Dumpable weight vs trim

[wetb4igetinthewater]

John, Thanks for the insight re PADI's thoughts on buoyant/CESA, etc. It is pretty much what is written in my '05 OW manual, so I apologize for not looking that up.
CT- Yes, with my 7 mil farmer john and (NOT overweighted) 42 pounds, I can release 20 pounds of it easily if needed.
wetb4-- Yes it is a common sense thing to try. Guess I never have due to above. I will empty the BC this week and see if I can do it from 20' or so.

I'd suggest shallow, and then try from gradually deeper depths until you reach the maximum depth you dive recreationally.

 

[TMHeimer]

I'd suggest shallow, and then try from gradually deeper depths until you reach the maximum depth you dive recreationally.

Thanks, will do at this site.
I think it's a good idea that you add this to your OW course. Of course, no agency would actually have students practice one for real (dropping weights), for the obvious reason.

 

[TMHeimer]

In my discussions (arguments) with PADI about ascent scenarios, what they told me in essence is that the buoyant ascent is used when you are not sure you can get to the surface on your own. They have given rule-of-thumb estimates about specific depths where you would go from CESA to buoyant, but it really comes down to your judgment. It used to be common for some training groups to require CESA's from 100 feet, although I don't think anyone does that now. Buoyant ascents have been done from 300 feet in training for submarine escapes.

In technical diving, steel doubles can be a problem because of their weight, and it is common to require redundant buoyancy when using them.

Question --(I gave up on Google-- too complicated mumbo jumbo)--
That example of 300' buoyant ascent escaping from submarine---
What pressure is the air they are breathing in the sub? 1.0 ata? If not, what?
If yes, they would probably have no fear of DCS shooting up fast from 300', no?

 

[CT-Rich]

I have noticed that much of the discussion has been about Making buoyant ascents. A far more common scenario is a diver who reaches the surface and then wants to stay there.

I had two occasions where I decided to drop weights, both were on the surface. One was on a night dive where my buddy was low on air. We surfaced together, my tank was almost full and we had a long swim in. I was negative because of all the air in my steel 120. When I tried to pump up my BCD I discovered my shoulder dump valve was jammed open. I dumped my weights so we could stay together for the swim in.

The other time was an overly tight seal on my dry suit was restricting blood flow to my head on a pretty choppy sea. Despite the tunnel vision and anxiety created by the asphyxia, I released my lead and was, without it, able to recover and make the swim in.

If you find a situation where you are going to be in the water for a long time at the surface, ditchable weight is a incredibly cheap and simple form of redundant buoyancy. That you can release some ballast is completely independent of perfect trim nor would I advocate overweighting so you have something to ditch. IMHO, if you are intentionally adding Weight to make yourself neutral during a dive, you should have a plan on how you are going to get rid of it when things go seriously sideways.

 

[wetb4igetinthewater]

I have noticed that much of the discussion has been about Making buoyant ascents. A far more common scenario is a diver who reaches the surface and then wants to stay there.

I had two occasions where I decided to drop weights, both were on the surface. One was on a night dive where my buddy was low on air. We surfaced together, my tank was almost full and we had a long swim in. I was negative because of all the air in my steel 120. When I tried to pump up my BCD I discovered my shoulder dump valve was jammed open. I dumped my weights so we could stay together for the swim in.

The other time was an overly tight seal on my dry suit was restricting blood flow to my head on a pretty choppy sea. Despite the tunnel vision and anxiety created by the asphyxia, I released my lead and was, without it, able to recover and make the swim in.

If you find a situation where you are going to be in the water for a long time at the surface, ditchable weight is a incredibly cheap and simple form of redundant buoyancy. That you can release some ballast is completely independent of perfect trim nor would I advocate overweighting so you have something to ditch. IMHO, if you are intentionally adding Weight to make yourself neutral during a dive, you should have a plan on how you are going to get rid of it when things go seriously sideways.

Couldn't you just dump gas?

 

[Imla]

What fins do you use?

 

[CT-Rich]

Couldn't you just dump gas?

So I should vent Breathing gas from my tank so that I can get to neutral? How long will it take to vent a 120? What is the rapid venting of air in water going to do to my regulator? I cast my own weights, but even so, I would gladly trade $40 or $50 of lead for immediate (in seconds) positive buoyancy.

My second instance had really nothing to do with buoyancy, but mor about body orientation. Underwater it was not a problem, I had good trim, on the surface all the air was pooling in my shoulders while my legs and torso were weighted to straight down. In this position the tight neck seal was restricting blood flow. I may have had other solutions, but during asphyxia, you get panicky and tunnel vision, simple solutions are best. Every one that talks about complicated things like ditching their rigs or or cutting equipment or what ever are not really being realistic. Pilots train in simulators to maintain calm in situations that require complex solutions.

Few recreational divers (or tech divers, for that matter) have a safe way to practice unforeseen problems. Instead we train for a few simple solutions that will get you out of most problems. Mask flooding, OOA drills, signaling buddy drills. Dumping lead is just plain simple. If you get to the surface, make it so you can stay there with little to no effort. Keep what ever breathing gas you still have because you may find a use for it. If I dump my rig to stay on the surface, I am dumping my GPS beacon, my knife, my DSMB, my rescue whistle, my BCD (which I might end up being able to fix) and my dive light. Lead is just a cheap and idiot proof.

 

[TMHeimer]

Yes, dumping lead is simple. I noticed PADI added that as a "skill" about 2015. Students did it in the pool or shallow water -- on the surface. The reason I was told is so they get the feel of how buoyant they immediately become. I had the fun job of collecting all those weight pockets.
CT-- I was thinking along those lines when you said it's so simple. You could also be at serious ("I don't think I can CESA") depth, OOA, and just release weight. Maybe the best easiest solution if you are near panic.

 

[lowwall]

I have noticed that much of the discussion has been about Making buoyant ascents. A far more common scenario is a diver who reaches the surface and then wants to stay there.

I had two occasions where I decided to drop weights, both were on the surface. One was on a night dive where my buddy was low on air. We surfaced together, my tank was almost full and we had a long swim in. I was negative because of all the air in my steel 120.

The other time was an overly tight seal on my dry suit was restricting blood flow to my head on a pretty choppy sea. Despite the tunnel vision and anxiety created by the asphyxia, I released my lead and was, without it, able to recover and make the swim in..

In the first instance you were clearly overweighted for that dive. If you are carrying an extra six or eight pounds of air for a future dive, then you should remove that much lead to compensate. Also, even if the weight wasn't immediately ditchable, you could have had your buddy hold onto your BC while you took it off and removed the necessary weight.

As for the second situation, I don't understand why adding air to your BC wouldn't be a simpler answer. Or maybe leaving the reg in your mouth and getting horizontal if your position was causing the issue.

 

[boulderjohn]

Would it be too outlandish to suggest for the recreational diver without redundancy in buoyancy to ditch their scuba kit at the surface?

I am not sure I understand the question, but I will take a stab at an answer.

A recreational diver without redundancy (redundancy should not be necessary in recreational diving) reaches the surface. What was the problem? If OOA, then a properly weighed OOA recreational diver should have no trouble staying on the surface without any adjustments. But if the diver is overweighted, the proper next step would be oral inflation. Dropping weights would be a second possibility. If no rescue is in sight, the next step would be to ditch gear, orally inflate the BCD to its absolute max, and sit on it while awaiting support.