Dual Bladders & DIR

[The Chairman]

Hey LY and all,

To clarify, first, I feel I need signifigant bouyancy to stay neutral with the dual LP 72s. How much, I never thought to figure that out.

Secondly, both bladders are contained by the the same outer nylon shell. You can't inflate both, just one at a time, so you can't come up with 200#s of lift. The second bladder is merely a redundancy in case of failure by the first.

Thirdly, I see some of the buoyancy from the DIR crowd as coming from their drysuit. It also acts as a redundancy in case of a bladder blowout. It also acts as a point of failure, or possibly points of failure. My question is, does it really matter WHERE the buoancy comes from??? Whether it be a drysuit or BC bladder, you still need to counter react the weight in order to be neutrally buoyant.

Would a consumate DIR diver feel that he/she should be able to surface without air in either BC bladder, OR Drysuit?

 

[Lost Yooper]

Pete, I'm not sure about everyone else, but my answer to your last question is yes.

What I have learned (and practice) as it pertains to DIR, is that the dry suit should not be RELIED upon as a redundant means of buoyancy. That doesn't mean that the suit can't do the job, but only suggests that proper weighting and balance is of utmost importance. IMO, the dry suit is meant to do its job -- to keep you dry.

The only point that I'm really trying to shoot for is that dual bladders are not required for wet suit divers if they adhere to a well balanced rig. From my readings on the subject, this would be double AL 80's, single 55lb wing, AL stages, and the appropriate weight belt. It just seems to me that this route is the most efficient in terms of simplicity and cost.

Great discussion guys.

Mike

 

[Liquid]

Bradymsu,

About the rig you mentioned for you Cave-Diving course: when you dive a cave, the last thing you want (and I belive what I am saying, is according to DIR, please correct me lost-yoopers if I'm wrong) Is to be a bit light, and get to the ceiling of the cave. That means the rig you use is a bit different. Much better being a bit too heavy than too light here. The risk of going down to the abyss dosen't exist here, you will be more troubled if your feet scrape the ceiling. On a dive with the same profile, not in a cave, sinking is a much greater risk than WITHIN a cave. So In a cave you may prefer Still tanks, while in open water you'll prefer Aluminum tanks.

 

[Lost Yooper]

Yeah, in an overhead environment, among the last things you want is to be too buoyant. I've never heard of such a rule that suggests using steel tanks for overhead stuff and aluminum tanks for openwater. If you're properly weighted and balanced, then I don't really see how aluminum tanks will be a hinderance in an overhead enviroment.

Mike

 

[rcohn]

Standard DIR parctice (according to GI3) is double 95s or 104s for caves and double Al80s for open water. I've never heard any discussion of serious cave diving with Al tanks for back gas.

Please explain how double 104s can be balanced so that you don't need buoyancy to swim them up when full.

Ralph

 

[Liquid]

Lost-Yooper,

I read about it in the links you gave me
Written by Irvine I belive, in an essay about rig types for use in different kinds of enviorments. He mentioned that in certain cases using aluminum tanks is not advisable, and in certain cases steel tanks are not advisable. Made quite a good explenation on the DIR view of rigs, which I really find to be the correct view, in my opinion.

 

[Lost Yooper]

Howdy Ralph,

His arguement (aside from the wet suit thing) for double 80's for open water, as I have heard them, is their lower weight (ie. easier to deal with) on a rocking boat than 104's or 120's. I have heard of DIRer's using aluminum tanks in caves with a wet suit.

I can't personnally attest to the buoyancy characteristics of double PST 104's, but I can easily swim up my PST 95's, SS plate, and a full stage with no air in either my BC or dry suit. I should say that with a shell dry suit, I don't think you're ever going to get all the air out, so that helps a great deal in the overall picture. As for 104's and shell suit, I've heard the same can be done quite easily and is usually the context of their discussions anyway since the 104's are their tanks of choice.

Take care.

Mike

PS. If I think about it later, I'll ask GI to clarify it a bit.

 

[100days-a-year]

LY,I just wanted to hear that you were heavy at the beginning. It sounded like someone had proposed a free ride. I also use the 2x95lp+stages. I'd hate to try to swim them up from depth. I'm only 180-190 and in very good Cardiovascular shape so there's little chance I'll ever need more gas.My buddies (all over 6' and 200lbs) use 120s, I'd hate to swim them anywhere. Another consideration for DIR is that it was designed to be used as a way to maintain a continuity amongst team members. I configure similarly to who I'm diving with, within the context of not diving with yahoos.

 

[TexasMike]

Just a quick comment to you folks that I appreciate this discussion about diving doubles, DIR outlook, and such. As an aspiring Tech diver, I know I will be putting this stuff on my back eventually. So reading about it now is helping me to gain both understanding and appreciation into this aspect of diving.

Keep up the good info!

 

[Lost Yooper]

TexasMike,

This has been a good exchange of opinions on the subject. I can't think of a better way to learn about stuff (other than personnal experimentation) than in this format.

Good luck on your tech quest.

Mike