Deco gas choice for this dive?

[Kyle0692]

Hi all,

I am planning on diving the Hydro Atlantic wreck this January with several others. Looking at dive plans with MultiDeco, 50% seems to make sense versus 65% that the other divers are proposing. When I look at the RT differences between the two, they are the same. My thinking was that you can get on the 50% sooner at a deeper depth instead of having to do deco on back gas, MOD of 72 ft vs 48 ft. This also would have the advantage of an OOA diver being able to get on his deco gas sooner should he need it. We are all AN/DP certified to use just one deco gas. Dive profile #2 at the bottom.

Just wanted to get some thoughts from the more experienced folks here in case I am overlooking something.

Merry Christmas!

Kyle

 

[ChuckP]

Not super experienced but my 2 cents. I won't dive 30/90 ever, I like more conservative and shallower stops. If I had a choice of lung full of water or lung full of too high PO2 gas - that decision is pretty easy for me - I don't think about if I had to breathe it at depth when picking deco gas.

The bottom of the hold in the Hydro is mid 160's, I think the sand is mid 170's. I like conservative and plan deeper but maybe you're not thinking penetration and sticking to AN/DP depths. Our single deco tank penetration dives, we used mid 60's deco gas, 26 minute actual run time, first stop 60', using 40/70.

 

[Tug]

Just use the 50%, there is zero reason to use 65% unless you want to make it more complicated for everyone.

 

[PfcAJ]

50%.

Your reasoning is sound.

 

[Kyle0692]

Thanks all for the thoughts.

Chuck, GFs are 30/80, not 90 - for some reason that photo turned out a bit blurry.

I will see what their reasoning is for 65% over 50%. The 50% is the better choice it seems.

Kyle

 

[WinfieldNC]

Thanks all for the thoughts.

Chuck, GFs are 30/80, not 90 - for some reason that photo turned out a bit blurry.

I will see what their reasoning is for 65% over 50%. The 50% is the better choice it seems.

Kyle

I haven’t run the two different scenarios but I’m guessing 65% will end up with you having shorter deco times.

 

[WinfieldNC]

Just use the 50%, there is zero reason to use 65% unless you want to make it more complicated for everyone.

How is it more complicated if everyone just uses 65%? Same plan, same mix for everyone that is diving together.

 

[tomfcrist]

50% is standard...and easy to mix. My guess is that most anyone who dives that wreck drags around 50% and O2.

 

[broncobowsher]

Also need to watch gas consumption. Doing both dives on the same deco bottle?
The leaner mix that you get on sooner, it is better in the 70 through 50 foot stops but as soon as everyone else switches to the 65 they will have a better deco mix than you. and there is a lot more time spent at 40' and above than those few minutes between 70 and 50.

 

[Tug]

How is it more complicated if everyone just uses 65%? Same plan, same mix for everyone that is diving together.

What Tom said below... plus the boats are familiar with the run times using 50%, not to mention that when 40’s are so cheap, just keep a bottle of 50 on hand and you don’t have to mess with changing mixes to account for different plans and mixes

50% is standard...and easy to mix. My guess is that most anyone who dives that wreck drags around 50% and O2.