Backgas Reserve in a Stage Bottle?

[kramynot2000]

My buddy and I are planning out a 245' dive. The one issue we're running into is that although he has twin 130's, I dive twin 95's. What we'd like to do is extend our bottom time but then I run up against not having enough gas in reserve. We've been training to always have 1/3 of backgas in reserve. I know there have been threads before on the amount of reserve but for now, we'd like to keep with the 1/3 reserve.

So, I was thinking of taking an extra stage bottle down with backgas. But then my buddy and I disagree as to whether I should breathe down the stage bottle first and make the switch to my doubles on the bottom, sorta like using a travel gas, or to breathe my doubles and then just keep the extra 40 in case of emergency.

Any thoughts? And yeah I know I can look for a larger set of doubles.

Thanks
Tony

 

[J1M1]

My buddy and I are planning out a 245' dive. The one issue we're running into is that although he has twin 130's, I dive twin 95's. What we'd like to do is extend our bottom time but then I run up against not having enough gas in reserve. We've been training to always have 1/3 of backgas in reserve. I know there have been threads before on the amount of reserve but for now, we'd like to keep with the 1/3 reserve.

So, I was thinking of taking an extra stage bottle down with backgas. But then my buddy and I disagree as to whether I should breathe down the stage bottle first and make the switch to my doubles on the bottom, sorta like using a travel gas, or to breathe my doubles and then just keep the extra 40 in case of emergency.

Any thoughts? And yeah I know I can look for a larger set of doubles.

Thanks
Tony

What type of bottom time are you planning. The extra 40 is not going to increase your bottom time by more than a few minutes at 250ft. Really it would be pointless, especially since you are going to have to save a third of that as well. Stick with your doubles unlesss you plan on taking an 80 for bottom gas to extend the bottom time. But then you are going to run into a serious deco obligation, and may need alot of deco gas which would be super task loaded between... say 3 bottles...maybe all 80's. My advice would be to do the dive with the doubles as is and your deco bottles as is. My buddy dives with 120's and i have 95's and we are not limited by that much. I can get over 20min at that depth on my 95's and any more than that, we may have to carry extra deco gas. Look at the deco obligation and how much your going to use for the bottom time desired and weigh the benefits of the extended bottom time versus the amt. of deco gas needed to complete te dive within acceptable limits for both you and your buddy...It does say in your profile that you are padi dsat tec deep diver. That only qualifies you to use air to 165 ft with deco on up to 100% (correct? I dont know?)...it also says you are progressing towards trimix...you need mix at this depth...i hope you are diving within the standars of your particular agency.....JD

 

[novadiver]

My buddy and I are planning out a 245' dive. The one issue we're running into is that although he has twin 130's, I dive twin 95's. What we'd like to do is extend our bottom time but then I run up against not having enough gas in reserve. We've been training to always have 1/3 of backgas in reserve. I know there have been threads before on the amount of reserve but for now, we'd like to keep with the 1/3 reserve.

So, I was thinking of taking an extra stage bottle down with backgas. But then my buddy and I disagree as to whether I should breathe down the stage bottle first and make the switch to my doubles on the bottom, sorta like using a travel gas, or to breathe my doubles and then just keep the extra 40 in case of emergency.

Any thoughts? And yeah I know I can look for a larger set of doubles.

Thanks
Tony

Sounds like it's time to plan this dive with your sac rate X 1.5. Good luck.

 

[msandler]

how about both of you carrying a stage with 50/50 (or other) Your double 95's should be plenty unless you are planning a loooong deco. What is the back gas? On a dive like that you need to make and commit to a plan, not just dive until you use a third. Plan the dive properly. Choose a bottom time and stick to it. Plan the deco (not just follow the computer). That is how you will know how much air you need. There is no excuse for not knowing exactly what the dive requiement is and adhereing to it.

 

[kramynot2000]

We're both new to diving to this depth so we plan our dives fairly conservatively. Probably too conservatively! Anyway, we're only looking at 20 min BT and also a 2 min deep stop at 180. I use a working SAC of 0.6 to plan. With that, I get a consumption of 150 cu ft' of backgas. So, to maintain a 1/3 reserve I need 225 cu ft'. I could try to pump up the 95's to 3100-3200 which can get me that amount of gas but then we thought about just taking down another stage and then came the discussion about which to breathe first if we went this way.

By the way, we use a Buhlmann algo program with GFs of 30-85% which gives about 60 minutes of deco.

Oh yeah, we're using 17/45 for our backgas and deco'ing on 36% and 02.

 

[ianr33]

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[novadiver]

We're both new to diving to this depth so we plan our dives fairly conservatively. Probably too conservatively! Anyway, we're only looking at 20 min BT and also a 2 min deep stop at 180. I use a working SAC of 0.6 to plan. With that, I get a consumption of 150 cu ft' of backgas. So, to maintain a 1/3 reserve I need 225 cu ft'. I could try to pump up the 95's to 3100-3200 which can get me that amount of gas but then we thought about just taking down another stage and then came the discussion about which to breathe first if we went this way.

By the way, we use a Buhlmann algo program with GFs of 30-85% which gives about 60 minutes of deco.

Oh yeah, we're using 17/45 for our backgas and deco'ing on 36% and 02.

You might be able to work a travel mix in the plan. Saving your back gas for BT

 

[msandler]

It doesn't appear you have adequate training to make the dive "properly" so you will either make it, be lucky (most likely) and get away unscathed or become a statistic. It appears you are diving air, how deep have you been on air? Realistically you should have a hypoxic back gas and an appropriate deco gas. You should also have experience with handling stages, lift bags and other logistics. Two narced. ill-equiped divers swimming around at 245 without proper training is just one of those things I question. -sorry

 

[msandler]

I just noticed you edited your post. Which addresses some of my concerns.

 

[jonnythan]

I'm no tech diver, but I notice that you're doing thirds as "1/3 of the gas on your back." I believe GUE teaches to take 1/3 of the gas on your back after you subtract out a rock bottom, which seems like a good idea to me. I sort of assumed this is just how thirds was done by everyone. Is there something I'm missing?