A week later, still can't see the problem.

[Ste Wart]

Just for my info, if you found an alternative to the GFs, another mean of adding conservatism to Buhlmann's model I mean, would you try it?

Difficult to say yes or no. What alternative could there be? Personally I like the stops occurring deeper as per VPM but a longer hang in the shallows, like Buhlmann. I can fudge that up with 10/75 on Decoplanner. As it stands, I've just moved back the UK, so I'll stick with the decoplanner and see how my body reacts in the colder waters.

I am curious why the owner even 'asked'. When he called initially, he could have said that the op preferred to have all divers on the same gasses (and schedules), he could have said he wanted the other divers in the group to know that you had asked for a different mix before agreeing to it, or that he normally considers all tec divers on a charter to be a single team, etc. etc. I don't happen to agree with those views, but I can understand ops that take that position. In other words, he could, and should, have let you know before you showed up to analyze the gas that there might be an issue. As you suggested and most have agreed, the difference in terms of dive parameters (deco schedules, gas compatibility across divers) was trivial. The only thing not trivial was the additional costs to you. Perhaps, some would even say the difference in cost was trivial (at least compared to the overall cost of the charter and the 20% helium to begin with), but that is your call and not someone else's. I REALLY don't like someone else telling me what gasses I am going to dive, without my input, and that issue has little to do with money. Having said that, I don't know the usual and customary procedures with the charter op you were using, the personality of the owner, etc. And, I don't think there would have been anything wrong with him telling you - when he first called - that 'policy' required you do what the rest of the 'team', or simply the majority of divers, was doing, and that would have given you the opportunity to choose to stay or bail in advance.

You're right, the 10% extra was a trivial extra. The funny thing was how the dive op let me analyse while watching over my shoulder and didn't mention that there was more helium in the mix until after analysis.
I was definitely not part of the team. The other guys all were diving ratio deco, with all the DIR trimmings. I'm on my own cruising around with my 50% happily strung on my right hand side wondering where I could get some bungee for my long hose. They probably wouldn't have wanted to share gas.

 

[Red Sea Shadow]

What alternative could there be?

An alternative to the GF-Hi is to assume asymmetric gas kinetics. This adds conservatism. An alternative to the to the GH-Lo is to just start your stops as deep as you want, but you have to use a software capable of calculating multi-level dives "correctly".

 

[GeorgeC]

....... The funny thing was how the dive op let me analyse while watching over my shoulder and didn't mention that there was more helium in the mix until after analysis.....

I have a problem with this move (Watching over your shoulder)….Was he waiting for “Whew he didn’t realize that he asked for 20/30 and now he has 20/20 I am glad I got away with that”. He should have given you the gas and said “We made a mistake on our end and gave you 20/20 what can we do to make this better for you?”

 

[PfcAJ]

Never seen anyone complain about more helium...

 

[Centrals]

Never seen anyone complain about more helium...

If the excess He is FREE of charge.
You will be suprised to know how expensive it is outside USA.
We requested 18/40 once to dive PoW(65m) but was given 11/60!!

 

[Spazzy]

20/30 is easy to mix if you have banked 32%.

 

[waterpirate]

20/30 is easy to mix if you have banked 32%.

So often blending gas is the last thing a dive op does at the end of there 18 hour day, prior to repeating it again tomorrow. I think it boiled down to what was the path of least resistance for the blender. Shame on him for not making that crystal clear prior to your arrival. If you run right at someone with the truth, no one is dissapointed.
Eric

 

[Ste Wart]

So often blending gas is the last thing a dive op does at the end of there 18 hour day, prior to repeating it again tomorrow. I think it boiled down to what was the path of least resistance for the blender. Shame on him for not making that crystal clear prior to your arrival. If you run right at someone with the truth, no one is dissapointed.
Eric

By chance I only used 50 bar on the dive and asked for it to be topped up with air the next day. Guess what mix I got? 20/20!