Browsing Tag weights
Diving with Ditchable Weights: What You Should Know
Why dive with weights?
One of your first lessons when learning to scuba-dive would (should!) be buoyancy. Divers use weights to counteract the buoyancy of other diving equipment, such as diving suits and gas tanks. During the dive, you will control your buoyancy by adjusting the air volume in your buoyancy compensation device (BCD) or buoyancy bladder (commonly referred to as wing), and dry suit, if applicable. At the end of the dive, you’ll need enough weight to be neutrally buoyant when you have breathed down most of your gas, and when holding your position at safety or decompression stops.
What are ditchable weights?
Most divers are familiar with the concept of ditchable weights, especially if you are trained to scuba-dive in cold water. You probably have been taught that if you have trouble with your BCD and are unable to inflate it, you should get rid of the ditchable weights to achieve positive buoyancy and surface (or stay on the surface if you are already there). But should you get rid of all the weight at once in such an instance? More on that later.
This is in contrast to fixed or non-ditchable weights, such as a steel backplate, V-weights or steel tanks. These are weights that either cannot be removed, or should not be removed for safety reasons. These weights form an integral part of the diving system and will not be considered in this article. We will discuss how to choose them in another post.
Where should you place your ditchable weights?
I do not recommend wearing all of your weights in one location, especially on a weight belt. Not only do weight belts affect your balance, they are also notoriously prone to coming loose on their own. I would first consider putting as much weight as possible directly above the centre of gravity of the diver. Once these locations are full, put some weights in a location that is easily accessible and where the weights can easily be ditched.
How much weight do you need?
This depends on the diver’s mass and body composition, buoyancy of other diving gear worn, water salinity (fresh water or salt water), and water temperature (which relates to a choice of diving in a wetsuit or drysuit). Read more about this here. The weight required is directly related to the amount of thermal protection worn. A thicker undergarment (worn with a drysuit) or wetsuit will result in the need for more weight. This is something cold water divers tend to forget when they dive in warm water. They’ve changed to thinner wetsuits but insist on having the same amount of weight that they used back home!
Should you dump all your weights if your BCD fails?
Let’s use the example of a drysuit diver: In order to sink, a drysuit diver would normally need between 6 and 10 kg (or about 12 to 20 pounds) of weight on him. That’s quite hefty!
The big question that relates to ditchable weight is then this: In the event of a BCD failure, is it possible for the diver to swim up to the surface with all that weight?
Chances are, the answer is no, for most regular divers. It would appear then that the simple solution (which is also commonly taught around the world) is to drop all your ditchable weights in such a scenario.
However, I strongly advise against doing something like that, because of the risks involved. A runaway ascent is very likely, and it can result in multiple issues, such as lung overexpansion injury, decompression sickness, boat strikes and so on. There are other ways to deal with a BCD failure, so dropping weights need not be your first option.
The first thing I would think of in the event of a BCD or wing failure is: How did the BCD or wing fail, and can it hold any gas at all?
For example, the picture below shows a wing in use by a diver. The red arrows show the position of the gas in the wing. In the event of the dump valve failure, the gas would still be able to stay in the wing as the dump valve location is lower than where the gas would be.
In contrast, a bungeed wing (shown below), would lose most of the gas in the wing due to the tension created by the bungee. Because of the design of the wing, this failure would result in a greater loss of buoyancy for the diver.
Scenario 1: Damage on one side of the BCD / wing
In a typical puncture or breakage, the damage is likely to be located on only one side of the BCD, so it would be possible to position oneself such that the gas stays on the side of the BCD that does not have the hole. If the diver can do this, the failure is less of a problem.
Because the BCD still holds gas and provides some buoyancy control (although it is harder to manage it), there is no need to drop all the weights and shoot to the surface. The diver can and should make a comfortable ascent to the surface with the help of his teammates.
Scenario 2: Damage on the inflator mechanism
The breakage might be harder to rectify when the elbow connecting the inflator mechanism is detached from the BCD fabric. This problem makes it impossible to inflate the BCD, and also allows gas to escape from the BCD due to its location on the BCD. How then can we solve this?
I would consider depending on my teammates. If my team is nearby and my buddies were aware of the problem, they could definitely lend a hand. They could hold on to my arm, and control our buoyancy using their BCD or by kicking. I would also pass on heavy items that I am carrying to lessen the weight and provide some lift. Diving together with someone has definite benefits, and you should both be able to ascend in a controlled fashion without having to dump any weights.
Another thing I would attempt to do is inflate a surface marker buoy (SMB), send it to the surface and use the spool to assist with the loss of buoyancy. The SMB may not provide enough lift for me to completely dangle on the end of the line, but coupled with my teammate’s help, it would be easier to do a controlled ascent.
Fourthly, if I was wearing a drysuit, I might inflate it a little more than I normally would to help increase buoyancy. This is one of the last things I would consider doing however, as more air in the suit might make it harder to kick and move around.
Lastly (and this is a distant last option), I would remove some but not all of my weights to help with buoyancy. I would never remove all of my weights at the same time, because this would most likely result in a very rapid, uncontrolled ascent. The dangers of lung overexpansion, decompression sickness and unconsciousness on the surface cannot be understated here!
Of course, to be in the situation where I would resort to ditching weights, I would have to be alone, and be low enough on gas that I couldn’t risk wasting it by doing a strenuous swim to the surface. Needless to say, we should never put ourselves in such a fix to begin with.
To put things into context, in all my years of diving, I’ve never seen a BCD or wing fail so completely that it couldn’t hold any gas at all. Plus, most of the time, with good team awareness, proper equipment and correct weighting, a BCD failure is easily rectified without having to resort to ditching your weights.
