Swapping reg protocols...
- Thread starter The Chairman
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hudson
Contributor
The former, but you wouldn't use a clip/snap. You'd just put the loop around the d-ring, tuck the regulator in when not in use, pull it out as needed.
I don't know any cave divers that would just take a reg without signaling.we're trained to signal and muscle memory should kick in. The one real air share I've done went exactly that way. The reason for putting it on the bungee is the rare dive I will go into a tight passage with someone else. A signal will likely not be seen (too much silt) so it's all by feel, which means we'lll be close enough for the bungee to stretch enough.
I haven't noticed much difference whether I breath from each tank alternately or one after the other.
However, I prefer using 1/3 from first tank, then 1/3 from second tank. At this point I turn around (or start diving to exit point) and then again switch tanks for another 1/3-1/3 session. Thus, I finish the dive with 1/3 on each tank.
Why? Since I dive solo, if something happens to one of the tanks, it leaves enough gas on the other tank to end the dive.
If I dive with a buddy and he's got gas shortage, I hand him one of my tanks and both are suppose to have enough gas for ending the dive. Of course, if there is a huge difference between air consumption it won't be enough, but it is the best we can do...
And if both tanks go bad, **** happens, then you just go out of the water, eh?
However, I prefer using 1/3 from first tank, then 1/3 from second tank. At this point I turn around (or start diving to exit point) and then again switch tanks for another 1/3-1/3 session. Thus, I finish the dive with 1/3 on each tank.
Why? Since I dive solo, if something happens to one of the tanks, it leaves enough gas on the other tank to end the dive.
If I dive with a buddy and he's got gas shortage, I hand him one of my tanks and both are suppose to have enough gas for ending the dive. Of course, if there is a huge difference between air consumption it won't be enough, but it is the best we can do...
And if both tanks go bad, **** happens, then you just go out of the water, eh?
GLENFWB
Contributor
GLENFWB
Contributor
Okay, I see what you are saying. I am just trying to find a way to do things that is better then what I am currently doing.
If you use 1/3 of your gas out of both tanks, turn your dive right before you switch to your other tank (half way back), you lose all the air from the tank with higher pressure ( not likely, but just for S&G let's say it is), you will have just enough air to get out...if your spg is accurate. If it's not you may take your last breath 100 feet from the exit (more likely). By switching sooner, you reserve more air in both tanks to get out. I solo quite a bit, too, and switch every 500-600 for this reason. Next time you dive, don't switch on the way back and let us know when you run out of air in that tank.
Thanks for your insight- I'll give it a try (without switching on the way back) and see when it runs out of air..
By the way, the main reason I opted for SM is diving solo (and reducing weight from my back too). Since I do not dive in caves, surfacing 100 or 200 feet from "exit" point is probably more of a discomfort rather than a real threat (such as in an overhead environment)
If such an event happens (losing the ability to breath from one tank), I'd probably abort the dive and start heading out at a shallow depth of, say, 5 meters.
I dove independent doubles for years and while you can switch more often to maintain less than a 600 psi or 300 psi difference between tanks, it is more work, involves no gain in safety and has more potential for making a mistake and overusing the intended gas near max penetration.
My preferred method was:
Start on the left (short hose) tank and use 1/3rd of it (1200 psi in a cave filled LP 95, etc), then switch to the right (long hose) tank. You will turn the dive after you use 1200 psi from this second tank, (at that point both SPGs will read 2400 psi). You then stay on the second tank and start your exit, switching back to the first tank after a total of 2400 psi has been used (1200 psi left on the SPG) and then complete the dive on the second tank, breathing it down to 1200 psi.
This leaves 1200 psi in reserve in each tank at the end of the dive and more importantly, leaves 2400 psi in each tank at max penetration. In the event you lose the entire contents of one tank, you have an amount equal to what you used getting there in the remaining tank at the worst case point of the dive. At every place shorter than that, you have extra gas in both tanks.
The only place you could argue it makes a difference to switch more often is at a point 300 psi short of your turn point. But whether you switch every 1200 psi or every 300 psi, one tank is at 2400 psi and the other is at 2700, so there is again no gain in safety with the more frequent switches.
The "switching sooner" argument as noted above to account for SPG inaccuracy, delays in exits, etc is overkill. What matters is the reserve in each tank at the turn point, not how many gas switches you make. For example, you can easily pad your reserve at all points to be more conservative by using 1000 psi or 800 psi thirds rather than 1200 psi thirds. 1000 psi "thirds" leaves you 2600 psi in each tank at the turn and 800 psi "thirds" leaves 2800 psi in each tank at the turn.
With 800 psi thirds, you would start with 3600 in each tank (3600/3600), then switch to the second tank at 2800 psi (2800/3600), turn the dive at 2800 psi (2800/2800), then swith to the first tank when you reach 2000 psi (2800/2000) and end the dive by the time you reach 2000 on the first tank (2000/2000). You end up with a 2800 in both tanks at max pentration with 2800 psi in each tank, against the 1600 psi you used on the way in - a generous 800 psi pad with only 2 gas switches during the entire dive and only a 1.9 pound weight differential between two 130s.
With 1000 psi thirds, the numbers look like this: Start: 3600/3600, 1rst switch: 2600/3600, turn: 2600/2600, 2nd switch 2600/1600), and end: 1600/1600. And this still leaves you 2600 psi in each tank at the turn against 2000 psi used to get there - a 600 psi pad and only a 2.5 weight differnetial.
In terms of trim, even with 1200 psi thirds in a 130 cu ft tank, the maximum differential between tanks is 1200 psi which equals about a 2.8 lb weight differential between tanks. The benefit of this approach is only having to switch regs twice during the entire dive, so unless a 2.8 lb weight difference creates problems with your trim, there is no reason to switch more frequently.
If anyone can explain a flaw in this reasoning and explain where a 300 psi differential is safer, I am all ears.
My preferred method was:
Start on the left (short hose) tank and use 1/3rd of it (1200 psi in a cave filled LP 95, etc), then switch to the right (long hose) tank. You will turn the dive after you use 1200 psi from this second tank, (at that point both SPGs will read 2400 psi). You then stay on the second tank and start your exit, switching back to the first tank after a total of 2400 psi has been used (1200 psi left on the SPG) and then complete the dive on the second tank, breathing it down to 1200 psi.
This leaves 1200 psi in reserve in each tank at the end of the dive and more importantly, leaves 2400 psi in each tank at max penetration. In the event you lose the entire contents of one tank, you have an amount equal to what you used getting there in the remaining tank at the worst case point of the dive. At every place shorter than that, you have extra gas in both tanks.
The only place you could argue it makes a difference to switch more often is at a point 300 psi short of your turn point. But whether you switch every 1200 psi or every 300 psi, one tank is at 2400 psi and the other is at 2700, so there is again no gain in safety with the more frequent switches.
The "switching sooner" argument as noted above to account for SPG inaccuracy, delays in exits, etc is overkill. What matters is the reserve in each tank at the turn point, not how many gas switches you make. For example, you can easily pad your reserve at all points to be more conservative by using 1000 psi or 800 psi thirds rather than 1200 psi thirds. 1000 psi "thirds" leaves you 2600 psi in each tank at the turn and 800 psi "thirds" leaves 2800 psi in each tank at the turn.
With 800 psi thirds, you would start with 3600 in each tank (3600/3600), then switch to the second tank at 2800 psi (2800/3600), turn the dive at 2800 psi (2800/2800), then swith to the first tank when you reach 2000 psi (2800/2000) and end the dive by the time you reach 2000 on the first tank (2000/2000). You end up with a 2800 in both tanks at max pentration with 2800 psi in each tank, against the 1600 psi you used on the way in - a generous 800 psi pad with only 2 gas switches during the entire dive and only a 1.9 pound weight differential between two 130s.
With 1000 psi thirds, the numbers look like this: Start: 3600/3600, 1rst switch: 2600/3600, turn: 2600/2600, 2nd switch 2600/1600), and end: 1600/1600. And this still leaves you 2600 psi in each tank at the turn against 2000 psi used to get there - a 600 psi pad and only a 2.5 weight differnetial.
In terms of trim, even with 1200 psi thirds in a 130 cu ft tank, the maximum differential between tanks is 1200 psi which equals about a 2.8 lb weight differential between tanks. The benefit of this approach is only having to switch regs twice during the entire dive, so unless a 2.8 lb weight difference creates problems with your trim, there is no reason to switch more frequently.
If anyone can explain a flaw in this reasoning and explain where a 300 psi differential is safer, I am all ears.
SuPrBuGmAn
Contributor
Recognizing a problem with an opposing regulator sooner than later is a pretty good reason to swap regulators more frequently IMO. I don't go as far to swap every 300psi, but make it a point to keep my tank pressures within a 6th of each other. I don't see any additional potential for mistakes while doing this and certainly an extra regulator swap isn't a reason to disregard this approach.
With steels, the difference in trim isn't noticable, but with lighter tanks, it can be. I've definately noticed it in AL80s and steel 72s. I will make my regulator swaps in the same manner, despite the tank.
With steels, the difference in trim isn't noticable, but with lighter tanks, it can be. I've definately noticed it in AL80s and steel 72s. I will make my regulator swaps in the same manner, despite the tank.
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