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Buoyancy control is a fundamental skill to enjoy diving in a safe and comfortable way. However, reaching an optimum ability level is more complicated, especially for less advanced divers.
For that reason, Víctor Córdoba, Human Resources Director in Dressel Divers is going to help us to improve our buoyancy control. He is a scuba diver with more than 6.000 dives in his log book, in addition he works as PADI Course Director and IANTD Instructor Trainer specialized in Cave Diving, Trimix and Rebreather Diving. In this post our knowledgeable diver offers us three secrets so you will know how to control your buoyancy during dives as he does. Let’s see them!
Scuba diving gear, its quantity and ballast weight distribution are the buoyancy control keys. Therefore, those people who know how to control their buoyancy are able to…
- Calculate precisely how much ballast weight is adequate (the exact right measure, neither more nor less than necessary)
- Know where the weights have to be positioned.
- Breathe correctly.
Too Much Ballast Weight, That’s the Mistake Every Diver Should Avoid for Proper Buoyancy Control.
One of the most common diving mistakes is carrying more ballast than necessary. Sometimes it is an involuntary error, other times, people really think it will make the dives easier. ─ “If we carry too much ballast weight, we will always be able to compensate it thanks to our BCD” ─ Some people say. Wrong! The truth is completely different. The excess weight forces us to add more air to our BCD, which exposes us much more to the pressure changes.
Let’s explain it! A properly weighted diver maintains fine control of buoyancy by playing with the air in his lungs. The variations of the buoyancy of this diver are voluntary and controlled.
However, all of us have seen divers underwater who suffer sudden oscillations in their buoyancy. Now up, now down, like a yo-yo.
Generally, their main problem is they are carrying too much weight and for this reason, they have to add air to their BCD. As you know, depending on just a little pressure changes the air inside your jacket expands or shrinks, this phenomenon produces variations in their buoyancy that these divers are not able to avoid or control by themselves. The key is calculating properly the number of pounds or kilos of ballast you will need to correctly control your buoyancy while scuba diving.
Proper Diving Buoyancy Control or How to Know How Many Pounds or Kilos I Need
In order to calculate the amount of ballast weight properly, you will have to take into account those elements with positive and negative buoyancy, and compensate them. The positive buoyancy elements make us ascend to the surface, so we must add weight to balance them and dive. The negative buoyancy components make us descend, so they subtract weight from the total computation. In other words.
|Ballast weight = human body + neoprene – equipment.
Positive buoyancy elements.
The naked human body has of 0.95 kg/liter density approximately. Therefore, it floats slightly, and we need to add approximately 5% of our weight as ballast to our gear in order to compensate for the inherent positive body buoyancy. To know how much weight you need, use this formula. (Your weight x 5) / 100
Neoprene suit causes positive buoyancy due to the gas bubbles it has trapped inside. So that, an 80kg person in a one-coat mono suit needs:
+ 3.3lb./1.5 kg, if it is a suit 3 mm thick
+ 5.5lb./2.5 kg, if your suit is 5 mm thick
+ 7.7lb./3.5 kg, if your suit is 7 mm thick
Negative buoyancy components
Diving tanks provide negative buoyancy to the diving gear, but depending on their weight they will affect ballasting in a different way. That is, we will have to decrease the lbs. or kg according to the tanks weight and density.
A 85 cu.ft. /12l. air tank and a weight of 31 lb./ 14 kg. Subtract -4.4 lb./ 2kg.
Regulator. Subtract – 2.2 lb. / 1kg.
You have to bear in mind that some tanks weight up to 35.5 lb./16 kg. In this case, you would have to carry less ballast. This information appears on the cylinder markings. On the other hand, in the case of aluminum tanks, we will have to remember that they float more than those made of steel. Nor should we forget the BCD, for example, a wing vest is much heavier than a technical vest and therefore we will need less ballast.
To be more accurate calculating ballast, do tests at the end of your dives (when there are only approximately 435 PSI / 30 bars of pressure left in the bottle). If at 16 feet / 5 meters deep, wearing every single piece of the gear, and with empty BCD, you can easily maintain neutral buoyancy, you’ve hit the nail on the head! On the contrary if you ascend or descend involuntarily, you must increase or decrease the ballast weight.
Weight Distribution, The Second Key to Improve Your Buoyancy Control.
As all divers know, the horizontal position is the best one because it offers the least resistance to forwarding movement. The correct and balanced distribution of the ballast will allow us to maintain this position easily.
Imagine that the human body is a rocker. In the water, the rocker axis or buoyancy center is located about 2.75 inches / 7 cm below the sternum, and between 3.95 inch. / 10 cm and 5.90 inch. /15 cm above the navel.
As we know, positive buoyancy is mainly provided by the body and the neoprene suit. Both are distributed evenly throughout the body. However, negative elements, such as the bottle and the ballast, are concentrated in specific sites.
The bottle weight is focused on a point above the buoyancy center. By placing the ballast at waistline, we can balance the bottle weight and maintain a horizontal position with very little air in the BCD. If we are properly weighted, we will avoid the sensation of the head and shoulders dropping down. If not, we would look like the character in figure 3.
If, on the contrary, the diver is over ballasting, he or she will need to move the fins constantly in order to raise the legs and maintain a horizontal position. As a result, air consumption increases and comfort decreases. The excessive ballast can also have consequences for others and for the natural environment. Because of the downwards flutter, our diver can raise sediment that hinders visibility not only for him or her but also for their dive buddies and could even damage the seabed and corals.
Breathing to Put Under Control Your Buoyancy.
The third key to buoyancy control is none other than breathing. Thanks to it we will achieve accurate management of this skill. By filling our lungs with air and emptying them we can ascend or descend into the water. In this way, we use the lungs as a natural BCD. When they expand or contract with a normal breath, they modify our buoyancy as ballast weight, approximately 2,2 lb./ 1 kg. If we over breathe, we can modify our buoyancy up to 5 or 6 kg, so you can see how important is proper breathing technique and control for buoyancy control.
Yes, buoyancy control requires that breathing be slow and deep. Remember, also, that in this manner, the diver reduces the risk of suffering from narcosis, decompression disease, and oxygen toxicity.
Dressel Divers can help you improve your buoyancy control. We would not want to end this article without offering you our help to improve your buoyancy control. It may have been a long time since your last dive, perhaps you have recently changed your gear or you are simply aware of your need to improve this diving skill. If you find yourself in any of these situations, we will help you take your buoyancy control to the next level through the PADI “Peak Performance Buoyancy” course. For more information, contact us.