How deep are you willing to go?

[Thalassamania]

A bounce to 190 would not bother me in the least.

 

[farsidefan1]

Interesting question. I'm heading to Coz Saturday and one of the signiture dives is at Punta Sur - The Devils Throat. From what I've read it comes out around 130 ft. I've had a few 100+ ft dives on al80s. My average sac rate is .52 so I'm certainly not the most efficient breather down there. The dive op I'm going with does have some al 100's which I will ask for if we do that dive. I see no problem either way. The only downside (unintended pun) is lack of bottom time. I assume it will be a fairly short dive.

 

[Trace Malinowski]

How deep are you willing to go on a specific size tank?

For example, on an Al 80 would you dive to 115 ft?

Depends upon what, specifically, is at stake.

Money?
Gold?
Jewels?
Diver in trouble?
Diver in trouble who happens to look like Jessica Alba?
Diver in trouble who happens to be Jessica Alba?
Bob Sherwood's lunch?
My girlfriend?
A lacrosse stick?

All of the above increase in order of motivation beginning with money. Depending upon what it is ... 200, 300, 400 feet? It might be okay.

 

[OldNSalty]

I think the suggested rule of thumb states 1 cu ft per 1 ft of depth-or something like that. So, an Al 80 (or any 80) is good to about 80 feet. so for you problem you would need 115 ft of air. Of course, this is just a guideline. I myself have done dives to those depths on just an 80 but I had no reason to stay at 115 for a protracted length of time. If there were some work that needed to be done at 115 then I might want a bigger tank.

 

[Paladin]

I get narced easily. At about 90 to 100 feet, I begin to feel the effects. At 130 feet or so, I get totally looped. For this reason, I limit myself to about 90 feet max, with an occasional drop to 100, regardless of what kind of tank I'm using. These days, most of the diving I enjoy is generally 70 ft or less, though. But, yeah, if I had a reason to go to 100 for a NDL dive, I'd be willing to use an AL80.

I think I might like to try heliox someday, just for the experience.

 

[scubadada]

Well, let's see, assuming:
-Normal SAC of 0.75, stressed SAC of 1.0
-Two minutes to sort out a catastrophic gas failure
-30 second stops every 10 feet starting at 50% max depth, with 30 seconds glide time to the next stop
-30ft/min ascent rate; 60ft/min descent

Gas burned sorting out the problem before starting ascent:
2 min * (1.0 cu. ft. / min) * 4.5 atm = 9 cu. ft.
Gas burned ascending to first stop:
60ft ascent / (30 ft/min) = 2 min
2 min * (1.0 cu. ft. / min) * 3.65atm = 7.3 cu. ft.
Gas burned doing stops at 60,50,40,30,20,10ft:
6 min * (1.0 ct. ft. / min) * 2atm = 12 cu. ft.
-------------------
28 cu. ft. per person * 2 people = 56 cu. ft. gas required

To do such a thing safely (and I agree with the earlier comment about wanting redundancy at that depth), you should turn the dive at 2100psi on an Al80. When was the last time you turned a dive at 2100psi? Seems hardly worth the bother for about 5 minutes of bottom time.

Wow, this is really extreme.

A bounce to 190 would not bother me in the least.

Thal, thanks for the sanity check. I've bounced to 153 ft and felt perfectly under control and safe. My SAC on easy wall dives is about 0.4 cu ft/min, on the wreck dives of the Spiegel and Duane, it is more like 0.5 cu ft/min. I plan my dives very carefully and am comfortable with the dives I execute. Interesting how some of the respondents have so few dives on which to base their responses.

Good, safe, diving, Craig

 

[Mayor]

Interesting question. I'm heading to Coz Saturday and one of the signiture dives is at Punta Sur - The Devils Throat. From what I've read it comes out around 130 ft. I've had a few 100+ ft dives on al80s. My average sac rate is .52 so I'm certainly not the most efficient breather down there. The dive op I'm going with does have some al 100's which I will ask for if we do that dive. I see no problem either way. The only downside (unintended pun) is lack of bottom time. I assume it will be a fairly short dive.

If I recall the depth was 125 feet at that location. Make sure you have a light because it's a bit dark in the devil. As for the tank I used Aldora and we had steel 120's on our back. Try and do a day with them if you can.

 

[diddydidit]

I'm reading a book right now where the author is bouncing to 300+ feet on a single al 80

 

[diddydidit]

with strait air, to boot

 

[Cave Diver]

How deep are you willing to go on a specific size tank?

For example, on an Al 80 would you dive to 115 ft?

Plan your dive, dive you plan.

There are a lot of variable to be taken into account before being able to give an adequate answer to such a question. What is the reason for going to a specific depth? What are the conditions? Temp, visibility, current, etc. What depth are you comfortable doing a CESA from? What is your SAC rate? What is your intended bottom time? What is your contingency plan if you have any sort of equipment problem at depth?


There is no real one size fits all answer to a question like this. It depends on what level of risk each individual is willing to assume and is capable of managing. Personally, I'm comfortable with any depth in recreational limits on a single AL80 in an OW environment. Anything deeper, or involving an overhead environment, deco or otherwise, and I prefer to have some sort of redundancy or reserve.

You're likely to get as many different answers to a question like this as there are posters on the board.