how deep max. when diving solo?

[Kevrumbo]

[

I looked at post #92 and I don't understand why you would imagine you need to do 1 minute stops all the way up from 100ft (30m). GUE's min deco calls for ascent to 1/2 max depth and then 1 minute stops. For non GUE/UTD folk the usual conservative plan is 1 minute at depth to solve problems, ascent at 30'/min, 3 minute safety stop. To make it simple you need three areas of calculation: 1.Time at depth. 2. Travel time. 3. Time at stops.
That looks like this with an assumed SAC of 1cuft:



1 minute at depth: 1X4atm = (4)

100ft divided by a 30ft/minute ascent rate = 3.3 minutes travel time at an average depth of 50' [2.5atm]. 3.3 X 2.5 = (9) [8.25 rounded up]

3 minute safety stop at 15' [1.5atm] = (5) [4.5 rounded up]

4 + 9 + 5 = 18cuft.




Another way to look at it is:

1 minute at depth: 1X4atm = (4)

3 minutes safety stop at 15' [1.5 atm] = (5) [4.5 rounded up]

travel is calculated at the highest atm value/minute

1 minute at 2 atm [travel between 0-33'] = (2)
1 minute at 3 atm [travel between 33-66'] = (3)
1 minute at 4 atm [travel between 66-99'] = (4)


4 + 5 + 2 + 3 + 4 = 18cuft.

* edited for corrected atm's and rounding up

Those are fine gas plans too . . .again you can make the arbitrary parameters (ascent rates, safety stops, breathing gas margin etc) as conservative as post #92, or as your calculations above. The point is to do the calculations, and find the proper amount of gas needed to fit your preferred ascent rate profile and emergency/contingency breathing rate at depth & on ascent, for yourself as a Solo Diver or as part of a buddy team.

When I dive OW Solo, I use conventional double manifolded Backmount AL80's or Z-system Sidemount double AL80's: having the peace of mind with more than enough breathing gas for me diving Solo is more important than the inconvenience & extra burden of carrying a larger redundant back-up gas supply.

 

[DaleC]

I edited my prior calculations because I calculated atm's at 30 instead of 33' and to round up. The values remain basically the same.

We were taught in Fundies to learn the calculations so we understood the theory behind the values and then we created a quick reference guide for varying depths. Then using tank factors we could quickly calculate psi values for various tanks to use as reserve. That was a very useful part of the course for me.

I'm not really a fan of the 30'/minute - min deco concept, though I understand it. I would rather move shallow faster and do a longer SS there knowing I was within cesa range, than to ascend slowly having already experienced one failure. Seeing as I am solo I do not have a redundant redundant airsource.

 

[dumpsterDiver]

That's funny. GUE's take is 40cuft for two people from 100'. This includes min deco and rounding up. Divided in half that's 20cuft. Is UTD doing something more conservative than that.

Since we are way off from the original discussion of: how deep solo??

A video I made of ascending from 60 with a 13 cu-ft pony - It seems to show there is plenty of air for an ascent (from 60).


[video=youtube;r-L9extLDZQ]https://www.youtube.com/watch?v=r-L9extLDZQ[/video]

 

[jnowak100]

Dive to the limits of your personal experience, training, gear, site, environment, and comfort level, but dont push them. solo should be easy and comfortable dives, if you are really pushing your limits or beyond a buddy is advised.
so,
0 = keep the dive plan simple for each dive
1 = you are alone, starting and ending the dive alone you rely on your own skills and gear
1 1/2 = gas management, adequate and ample gas reserves for the dive
2 = redundant gas and all life support gear,
3 = respect the general rules and your own standards dont cut corners
4 = respect the limits and risks of depth, time, site conditions
high 5 = have fun

 

[Kevrumbo]

Here's an interesting claim:

Just my 2 cents. First, if you don't lose your head 6cf will get you up from 130 feet. Let's do the math. 130 to 70 - one minute at 60 feet/minute. 70 to 40 - another minute at 30 feet/minute. 40 to safety stop depth, another minute. If you are sucking down air - even at 2 cf/min - you will be fine. Sans panic, at a SAC of 1.0 (conservative) you will still have time for a short safety stop.

I (very recently) downsized from a 13cf to a 6cf for just that reason. It's a last resort, get me up safely resort. Too many over complicate the issue. Too many think you need more air than just to surface. Nonsense. If your equipment is well cared for a pony is very good insurance. However, you don't need to carry vastly more than you need.

As an aside, if you want a 13 cf pony i have one that just had hydro & vis and set up with sling. PM me if interested.

This diver should think again --keep the 13cf bottle and go no deeper than 30m/100'. . .

 

[MXGratefulDiver]

I agree with Kevin. Do that math again. If your SAC rate is 1.0 cf/min (not uncommon for a diver experiencing the stress of an OOA), you'll suck down about 4 CF that first minute going from 130 to 70 (average depth 100 feet/4 ATA). You'll run out of air before you reach 40 feet and have to bolt to the surface from there.

One thing you forgot to remember is that your consumption increases proportional to depth, and your SAC is calculated at surface pressure (1 ATA). At 1.0 cf/min you'll need roughly 8.5 cf to make a direct ascent (skipping the safety stop, which isn't recommended from a 130-foot ascent).

Suggest you re-think your bail-out strategy, and follow Kevin's advice about keeping the 13 CF bottle. For that matter, if you're basing your bail-out on running OOA at 130 feet, suggest you re-think your whole dive profile, and put more effort into your dive plan before deciding to go that deep ... this might be helpful ... NWGratefulDiver.com

... Bob (Grateful Diver)

 

[tursiops]

It is certainly possible to get to the surface from 130 ft b on a 6 cut bottle. The average depth is 65 ft so the average Ata is 3. If you go at 60 fpm it will take 130 s. So that means an average air consumption rate of 6/130 >> 2.8 cuft/min, thus a SAC of 2.8/3 = 0.9. Of course, you can't get access to the entire 6 cuft because of the way regulators work, and you shouldn't go 60 fpm for the last half of the trip, and a safety stop would be nice, and you better not be stressed. So, it can certainly be done, but it is certainly not a good idea.

 

[Tigerman]

It is certainly possible to get to the surface from 130 ft b on a 6 cut bottle. The average depth is 65 ft so the average Ata is 3. If you go at 60 fpm it will take 130 s. So that means an average air consumption rate of 6/130 >> 2.8 cuft/min, thus a SAC of 2.8/3 = 0.9. Of course, you can't get access to the entire 6 cuft because of the way regulators work, and you shouldn't go 60 fpm for the last half of the trip, and a safety stop would be nice, and you better not be stressed. So, it can certainly be done, but it is certainly not a good idea.

Hey, if were going up at a fast rate and skipping the safety stop anyways, you don't really need gas the last 60 ft anyways, as you can just CESA it... (Yeah, still not my favourite plan)

 

[Kevrumbo]

It is certainly possible to get to the surface from 130 ft b on a 6 cut bottle. The average depth is 65 ft so the average Ata is 3. If you go at 60 fpm it will take 130 s. So that means an average air consumption rate of 6/130 >> 2.8 cuft/min, thus a SAC of 2.8/3 = 0.9. Of course, you can't get access to the entire 6 cuft because of the way regulators work, and you shouldn't go 60 fpm for the last half of the trip, and a safety stop would be nice, and you better not be stressed. So, it can certainly be done, but it is certainly not a good idea.

Let's just do an easy quick estimate from 130' to 70':
Tally the ATA's:
4.9
4.6
4.3
4.0
3.7
3.4
3.1
----
Total: 28

Multiply 28 ATA by 1 cuft/min*ATA stressed SAC/RMV equals 28 cuft consumed at a slow controlled conservative ascent rate of 10'/min; But for an emergency max ascent rate of 60'/min then, estimate 5 cubic feet consumed.

Therefore an AL6 pony bottle should last from 130' to 70' with a stressed SAC rate of 1 cuft/min. (And then for argument's sake, now figure in a panicked SAC rate of "2cuft/min" instead???) It's all academic --you're obviously gonna exhaust that AL6 before making it to the surface. . .

Of course, if you can maintain a SAC rate of 0.5 cuft/min, you can make it to the surface per the parameters posted above by diver Kharon.

More power to Kharon if this diver can keep that nominal SAC rate to ascend & surface from 130' on an AL6 pony bottle.

 

[Germie]

I did in october a solo cavedive of 3 hours with a maximum depth of 76m. Approx 1050m from entrance in the cave. On ccr.