Redundant Bouyancy

[darylm74]

To answer your scenario,
Failed wing, at surface, almost full load of gas, wetsuit, you're still heavy and having a hard time keeping your head/mouth dry. Simple solution here. Ditch the gas in your tanks down to 500psi or so. Now you're close to neutral, problem solved.

If you are still heavy with 500 psi, you are overweighted in the first place. Take AL80s (plus stage if you need even more gas). But needing that much gas suggests a long exposure, you'll want a drysuit for that. In which case you could skip the stage and take bigger steel tanks.

Wetsuit= short exposures only = AL80s adequate

Lots of gas aka Long exposures = drysuit. Allowing bigger steel tanks.

Redundant bladders cause almost as many problems as they solve. I'd skip it.

With that response, do most FL divers wear a drysuit on tech dives where they have long exposures? I guess I am so used to wearinig a drysuit on the 37 degree dives in dark cold quarries such as Gilboa, that I think of roasting on the long 80 degree dives. Please excuse my lack of knowledge in this scenario.

 

[texdiveguy]

With that response, do most FL divers wear a drysuit on tech dives where they have long exposures? I guess I am so used to wearinig a drysuit on the 37 degree dives in dark cold quarries such as Gilboa, that I think of roasting on the long 80 degree dives. Please excuse my lack of knowledge in this scenario.

You will see a mix of exposure suits from dry to wet....there is no one answer. You have many things to consider when doing a tech dive of any duration....one is the type of thermo protection. Dry suits are very popular in that they do offer your redundant bounc. control and protection,,,,but a quality wet suit is also viable in many situation. In the south/Tx. we here dive tech in both wet and dry year around. Mainly dry in our winter and many divers including myself go to wet suits for tech in the summer months.....unless that 'special condition' calls for a dry suit in the summer here in Tx..

 

[LG Diver]

There was a post on SB recently that got me thinking about the use of a bag as redundant buoyancy. A lot of people talk about it, but it seems like it's not usually very well thought out. In order to be able to use a bag as redundant buoyancy, you need to be able to modulate the amount of air in the bag to stay neutral. To do this you need a bag with an OPV, so rule out all open bottom bags with no OPV. Next, rule out all bags with the OPV at the bottom, since this would be totally ineffective in releasing gas in a controlled fashion to stay neutral. Closed circuit bags with an OPV at the bottom have it there stricty to prevent rupture. So, you'd need a bag with an OPV at the top. Ah, but how do you reach that OPV to release gas, especially if you're talking about a sausage-style bag? The best solution in my mind is a bag with an OPV at the top and a string reaching to the bottom of the bag that can be accessed by the diver while holding on to the bottom of the bag. How many people here that carry a bag as redundant buoyancy carry a bag like this? I'd wager not many.

 

[H2Andy]

Ever think of mounting a sealed piece of 3" PVC between the doubles? That would add bouancy and you could counter with some ditchable weights.

lol ... i'm not too worried ... i can swim my tanks to the surface (without any extra bouyancy)

and i have the drysuit for extra bouyancy if needed

and i wouldn't dive doubles on a wetsuit unless i carried an extra wing

so i'm covered

 

[rjack321]

There was a post on SB recently that got me thinking about the use of a bag as redundant buoyancy. A lot of people talk about it, but it seems like it's not usually very well thought out. In order to be able to use a bag as redundant buoyancy, you need to be able to modulate the amount of air in the bag to stay neutral. To do this you need a bag with an OPV, so rule out all open bottom bags with no OPV. Next, rule out all bags with the OPV at the bottom, since this would be totally ineffective in releasing gas in a controlled fashion to stay neutral. Closed circuit bags with an OPV at the bottom have it there stricty to prevent rupture. So, you'd need a bag with an OPV at the top. Ah, but how do you reach that OPV to release gas, especially if you're talking about a sausage-style bag? The best solution in my mind is a bag with an OPV at the top and a string reaching to the bottom of the bag that can be accessed by the diver while holding on to the bottom of the bag. How many people here that carry a bag as redundant buoyancy carry a bag like this? I'd wager not many.

Don't fart with the dumping/adding from the bag, send it to the surface. Hold onto the line.

 

[rjack321]

With that response, do most FL divers wear a drysuit on tech dives where they have long exposures? I guess I am so used to wearinig a drysuit on the 37 degree dives in dark cold quarries such as Gilboa, that I think of roasting on the long 80 degree dives. Please excuse my lack of knowledge in this scenario.

80F is not that warm after an hour plus. Esp if you had significant suit compression at 130+ft, got chilled, now you're just hanging on deco not moving much, lots of vasoconstriction is not an asset here. Dumping heat by pulling your hood away is easy. Getting warmer in a wetsuit is almost impossible.

 

[LG Diver]

Don't fart with the dumping/adding from the bag, send it to the surface. Hold onto the line.

I've tried to play this scenario out in my head to visualize what I'd do in such a situation. I'm assuming you mean shoot the bag and then pull yourself up, vs hold on and head up like a missile. The two concerns I'd have with doing what you say are:

1) how easy would it be for me to pull myself up along a thin piece of 24# line in drygloves if I'm significantly negative?

and

2) If this is my last chance at buoyancy, do I really want to send the bag out of sight and out of my direct control?

 

[texdiveguy]

I've tried to play this scenario out in my head to visualize what I'd do in such a situation. I'm assuming you mean shoot the bag and then pull yourself up, vs hold on and head up like a missile. The two concerns I'd have with doing what you say are:

1) how easy would it be for me to pull myself up along a thin piece of 24# line in drygloves if I'm significantly negative?

2) If this is my last chance at buoyancy, do I really want to send the bag out of sight and out of my direct control?

IMO---Another reason for a redundant bladder/wing. When using a lift bag as your means of bc for an ascent it is not suggested to 'shoot' the bag and 'pull' yourself up. You need a bag with an upper dump to control your ascent and hold deco stops as reqd.. Some folk clip the bag off to themselves, some divers clip to a reel, others don't. It takes practice and practice to get this smooth....if you do get into the tech level of training you will cover this skill in your courses (I hope--you should!). I have practiced often this exercise outside of my tech courses to keep fresh on it....though I wear a redundant wing when diving wet/doubles.

IMO---NO,,,,keep your lift bag, now your means of gaining a safe ascent to the surface under your direct control. I pers. use an open bottom lift bag(s) with upper dumps.

 

[LG Diver]

I'm thinking worst case scenario. You are in a wetsuit, and double steels(AL80s would be best possible positive bouyancy characteristics). You dive down on a wreck and a wire punctures your BC going in the door for a short swim through/penetration.

Going back to the OP's question and scenario- one of the chief criticisms that I've read of dual-bladder wings is that if something is going to puncture one bladder it's just as likely that it will puncture both and your redundancy is out the window.

That aside, I've only used a dual-bladder wing once, and I found the extra inflator on the right side thoroughly annoying.

 

[texdiveguy]

Going back to the OP's question and scenario- one of the chief criticisms that I've read of dual-bladder wings is that if something is going to puncture one bladder it's just as likely that it will puncture both and your redundancy is out the window.

That aside, I've only used a dual-bladder wing once, and I found the extra inflator on the right side thoroughly annoying.

The VERY reason I don't dive a dual bladder wing.....I use a stacked wing....the chances of an incident taking both wings out is very low. In terms of the right side LP inflator I pers. keep it secured to the redundant bladder via a rubber snorkel keeper looped around the manual dump valve hosing....it is now out of the way and still easy to get to if I need it.