i am respecting the precautions ( sleeping hours, alcohol ....)

Ok, sounds good, have fun!

As to your original question about whether to switch from one computer, which says its decompression calculations are for emergency use only, to another computer that says in its manual that

If you exceed certain limits, the XP 5 will not be able to tell you how to get safely back tothe surface. These situations exceed tested limits and can result in loss of some XP 5functions for 24 hours after the dive in which a Violation occurred.

and

The XP 5 enters Immediate Violation Mode when a situation totally exceeds its capacity topredict an ascent procedure. These dives represent gross excursions into decompression that are beyond the boundaries and spirit of the XP 5 design. If you are followingthese dive profiles, SEEMANN advises you not to use an XP 5 dive computer.

and advises that

Making decompression dives without the proper preparation and train-ing will place you in an unnecessarily dangerous situation. Existing data for making planned decompression dives is extremely lim-ited, and virtually non-existent for repetitive decompression diving. Decompression diving greatly increases your risk of decompression sickness. Special training, equipment, and support are necessary for divingdeeper than the maximum recommended sport diving depth limit(s).

also warns that

XP 5 cannot calculate decompression times for StopDepths much greater than 60 feet (18 meters) and offers no indication of how much dive time would result in the need for a greater Stop Depth

and finally has a deco model as described here... I have to say you should at least get a computer designed for decompression diving.

But don't worry about wearing it--just keep it on the boat with the spare tank.

 

[Diverlb00]

I am taking your advise into consideration and im answering the questions that i am being asked, should i ignore them or what ?


an extra tank on the boat will help when i blow up the emergency parachute, in case of regulator free flow or insufficient air!

 

[supergaijin]

Wow, OP the more you respond to this thread the clearer it is that you have very little idea about what you're doing down there. The bliss of ignorance.

we are spending about 30 min in between 40 - 50 m
i am usign 15 L tank compressed at 200 bar and im always ending up after the dive with minimum 60 bar left

This sounds strange. Perhaps you worded this incorrectly. If you're at 40m (5ata) and you consume a total of 2100L (140bar x 15L) in 30mins (time at depth), that means you're breathing 14L/min (SAC) which is low already.... but feasible. Once you factor in time to descend, ascend and another 30mins for deco stops between 9m and 3m.... well you've got gills mate.
Alert Diver | Estimating Your Air Consumption Calculating SAC

and we always bring with us an extra tank on the boat

A tank on the boat is about as useful as a lifejacket in the boat trailer. If you're anchored, at least hang the tank as an emergency deco tank.

guy thanks for your concerns, but what we are doing is extra safe . i know my limitation, like for example when u go deeper than 60 m the air become toxic, and i also i know and i am respecting every precaution to avoid DCS.

Air is not toxic below 60m, what you are doing is not extra safe, you don't know your limitations (this should be obvious seeing as you started this thread with such simple questions), and you are respecting nothing as far as I see about even basic deep diving procedures in order to avoid DCS.

Like I said in my first post- I don't think you'll need to worry about the long-term effects of this kind of diving.

 

[Dr. Lecter]

an extra tank on the boat will help when i blow up the emergency parachute, in case of regulator free flow or insufficient air!

I am now convinced that I am posting below the troll line. Ta-ta.

 

[Diverlb00]

Wow, OP the more you respond to this thread the clearer it is that you have very little idea about what you're doing down there. The bliss of ignorance.



This sounds strange. Perhaps you worded this incorrectly. If you're at 40m (5ata) and you consume a total of 2100L (140bar x 15L) in 30mins (time at depth), that means you're breathing 14L/min (SAC) which is low already.... but feasible. Once you factor in time to descend, ascend and another 30mins for deco stops between 9m and 3m.... well you've got gills mate.
Alert Diver | Estimating Your Air Consumption Calculating SAC

air consumption on 3m ceiling is 5 time less of what is on 40 m! i only consume about 30 Bar on deco stop, becz im relaxed to the max and neutrally buoyant.

A tank on the boat is about as useful as a lifejacket in the boat trailer. If you're anchored, at least hang the tank as an emergency deco tank.

we used to do it before, but we found that it is necessary as long as someone can handle it to use whenever we need it! ( we never had to )

Air is not toxic below 60m

Scuba Dive Medical Articles

Like I said in my first post- I don't think you'll need to worry about the long-term effects of this kind of diving.

Thanks for answering my question!

 

[DevonDiver]

How does having the extra air onboard the boat help you 130' down?

I'm assuming there is a language issue at play. I'd further assume that he means they deploy a drop-tank @6m below the boat.

That still doesn't solve many problems - none that occur at depth and none that could occur away from the boat.

...which is why it isn't recognized as any sort of valid technique for decompression diving.

But that's ok,... because the OP "doesn't have problems" on his dives. Same as all the paraplegics and corpses who pushed their diving beyond the limits...

 

[616fun]

Bottom line. A decent deco computer is going to cost about the fees of an Adv Nitrox/Deco class, and the instructor won't let you use the computer in class anyway, as you manually cut tables and execute your dive from those with a gauge and timing device.

Go take a class and learn what you do not know. Gas planning, team diving, dive planning, pre dive check procedures, emergency procedures, equipment setup, and just getting into good habits are all things you are missing by not taking a class. Once you have the class a deco computer can wait as you will have the skills to cut tables and plan you dives and dive your plan.

 

[supergaijin]

air consumption on 3m ceiling is 5 time less of what is on 40 m! i only consume about 30 Bar on deco stop, becz im relaxed to the max and neutrally buoyant.

60bar remaining on the surface. A very healthy reserve.

30bar consumed at the Deco Stop.
30bar x 15L = 450L. If you're at a 3m ceiling (1.3ata) for 30mins, this means a SAC of 11.5L/min. Normal deco requirements would require a 6m ceiling before the 3m ceiling, but let's keep it simple.

110 bar left for the dive.
Just for giggles, let's say you use 10bar going up and down, leaving you half your 15L tank gas (1500L) to play with at 5ata for 30mins. 1500L of air at 5ata for 30mins meaning you consume your gas with a SAC of 10L/min. (1500/5ata = 300L. 300L/ 30mins = 10L per minute)

So according to your numbers you're using more gas at your deco stop, "becz you're relaxed to the max and neutrally buoyant". This means you must be positively catatonic at depth. Something doesn't sound right here.

The consumption rate here (SAC of 10L/min or 0.35 cubic ft) is low but not unheard of.
If you experience a problem at depth however, this can never be maintained and you'll more than likely double if not triple this rate.

Consider your buddy running out of gas at your max depth due to equipment failure. Consider that you've got decompression obligations..... and you've got your reserve deco tank sitting on the boat. Honestly, how do you think that will help you. Even if you're at 3m underwater- the tank is still 3m above you!

Do you at least have enough O2 on the boat to get you both back to a chamber?

For your own sake please read and learn from Bob Bailey's clearly written (albeit in imperial units) article on ROCK BOTTOM gas management- it will save both your lives.

At the minimum please rethink the idea of having only a 15L tank with you.

 

[HIGHwing]

So according to your numbers...you're relaxed to the max and neutrally buoyant". This means you must be positively catatonic at depth...

This thread is headed to the Accidents and Incidents section...

 

[live_2_dive]

iv been doing this for 2 years and my buddie for the past 11 years on a daily basis, and he is not even technical dive , and we never had any kind of problems.

Well, if you've been doing it for TWO whole years then we definitely shouldn't be telling you how to dive safely. You absolutely have the experience and knowledge to dive safely. Or not.

He isn't a technical diver...oh that's good. No reason to waste money on that silly extra safety training and equipment.

Certainly if you haven't had any problems yet, you definitely won't have any problems in the future. This all sounds totally safe and on the up and up.

/sarcasm

The posts by OP are so ridiculously absurd I have a hard time believing its NOT just a troll...but OP if you are seriously doing this I would a) buy a lottery ticket, 2) have your friend buy one and d) STOP diving like this!



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