No Ditch-able weights with BP/W

[shurite7]

I've seen the suggestion of using an SMB for additional lift in two threads today. At first glance this seems a little dangerous to me. The time it takes to inflate an SMB, figure 30 seconds to 1 min is time wasted in an emergency, which is the context of the question about ditchable weight. Curious the logic behind suggesting using an SMB for extra lift in this context?

It doesn't take that much time to pull out a lift bag or smb and inflate it, especially if one practices every so often. My open water students do it in less 30 seconds in the late wearing gloves and hoods. Perhaps practicing a skill a few times is too much for a recreational diver and asking too much. Hopefully not the case for you.

Its not logical.

If you jump in the water and the elbow pops off your BC, the immediate direction you're going is DOWN. Unless you can swim against the weight of your gear and/or ditch enough lead to allow you to swim against the weight of your gear, you're going to continue to go DOWN. As you fatigue and your suit compresses, your rate of DOWN is going to increase. Lawn dart.

Trying to deploy some sort of lift bag or SMB when you're nosediving toward Davy Jones Locker is fantasy at best.

I've dealt with a diver who got my attention and handed me his corrugated inflator hose which came off at the elbow during the descent. I took it from him and pushed it back onto the elbow then borrowed his slate and wrote "don't pull this to deflate, use your right shoulder dump." The diver held his place without sinking or floating up while I reinserted the hose. He did a nice job keeping his composer and kicking to maintain depth. We were at a hundred feet when he handed me the inflator hose.

If one is descending because of an overweighting or bcd issue then he/she needs to get kick like mad (feet in the down position, obviously) and ditch the scuba unit. But then again, this goes back to my comment above, this might be asking too much for the person who doesn't want to practice skills or become a proficient swimmer because it takes effort.

 

[johndiver999]

Right, except a lift bag is the proper tool for that. SMBs generally have a dump valve positioned at the bottom of the tube. As gas expands during ascent, the diver will have no way to dump the expanding gas manually to control the ascent.

A lift bag, in contrast, has the valve at the top of the bag. This allows the diver to vent gas as needed to maintain control.

IMO, the only argument for a SMB as lift device following a failed BC is to establish permanent positive buoyancy when you're on the surface as a matter of convenience, not necessity.

If the diver sits on it, with half on one side and half on another, he should be able to vent gas from one half of the smb. so I could see that be somewhat workable, but dropping some lead sure seems like a better idea, especially with an uncontrollable descent.

 

[Daebado]

Here are 42 pages of discussion for you.
Question about “balanced rigs” and having all ballast unditchable

Bottom line, there's nothing "unbalanced" about having a small amount of ditchable weight.
See also
Buoyancy, Balanced Rigs, Failures and Ditching – a comprehensive tool

Thanks for the links. I must have done something wrong in my search.

I got to page 30 of the first link before I finally bailed. People are quite passionate about this subject! Came back to this post to find 3 more pages had been added in what amounts to basically a continuation of the 42 pager! I think the message is imprinted on my skull, now. I can be neutral at 80' with almost no air in my wing. I can fin any direction (up, down, sideways) with ease and all it takes to start to ascend is a deep breath so I am not worried anymore. What little air I do have in my wing expands just enough as I ascend that I have to let a little out to be neutral at my safety stop.

Just hadn't thought about it in those terms until the members in here showed me the light. I can see advantages to having ditch-able weights but until I'm in a much thicker wetsuit, it doesn't look like I'll be using them.

Now, on to the second link and more reading!

 

[rongoodman]

If you're neutral with a full tank and no air in your wing, how are you not going to be too light after you've used 5 lbs of gas?

 

[Ayisha]

Perhaps have a play with @rsingler's SS tool. When I've done that for my setups the most I need to kick-down isn't much and mainly relevant at very shallow depths.

There isn't any need to kick down if you dive a balanced rig. Honestly.

 

[Ayisha]

Yep, that's the official story.

I’m not an official and I'm not giving you a story.
The harness is a continuous webbing that is almost infinitely adjustable. How is it difficult to have it as loose as you would like? If it's not easy to get in or out, loosen it up. Half an inch to an inch (1.25 - 2.5 cm) loose is enough to have a comfortable fit. Want it looser? No problem. It has a crotch strap that is extremely adjustable and the wing's not going anywhere.

 

[NAM001]

I would look at the possible failure of some sorts. like being 100 ft and gettng a blown wing. If it is at the start of the dive you go heavyperhaps -12 in a shorty but only -6 at mostt ifg only a skin. I dont see a problem as opposed to being in cold water with a thick suit. You can swim it up and let the wet suit take over your lift.

 

[Jay]

There isn't any need to kick down if you dive a balanced rig. Honestly.

I think you're confused or we've got crossed wires .... You had said that when ditching some weight "they certainly can have an uncontrolled ascent by the time they get shallower." and I suggested playing with Rob's SS tool, and that shows it's not uncontrolled and kicking down would be a way to mitigate that.

 

[Daebado]

If you're neutral with a full tank and no air in your wing, how are you not going to be too light after you've used 5 lbs of gas?

I actually said, "almost" no air in my wing. There is some air in there to be sure, just not much. As stated in my post, it's enough that as I ascend, it expands and I have to let a little out. This is normal, is it not?

 

[Trailboss123]

all it takes to start to ascend is a deep breath

Not sure who recommended this or what the context was, but taking a deep breath and ascending is a recipe for a lung over-expansion injury and should be avoided at all cost.