K as kilo

Any body immersed in a liquid sometimes has a big belly!

Definition

Sink like a lead: this seems to be the key word of diving as the destiny of any body dressed in neoprene immersed in a liquid is to rise. Great is therefore the temptation to weight the said body with lead in order to finally be able to sink; and therefore dive.

Synonymes

Kilogram | Kg | pounds | Weight | Ballast | Leads | weight belt

Starter

Two more letters! When I started writing this “scubabécédaire” with its 26 letters of the French alphabet, I had no idea of ​​the difficulty of the exercise and the time I would need to complete it. But I'm approaching the end of the opus and that takes a great weight off me.

Lead in the head

K… It's true that with such a subject, it's easy to pile on the pounds. I want to talk this time about the unit of measurement of weight, the kilo. Which indicates the value of the ballast, in the form of weights that divers are obliged to lug around their waists; and often too many – remember that a good diver is an old diver and that he must have more lead in his head than in his belt…

It is therefore necessary to weigh down to practice diving. For several reasons. First, to compensate for the buoyancy of the neoprene wetsuit (and even more of an inflated dry suit) which behaves like a real buoy. In fact, in principle, a naked diver does not need to weigh down to descend and stay at the bottom. But it sucks!

Then, in relation to the salinity of the water, which is more or less dense and which greatly modifies buoyancy: in fresh water, 2 or 3 kg can easily be removed from the belt, whereas in Red Sea (very salty) my almost quintal requires 12 kg to deign to evolve in clear water…

Finally, the capacity of our lungs! Healthy people have on average a lung capacity of 4 to 5 liters but some freedivers (who are not short of air) display a chest inflated to 10 or 12 liters! Which, mathematically, represents all the same from 4 to 12 liters of air between inspiration and expiration and therefore, since Archimedes took his bath, is equivalent to 12 kg displaced.

This is called the “ballast lung“, technique that (old) and good divers know perfectly well to balance: when you blow, you sink; when you inflate your lungs, you go up. But blow, name of a pipe! You will explode your cells. This is not a column about pneumothorax…

Finally, a last factor that we do not always think about: the weight of the gas carried and breathed (1,293 g per liter of air!) which quickly amounts to kilos! All beginners have had the experience of finding themselves too light at the end of the dive and of not being able to hold a level with an almost empty tank. Fortunately, the good-natured instructor will then take a few excess pellets out of his pocket, in the condescending gesture of a magician...

Main course

This is how during our long underground dives, to ballast the inflated waterproof suit and the enormous quantities of gas carried away, the ballast to be provided easily exceeded ten kilos...

This is why we replaced the lead as much as possible with cadmium/nickel or lead (!) lighting batteries – weighing an anvil at the time, as we explained in thearticle on Lumen...

Fill the mood

Of course it would have been stupid to lug weights around when planning a dive requiring a long and strenuous approach walk. I want to talk about the distant dives of the siphons at the end of endless caves or at the bottom of chasms or even in high altitude lakes. In this case we used with more or less success stone slabs collected on the spot, fixed on the bottles and in belt bags. Due to the relatively low density of the stone, a lot was needed, which made us look like “wooden gate” larvae of caddisflies…

We proceeded in this way for the exploration of the terminal siphons of the Padirac chasm or for dives in the Green Lake in the Italian Alps where for the same reasons of lightening, we had decided to immerse ourselves with wet suits of 3mm… in water at 5 degrees! My testicles still remember it.

Dessert     

So ? When and how did we proceed to weigh down the divers who, as soon as they were dressed in rubber, dabbled like the corks of fishermen, with no hope of ever sinking?

History has forgotten him. But very quickly, the first divers with helmets (a copper and brass accessory to experience claustrophobia) equipped themselves with a heavy lead pectoral and shoes with soles of the same metal in order to be able to descend and literally walk under water, which which is the origin of their nickname “heavy feet".

A light story

Then, for the “autonomous divers” appeared the “belts” where one threaded the number of weights of one kilo necessary. They were made of white braided cotton with a red band and “quick release” buckles.

At the time, we were diving with the fantasy of having one day or another to “drop our belt” – which, by the way, has never happened to me in fifty years of diving. Still, in training, during a "drop", we regularly found ourselves with the heavy belt stuck behind the knees or behind the fractured heels, irreparably dragged to the bottom...

These pellets, which deformed over time, pinched the belt so much that it was almost impossible to change their number or position. And we all remember the long sessions of hammering with a screwdriver or a wood chisel to try to remove the holes! Something to fill the mood…

At the same time, some die-hards used the “Marseille belt”, ignoring any “quick release” in favor of a classic pin buckle, an oversized version of the trouser belt.

These “Marseillais” often passed for fads even if the big black rubber belt with holes tended to fit better to the body.

Today, for fans of the weight belt, we use a clasp closure, in metal or plastic, which allows you to adjust it as best as possible to your waist size. You always have to tighten like a deaf when fitting because, with the crushing of the garment under the pressure, you tend to end up with the belt at the knees.

 

 

It's in the pocket !

But the real revolution of the century, what am I saying, centuries of centuries, is the advent of the famous “weight pockets” in stabilizing jackets. Because, in their pathetic tendency to reinvent hot water, manufacturers have been introducing “weight pockets” for years, which are supposed to make belts obsolete and facilitate ballasting. A solution based on clips, pockets, Velcro and raccoons, hopelessly different from one manufacturer to another and which does not have my favors, you can imagine. Moreover, while diving recently in Egypt with a “PADI Instructor Instructor” who posted several thousand dives, I noticed with pleasure that she also used a belt…

The principle is to unite the weighting of the vest and therefore of the diving suit. With, from my point of view, major disadvantages: nothing could be easier than losing similar lead pockets that you don't really know where to put, not to mention the system engineer diploma necessary to hope to understand how to use them...

Then, you can practice an academic straight jump and, as soon as you enter the water, lose the weighted pockets which will go straight towards the bald spots of the colleagues already on the bottom... But the major drawback in my opinion relates to the center of gravity of the diver. It is in our best interest to carry the weights as close to the body as possible to maintain good mobility; however, the use of these pockets (front, rear, cows, pigs, etc.) totally unbalances the diver, transforming these already obese vests into irremovable elevators!

See you soon for a new definition of Scuba Bécédaire. The irreverent lexicon of diving, but not only. Because sometimes ...

Francis Le Guen

Café

And finally, the Cornelian problem: to calculate its ballast as well as possible! Explanations by the essential Vincent Defossez from Aquadomia in Marseille.