Dual Bladders & DIR

[blacknet]

Hello,

Sorry that was not intended to be taken as a 'soapbox' I tried to present an unbiased statment and urged them to look at the studies and form your own conclusions as there is not a single 'correct' method. Please dont' take what I say out of context nor please don't read anything into it.

As for the studies and cases I mentioned I recomend you contact rainreg for all the details. He can point you in the direction if he doesn't have it in his extensive library (i've seen it and it is impressive)

Ed

 

[blacknet]

Hello,

bradymsu, a couple of questions. A) what does it matter if it's 'dir' or not? and B) What type of enviroment(s) and type are you going to be doing that may involve dual bladders?

BTW i've seen alot of twin al tanks probably the same as if not more than dual steel tanks.

Ed

 

[bradymsu]

Ed,

I'll be taking my full cave course and I'll be doing it in a 7mm wetsuit, probably with double steel tanks and a double OMS bladder.

As far as your question about why DIR matters to me, it doesn't in a religious sense. I'm not a DIR diver (partly because I dislike the type of macho attitude so characteristic of almost all the DIR divers I've met) but I recognize the great value in a lot of the DIR beliefs and try to learn from them as well as from other sources. I'm constantly reconfiguring my gear in my mind and weigh the merits of different arguments & opinions I hear. Most of the time the explanation of a DIR idea is clear and makes sense to me. Sometimes it does not and I try to find out more detail from DIR divers, several of which are on this board. I won't always agree with them, as in the case of their rejection of dive computers. I'm not sure I see the logic in their rejection of double bladders either.

First off, the way I see it, most tech divers who are diving wet or dry are going to be diving with steel doubles. Maybe a lot of people are diving with alum. doubles in other parts of the country/world but I haven't seen much of it yet. Does DIR even allow alum. doubles? Secondly, anyone with steel doubles (wet or dry) needs a backup bouyancy source. I haven't been able to accept that it's a good idea to consider a drysuit an acceptable alternate bouyancy source to a second bladder. The second bladder seems a lot safer to me for that purpose.

 

[blacknet]

Hello,

AH, thanks for the update makes things alot clear now. Personaly I can see both pro and con with the dual bladder bc's and using a dry suit as a backup and it would seem to me that there's a time and a place for both forms.

I guess a pro to a dual bladder would be something like redundancy and convience in the location. A con would be if something, like a section of metal, punctured one of the bladders it could just as well puncture both.

A pro to the dry suit as a backup would be it's seperated from the bc and the con would be it $ more and need more equipment to use.

Anyone have anything else to add to this?

Ed

 

[Lost Yooper]

BradyMSU,

First, a dry suit isn't necessary for DIR. Second, double AL tanks are fine for DIR. Even doubles aren't necessary for DIR.

In your case (wet suit diving), you could substantially reduce the efficiency of your gear (and substantial cost) by going with AL tanks for back gas and regular BP and wing. If double 80's aren't enough air, take an AL stage (or two or three) with you. DIR is more about getting things simpler than more complicated.

It can't be emphasize enough -- your gear must be balanced if, for no other reason, than good dive practice. I just don't believe dual bladders are a viable solution to anything but to correct poor diving practices. If you're loaded down with a ton of negative buoyancy, your dual wings will be blown up like baloons, will require more task loading to deal with, create greater drag, and the end result will be greater air consumption, less dive time, and probably less fun. A dry suit is NOT for back up buoyancy as often said, and it doesn't have to be if you're properly balanced.

I commend you for at least being open minded enough to look at DIR for its merits as many people can't get passed the BS that sometimes comes with it. I don't particulary care for the attitude of some of the people who dive DIR, but most are just like any other divers -- opinionated. The really closed minded folks are the ones who can't see past the acronym and the few loud bad apples out there. The merits speak for themselves.

Take care.

Mike

 

[blacknet]

Hello,

Lost Yooper, please define 'balanced'.

Ed

 

[Lost Yooper]

The way I interpret and use the word balanced is that divers should be weighted in such a manner that they can swim up with no air in their BC. This would be opposed to someone laden down with an enormous amount negative equipment. I've read accounts of people diving dry, with double steels, steel stages and deco bottles, and various tools and not being able to get off the bottom and dying. I'm not positive, but I think one such account was on the Doria.

As I am currently set up with double 95's, 10lb V-weight, AL stages, and dry suit, I can completely empty my BC and dry suit on the bottom and easily swim to the surface. Once upon a time, I used double 95's and just a surfers shorty, and I was completely dependant upon the wings getting me up -- DIW.

If someone is genuinely nervous about not having a redundant way of getting to the surface, then I would suggest carrying a lift bag and spool and diving with a good buddy. Between being properly weighted (balanced), having a lift bag, and diving with a buddy who is properly weighted and has a lift bag, 'ole Murphy would have to show his ugliest side for one not to make it to the surface as the result of a very unlikely BC failure.

Mike

 

[The Chairman]

That is SOOOOOO true LY! You can learn a lot from many different sources, and it is best not to close your mind until you have all of the facts.

Over weighted... Now, where does the extra buoyancy needed for the steel doubles come from??? What is the difference if it is from your dry suit or from a large lift capacity BC??? It appears to be six of one, half dozen of another at first glance. I think that’s what I would like to see the DIR answer to. Please note, I am not itching for a DIR fight either way, but I really want to understand what I see as an ultra fine point of this "balanced" diving concept. I dive a 5mm, and don't own a dry suit. I do dive 120 HP PSTs and dual 72 LP OMSs... I need NO weight with either in fresh, and am significantly over weighted with the dualies. In salt I need a few pounds with the 120s and am still a tad negative with the dualies. I can surely fin to the surface with either rig w/ no air in the bladders in either fresh or salt environment. While I claim to be nothing more than a Stroke, I would seriously like all opinions of this practice. I am comfortable with my OMS IQ and Dual 100# bladders, and never hook up the second inflator hose for precisely the reasons mentioned... just in case the inflator leaks. Still, I band the inflator hose next to the valve (which is also banded to the side of the BC) in case I do need to plug it in. If nothing else, I could always orally inflate it!!!

:tease:

And please, let’s let all who want to comment do so, DIR and non DIR alike. I appreciate all opinions, and will make my own decisions in the end. We do not need to polarize the issue with name calling etc.

Oh yeah LY... that was really Murray's law, but there was a typo at the printer...

 

[100days-a-year]

Just one question. OK assuming 2x95lp and say 2x40al for stages nuetral at the bottom to start. At the end of the dive you will be 16 lbs positive roughly if following rule of 1/3s. Where does this figure in. I don't know of any way to cheat Father Physics. We are either heavy to start or light at end due to air consumption...can't be both. So if your single bladder goes out at the bottom at the beginning of the dive and you can swim up ,then you wpuld have been light at the end. What Gives? I actually dive this configuration most of the time when going deep unless I'm staying long then its 2x72 or 2x80al for stages.

 

[Lost Yooper]

Howdy Pete,

I certainly can't argue against your experiences. I can only say that there are many people I have talked to and read about that claim different -- especially with HP tanks. Dual HP 120's full come in at around -23#, and if you add the rest of the stuff you're probably at -26# or so, right? I know that I wasn't able to swim that much weight up with a shorty from 20', but you might have better luck with a full wet suit that's paper thin at say 150'.

My question to you is if you're so well balanced and can, in fact, swim up with empty wings, then why would you need dual 100# bladders? It seems to me that even a single 100# bladder is over kill. If, by that token, you don't need dual wings, then why pay the big bucks for them and never have use them?

In my very humble opinion, if one brings gear they don't need, then the extra stuff adds to a convulation of gear that can only hinder some aspect of the dive (streamlining, air consumption, task loading, etc). I could be way off base here, and probably am, but that's kind of how I see it.

Mike

Tony, I'm not sure if I quite understand your question. Of course you're negative at the beginning of the dive. The question is how much is too much to swim up.