DECO the Dark site in recreational Diving

[LeadTurn_SD]

Remy:

No "safety factor" built into the US Navy dive tables. They are what I used.

If you push the right up to the limits on a current table (or dive computer), you are at risk. The limits should be safe, mostly, for most divers, most of the time, maybe. But do not assume a "safety factor" exists. It really does not.

Go past the limits even a little as far as bottom time, ascent rates (too fast or too slow), stop times; and you exponentially increase your risk of a DCS hit.

Go past the limits more than just a little bit, get sloppy, get distracted.... reference my friend in the wheelchair.

Best wishes.

 

[rivers]

The move to teaching deco diving is a money cow for the majority of agencies. In the UK BSAC have always included how to dive with decompression stops; its not rocket science.

Adding an extra 10 minutes of bottom time at:
* 35m will give you about 3 minutes of deco at 6m.
* 30m will give you about 3 minutes of deco at 6m.
* 25m will give you about 1 minutes of deco at 6m.
* 20m will give you about 1 minutes of deco at 6m.

This is based on BSAC 88 Tables; other tables will give difference numbers, but they won't be that far out.

Your need to calculate the extra gas requirements for each dive, and what bailout you want, if any.

Kind regards

I wouldn't touch the BSAC 88s with a barge pole. They are ridiculously aggressive. I just ran a profile for a 20 minute dive at 30m using air and a profile for a 30 minute dive at 30m on air. Both using a GF of 30/85. The 20 minute dive had a 4 minute stop at 6 and the 30 minute dive had a 19 minute stop at 6. I don't know anyone in the UK who would actually use any of the BSAC tables (air, nitrox, ox stop) to plan any dive.

 

[Searcaigh]

VPM-B+3 for a 30 min air dive to 30M will give you;

20 sec stop at 15M,

3 mins at 12M,

5 mins at 9M and

32 mins at 6M

Total run time of 72 mins

Switch to EAN32 and you get;

9 mins 20 sec at 6M with a total run time of 42 mins

 

[AfterDark]

I didn't choose to be certified PADI, dive tables for air go to 42m ( US Navy Standard air decompression table ) I believe Most agencies/shools use the same, you can stay 15min on BT and only need 2 min DECO stop at 5m, put 4min as extra safety, and keep an ascend rate in check, if you make good use of air you should come up with enough air, but that is IF everything is nice and smooth, if Sh... hit the fan you are in trouble.

50m dive, full square, less than 8min BT is the profile from that dive and you come up with enough air, that is the profile choosen and minimum 4 divers, not saying it will happen, it had been done many times this way, but everybody is more afraid that one get deep in to narcosis than run out of air.

Those Navy dive tables you have there, be very careful with those. I have used those for years. Those tables were created using real divers doing real dives; except those divers were in very good physical condition. Better condition than most divers, low body fat, good blood 02 /C02 exchange rates..etc. I've always fudged those stops with more time because I am not a navy diver. So a 5min stop at X becomes a 8 min stop. The next stop might require 10min @ X that becomes 15min @ X. DON'T cut those time close sooner or later you will get hit.

---------- Post added October 3rd, 2014 at 07:21 AM ----------

Check the table, remember you need to count the ascent rate, there restrictions on that more that what your time of DECO

And I'm 100% sure the Navy and other persons that have made public their DECO times have a a safety factor build in, with that said you don't want to pass what the reflected in table you use because you don't know what the safety factor is, is like the DC programs manufactures use different calculations one more conservative than others.

Every body have different perspectives as well, many of you find it unsafe and dangerus more that I see it, yes it is dangerus yes it is unsafe, but if it has been done taken in account many factors and the What IF's situations had been covered, you understand the plan, I don't see why It can't be done

But if you are afraid Stop, don't do it the mind is not set, and even if the conditions are right you make it unsafe.

The navy doesn't need safety factors. They have chambers and trained medical personnel. Do you?

 

[RJP]

Why would PADI's deep diver course, which supposedly allows successful graduates "to scuba dive with confidence at depths down to 40 metres/130 feet," be limited to 30m?

As boulderjohn mentioned above, the limit is indeed 130ft. (I was looking at the deep "adventure" dive.) In either event, a dive to 50M still violates the established standards for the course, albeit not as egregiously as I had originally thought.

 

[Edward3c]

I wouldn't touch the BSAC 88s with a barge pole. They are ridiculously aggressive. I just ran a profile for a 20 minute dive at 30m using air and a profile for a 30 minute dive at 30m on air. Both using a GF of 30/85. The 20 minute dive had a 4 minute stop at 6 and the 30 minute dive had a 19 minute stop at 6. I don't know anyone in the UK who would actually use any of the BSAC tables (air, nitrox, ox stop) to plan any dive.

Your not comparing like with like. Bottom time for the 88 is leaving the surface to reaching the first stop (for the example 6m). What is the definition for bottom time you are using? The asent rate?

 

[RJP]

My reaction to the OP can at this point be summed up as: "This can only end well." Just need some

Jajajaja, By all means, if something positive come out for somebody, all sums out at the perspective of each individual, I find very interesting, positives and informatives interventions.

sar-chasm: (n) the gulf between one poster's joke and another poster's ability to detect it

---------- Post added October 3rd, 2014 at 08:27 AM ----------

Maybe we should move this to the accident and incident forum?

 

[Remy B.]

Remy:

No "safety factor" built into the US Navy dive tables. They are what I used.

If you push the right up to the limits on a current table (or dive computer), you are at risk. The limits should be safe, mostly, for most divers, most of the time, maybe. But do not assume a "safety factor" exists. It really does not.

Go past the limits even a little as far as bottom time, ascent rates (too fast or too slow), stop times; and you exponentially increase your risk of a DCS hit.

Go past the limits more than just a little bit, get sloppy, get distracted.... reference my friend in the wheelchair.

Best wishes.

Thanks LeadTurn, something new I learned, I had the wrong assumtion there was a safety factor build in ( that is basically the standard ) I guess this was not the case of the person how made the US Navy dive tables.

That is the reason of what I post, to learn those things, thanks I appreasiate that light, I got me a DC for safety but I use the dive table for planing in case the DC go south on me, ascent rate is what I pay attention the most, and of course the required safety stops and DECO stops.

And right practice is the buddy system, if my DC go bad, you still have his to go by, that one go bad to, you have the depth gauge and your watch and review your table before dive, basically redundancy

 

[rivers]

Your not comparing like with like. Bottom time for the 88 is leaving the surface to reaching the first stop (for the example 6m). What is the definition for bottom time you are using? The asent rate?

Even if I adjust to a 15m/ minute ascent and an 18 or 28 minute bottom time to accommodate for the BSAC ascent rates and time to first stop, this is what I get:
20 min on air at 30m:
43 second stop at 12m
1 min at 9
2 min at 6

30 mins on air at 30m
56 seconds at 15
1 min at 12
1 min at 9
13 mins at 6.

Edward, the BSAC 88s are extremely aggressive, no two ways about it. There is a reason they are known throughout the UK as the Bendy 88s

Even if I use a GF of 100/100, I still get 6:20 at 6 for the 30 minute dive and 20 seconds at 6 for the 20 minute dive.
Using VPM with a conservatism of 0, I still get 3:20 at 6 for the 20 minute dive and 3 minutes at 9 and 17 at 6 for the 30 minute dive.

 

[Lorenzoid]

. . .
That is the reason of what I post, to learn those things, thanks I appreasiate that light, I got me a DC for safety but I use the dive table for planing in case the DC go south on me, ascent rate is what I pay attention the most, and of course the required safety stops and DECO stops.
. . .

Seriously, deco diving is something to be learned from a competent instructor, not from posts on SB. SB is a great resource for supplementing what one learns in a course, but I hope you're not relying on what you read here as though it were actual training. I sure wouldn't.