DIR- Generic dual bladder wings...

[Wibble]

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Interesting the pricing. The $5/cf I heard about was from people in the north (not Canadians!)

For the same 50% fill of twin 120's, the cost would be 120 X $1.35 = $162 for the helium. A lot cheaper than $600, but still way more than the 3cf required for a rebreather =$4.

 

[beester]

The most interesting result for me coming out of this very long topic is, me reading up on GPT-3. I was totally unaware. That and the cycling and beer topics ;-)

To bakodiver391 who signed off. The reason why people are reacting to you the way they are is very simple, you are defending a system that's just not very useful for the majority of divers part of this "DIR" group. So of course they will react from their point of view. It's the same as going in the "sidemount" forum and defending backmount diving as the end to all. See what kind of reactions you'll get. There is no right or wrong, there is just different ways of doing things.

However you are telling people that we are biased (which we of course are, everybody is in certain contexts), but fail to notice how biased you are?! Your off the cuff remark about instructors needing to teach their "acolytes" to behave better... well that's just bad form! It also clearly shows that you have no idea how for example GUE instructors teach or how the community works. Most of them are super friendly and inclusive ;-) They also don't need to throw around their experience and who they dived with... it's a given ;-)

 

[Adobo]

Interesting the pricing. The $5/cf I heard about was from people in the north (not Canadians!)

For the same 50% fill of twin 120's, the cost would be 120 X $1.35 = $162 for the helium. A lot cheaper than $600, but still way more than the 3cf required for a rebreather =$4.

You breathe your backgas empty on tech dives? I would think that you would have at least 1/2 of min gas in your doubles after any dive, especially a tech dive. The exception being if you had an emergency that necessitated you going below min gas.

 

[Wibble]

You breathe your backgas empty on tech dives? I would think that you would have at least 1/2 of min gas in your doubles after any dive, especially a tech dive. The exception being if you had an emergency that necessitated you going below min gas.

Of course you breathe it all if the brown stuff hits the fan. If you don't, why take so much with you?

My point is that there's a ton of circumstances where you could breathe it all. After a very rough time of playing the "one failure only" game, it results in you having to use everything as, of course, that one failure happened at the end of a decent bottom time, possibly with a bottom stage.

Yes, there's plenty of mitigation strategies such as sending the empty bottom stage up the SMB line. But you've still consumed a lot of gas and you SHOULD have factored this into your planning.

There's also the "don't dive overweighted" mantra. The time to discover that you're actually relying on the weight of all the gas is not when you've used most of the gas and still have a deco obligation and are too light.


Bring on the dancing girls: why are you diving alone, your team mates will save you....

 

[Adobo]

Of course you breathe it all if the brown stuff hits the fan. If you don't, why take so much with you?

My point is that there's a ton of circumstances where you could breathe it all. After a very rough time of playing the "one failure only" game, it results in you having to use everything as, of course, that one failure happened at the end of a decent bottom time, possibly with a bottom stage.

Yes, there's plenty of mitigation strategies such as sending the empty bottom stage up the SMB line. But you've still consumed a lot of gas and you SHOULD have factored this into your planning.

There's also the "don't dive overweighted" mantra. The time to discover that you're actually relying on the weight of all the gas is not when you've used most of the gas and still have a deco obligation and are too light.


Bring on the dancing girls: why are you diving alone, your team mates will save you....

I thought your point was around the cost of tech diving on open circuit vs. rebreathers. That's what I am responding to. The way your post came across, you always put about 120cu ft of helium in your double 120s when you get fills. That would only be true if you had to dip into gas reserves you have set aside for your dive buddy. Hopefully, that is an incredibly rare situation. If it happens repeatedly, someone is doing something wrong.

In practice, when things go to plan, you end with at least 1000psi. That's my experience on double hp100s doing tech 1 dives anyway. So while these fills are still expensive, they are not as expensive as filling empty doubles.

 

[Gene]

I've been diving Florida caves and some wrecks since 2005 with the same DiveRite double bladder wing and a 3mm wetsuit. My max depth so far is 285 ffw years ago and I doubt I'll see anywhere close to that again.

 

[crofrog]

I thought your point was around the cost of tech diving on open circuit vs. rebreathers. That's what I am responding to. The way your post came across, you always put about 120cu ft of helium in your double 120s when you get fills. That would only be true if you had to dip into gas reserves you have set aside for your dive buddy. Hopefully, that is an incredibly rare situation. If it happens repeatedly, someone is doing something wrong.

In practice, when things go to plan, you end with at least 1000psi. That's my experience on double hp100s doing tech 1 dives anyway. So while these fills are still expensive, they are not as expensive as filling empty doubles.

For tech 1 limits I'm assuming you're limited to about ~20 minutes at 170ft based on the 30 minutes of deco. Decoplanner spits out 92cuft of 18/45 for a 20min dive to 170ft. So about 75 dollars for the bottom mix, and 8 dollars in NX50.

So that's about 100 T1 dives before you've covered the purchase price of a JJ (not including any training or consumables for the CCR)

Did I do that math right?

 

[Doby45]

For tech 1 limits I'm assuming you're limited to about ~20 minutes at 170ft based on the 30 minutes of deco. Decoplanner spits out 92cuft of 18/45 for a 20min dive to 170ft. So about 75 dollars for the bottom mix, and 8 dollars in NX50.

So that's about 100 T1 dives before you've covered the purchase price of a JJ (not including any training or consumables for the CCR)

Did I do that math right?

Yup that covers about 100 dives with the requirements you set forth, but is that all your doing the rest of your life? If you are even doing 101 dives or more you then start to see immediate cost savings. Think of it when you buy your house. If you only stay in your house2 years, and then move, you are only really ever paying the taxes on the house. If you stay longer you start hitting on the principal and the value of owning a property. Same for CCR ownership, if you plan to continue doing those hundreds of T1 dives the CCR pays for itself many times over. When is it you have decided that you are throwing away enough money?

 

[crofrog]

Yup that covers about 100 dives with the requirements you set forth, but is that all your doing the rest of your life? If you are even doing 101 dives or more you then start to see immediate cost savings. Think of it when you buy your house. If you only stay in your house2 years, and then move, you are only really ever paying the taxes on the house. If you stay longer you start hitting on the principal and the value of owning a property. Same for CCR ownership, if you plan to continue doing those hundreds of T1 dives the CCR pays for itself many times over. When is it you have decided that you are throwing away enough money?

So in running some math, if you just keep doing T1 dives to 170ft for 20 minutes and you assume an ACE of 200 minutes, 20kg of sofnolime is 170 bucks, and $237 for 3 O2 sensors every 50 dives (annual replacement.) You are looking at ~40$/dive on CCR in consumables, completely ignoring gas costs for the diluent and O2 you do use.

It would take 213 dives for the crossover between the OC and CCR to occur assuming no other parts needed to replaced or serviced in either system, and you never touched your bail out gas, I fully admit I could be misunderstanding some of the cost of CCR diving.

I'm not sure if that savings to me would make it worth switching to CCR for cost savings, I think there are other valid reasons to dive CCR when the logistics or parameters of the dive require it but for the T1 level it really seems like a lot of additional complexity and risk, but maybe that's my ignorance.

 

[Doby45]

So in running some math, if you just keep doing T1 dives to 170ft for 20 minutes and you assume an ACE of 200 minutes, 20kg of sofnolime is 170 bucks, and $237 for 3 O2 sensors every 50 dives (annual replacement.) You are looking at ~40$/dive on CCR in consumables, completely ignoring gas costs for the diluent and O2 you do use.

It would take 213 dives for the crossover between the OC and CCR to occur assuming no other parts needed to replaced or serviced in either system, and you never touched your bail out gas, I fully admit I could be misunderstanding some of the cost of CCR diving.

I'm not sure if that savings to me would make it worth switching to CCR for cost savings, I think there are other valid reasons to dive CCR when the logistics or parameters of the dive require it but for the T1 level it really seems like a lot of additional complexity and risk, but maybe that's my ignorance.

It is your ignorance.