Backgas Reserve in a Stage Bottle?

[boomx5]

If it was me I would just 'cave fill' my 95s but it's your tanks.

Lol...that's a great idea, however if you new the LDS doing the fills you would realize how funny that statment is. On the other hand there is a shop in Monterey that gives excellent fills but I don't think Tony will have time to do it down there before the class.

 

[wedivebc]

Actually..I really like the stage 36% until 110 ft to conserve back gas...I wonder who teaches that

OK so that will save about 3cuft of gas, then what?

 

[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

Hey Tony, I just ran the numbers through deco planner. I used the info you posted and gas mix. I counted Three stage tanks.100%,50%,36% for deco stops,and trymix for back gas, and you want to bring another stage? For five min?

With the po2 running to 87% at the end of the dive. One wrong reg switch and you are going to take an o2 tox hit.

If you still feel you need to do this dive, Than you should stay real close to your buddy with those 130s, and make sure you check each others tank mods for the correct gas switch at all the stops. Good luck ,.

 

[Viscya]

Nova,

He said he is using 36% for deco. I was assuming the would just be on 80cf bottle of 36%. If this deco bottle fails, he will need 300+ cf of back gas. Can you carry that much?

 

[novadiver]

Nova,

He said he is using 36% for deco. I was assuming the would just be on 80cf bottle of 36%. If this deco bottle fails, he will need 300+ cf of back gas. Can you carry that much?

I wouldn't even try this dive decoing on 36% only. Using 36%,50% and 100% I got this down to 68 min. you could shave a minute here and there with excellorated ascent.

This dive , with his gear, has to much risk for me, I think it would be wise to cut the BT to 15 minutes.

And Viscya, If I could carry 300+ cf of back gas ,I would look like a scuba diver glued to a hot water heater.LOL

 

[Scuba_Steve]

If you still feel you need to do this dive, Than you should stay real close to your buddy with those 130s, and make sure you check each others tank mods for the correct gas switch at all the stops. Good luck ,.

No offence Ole chap, but this type of thinking isn't what should be going on for any dive, never mind a technical dive. They could kiss their a$$e$ good-bye if the Buddy got into trouble too, so what good would it be to stick closely for this reason? This plan is screwed long before they hit the water.

I think he knows it now, so brow beating won't get us anywhere beyond this. Lets just hope he takes the advice and cans this foolish plan before it gets someone dead.

Unfortunately any door-knob can run a plan on their deco software of choice, but it's entirely different to be able to this dive with the safety required, including not only gas reserve, but diver knowledge and skill. It ain't happening here. Odds are pretty good most people could do this, even when not properly trained, but that's hardly the point. Hell, to be honest, I've come fairly close to this profile (a bit shallower and for less time) at one point in my life, but I wouldn't do it again simply because I NOW know I am not truly up to the task of this particular dive as far as I am concerned. If you don't give it the respect it deserves, it'll hurt you bad sooner or later.

Regards gents

Steve

 

[kramynot2000]

Hey guys,

Thanks for the all the comments. I'll keep them all in mind.

 

[msandler]

No offence Ole chap, but this type of thinking isn't what should be going on for any dive, never mind a technical dive. They could kiss their a$$e$ good-bye if the Buddy got into trouble too, so what good would it be to stick closely for this reason? This plan is screwed long before they hit the water.

I think he knows it now, so brow beating won't get us anywhere beyond this. Lets just hope he takes the advice and cans this foolish plan before it gets someone dead.

Unfortunately any door-knob can run a plan on their deco software of choice, but it's entirely different to be able to this dive with the safety required, including not only gas reserve, but diver knowledge and skill. It ain't happening here. Odds are pretty good most people could do this, even when not properly trained, but that's hardly the point. Hell, to be honest, I've come fairly close to this profile (a bit shallower and for less time) at one point in my life, but I wouldn't do it again simply because I NOW know I am not truly up to the task of this particular dive as far as I am concerned. If you don't give it the respect it deserves, it'll hurt you bad sooner or later.

Regards gents

Steve

blind leading the blind

 

[novadiver]

blind leading the blind

Is that like the blind following the deaf?

 

[DA Aquamaster]

I tend to be a little conservative but my thoughts are that you need to be independently capable of finishing the dive and should not even consider using the air in the buddies 130's. There are some potentially nasty ethical decisions that may have to be made with that practice that are best avoided in the first place.

In addition to normal dive planning where I want to have sufficient gas to meet 1.5 times the planned back gas requirements and 1.2 times the planned deco gas requirements, you also need to ensure you have suffcient gas to do the whole dive on your backgas if the need arises. Sometimes the 1.5 (1/3) backgas reserve is enough and sometimes it isn't. If it isn't and you still need to do the dive as planned, then you are definitely going to be hauling at least another 80 along for use during descent and on the bottom to leave an adequate backgas reserve in case things do not go as planned.

Personally, I usually find it to be a whole lot smarter and practical to shave some bottom time and reduce the bottom and deco gas requirements substantially that way than to haul along an extra 80.

I also do not see the point in using Nitrox 36 for deco. You'd be better off with Nitrox 50 and if using two deco gases, I'd go with Nitrox 50 and Nitrox 80 or Nitrox 50 and 100% in that order of preference.