Just a question??

[padiscubapro]

nradov once bubbled...

Those buoyancy numbers are a little off. I assume you're thinking of an air or nitrox fill, but for any dive that would require more than minimal decompression you would have some helium in the mix. The real world buoyancy swing for an 80ft^3 tank would be closer to 4lbs.

Keeping the gas weights down is a necessary part of having a balanced rig. A lot of divers seem to miss that point.

-Nick

lets do some simple math.. from luxfers site they claim their s80 is 4.4 lbs pos empty thats out starting point..

we need to figure out our weight of the gass lets choose a 21-40 trimix

we need to convert the volume into liters so 77.4cu ft is approx 2192 liters of gas.. why is this important because 1 mole of gas is 22.414 liters, and we can then use the atomic weight to figure out the weight for 1 liter in grams..

using the atomic weights of he, n and o it works out to about 1.5 grams per liter of gas.. this works out to 3289 grams of gas or 7.25 lbs, add this to the buoyancy of 4.4 lbs, means a 21-40 trimix is 2.85 lbs negative at the start of the dive.. luxfer doesn't specify if valve is included in their buoyancy specs.. this is about 1lb ,pre negative than they state.. so I don't know what they used as a gas. or if their empty buoyancy is wrong.

 

[faye]

Keeping the gas weights down is a necessary part of having a balanced rig. A lot of divers seem to miss that point.

Well this is the most assinine thing I have ever heard.
I dive air. I can't afford HE on a regular basis. I usually do dives around a 70-90min run time. I do some diving in warmer water. If my options are
1) dive in a drysuit and sweat in order to have redundant boyancy
2) Purchase expensive HE in order to have a "balanced" rig

I'll take option 3

3) walk the razors edge of life and strap on satans BC (insert dark ominous music)....The DOUBLE BLADDER BONDAGE WINGS OF DEATH

:drown: :help: :whoa:

Why are people so scared of the dual bladder???
It is just like having the drysuit inflator plugger into another spot!!
No more failure points. Seems like alot of bending over backwards with the possibility of spending HUGE amounts of cash to avoid these things. They MUST be absolute death traps.

can't you drop your cannister light

you *could* bleed off backgas to get yourself more positive if needed.

with multiple stages, what do I need them for? I'm not extending my bottom time, I'm aborting the dive....why not dump them

Discard a whole bottle or cannister or vent back gas just to avoid dual wings. CRAZY. I wish I had that kind of money.

ut:

 

[MrBlue]

You asked what the GUE stance on redundant bladders, and you got your answer. That answer led to balanced rigs.

It's obvious that this thread could go on forever without resolution.

If you place losing some $$ over losing your life, you probably shouldn't be tech diving. Heck, you shouldn't be diving.

 

[faye]

I guess if you take that extreme aproach to diving it makes sense.
Dive with the minimal equipment that is safe.
When a problem occurs, ditch everything on your body except life support equipment.
Get out of the water...ALIVE

Me I'll spent the extra 300 bucks for the dual bladder
make sure the second lp hose isn't leaking
Deal with a tinny bit of drag
use it when the problem occurs
come home with everything I left with...ALIVE

Sorry
I know I meant to just get an answer regarding what GUE says regarding wet diving; I didn't mean to challenge your philosophy.
Just not happy with the party line. I guess I will have to take the DIR-F corse to experience it for myself,mabey challenge the founders of the philosophy instead of the followers.

 

[MrBlue]

You're talking about an extreme problem that is not going to happen in the real world. And, if that extreme problem occurs, extreme measures need to be taken to survive.

You're talking (from your example previously) of a catasrophic failute of the entire wing (a swordfish impales my wing and destroys it). If that were to happen, what makes you think the redundant bladder is going to be unaffected. Not to mention that you are extremely overweighted; so much so that you can't swim up with the damaged wing.

With these types of scenarios you have completely overthink your gear and plan for the unimaginable 'whatifs'. Then yeah, maybe triple or quadruple wings are the answer.

But in real life, do you need a redundant bladder if you are properly weighted (just negative by the amount of gas you are carrying in your backgas)? That is the premise of a balanced rig.

You also have to look at and weigh the risk vs benefit of the extra gear you are carrying. Do you want to be less streamlined, less efficient, work harder, have extra maintenance and extra failure points during each and every dive just in case the stray swordfish shows up or the wing somehow explodes at depth?

This is where the 'mainstream' and 'DIR' approach differs. Mainstream says redundant bladders, 100lbs of lift, etc... But are they needed if you organize your gear and think it out from a complete prospective? Do you need a 100lbs of lift in a wing when you are at the most negative by the weight of your gas and some equipment (say at the extreme 30lbs with multiple stages and deco gas....which is at the complete extreme edge) so why have 100lbs of lift when a 55lb wing is more the sufficient? The same goes for redundant bladders. In wetsuit diving with AL80's you should never be so negative that you couldn't swim the rig up without dropping all of your gear or having to take other drastic measures. Maybe you need to drop the little bit of ditchable weight that is there to counteract your gas in the tanks.

When I mentioned bleeding off backgas, or dropping a canister light, or stages, I was 'talking' about an extreme life or death situation.

I have tried to swim my rig up with full AL80's (21x35 mix) an AL40 stage, Pro6 can light) wearing a SS plate and 3mm suit. I emptied my wing completely at 160fsw and was able to swim up without any problems. This proved to me that the system does indeed work. Have you tried this concept out? Or only relying on what you think would happen.

As far as bringing your issues to the founders of the philosphy and not the followers.... Please don't treat 'us' as mindless lemmings following the herd. We 'follow' because we have thought out the issues, weighed the pro's and con's and made the decision that the system works for us. Treat 'us' with respect and the same will be afforded to you.

Personally, I've looked at the issue of redundant bladders and have decided that I don't want all of the con's (streamlining, work effort, maintainence, etc) for the .001% benefit of having the un-imaginable happen to me. Having a single wing and being properly balanced is enough for me, as I know it will work for me in any instance I could get myself into.

 

[padiscubapro]

twin 80s and an al 40.. thats not much gas...

using 50/50 as the primary deco mix for a simple 200 for 30 minutes and assumming an RMV of .5 cu ft/min (which is lower than most) you'd need about 50 cu ft of deco gas followin straight buhlman and 38 cuft following RGBM (This is using a slightly richer mix) Its a profile I do often so I know the numbers off hand..

 

[MrBlue]

You're absolutely right in the gas regard. I've never said I was doing 200+ foot gas dives.

I'm a normoxic/Tech 1 person right now, and am taking the progression into the deeper stuff slowly and deliberately. Right now there is plenty in the 100-150 range for me to be happy with. For longer BT's and extra gas cushion, I'll sometimes dive an AL80 with 50/50 or bring along an extra AL40 of 100% for backup and only deco'ing on the 50/50 as the savings in deco times isn't worth adding the second gas at the 150-160ish depths.

When doing wetsuit dives, it's AL80's and a single AL40 for 150 for 30 profiles and about 60 minute runtimes. When doing my regular diving (new england), it's LP95's and either a single AL40 (130ish dives) or an AL80 for the slightly deeper profiles.

With all that is available in the 100-150 range here at home and the caves of Florida when I can get down there and dive them, I have plenty to experience and grow with right now.

I don't need the extra gas right now and don't need the additional bottles to do my dives safely.

 

[Divesherpa]

MrBlue once bubbled...
You're absolutely right in the gas regard. I've never said I was doing 200+ foot gas dives.


With all that is available in the 100-150 range here at home and the caves of Florida when I can get down there and dive them, I have plenty to experience and grow with right now.

I don't need the extra gas right now and don't need the additional bottles to do my dives safely.

I only know of a few caves in florida in the 120-160 range and only one that is accessible to the public. I'm doing the survey in one of the closed systems (with redundant wing). Are you referring to the 100 foot systems like Ginnie and Manatee where mix isn't necessary?

 

[MrBlue]

I was just referring to the opportunities I currently have available to me divingwise.

I wasn't trying to tie gas diving and cave diving together at all. Merely saying that I have ocean 'stuff' close to home in the 100-150 that will keep me busy for quite sometime AND in addition to that there are the caves in MX and FL that I've barely scratched the surface (so to speak) with.

So, the 200+ foot dives can wait for a long time.

As for caves in particular, I love the weenie dives in peacock (orange grove, peanut tunnel, etc) as well as ginnie, LR, and the like.

I have no reason to rush to go deeper, or longer, just for the fact of going deeper, longer, or carrying more gear.

 

[Divesherpa]

MrBlue once bubbled...


So, the 200+ foot dives can wait for a long time.

As for caves in particular, I love the weenie dives in peacock (orange grove, peanut tunnel, etc) as well as ginnie, LR, and the like.

I have no reason to rush to go deeper, or longer, just for the fact of going deeper, longer, or carrying more gear.

That's a very nice way to look at it. I made the mistake of moving to cave country so I could dive 5-7 days per week in the cave systems. If I were only able to dive a few caves per year (less than 35 dives), I would definately stick with those systems too, at least, for a while. Right now, they are all blown out except Ginnie, Manatee, and Merritt's Mill Pond systems. The exceptions are Diepolder and the other deeper systems (200+)

What can you do? If there's nothing else open, we dive the deep stuff out of necessity.

We also use redundant wings due to NASTY egressions and excessive dropoffs.

Cheers and safe diving