Trimix in Austin

[FIXXERVI6]

I have no suggestions, if your here to post then something had to have gone correctly.

I myself prefer 50 and 100 and am just curious about why other people choose the gases they do, I know why I choose mine, so I like to hear other peoples reasons for their choices, maybe I'll learn something. For travis normoxic mixes using a single 50% deco gas works wonders, run the profiles and see the differences.

I'm not going to hijack a thread or anything, (further than I already have) scuba board doesn't need another 80 vs 100 thread and I'm not the type of person to make that argument.

and just FYI for the peanut gallery I'm not going to sling dirt in this forum on people that dive gases other than my preference, last I checked this was a semi-free country and to date you can dive whatever gases you want.

What sets me off is others putting others in danger or spouting BS information on the board that can lead to putting others in danger.

 

[ianr33]

Suggestions? I'm all ear...or eyes as the case may be.

The DIR comment was a joke. (I'm not exactly DIR myself)

Comments? I dont see the point of using 33% for a first deco gas. the first stop on this profile would be at what,80 feet? Why not use 50% and switch to it at 70 feet. Using 33% you would be switching below your first deco stop which seems kind of pointless and also complicates things as you will be switching on the fly rather than at a stop.
(If you were planning a multi level profile ignore the above!)

IMHO the 80%/100% argument is way overdone. I really dont care either way that much.In practice I use 100% as it makes life easy.Dedicated O2 bottle,no mixing needed,get several dives from one fill.

Why 2 deco gases? You dont save much time on this profile over using one tank of 50%

Finally,I dont think I would like the idea of having 2 deco tanks with the current viz in Travis,too much chance of screwing up.

I'm pretty new to trimix so take the above for what it is worth,gas selection makes for an interesting discussion though.

 

[ianr33]

I myself prefer 50 and 100 and am just curious about why other people choose the gases they do, I know why I choose mine, so I like to hear other peoples reasons for their choices, maybe I'll learn something. For travis normoxic mixes using a single 50% deco gas works wonders, run the profiles and see the differences.

Agreed. Diving square profiles with large steel tanks 50% and 100% is the way to go.I did some dives in Cayman over Thanksgiving and we used 18/35,32% and 80%. Why?

Typical profile was 200 feet for 20 minutes. Double Al 80's for backgas,an 80 of 32% and a 40 of 80%. Double 80's dont give you a lot of backgas at 200 feet.Switching to 32% at 120 feet makes the rock bottom on the back gas look a lot better. The END was 118 feet. More than is normally recommended but clear blue water and within my comfort zone.

Also the terrain had a 10 minute swim over a sandflat at around 65 feet. Using 50% would have pushed up the CNS and would have cost more $$$$.On one dive we met a strong current and I was glad not to be kicking hard at a PO2 of almost 1.6.

There is a lot of life at 30 feet but at 20 it is fairly barren hardpan so the 80% worked very well as we did most of our deco at 25-30 feet.

Gas selection depends on the site.One size does not fit all.

Oh yeah,the dives were great !

 

[Phreatic Fanatic]

Gas selection depends on the site. One size does not fit all.

I agree!
That is an excellent example. I dived similar profiles using those same mixes while teaching in Cayman in December, yet when cave diving, I typically use 100% for deco.

 

[texdiveguy]

One size does not fit all.

........

 

[Mack Diver]

The DIR comment was a joke. (I'm not exactly DIR myself)


I'm pretty new to trimix so take the above for what it is worth,gas selection makes for an interesting discussion though.

Sounds like a couple more D.I.M.W.I.T. divers. Doing It My Way In Texas.

I appreciate threads like this. It allows the experienced to share information, the newbies to gain information and the curious to gain insight. God Bless America, Texas, John Wayne and ScubaBoard!

 

[amascuba]

One of the nice things about DIR gas selections for back gas is that you can just top up with 32% and have a proper mix... 30/30 being the bastard child and doesn't work..lol

For example:

(Assuming empty tanks)

500psi of helium and topping up with 32% gives you 25/25 (OK... so it's not a GUE standard gas... sue me)
750psi of helium and topping up with 32% gives you 21/35
1000psi of helium and topping up with 32% gives you 18/45
etc, etc, etc... You get the point.

It makes blending back gas easier.

I'm also in the 50%/100% camp.... Like the others ... we don't need a debate here.

 

[texdiveguy]

God Bless America, Texas, John Wayne and ScubaBoard!

Mack, now your talking....but not sure I would go as far as adding SB in there though!

 

[FIXXERVI6]

One of the nice things about DIR gas selections for back gas is that you can just top up with 32% and have a proper mix... 30/30 being the bastard child and doesn't work..lol

For example:

(Assuming empty tanks)

500psi of helium and topping up with 32% gives you 25/25 (OK... so it's not a GUE standard gas... sue me)
750psi of helium and topping up with 32% gives you 21/35
1000psi of helium and topping up with 32% gives you 18/45
etc, etc, etc... You get the point.

It makes blending back gas easier.

I'm also in the 50%/100% camp.... Like the others ... we don't need a debate here.

In bold, I've said for a while now among my buddies that banking 32% will give us the greatest flexibility for the gases we use local as 21/35 is a great travis gas, and when the lake is down 25/25 is great too. I plan on banking mix at home eventually but the largest volume of my bank will be devoted to 32%.

Another benefit of GUE gases is if you look at deeper profiles, if you stick to standard mixes only there is some built in "IBCD" prevention. for example, air is not an option so if you come up from a deep dive and switch to air, your more likely to get hit rather than switching to 21/35 or 30/30 standard mixes etc.

Not sure if that makes sense, if not I can post a standard gas list or whatever, they can be found all over the web.

And lastly all of my buddies currently dive standard gases, so if we are talking on the phone about an X dive, I already know what gases he intends on using during the dive, or at least pretty durn close.

I do not ever use best mix, pita.

 

[k-valve]

Why 2 deco gases? You dont save much time on this profile over using one tank of 50%.

All good points...I appreciate all the feedback and input...and since I started this thread I don't care if it gets hijacked for this discussion.

The reason we used two deco gases is because these were the last certifying dives for my normoxic trimix cert. That said, I'm REALLY new to diving trimix. Even though my instructor could have certified me with just one deco bottle he wanted to make sure I could handle two...thus the 32 and 80. It was more about skills than deco time. Although I did see a couple of really nice catfish at 20' and 30'.

I have to say I appreciate the practice and thinking he made me do when it came to using two deco bottles.