JeffG
Contributor
Not all alum tanks are made equal though. Look at Cat 40's...they suck as deco tanks.MonkSeal:
steel aluminum tank
- Thread starter seiff
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OP
seiff
Registered
ok, I see, but that means you are definetly a little negative at the start of the dive right? So, given bladder failure early in the dive, the dry suit becomes the backup BC to get to the surface. But what is the contingency if you lose ALL inflatable buoyancy control? Can't swim up your fully gassed rig, like you can in single tank diving. Do you start ditching stuff? I'm not being skeptical I am just curious about the practice. -tadd
limeyx
Guest
seiff:
You can start ditching stuff (your AL80 stages will be a bit negative to start with when full, so you can hand those off to another diver)
You can also use a buddy to help balance you (as they should have a working wing hopefully)
the short answer is that you cannot plan for every contingency 100% so you have to set the level of risk you are willing to take.
Since we'd normally abort the dive as soon as a suit flood or wing failure occurred, the chances of *both* happening to the same diver same dive are (generally) considered unlikely enough.
It is inevitable with big doubles that you probably have a hard time swimming up (say) double 130's with no wing/dsuit. One solution is to take smaller doubles and more stages (which can be ditched)
Also, you definitely need a balanced rig in a cave just as much as in open water, as you really dont want to drag the bottom of the cave for an hour exit (and sometimes the line is going to be a long ways off the bottom)
To an extent it's a series of compromises that the team has to feel happy with.
MonkSeal
Contributor
Ok, we use Luxfer Al tanks for deco/stage.JeffG:
RonFrank
Contributor
Mod Post
This is a very restrictive forum. However we do not want to make the area an unfriendly place where posters are not welcome, or where the mention things outside of DIR result in attacking folks. DIR is a very small community, and we try to nurture that philosophy. However alienating posters who are here and wanting to learn is not good for DIR or for SB. IOW's play nice, and respond unto others as you would see fit to respond to a family member (that you like!).
Mod Post
OP
seiff
Registered
not sure why that mod post came up, and I hope it wasn't something that I said, but thanks to all that responded. -tadd
Wasn't you, Tadd. Please feel free to post any questions you have on the DIR perspective on things -- We may not always be able to answer them, but we'll try!
OP
seiff
Registered
word.
Miami_Diver
Contributor
I dive with double 80s and a 40al stage when tech diving.I have a Steel backplate and wear no weights and still neg at 10ft with 500psi on a 3mm wetsuit,the manifold and SS/BP provide all the weight I need , water temp right now is 88deg so a drysuit would be laughable, in the "winter" it drops to 74deg so I add a 5/3 hooded vest and Im neutral at 10ft with 500psi on AL doubles.so I dont understand why you would need 20 to 30 pounds of weight. I started my IANTD trimix class last week and one of my driss was to swim up a rig with a empty wing and full of gas , I had no problems doing it.
on anothe topic , I know the double wings are not DIR, can someone explain why?. it seems to me that the extra redundancy provided would overweight the trim issue.
as long as you have your backup inflator disconnected from the wing It would prevent an accidental inflation of the backup. I do not dive steel doubles because I have a more balance rig with AL but if I did dive with steels the redundant bladder would give me great piece of mind.
on anothe topic , I know the double wings are not DIR, can someone explain why?. it seems to me that the extra redundancy provided would overweight the trim issue.
as long as you have your backup inflator disconnected from the wing It would prevent an accidental inflation of the backup. I do not dive steel doubles because I have a more balance rig with AL but if I did dive with steels the redundant bladder would give me great piece of mind.
OP
seiff
Registered
Miami:
The water is a bit colder here so we wear 7mm, not 3mm wetsuits, so that is why we need so much weight. So, you may ask, why doesn't everyone here just wear dry suits? Maybe we could, but the water does warm up here as well sometimes, and a drysuit becomes, as you put it in not so many words, not needed.
I am not DIR trained, but I believe that the philosophy behind not using double bladders is that the safety inherent in the redundancy does not balance out the extra liability added because of the extra equipment/failure points that come with the equipment. I know what it is like to be a little panicked and in this case battling just one power inflator is a chore let alone juggling 2 hoses and making sure it is workin AND controlling your asent...etc... Also, with 2 bladders jammed into the same casing, you add rupture or snag risk inside the wings. Also, think what happens if both bladders end up inflated and the overpressure valve gets squeezed off....*POP*.
Double-wings is different than dual-bladder though, right? You mentioned both. Not sure why double wings wouldn't be DIR except for the same reasons I gave above for the dual bladder. And if both wings get inadvertantly inflated simultaneously or one is not deflated before switching to the backup, maybe the overpressure valves could get covered and then....*POP* again. Also, since elastic wings are out of the question, having twice as much wing flapping around at depth just becomes more undesirable, and the snag-and-drag factor is just not worth the redundancy.
Again, I am only a DIR wannabe, so this is all my thoughts on the issue, not OFFICIAL DIR, so someone feel free to add to or correct my ideas. Also, isn't your drysuit considered your back-up bladder? -tadd
The water is a bit colder here so we wear 7mm, not 3mm wetsuits, so that is why we need so much weight. So, you may ask, why doesn't everyone here just wear dry suits? Maybe we could, but the water does warm up here as well sometimes, and a drysuit becomes, as you put it in not so many words, not needed.
I am not DIR trained, but I believe that the philosophy behind not using double bladders is that the safety inherent in the redundancy does not balance out the extra liability added because of the extra equipment/failure points that come with the equipment. I know what it is like to be a little panicked and in this case battling just one power inflator is a chore let alone juggling 2 hoses and making sure it is workin AND controlling your asent...etc... Also, with 2 bladders jammed into the same casing, you add rupture or snag risk inside the wings. Also, think what happens if both bladders end up inflated and the overpressure valve gets squeezed off....*POP*.
Double-wings is different than dual-bladder though, right? You mentioned both. Not sure why double wings wouldn't be DIR except for the same reasons I gave above for the dual bladder. And if both wings get inadvertantly inflated simultaneously or one is not deflated before switching to the backup, maybe the overpressure valves could get covered and then....*POP* again. Also, since elastic wings are out of the question, having twice as much wing flapping around at depth just becomes more undesirable, and the snag-and-drag factor is just not worth the redundancy.
Again, I am only a DIR wannabe, so this is all my thoughts on the issue, not OFFICIAL DIR, so someone feel free to add to or correct my ideas. Also, isn't your drysuit considered your back-up bladder? -tadd
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