Request for opinions about standardizing on EAN80

[Searcaigh]

Hi Mike

I have been reading this thread with interest, primarily as I usually carry a DSLR on all of my dives and generally only carry one stage (50%) for most of my deep dives where I find that I am usually clear fairly early after shallower deco dives (30M) using that gas.

My most recent deeper dives 60-70M I have been carrying 50% (AL50) and 100% (AL40) and switch accordingly at the prescribed depths for these gasses. I also tend to use my 50% as a travel gas to 20M then do my switch to backgas (19/40) for the main part of the dive.

It has also been my practice to shoot a bag before I get to 6M and when I go on to 100% it's easier to hold depth usually at 5M and still take photos during the last deco stop of my fellow team members.



Despite what was mentioned about a natural progression to CCR I am still of the opinion that I will stay on OC and not move on to CCR for several reasons;

1. The cost of CCR rebreathers (at least where I live)
2. Preparation time and additional steps to set up the rebreather - I spend just as long preparing my camera equipment before a dive, I don't need to double that.
3. And look at these guys, they still have to haul as many bail out tanks (in fact more) as I do just in case of a failure

 

[nadwidny]

3. And look at these guys, they still have to haul as many bail out tanks (in fact more) as I do just in case of a failure

But they don't have to fill them at the end of the dive.

 

[Searcaigh]

But they don't have to fill them at the end of the dive.

That's true but not my point, still got to haul them around though.

 

[Centrals]

But they don't have to fill them at the end of the dive.

But they still have to pay for it(bail out) even they never used it. 10/90 is pretty expensive for inflating ballons.

 

[nadwidny]

But they still have to pay for it(bail out) even they never used it.

Not in my world. Maybe I'm the exception but I do my own fills and bring my own cylinders to my dives. Some of my bailouts are going on 2 years without having to do more than a bit of a top up and monitoring to make sure that the gasses are still correct.

 

[manni-yunk]

To the questions:

1/ A tank of 80 needs to be drained and refilled every time, while the tank of 100 is just topped off. You need to take a full tank of 80 for every dive, but a tank of 100 can be re-used because you need less of it. A tank of 80 can be harder to make when the O2 supply is getting low, while you don't need to take a full tank of 100.

.

HUH???? Nothing could be further from the truth, unless you go to 1998 for your gas fills. There is this pretty cool piece of software called V planner, perhaps youve heard of it (lol) that has a "tools"
section which will show you how to take a partial tank of 80% and top it off to keep it at 80%.

I do it every week. Very, very, simple.

 

[kwinter]

HUH???? Nothing could be further from the truth, unless you go to 1998 for your gas fills. There is this pretty cool piece of software called V planner, perhaps youve heard of it (lol) that has a "tools"
section which will show you how to take a partial tank of 80% and top it off to keep it at 80%.

I do it every week. Very, very, simple.

 

[Patoux01]

First, the benefits touted for the oxygen window went out that window a while ago. The theory behind that has pretty much been forgotten.

Sorry, I'm kind of gonna be a digger here (kind of, it's only the 3rd post of a 6-page thread). Would you happen to have some reference for that? Not that I doubt it, but I still seem to find many information going "oxygen window this, oxygen window that".

Cheers

 

[Michael Guerrero]

I think what BoulderJohn was referring to was that it was previously believed that going onto oxygen had some additional positive effect outside of increasing the inert gas gradient. This was acceleration beyond what is now expected and has been debunked. What people often refer to these days as the oxygen window relates to decoupling the rate of off-gassing from your depth by increasing the difference (gradient) between the partial pressure of the inspired (inhaled) inert gas and the partial pressure in the tissues. By going onto pure oxygen the difference is maximized because no inert gas is present in the inspired gas and so the maximum rate of offgassing can occur.

 

[rjack321]

For the relatively short bottom times and total deco you are talking about 50, 70, 80, 100% whatever really doesn't mean much at all. You still end up with pretty much the same about of total time for the ascent. EAN50 is the deepest switch and reduces your minimum backgas requirements the most. If you are having a problem at depth or on the ascent you can get on your deco gas sooner and hopefully get control of your issues quicker before they snowball. Starting deco deeper is also easier buoyancy wise. So for now, EAN50 is a good single deco gas choice for beginners.

Once you have 40 to 70 (a rough guess) deco dives under your belt and don't have to ask on SB, you can make a more educated decision for yourself about what is "optimal". Personally I have EAN50 and 100% in the garage, which is what all my buddies use as well.