Why the Prejudice about DIR or GUE

[MXGratefulDiver]

This is a bit nosy but several people posted that Lynne (sp?) and her husband's SAC rates are pretty decent, but I didn't see any numbers. NWGD say that Lynne's SAC rate is extra good, so now my curiosity is piqued!
Not being competitive or judgemental or anything of that matter, I'm just curious--what kind of SAC rates do you guys have? If you don't feel like answering, just cyber-slap me.

On a recent dive I used 92 cubic feet of gas for a 77 minute dive with an average depth of 54 feet ... let's see if you can do the math ...

... Bob (Grateful Diver)

 

[Soggy]

Maybe this should be a new thread.

In doubles mine is about .45cf/min.
In singles it's about .34cf/min. though it's been as low as .20cf/min. on very relaxing dives.

Not to be a skeptic, but I'm pretty sure that .20 is not enough to support consciousness. Are you sure you are calculating right? I've never heard of anyone anywhere ever getting below a .3, and usually they are skip breathing.

My SAC rate can be anywhere from .4 in warm water single tank to .75, cold water, doubles, drysuit, and deco bottles. Normally, in cold water with doubles I'm around a .65. With a single tank it drops to .55-.6 or so.

 

[SparticleBrane]

Well, since SAC is in cf/min/ata...
(92cf) / (77mins) / [(54/33)+1] = 0.45 cf/min/ata

I'm just starting to get to around 0.47 myself, on relaxing dives.
If I'm escorting new OW students, or if it's a bit chilly, it can be a bit higher. As Soggy mentioned it definitely depends on the situation. I've had as high as 0.8 on my first dive with doubles. An hour and a half later I was back down to 0.55 for my second doubles dive.

0.20 sounds a bit low, although I will say that I know someone who will hit 0.30 on relaxing river dives. But, 0.20 sounds almost "too low".

 

[amascuba]

Not to be a skeptic, but I'm pretty sure that .20 is not enough to support consciousness. Are you sure you are calculating right? I've never heard of anyone anywhere ever getting below a .3, and usually they are skip breathing.

Not quiet .20cf/min, but here is a dive from June.

Tank: HP100cf
Depth: 18ffw
Bottom Time: 36min.
Start Pressure: 3500psi
End Pressure: 3000psi

1. 100cf/3500psi = .028cf/psi
2. 3500psi - 3000psi = 500psi used
3. 500 x .028cf/psi = 14cf used
4. 14cf / 36min. = .39cf/min. used
5. 18/34 + 1 = 1.53ATA
6. .39cf/min./1.53ATA = .25cf/min. at 18ffw.

Am I doing it correctly?

Also note that this is a site that I have about 90 logged dives in and the water is about 74-78 degree's year round.

 

[Soggy]

Were you at 18ffw the entire dive? You need to calculate from average depth. Your math is fine, though, assuming 18ft was your AVERAGE depth.

Did you come out with a headache?

Not quiet .20cf/min, but here is a dive from June.

Tank: HP100cf
Depth: 18ffw
Bottom Time: 36min.
Start Pressure: 3500psi
End Pressure: 3000psi

1. 100cf/3500psi = .028cf/psi
2. 3500psi - 3000psi = 500psi used
3. 500 x .028cf/psi = 14cf used
4. 14cf / 36min. = .39cf/min. used
5. 18/34 + 1 = 1.53ATA
6. .39cf/min./1.53ATA = .25cf/min. at 18ffw.

Am I doing it correctly?

 

[Puffer Fish]

Well, since SAC is in cf/min/ata...
(92cf) / (77mins) / [(54/33)+1] = 0.45 cf/min/ata

I'm just starting to get to around 0.47 myself, on relaxing dives.
If I'm escorting new OW students, or if it's a bit chilly, it can be a bit higher. As Soggy mentioned it definitely depends on the situation. I've had as high as 0.8 on my first dive with doubles. An hour and a half later I was back down to 0.55 for my second doubles dive.

0.20 sounds a bit low, although I will say that I know someone who will hit 0.30 on relaxing river dives. But, 0.20 sounds almost "too low".

Have seen a lot of small, health females with SAC rates below .3, and I hate them all. Little non-breathers making everyone else look bad.

Actually, I don't know if I have seen .2, but something close to that is easy if you are 100 lbs and have a slow, relaxed dive style, although I have never seen a male get that low, no matter how small. Perhaps all that fast twitch muscle is being used too much.

 

[SparticleBrane]

That's one way to calculate it, although--Is 18ffw is your MAX or your AVERAGE depth? (speaking to amascuba)

 

[amascuba]

Here is another profile from that same day. Slightly better SAC.

Tank: HP100cf
Depth: 20ffw
Bottom Time: 40min.
Start Pressure: 2500
End Pressure: 2000

1. 100cf/3500psi = .028cf/psi
2. 2500psi - 2000psi = 500psi used
3. 500 x .028cf/psi = 14cf used
4. 14cf / 40min. = .35cf/min. used
5. 18/34 + 1 = 1.59ATA
6. .35cf/min./1.59 = .22cf

 

[SparticleBrane]

Again, is 20ffw your max or your average depth?

 

[amascuba]

18ffw is the max. It's a warm water spring (74-78 degree's year round). I've got about 90 logged dives at the location and know it very well. Most of the dive is spent hovering over the bottom looking for crawdads and catfish hiding in the rocks. On this particular dive 0 - 15 minutes is spent at 18 feet. 16 - 24 is spent between 12 - 15ft (probably looking into the grass on the wall for a softshell turtle). The remainder of the dive is at 18 ft until I make my ascent.

I don't ascend from dives very often with headaches, but on these dives? Nope. Have I made an ascent from dives with headaches? You bet. I've researched the problem and contributed it to C02 retention, which I'm sure that's what are thinking correct?