Proper weighting

[kwinter]

I just read Joe Citelli's article in the current issue of Underwater Speleology titled "Breathers, Buoyancy and Caves." In talking about weighting for rebreather divers, Joe says, "Ideally, a properly weighted diver should be slightly positive on the surface and need to make a small effort to descend the first five or 10 feet, after which gravity takes over and he should begin to drop relatively freely." Let's ignore the fact that gravity has nothing to do with it, and its actually the compression of air in all air spaces that makes descent easier. My concern is with the "proper" weighting being slightly positive on the surface.

As rebreather divers, shouldn't we be aware of the possibility of bailout? This is true in cave, wreck or open water environments. Even if you drop bailout tanks as you use them up, your buoyancy is going to change during the dive much more than in a non-bailout situation. I think the ability to hold a depth at the end of a dive is critical, whether its a deco stop or staying off the ceiling. I'm not in favor of gross overweighting, but I think Joe's suggestion is not necessarily wise.

Your thoughts?


Ken

[loquat149]

Let's ignore the fact that gravity has nothing to do with it

Okay.

Dave

[Dsix36]

Personally, I ignore what everybody tells me is proper and do what works for me and makes me feel all warm and fuzzy.

Regardless of the dive, the very minimum that I will ever possibly have for BO is an AL40. I would like to be able to hold a 10' stop with an empty tank so that if it were a real BO, I would not have to fight to stay down on deco. Then I add an extra 2 pounds so that I can have just a bit of air in my drysuit for warmth.

Granted this might make me a tad overweighted with 4 or 5 BO tanks, but I really don't give a damn.

[kwinter]

Personally, I ignore what everybody tells me is proper and do what works for me and makes me feel all warm and fuzzy.

Regardless of the dive, the very minimum that I will ever possibly have for BO is an AL40. I would like to be able to hold a 10' stop with an empty tank so that if it were a real BO, I would not have to fight to stay down on deco. Then I add an extra 2 pounds so that I can have just a bit of air in my drysuit for warmth.

Granted this might make me a tad overweighted with 4 or 5 BO tanks, but I really don't give a damn.

If the 4 or 5 bailout tanks are aluminum, you could still be underweighted at the end of the dive unless you jettison the empties. I guess that's part of the question. Do you plan to dump your empties? No way you should carry an extra 20 pounds of lead to compensate for the gas used in four 80s of bailout.

[Dsix36]

If the 4 or 5 bailout tanks are aluminum, you could still be underweighted at the end of the dive unless you jettison the empties. I guess that's part of the question. Do you plan to dump your empties? No way you should carry an extra 20 pounds of lead to compensate for the gas used in four 80s of bailout.

There are a couple of different things at play here.

First off, since I dive a rEvo, I will never need to use my BO gas other than just for practice drills.

If I am in a cave, then dumping the empty tanks is a no brainer as they will float at the ceiling for easy retreival at a later date. If I happen to be in the ocean, then I will either clip them to the upline or let them slide up my deco reel and float with my SMB

If I am in a real life and death BO, then I ain't droppin' anything until I absolutely have to in order to maintain bouyancy or the tank is completely drained. Can you imagine how it would feel to realize that you just sent up your only other tank as you suck the current one dry???

[rjack]

How is this any different than proper weighting on OC? i.e. weight yourself to be neutral with empty tanks. Whether that tank is an OC tank or a BO tank doesn't really matter does it?

I don't have the article so I can't tell what the author meant, but at least in freshwater empty 40s and 80s with regs on them aren't going to be very positive at all so maybe the author ignored them?

[jcook]

I think Forrest said it best, "You can't breathe lead" I carry steels as my bottom gas bailout so they are always negative even when empty. I had to flood my unit once to keep from floating to the surface when I was just carrying 2 AL80's and had drained them doing a practice bailout.

Don, I know you are just joking about the rEvo thing keeping you safe, but please be cognizant and don't get complacent with it.

[PfcAJ]

How is this any different than proper weighting on OC? i.e. weight yourself to be neutral with empty tanks. Whether that tank is an OC tank or a BO tank doesn't really matter does it?

I don't have the article so I can't tell what the author meant, but at least in freshwater empty 40s and 80s with regs on them aren't going to be very positive at all so maybe the author ignored them?

They add up quickly.

[kwinter]

There are a couple of different things at play here.

First off, since I dive a rEvo, I will never need to use my BO gas other than just for practice drills.

Bite me!

If I am in a cave, then dumping the empty tanks is a no brainer as they will float at the ceiling for easy retreival at a later date. If I happen to be in the ocean, then I will either clip them to the upline or let them slide up my deco reel and float with my SMB

If I am in a real life and death BO, then I ain't droppin' anything until I absolutely have to in order to maintain bouyancy or the tank is completely drained. Can you imagine how it would feel to realize that you just sent up your only other tank as you suck the current one dry???

Gotta admit letting the empty Aluminums slide up the deco reel is a nifty idea. But it won't work with steels.

How is this any different than proper weighting on OC? i.e. weight yourself to be neutral with empty tanks. Whether that tank is an OC tank or a BO tank doesn't really matter does it?

I don't have the article so I can't tell what the author meant, but at least in freshwater empty 40s and 80s with regs on them aren't going to be very positive at all so maybe the author ignored them?

I agree that the same philosophy should apply as it does for OC. That's why I questioned what he wrote. As for the empties not being very positive in fresh water, that doesn't matter. They're still going to be about 4-5 pounds lighter when empty.

I think Forrest said it best, "You can't breathe lead" I carry steels as my bottom gas bailout so they are always negative even when empty. I had to flood my unit once to keep from floating to the surface when I was just carrying 2 AL80's and had drained them doing a practice bailout.

I also use steels for bailout. But that doesn't matter for the same reason. You are still using up the gas, and that makes the tanks lighter/more buoyant. They might be negative when empty, but still 4-5 pounds less negative than when you started.

[Dsix36]

I set my weighting for the lightest that I will ever be and leave it there even if carrying more tanks. That way I am never too light if i have to get rid of tanks or they get lost. I don't use steel tanks for BO