Weighting the key to Trim, Comfort and Safety

I have recently been asked for my opinion and advice on weighting and weighting systems. When it comes to deciding on the weight that you need is falls into main areas: The Amount of Weight, needed to offset you buoyancy, and The Distribution of Weight, for comfort, trim and emergency procedures.

How Much Weight?

During a divers education they are taught how to calculate and test their buoyancy to ensure they are properly weighted to maintain their position in the water throughout a dive. For many divers this is where it stops and only re-examine the issue if they make a kit change or dive in a new environment, and sometimes not even then.

I think weighting is a much more on-going process than this because many divers, especially to begin with, are constantly making subtle changes and modifications to their kit configuration and the way they dive until the find a system that they are comfortable with. With this in mind I define weight into 2 categories: Useful Weight and Dead Weight. Useful weight is any negative buoyancy that is offered to you through kit that you carry for another diving purpose and is permanently attached throughout the dive. This includes things like the empty weight of a cylinder (but not stage cylinders), torches and battery canisters regulators and empty BCDs and wings. Dead weight is any extra weight (lead) that we add to make our system neutrally buoyant, this could be added to a weight belt, integrated pockets or similar.

 To have the most efficient system possible we want to maximise the useful weight and minimise the dead weight. If we can do this we are then not just lifting and moving extra weight that we don’t really other than to sink. To do this when you are configuring your gear think about every item you are using, do you need it and what benefit does it offer. So if for instance if you are diving in the UK with a dry suit and you know you will need to carry more weight then why not take a larger cylinder (which will also give you more gas for the dive) and make sure it is made of steel. While doing this process don’t get too carried away by just added more kit to your set up that you don’t really need as this just becomes dead weight, and worse can lead to a greater chance of entanglement and confusion. When configuring you kit you should still always be looking to reduce waste and complexity while maintaining everything that you need to complete the dive at hand.  When working the other way to a warm environment where you will typically be less buoyant, and so need less weight, take an aluminium cylinder.

Finally when carrying out a buoyancy check, make sure you do it with an almost empty cylinder and with only items that you always carry and are not disposable. This will give you the minimum weight that you will need to carry even at the end of your dive when you will be the most buoyant.

Weight Distribution: Trim, Comfort and Safety

At the early stages of diving getting down is the most important thing and you have more to worry about than the specific location of your weights. As you develop your diving this should be something that spend a little more time considering.

First let’s look at trim and comfort. Improving your trim allows you to move more easily in the water, reducing drag and therefore reducing your physical exertion and so reducing your air consumption.  The most efficient trim position is a flat body with your knees up in line with your body and your feet above you. To begin with this can be a strange position to be in as we are used to moving with our feet at the lowest point and not above our head. To be able to maintain this position comfortably we need to be in balance and this means having our centre of mass and centre of buoyancy in the same location.

The natural centre of mass of a person is towards the centre of the torso, for men this is slightly towards the shoulders and for women this down towards the hips.This position is the point around which we can naturally balance in equilibrium. For diving this is the point around which we want to balance our buoyancy and weights. Firstly we position all of our standard kit (tanks, Torches, BCD) around this point and should end up with relatively comfortable set up. The easiest way to start positioning weight is to start close to the centre of mass with larger weights and as you move away the weights should be smaller. This is due to the relationship of the moments around the centre.

For men typically using integrated weights or weights attached to a cylinder dives a better trim position and comfort as it is closer to his centre of mass. Women will typically find low integrated pockets and weight belt s more comfortable for the same reason. Women have another added advantage with weight belt comfort and that is their hips, or welt belt retainers, which help to keep a belt from slipping down.

For added comfort splitting weights across multiple locations (less on weight belts to reduce slipping) ensures that no one item is too heavy during kit up, it also has added benefits when it comes to emergencies which we will discuss later.

With regards to trim and comfort the last aspect is ankle weights. Many people have strong views on this and at the end of the day it comes down to personal choice. These are my thoughts on the issue. I personally am not a big fan as I believe that they have the biggest effect on trim as they provide a large moment away from the body centre which drops the feet.

I also think that they are working against you as, with a dry suit especially, the buoyancy in your feet should naturally float your feet to above your head and into a low drag position with no effort to the diver. If you become comfortable and confident with you set up then feet high orientations should not be an issue.

My final thoughts on weighting are to do with emergencies and were touched on earlier.  I strongly believe that a diver should not have their weight all in one location as it doesn’t provide many options in an emergency, you can either dump your weights or not. If you distribute your weights across 2 or 3 locations it means that if you did have a situation when you believed dumping your weights in the only option then you can dump a small amount to make you slightly positively buoyant and allow you to have a slightly more controlled ascent than just dumping all of your weight. Also in terms of diver problems I think that many could be solved before you dive by having proper weighting as it is surprising how many divers dive with wrong weights, especially too many.

I hope that this blog helped and might have sparked some new thoughts along the way. I would be happy to learn your views and opinions because at the end of the day it all comes down to personal preference.