Weight Belts
Weight belts are used to compensate for the positive buoyancy that your body experiences when submerged in salt water and wearing a rubber wetsuit. Without a weight belt, it can be very difficult to descend under the water. However, too much weight can make it easy to descend but very hard to ascend. Therefore a good understanding of correct weighting is essential to safe diving practice.
Objectives
Compare and contrast various types of weight belts
Understand the factors that make up ideal weighting
Understand how to weight yourself correctly
Basic understanding of where to wear a weight belt
Appropriate weighting
Weighting yourself appropriately can be one of the biggest challenges when starting out freediving. Having the right amount of weight for a dive can mainly be influenced by the depth you intend on diving, wetsuit thickness, water salinity and the composition of your body type.
As a general rule of thumb, you should always be positively buoyant on the surface after an exhalation. This is to ensure that if you have a very rare shallow water blackout, you will float up to the surface and not sink.
Another guide to work on is the rule of thirds. For example, if you intend to dive to 30 metres deep. You want to be positively buoyant at less than 10 metres, neutrally buoyant between 10 – 20 metres and negatively buoyant at 20 – 30 meters. This formula, in combination with the rule of positive surface buoyancy after an exhalation can be applied to nearly all intended depths.
Looking at specifics, below is a guide to help you weight yourself appropriately for the main variabilities that affect buoyancy.
Factors that affect weighting
Wetsuit thickness
Simply put, the thicker your wetsuit, the more buoyancy you will have which requires more weight to compensate.
In practical terms, when diving in winter, you may be using a 5mm thick wetsuit and in summer a 3mm suit. Therefore, to have the same amount of buoyancy, you will require more weight in winter than what you would in summer.
Intended Depth
As explained in the basic freediving physiology lesson, the deeper you dive, the heavier you become and the faster you sink. When it comes to weighting yourself, you always need to keep this in mind and weight yourself for the deepest dive that you intend on performing then apply the above ‘appropriate weighting guide’s’.
For example, if you intend on diving to 10 metres deep as the maximum depth during the diving session, but most of the dives you perform will be at around 6 metres, then weight yourself to 10 metres. This may mean that you will have a small amount of positive buoyancy at the main depth of 6 metres, however if you were to have an accident at 10 metres, you would sink, rather than float up.
Salinity
Salinity becomes a factor when diving in freshwater or saltwater. More weight is always required in salt water, compared to that of fresh water. For example, If you use 4kg of weight to dive 10m in a 5mm suit in the ocean, you will only need 2kg of weight to achieve the same depth in fresh water.
Belt Types
Rubber weight belts
Components
The rubber weight belt (and most belts) are made of the long strap, known as the belt and a buckle. The buckle can be designed as a pin or a quick release.
When you descend under the water, your wetsuit will begin to compress / reduce in physical thickness. For example, it may go from a 5mm – 2mm thickness. If you are wearing a rubber weight belt, it will constrict as you descend and stretch as you ascend. This ensures that it maintains the correct position on your body and does not move about.
Pocket & Nylon Belts
Pocket belts are generally used for SCUBA divers and they allow the quick subtraction or deposit of weights, without the need to thread through the belt. They are ideal belts for SCUBA divers, as they are generally more comfortable than a rubber belt and can be shifted around easier under the water. However, these types of belts do not constrict, as they are made of a tough nylon.
If you are wearing a nylon belt and dive down, as your wetsuit constricts, the nylon belt will become loose and move position, often moving right up to your chest.
How to apply a weight belt
Where to position
When placing a weight belt, make sure that it sits just on the upper portion of your hips, not over your stomach or lower buttocks. Avoid placement over the stomach because it will restrict your ability to breathe in fully and you may find that the weight belt will ride up more frequently as well. If placed over the buttocks, when you invert yourself to descend, the weight belt will ride up and become loose.
Make sure that the weight belt is comfortably tight and not loose and keep in mind that when you enter the water and descend, your wetsuit will compress, so tighten enough to compensate for this occurring.
With the excess rubber from the strap, an important safety tip is to fold it underneath the belt. This ensures that the belt will be released easily by pulling hard on the tag end in the need of an emergency. Never tie the tag end into a knot, as it can become stuck and prevent quick release.
How to add or remove weights
Simply thread the tag end (end without the buckle) through the weights.
Evenly space out the weights, to ensure that there is equal weight on either side. This is important, as being over weighted on one side will roll you to that side when not floating on the surface.
