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Thursday, 30 May 2013

A weighty Subject...

For this blog, I am going to touch on a subject that is extremely important and yet quite often disregarded in the Diving World. Weighting!!!

weight belt for diversNow, for those of you who know me, you will know that I believe correct weighting is the most important step in becoming a competent Scuba Diver. For those who don't know me yet, I believe that correct weighting is the most important step in becoming a competent Scuba Diver.

Why is Weight so important?

There are so many things to think about when you are Scuba Diving, why is making sure divers are correctly weighted so important? There are a number of reasons why... Let's look at a few

ARCHIMEDES PRINCIPLE

Think back to your first Scuba Diving Course. If you took the PADI Open Water Training, you will remember the very first thing on the very first page of your manual talks about Archimedes Principle.

An object placed in water is buoyed up by a force equal to the weight of the quantity of water it displaces


archimedes principle
quizlet.com
Which, in diving terms means, that to be neutrally buoyant a diver must displace an amount of water equal to their weight. Neutral buoyancy is achieved by finding a balance between the weight of equipment and lead weights and the use of a Buoyancy Control Device (BCD).

When a Diver over weights themselves, much more gas is needed in the BCD to increase the displacement of water and make the diver neutrally buoyant. The deeper the diver goes, the more gas is required.

STREAMLINING

Ok, so now moving on to lesson number 2 in the course... streamlining. Have you ever tried running in a swimming pool. It takes a lot more energy than swimming through the water and this is a result of resistance.

well weighted scuba diver in cyprusOverweighting has 2 effects on the diver. Firstly, the diver's bottom half is dragged down by the weight around their waist, meaning their position is less like the swimmer through the water and more like the runner, increasing resistance and using more energy.

Secondly, the diver has to put more gas into the BCD making them bigger in the water and therefore not as streamlined. Again, this makes the Diver require more energy to make the Dive.

GAS CONSUMPTION

We already know that we are using more of our tank air to add to our BCDs to compensate for over weighting but look at those last comments with regards to energy used.

The more energy our bodies need, the more Oxygen our bodies must burn in order to provide it. This results in a higher heart rate and faster breathing rate, which means you will use your limited air supply much faster than a Diver who is correctly weighted and breathing normally would.

Weighting isn't the only factor in this but the amount of divers who have come to Scuba Tech telling us they use lots of air and require a 15litre cylinder is phenomenal. Once we have corrected their weight, not one of these divers have left here needing a 15litre. It is a BIG factor!

THE DANGER

So, we use a bit more air and we aren't perfectly streamlined, what is the big deal?

When we are overweighted, buoyancy becomes more difficult to control. We find ourselves having to add and release air from our BCDs much more often.

We are already breathing heavier and faster than we would, if we were correctly weighted.

Now, imagine something happens...

It isn't overly serious. For example, you get  bit of cramp in your calf muscle.

The added workload of solving the problem, means you start to breathe more heavily than you were before.

Your buoyancy adjusts with your breathing, you have to correct it and now you are dealing with 2 things at once. The increased work load and the heavy breathing means the level of Carbon Dioxide in your body is increasing, which your brain detects and triggers a faster heart rate and a need to breathe faster to reduce the level of CO2.

This can become a vicious circle, as your breathing becomes less efficient and shallower meaning you cannot reduce the levels of Carbon Dioxide and your brain keeps triggering the heart to beat faster and increase the breathing rate in response.
....and eventually your buoyancy goes out of control...

And this is where accidents happen. It is a downward spiral that started as a very simple problem but can easily compound into something much bigger and potentially life threatening.

Do Not misunderstand me, accidents happen even to those who are correctly weighted, but you probably wouldn't be starting out with an elevated breathing rate when you are correctly weighted and buoyancy is much easier to control, meaning it shouldn't become an added stressor.

Our Weights

To give you an idea of what we use...

Me
12l steel cylinder
Halcyon Wing with a Steel Backplate
Weighted Single Tank Adaptor
2kg lead weight
Brand new 6.5mm full wetsuit

Taking into account the steel backplate and the STA, you could say 6KG

Shell
10l steel Tank
Buddy BCD
6KG lead weight
10mm crushed Neoprene Drysuit with Thinsulate undersuit

So you can see, you do not need to plaster yourself to the bottom. Buoyancy and Trim will all be easier to control when you are correctly weighted.

Start dropping the weights, your breathing rate will reduce, which will naturally make it easier to sink (less air held in your lungs) and you will probably find you can take more weight off.