Signalling air remaining when diving with single tank divers.

[turt1e]

Reading through all the replies has been very interesting and I appreciate all the feedback everyone has given on the issue. Yes, I realized from the beginning that just diving one tank sidemount would be the easier solution, and probably what the DM will require. And I'm ok with that, even though it may require some hose changes on my regulators and SPG. However, if given the chance to use both, I wanted to make sure my air remaining signals wouldn't cause confusion.

So, simplist approach appears to be for me to signal when I've approached my turn around and ascent times based on what I determine those pressures should be. I think I'll use this method when diving with the wife and other buddies. Of course this only works if my buddies feel confident that I'm managing my gas appropriatly to provide them adequate air in either tank in case of an emergency.

I would think the above method would also be simplest to use with DM lead dives as well, and if they agree, then problem solved. If not, I either just dive a single tank or work out some form of air signels. Still not clear on the best way to handle what that would be though. If I signal each tanks pressure then the DM has to try and calculate what my gas state is. One thought I had was to keep a gas management table on a wrist slate to refer to that might look something like this. Keeping in mind though that I only get two tanks for both dives and that they usually don't want to see less than 500 psi in each tank when the dives are over.

	Tank 1	Tank2	Air Used
Start PSI	3000	3000
Turn Around PSI	2500	2500	1000
Ascent PSI	2000	2000	2000
Remaining PSI at surface	1800	1800	2400

Dive 2 would then start with the following pressures.

	Tank1	Tank2	Air Used
Start PSI	1800	1800
Turn around PSI	1300	1300	1000
Ascent PSI	800	800	2000
Remaining PSI at surface	500	500	2600

And then use these as a starting point for adding another column that would show a "Single Tank equivalancy" based on air used column. That way I could give air signal as if diving a single tank. But that sounds confusing just trying to explain it here! :depressed: Oh well... this is all more a mental "what if" at this point. Once I get more sidemount dives in I'm sure I'll find a method I'd be comfortable using.

Thanks again for the feedback, feel free to keep it coming

Paul

 

[rjack321]

Just as a general comment on this I'd say it's never a bad thing to carry too much gas unless you really take it too far. There's not many things I'd rather had over spare gas, except for maybe common sense - on that note...

Most sidemount divers set-up their tanks with a single regulator on both tanks, diving with a single reg on a single tank isn't really ideal and I'd say the hassle of reconfiguring regulators would outweigh the hassle of carrying the second tank which really doesn't take much effort?

Solving the communication issue seems a much simpler solution than having to reconfigure regs or bring a second set-up to me so it seems a valid question. Maybe I'm missing something?

The fundememtal problem is the required DM is thinking in psi when different people in the group have (effectively) different sized cylinders. So you basically can't think in psi anymore. You must convert everything to volume, figure out the gas plan in cf or liters, then convert those plans back into psi. Personally I don't think its worth arguing with DMs about this since with various language and education barriers they are unlikely to ever "get it". They may figure out you're fine since you have 2x as much gas or more and stop asking like in BoulderJohn's case. Personally I would just dive with one tank.

 

[DevonDiver]

Personally I would just dive with one tank.

Is that a decision to amend your desired configuration, based on the notion of DM unprofessionalism?

Personally, if I encounter a dive 'pro' that can't get their head around a very simplistic principle...and something which you might expect a dive pro, who was abreast of current diving developments, to understand... then I'd say it was their problem. They could always forgo 30 minutes in the beach bar and hit up on Scubaboard to educate themselves to do their job properly...

 

[MXGratefulDiver]

Is that a decision to amend your desired configuration, based on the notion of DM unprofessionalism?

Personally, if I encounter a dive 'pro' that can't get their head around a very simplistic principle...and something which you might expect a dive pro, who was abreast of current diving developments, to understand... then I'd say it was their problem. They could always forgo 30 minutes in the beach bar and hit up on Scubaboard to educate themselves to do their job properly...

... this is what happens when you can become a dive "professional" at 50 dives without even having to learn how to dive. Most of those folks have never heard of ScubaBoard ... and if it wasn't in their PADI books, they wouldn't understand it anyway.

Like the "professional" who insisted that the only way he could tell if I was "properly weighted" was to see me on my knees ...

... Bob (Grateful Diver)

 

[boulderjohn]

... this is what happens when you can become a dive "professional" at 50 dives without even having to learn how to dive. Most of those folks have never heard of ScubaBoard ... and if it wasn't in their PADI books, they wouldn't understand it anyway.

Or a dive professional who has completed several thousand dives at a typical resort area where he has never seen anything other than single AL 80s.

 

[Quero]

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[rjack321]

Is that a decision to amend your desired configuration, based on the notion of DM unprofessionalism?

Personally, if I encounter a dive 'pro' that can't get their head around a very simplistic principle...and something which you might expect a dive pro, who was abreast of current diving developments, to understand... then I'd say it was their problem. They could always forgo 30 minutes in the beach bar and hit up on Scubaboard to educate themselves to do their job properly...

Yup happens all the time at resorts:
I like EAN32, not available.
I like hp100s, they rarely have them.
I want helium or doubles for XYZ, they don't have them.

This change just happens to be human induced. Just as I may steer away from a resort if they only offer air, people can avoid places with required DMs. Or if you get stuck with one anyway, just dive the DMs way. I can't understand why you need 2x as much gas as anyone else on the dive. In the case of the ignorant DM all that gas is not helping you, its just increasing the confusion and misunderstandings.

 

[turt1e]

Yup happens all the time at resorts:
I like EAN32, not available.
I like hp100s, they rarely have them.
I want helium or doubles for XYZ, they don't have them.

This change just happens to be human induced. Just as I may steer away from a resort if they only offer air, people can avoid places with required DMs. Or if you get stuck with one anyway, just dive the DMs way. I can't understand why you need 2x as much gas as anyone else on the dive. In the case of the ignorant DM all that gas is not helping you, its just increasing the confusion and misunderstandings.

I fail to see how your three examples really apply in this situation seeing as they wouldn't be options anyway. Now if I brought my own EAN32 filled tanks, hp100s, or helium, would your suggestion still be to just dive the provided AL80s on air, so as not to cause to much confusion for the DM?

Maybe I should have refraised my original post to say something more along the lines of "If the DM at such and such resort is open to they idea of me diving double AL80s in sidemount, what are they best methods for communicating air remaining during the DM lead dives? When said DM and the rest of the divers are all diving single tanks?"

I also don't look at it as I'm diving 2x the amount of air as other divers. On a 2 tank dive, all divers are provided a total of around 6000 psi of air spread between two tanks. I just happen to have all that air availble on the first dive, but I still have to make that first dive as if I only have 3000psi available if I want to be able to make the 2nd dive. By the second dive (when I have to reuse the same two tanks), I would be diving with just as much air as the other divers with a single tank. I don't get two more full fill tanks for the second dive.

 

[DA Aquamaster]

Reading through all the replies has been very interesting and I appreciate all the feedback everyone has given on the issue. Yes, I realized from the beginning that just diving one tank sidemount would be the easier solution, and probably what the DM will require. And I'm ok with that, even though it may require some hose changes on my regulators and SPG. However, if given the chance to use both, I wanted to make sure my air remaining signals wouldn't cause confusion.

So, simplist approach appears to be for me to signal when I've approached my turn around and ascent times based on what I determine those pressures should be. I think I'll use this method when diving with the wife and other buddies. Of course this only works if my buddies feel confident that I'm managing my gas appropriatly to provide them adequate air in either tank in case of an emergency.

I would think the above method would also be simplest to use with DM lead dives as well, and if they agree, then problem solved. If not, I either just dive a single tank or work out some form of air signels. Still not clear on the best way to handle what that would be though. If I signal each tanks pressure then the DM has to try and calculate what my gas state is. One thought I had was to keep a gas management table on a wrist slate to refer to that might look something like this. Keeping in mind though that I only get two tanks for both dives and that they usually don't want to see less than 500 psi in each tank when the dives are over.

	Tank 1	Tank2	Air Used
Start PSI	3000	3000
Turn Around PSI	2500	2500	1000
Ascent PSI	2000	2000	2000
Remaining PSI at surface	1800	1800	2400

Dive 2 would then start with the following pressures.

	Tank1	Tank2	Air Used
Start PSI	1800	1800
Turn around PSI	1300	1300	1000
Ascent PSI	800	800	2000
Remaining PSI at surface	500	500	2600

And then use these as a starting point for adding another column that would show a "Single Tank equivalancy" based on air used column. That way I could give air signal as if diving a single tank. But that sounds confusing just trying to explain it here! :depressed: Oh well... this is all more a mental "what if" at this point. Once I get more sidemount dives in I'm sure I'll find a method I'd be comfortable using.

Thanks again for the feedback, feel free to keep it coming

Paul

I have not dove a single tank since July 28, 2010, and the last two occasions were 1) a few days of boat and beach diving in Bermuda (May 2010) and 2) a week long trip of pretty fish diving on the Spree (July 2010). At the time I had only been side mount diving about a year and was not totally comfortable doing it off a boat, and no doubles were available in either location.

If I did either trip now, I'd use AL 80s in side mount with my SMS 50. If DM was concerned, I'd just report the pressure for the fullest tank. The reality is that I am the person responsible for conducting my dive safely, and while I appreciate the dive industry now churns out herds of crappy divers who are not able to dive safely absent the oversight of a 50 dive wonder of a DM, that model just does not apply to me and I refuse to play that game. But I'm not above giving gas numbers that make the DM go away.

 

[rjack321]

I fail to see how your three examples really apply in this situation seeing as they wouldn't be options anyway. Now if I brought my own EAN32 filled tanks, hp100s, or helium, would your suggestion still be to just dive the provided AL80s on air, so as not to cause to much confusion for the DM?

Maybe I should have refraised my original post to say something more along the lines of "If the DM at such and such resort is open to they idea of me diving double AL80s in sidemount, what are they best methods for communicating air remaining during the DM lead dives? When said DM and the rest of the divers are all diving single tanks?"

I also don't look at it as I'm diving 2x the amount of air as other divers. On a 2 tank dive, all divers are provided a total of around 6000 psi of air spread between two tanks. I just happen to have all that air availble on the first dive, but I still have to make that first dive as if I only have 3000psi available if I want to be able to make the 2nd dive. By the second dive (when I have to reuse the same two tanks), I would be diving with just as much air as the other divers with a single tank. I don't get two more full fill tanks for the second dive.

No I was responding to the concept of changing from your preferred configuration because of external forces. Whether that's the lack of EANx or helium or an ignorant DM who wants to baby sit you. Happens all the time, just do a different type of dive minus EANx or helium. In your case, just dive 1 backmount or sidemount tank to shut the DM up. Or do what DA suggests and just get him (her) to go away by giving the pressure in the fuller tank.