check my logic?

[Jason B]

Wow, you must dive some ferocious places if some redneck is going to swoop down on you at 100 feet and cut your O2 bottles off you

Not everyone does their deco dives in OW. When cave diving, deco bottles are dropped off. We don't haul them through the cave.

 

[T-Dog]

Wow, you must dive some ferocious places if some redneck is going to swoop down on you at 100 feet and cut your O2 bottles off you

And sometimes they're tottin' guns - At least at Little River!

 

[JimC]

I can't wait for someone to actually read your deco profile and come in guns blazing. Aught a be good for a few belly chuckles.

 

[JeffG]

I can't wait for someone to actually read your deco profile and come in guns blazing. Aught a be good for a few belly chuckles.

He is a scuba instructor you know.

 

[Thalassamania]

I worked a few examples and I find 1.6 rather high. My examples were random and might not be representitive.

 

[limeyx]

Not everyone does their deco dives in OW. When cave diving, deco bottles are dropped off. We don't haul them through the cave.

Sorry, I was just trying to make a joke. But agreed, in a cave environment as long as there is nobody trying to make off with your tanks, then that's a good option.

If I thought there was really a good chance someone would walk off with my O2 bottle, then I am either going to not do the dive or come up with another solution -- but since I'm not a cave diver, I'm not sure what the real answer is. I'd say carry the darned bottle if that's what you have to do. Much better than to have to plan on one being gone a significant number of times.

 

[loosebits]

I am not a deco diver, but, I think unless you start carrying AL80s for deco bottles, it might be tough to carry enough deco gas for 2 divers in an AL40. Does the agency you trained with not advocate planning lost deco gas and doing deco on backgas? If you've done your dive correctly, you should have enough backgas to complete your deco obligations.

For small deco requirements, an AL 40 with O2 has plenty of gas if you get a decent fill. For example a dive to 150 on 21/35 for 30 mins only requires 13.5 cuft of O2 (not that O2 would be my first choice in deco gasses). Of course this is really a moot point since my deco bottles only have one second stage on them anyway and my gassless buddy will be doing a significant portion of his deco on backgas (I'm assuming his - what's the chances of him losing backgas AND his deco bottle). We've practiced buddy breathing off deco gas - doable but not all that fun, especially for 15 mins.

Now get yourself a LP45 and pump it to 3000+ with EAN50 and you have a nice little deco bottle with plenty of gas for that profile (even filled to 2640 would get you the 1.5x of what's required).

 

[limeyx]

For small deco requirements, an AL 40 with O2 has plenty of gas if you get a decent fill. For example a dive to 150 on 21/35 for 30 mins only requires 13.5 cuft of O2 (not that O2 would be my first choice in deco gasses). Of course this is really a moot point since my deco bottles only have one second stage on them anyway and my gassless buddy will be doing a significant portion of his deco on backgas (I'm assuming his - what's the chances of him losing backgas AND his deco bottle). We've practiced buddy breathing off deco gas - doable but not all that fun, especially for 15 mins.

Now get yourself a LP45 and pump it to 3000+ with EAN50 and you have a nice little deco bottle with plenty of gas for that profile (even filled to 2640 would get you the 1.5x of what's required).

I had missed this one originally. First, as you say, 100% O2 is not the ideal gas for a 150 dive, partly because it drastically increases your minimum gas to get to the gas switch.

You need to reserve enough back gas for deco in case of lost AL40.
Generally I wouldn't buddy breathe a deco tank, but "swap" it between to divers
(i.e. if I am using 50% then I take the bottle for the 70 foot stop, and my buddy on BG, then we swap at 60 feet -- extend the stops by 1.5 times or so and you should have enough gas) By the time you are shallow it doesn't really matter if you do the 20 and 10 stops on BG if you did deco on the 50% from 70-30

 

[loosebits]

I'm just pointing out that an AL40 has plenty of gas for two divers to deco on O2... wasn't going to get into the mechanics of passing around a deco bottle but I would simply do my 20' stop then hand the bottle off to my buddy and hang out there with him while I breath backgas (don't like leaving a buddy on O2).

 

[limeyx]

I'm just pointing out that an AL40 has plenty of gas for two divers to deco on O2... wasn't going to get into the mechanics of passing around a deco bottle but I would simply do my 20' stop then hand the bottle off to my buddy and hang out there with him while I breath backgas (don't like leaving a buddy on O2).

Yes, absolutely it has enough gas, as does an AL40 of 50%
And the general rule is if you need more deco gas, take 2 gases (50% and 100%) rather than a big bottle of one (this helps with lost deco bottle scenario and reduving rock bottom etc.)