Why can't I dive twice on the same tank?

[Papa Bear]

I think of them as passion points!!!! And I am very passionate about my diving

[scuba smurf]

First, you are talking about diving in a overhead environment! You should always have a topped off tank and should never dive a tank smaller than your buddy! In Cave Diving that can get both of you killed! When you are in an overhead situation you have to think of your buddy team as one unit. You have to carry enough air to get both of you to safety! It is the rule of thirds! And you are going in a third down to start! If your Caribbean diving in open water I could care less! But if your doing a 63cft in wreck dives you won't be my buddy or I wouldn't let you in the water on my boat! Take a wreck course or a cave course! You can't make more are at 80ft! For Some people a 63cft is a bailout bottle! you can always dive a bigger tank than your buddy but never smaller!

I definitley agree with getting the proper training portion of your post papa. However, in a perfect world everyone would be diving the same tanks, this isn't the case however. When planning ANY dive turn pressures/volumes should be calculated based on the person with the smallest amount of breathing gas and/or the highest sac rate.
I'm not a cave diver..........yet, but I have heard of cave divers re-calculating 3'rds/6'ths and heading back in for a little jaunt in the cave so I'd say these folks are heading in with a less than full gas supply. For any overhead diving, the team should be configured the same with redundant gas supplies, proper training.

[Papa Bear]

If I am in A OH environment with a diver with a 63 and their sac rate is great and they get into trouble we have no problem, unless I screw up, but if have a problem and have to put my life and theirs on whats left in their tank we have a big problem. It happen in Caving where the team is H & W or B & G and one sets up with twin 72s or 80s and the the hog sets up with 105s or 120s! The trouble is on the horizon, what happens if you just before turn around and the hog has a major problem with the air supply? Is 2/3rds of a set of 72s enough to get both of you out? Maybe, and I am not putting my life on the line for a maybe! Never go in an Overhead environment unless planned and with the amount of air you planned on! So its not about her or her sac rate, its about the dive, and where your going and what your doing!

[scuba smurf]

from the sounds of it maybe some proper overead/dive planning training would be in order for you

[Papa Bear]

Really? Why do you say that? I was trained by Bill Rennaker and John Orlowski can you think of any two that are better? If you have some constructive criticism of my explanation then post it! Otherwise I don't see the reason for your statement? Even with a wink? You lost me some where deep in the cave I guess? Or maybe its your rant?

[scuba smurf]

now who needs to lighten up ROFL

[Papa Bear]

I have been working on that! Yo Momma!

[BamaCaveDiver]

I definitley agree with getting the proper training portion of your post papa. However, in a perfect world everyone would be diving the same tanks, this isn't the case however. When planning ANY dive turn pressures/volumes should be calculated based on the person with the smallest amount of breathing gas and/or the highest sac rate.
I'm not a cave diver..........yet, but I have heard of cave divers re-calculating 3'rds/6'ths and heading back in for a little jaunt in the cave so I'd say these folks are heading in with a less than full gas supply. For any overhead diving, the team should be configured the same with redundant gas supplies, proper training.

SAC rates have no affect here, you simply calculate your turn pressure based upon the minimum capacity within the group. If diver A starts the dive with 90 cuft and diver B starts with 250 cuft, diver A's supply would dictate turn pressure, in this case 30 cuft. Convert that back to PSI and note your turn pressure. Thus both divers are limited to using 30 cuft of gas before turning the dive. It makes no difference who has the highest SAC rate, as when the number is hit by either diver, the dive gets turned. Nothing at all wrong with recalculating as long as you adhere to your rule of thirds (the dives will be shorter in duration, but just as safe.)

You make use of your SAC rate to determine the minimum gas requirements for your dive. If you want to dive to x feet for y minutes, you would make use of your SAC rate to determine how much gas you will need to accomplish the dive. You would then calculate thirds as usual, with no reference to individual SAC rates.

[scuba smurf]

Thanks Bama, my bad, you explained it much better

[Papa Bear]

Bama, you did make it simple! You did a better job of explaining it than I did! Thats for sure, but the out come is the same!