Dual Bladders & DIR

[bradymsu]

I read on the DIR website that dual bladders are "an invitation to disaster" but without any explanation as to why. What are the reasons? What does a DIR diver use as a substitute when wearing a wetsuit since the far majority of tech divers dive with steel doubles?

 

[TexasMike]

Clarify please.....susbtitute for the double bladders or substitute for the wetsuit (exposure protection)?

 

[bradymsu]

I mean substitute for the dual bladders. I haven't seen anything yet that says it's not DIR to dive wet.

 

[blacknet]

Hello,

First off if you look at the dual bladder concept you'll note that it looks like a normal bc at first. One the second look you'll see 2 inflator hoses and the design is quite nice.

The person you need to direct this question to is rainreg, he's spent the last several years working with bc's and regulators for the navy and if he can't answer the question then my money's on the fact that he knows someone/where you can find the correct answer/facts.

The iantd technical diving encyclopedia states that redundancy is needed in some things but if you have a dry suit you do not need a dual bladder bc. Also state that it's recomended (a good idea but not a must have thing) to use dual bladder's in case one was ruptured, but they are also assuming you are going around structures like caves, wrecks and other similar objects that could easily rip you open like a can opener. Perhaps that this is what the dir people are doing, diving single bladder bc's with dry suits, so in essence they have a dual bladder bc.

I urge you to look at the many studies done on this situation and see the results, then make up your mind. Gear selection is a personal decision that should not be decided by someone you've never met. It should be customized to the job at hand (i.e. the dives that you will be doing), afterall it is just a tool.

Ed

 

[JoelW]

Wow Ed, I am not even sure why you bothered to answer this question. What started as a simple question about a methodology in which you have no interest has become a little soapbox just for you. The question asked about DIR, IANTD was not mentioned anywhere.

As a good little beginner sheep I will try to answer the question. One of the first tenets (like that religious term, you know, since DIR is a cult and all) is that a rig should be balanced. If it is, the diver should be able to swim up with little or no lift from a BC by dumping weight. If that is the case, a second bladder should not be needed, especially one with 100# of lift. Another issue has to do with a rig where both inflators are connected. The belief (religious term again)is that if the backup bladder inflator has a slow leak it will not be detected by the diver. As the diver dumps the primary bladder the backup bladder keeps pulling the diver up. It's a task loading issue.

If I have the above wrong, someone with a better understanding please correct me.

JoelW

 

[Green_Manelishi]

If you NEED 100 pounds of lift you are wickedly over-
weighted. If you NEED dual bladder redundancy you are
likely diving steel doubles with a wetsuit and therefore
you are wickedly over-weighted.

 

[svs3]

BradyMSU,

If you're rig is balanced then dual bladders are "an invitation to disaster" because they are not needed only serve to introduce more failure points and the potential for greater task loading at times of great stress.

Blacknet,

You make constant references to reports and studies. Can you post some links to the studies you are refering to in this case.

Dive Safe,
Sam

 

[Lost Yooper]

Greetings,

By introducing dual bladders, you are trying to solve a problem that shouldn't exist in the first place. In realility, whether you're a dry suit diver or not, the rig should be balanced so you can swim up if your BC fails. Yes, the dry suit can get you up (as can a lift bag), but that's not what they're all about.

By introducing dual bladders, you are introducing more potential failure points that are completely unneeded if you are well balanced. In my opinion, dual bladders are just another gimmick out there that encourage poor diving practices and are supported only by those people and agencies that encourage poor diving practices. These poor diving practices are, in part, what is being referred to when they say "an invitation to disaster".

Example: A "tech" diver in a wet suit + double steels + 3 steel stages + canister light + helmet + a bag full of tools = "invitation to disaster" -- double bladders or not.

Mike

 

[bradymsu]

Thanks everyone. From interpreting the answers given, I've concluded that it is not DIR to dive in a wetsuit with steel doubles and that is you are diving in a wetsuit, only alum. doubles should be used. Is this accurate? Is a drysuit mandatory for DIR diving? I haven't come across a whole lot of divers with alum. doubles.

 

[100days-a-year]

I guess all those experienced (notice I didn't say old) divers with tens of thousands of safe dives or more using dual bladders are really, really lucky. While all the DIR stuff is true. A few of these things are moot or even contradictory. While it is my choice to dive DIR as much as it suits my dive. I have this to say. How can a drysuit be so infallible a back-up bouyancy device ,when all things considered it essentially is a second bladder with even more failure points. If you stop to consider the loading on neck, wrist and ankle seals (if any) surely the drysuit has more potential for failure. And just exactly how many of you have ever seen one bladder fail. I met one of the GUE instructors in my LDS last fall. As always I make no mention of my experience to people I meet. I was amazed when he told me that aluminum stages will float up a line when finished with that gas. Can anyone guess what I told him?