Question Do you ever practice dropping weights and handling the unexpected ascent?

[boqurant]

In tropical waters (skinsuit or a 3mm) with steel BPW I use 3kg, 2kg of which in waist trim pockets (ditchable), 1kg is tank-mounted trim. TBH that's a fraction overweighted (the boats I use never seem to have 0.5kg weights) and I could very probably drop the 2kg without zipping upwards, so I've not tried.

I did however, try to imagine myself heavier and get within a few fins reach of an OW chap on a recent set of dives who explained on the first dive that his (rented) BCD seemed to be inflating slightly over time (!) Even worse he then explained that wasn't a problem because he was "always" using the in/deflator to ascend/descend anyway and he could adjust frequently... Thankfully he swapped the BCD a few dives later, though he might still be DJing the in/deflator buttons to this day.

 

[crofrog]

Your ditch-able weight should ideally not exceed the weight of the gas you're carrying.

 

[johndiver999]

Your ditch-able weight should ideally not exceed the weight of the gas you're carrying.

Why? Seriously what sense does that "rule" make and under what conditions?

 

[Seaweed Doc]

Why? Seriously what sense does that "rule" make and under what conditions?

I'm guessing the idea here is that you have no more weight total than would make you neutral with an empty cylinder. If your ditchable weight is just the weight of the air in the full cylinder, then throughout the dive you could become immediately neutral or positive by dropping that weight.

But I'm not sure this accounts for doing a rapid descent wearing a compressible suit.

 

[Eric Sedletzky]

An event like this can be scary (and dangerous).

Many folks will read your post and say things like, "clearly no predive safety check." It is easy to be dismissive and assume diver error. Some weight pockets "feel" like they are locked, others make an audible click. You can be fooled sometimes -- even when you check.

Recommend you take a look at your equipment manufacturer's website and see if there is a recall on your weight pockets. (I had a recall on my gear a couple of years back as the clips were known to fail on a specific batch.)

Also recommend you look at your BCD manual and verify that your weight pockets are rated for the amount of weight you are using. (Depending on your body type, exposure suit, etc ... you can actually put more weight in the pockets than the manufacturer has included in the design.)

If I am diving in a 5 mil or 7 mil and need "lots of weight" I am always certain to consider distribution. I use my trim pockets, my weight pockets, AND a weight belt. This allows for me to have to progressively change my buoyancy. First swift motion and the belt is gone, weight pockets are a pull a each ... 2 seconds overall but I am in control -- not flying toward the surface if I need to drop.

I would encourage you to get in the pool with an instructor if you are going to practice weight drops. The first atmosphere (shallow diving from surface to 33 feet) is the biggest change in volume we experience. We often see shallow water as somehow exempt from the risk, particularly the risk of expansion injuries.

You can work with your instructor to "keep it safe." There is quite a difference between equipment practice and emergency drills. Many agencies only drop weight on the surface and "remove and replace" weight below. This is also further complicated by rental gear. Not all manufacturers are created equal and not all maintenance folks to what needs doing.

He was in a rental BC

 

[WillieJustice]

In tropical waters (skinsuit or a 3mm) with steel BPW I use 3kg, 2kg of which in waist trim pockets (ditchable), 1kg is tank-mounted trim. TBH that's a fraction overweighted (the boats I use never seem to have 0.5kg weights) and I could very probably drop the 2kg without zipping upwards, so I've not tried.

I did however, try to imagine myself heavier and get within a few fins reach of an OW chap on a recent set of dives who explained on the first dive that his (rented) BCD seemed to be inflating slightly over time (!) Even worse he then explained that wasn't a problem because he was "always" using the in/deflator to ascend/descend anyway and he could adjust frequently... Thankfully he swapped the BCD a few dives later, though he might still be DJing the in/deflator buttons to this day.

I had a rental BCD that seemed to be self-inflating. I have my own now. If it doesn't work, that is a maintenance problem on my part, not somebody else.

 

[LI-er]

Your ditch-able weight should ideally not exceed the weight of the gas you're carrying.

What does this even mean? The gas in an AL80 is maybe 5 lbs.

Most divers carry a heck of a lot more than that in ditchable weight.

 

[crofrog]

The goal of ditching weight is to become neutral in event of a bc failure; at safety stops depths.

If you’re neutral at the end of the dive with say 15lb of total negative weight, and you’re diving an AL80 which contains about 6lb air when full. If you experience a wing failure at your heaviest point of the dive (the bottom of the descent) then by ditching 6lb weight you should be able to swim up the rig without becoming uncontrollably positive.

If you limit your ditch-able weight to that amount of your gas weight you’re not at risk at losing all of your weight and having an uncontrolled buoyant ascent, or if you’re in an overhead getting pinned to the ceiling.

If you’re going very deep in a very thick and compressible wet suit something like a 7mm with a 7mm 3/4 zip step in this could start to fall apart because you’ll lose more buoyancy from the suit compression than you can swim up, but you probably just shouldn’t do that. There is no way good way to solve that problem with just ditching weights,

 

[johndiver999]

The recreational diver should be able to swim to the surface with a busted bc. They should have enough ditchable ballast to accomplish that. It may or may not be more than the weight of the gas in the tank. To think otherwise is to misprioritize the various dangers in recreational diving.

 

[dmaziuk]

The recreational diver should be able to swim to the surface with a busted bc.

Full stop. The only case for ditchable ballast that I can see is if you're doing 40 m dives in three layers of 7 mm neoprene, in which case... I'd consider a drysuit, myself.