Scuba Gear: Becoming a Christmas Tree

With Christmas just a few days away, all of the city of Rotterdam is decorated with light, bells and all sorts of other Christmas decorations. More special even, the city is covered with a decent amount of snow....And of course, our house is pretty much the same. Without the snow of course. And as I am a member of the declining race of people who buys a real tree, I was dragging a nice and green, great smelling, tree into my house.

While my girlfriend was decorating the tree, I was catching up on some dive reading and thinking about all the scuba gear I still wanted to buy. And when I looked at the tree again it hit me.......

All suited up, I am the Christmas tree.

I will try to explain what I mean.

When I took my first scuba lessons, I started with the basic scuba gear.
So starting with a mask, snorkel, fins, wetsuit, BCD, regulators, a weightbelt and a console, I hit the pool and later Lake Oostvoorne. Like most novice divers I had my hands full with all of that gear. It was hard to check the compass, stay trimmed at the same time and look at my instructors, divemasters and fellow students, but I managed, no more, no less.

After the open water course I started diving with the dive team of the divecenter and after I made sure I loved scuba diving, I started to acquire my own gear. Of course I started buying the list above and (tried to) get familiar with it.
Wanting to improve my diving skills en experience all sorts of different types of dives, I enlisted in more diving courses. And those courses needed me to by more gear.
Starting with the advanced open water course, I needed two (regular and backup) lights. Then I needed a dive slate, to determine a course during the navigation specialty course. And last, for the deep diver specialty I had to get a safety sausage (SMB) to use during safety stops.

Now back to the tree. When it was still in the forest, all it's branches were free. At most there was a bird's nest on one of them.... But now, all decorated, every branch had something on it; whether it's a light, a ball or some artifical snow.
And my BCD is the exactly the same. At first there were just the console and the octopus, but now all the rings are used to hang all my stuff....



See what I mean?



The worst thing is, I still need (want) more gear... I still have quite a long wishlist that I sent to Santa....
I always thought of myself as a pretty down-to-earth guy, but looking at all the gear I have acquired in two years time, I have to ask myself:

Am I a scuba gear junky?

Something to ponder about during the Holidays.

Have a nice Christmas and a happy new year....

Menno

Deep diver specialty

Lot's of beautiful wrecks and reefs are located deeper than the 18 meters you're allowed to dive when having an open water diver certification or even deeper than the 30 meters with the advanced open water diver certification (padi). So if you ever want to dive those wrecks or reefs, extra training is required. The last two weeks I've taken the deep diver specialty course so I can dive those spots in a safe and responsible way.  I want to share with you what I've learned during this course.

When doing a specialty course, you learn in two ways, from the textbook and from the dives. And I must say, I've learned the most from the last dive. Because for that dive, I had to make the dive plan, do the briefing and go through the safety procedures.

From the textbook

Before the dive
Before you even put on your gear set a goal that is realistic for you and your buddy. Take into account the expected circumstances underwater and both your experiences with them. Making a 35 meter dive in tropical water just isn't the same as making a dive to that depth in cold, dark water.

A goal and a plan
First of all you need a goal for your dive and a decently set up plan. Don't just go in and see what happens. It will put you and your buddy at great risk. Make a decent and conservative plan to visit that great wreck and stick to it. Because of the short bottom times at depth (no deco time), make sure you can descend and descend very close to the goal of your dive.

Buddy check

Well, of course, you should check your gear before each dive, but before a deep dive you should do this even more carefully. Gear failure at depth can cause a lot more problems than at 10 meters, and it's a long way to the surface. So, do a very thorough buddy check...

While diving
Check your air regularly. At 30 meters your air consumption is twice as much as at 10 meters. So check it regularly and that of your buddy as well. And for that matter, maintain contact with your buddy very often, so you'll notice the signs of nitrogen narcosis. Turn back well before you're low on air. You still need to do a safety stop, so make sure you both have enough air for that.

Ascending
When you're at the spot where you want to ascend, release your safety sausage. The safety sausage makes people on the surface aware that there are divers below. It will reduce the chance of being run over by a boat. Then ascend slowly and maintain (almost) neutral buoyancy. At 5 meters, do at least 3 minute safety stop. And then continue to ascend.

The dives

From the four dives we made in the course doing different kinds of exercises like answering diving theory questions and doing math. Also we looked at colour changes underwater and the effect of pressure on object filled with air. And for the first time, I had to use a safety sausage.
But the most educating dive was the final one. I had to prepare the dive, determining bottom time, descending and ascending procedures, agree on hand and light signals. And of course, navigate the whole dive.

Also I had to prepare emergency procedures and had to do the briefing.


The dive itself was cold (5 degrees at the bottom) and dark. But with our lamps, visibility was very good. And everything went as planned.
This course has made me look at a dive in a more serious way and taught me a lot, especially when I have to lead a dive.

European Shark Week

This week it´s European shark week. Project Aware is working together to with the shark alliance to ask the European parlement to sharpen European shark finning ban.

And because shark fins should be on sharks and not in some bowl of soup, I support the shark week with the post in my blog.

You can find more on the European Shark week on Project Aware.

Esspecially for Shark week, I looked on the net for some shark cartoons to make you think about us people..

More shark cartoons on http://www.shaaark.com

Physics in diving (2): Underwater pressure and gas compression

We can all feel it in our ears when we descend for a dive, or when we ascend at the end of a dive. The pressure changes with depth.


Water pressure
At sea level, the pressure is 1 atmosphere or 1 bar. This pressure is caused by the weight of all these kilometers of air in the atmosphere above us.
In water it works the same. The weight of the water above us determines the pressure working on us. As a rule of thumb, every 10 meters we descend, the pressure we endure increases with 1 bar.
It is easy to calculate the pressure at any depth. Just divide the depth you are at by 10 and don't forget to add 1 for the pressure the atmosphere is already giving you.

So at 10 meters the pressure is 10/10 + 1 = 2 bar. In the table there is more.

Depth	Pressure
Surface	1 bar
10 meters	2 bar
20 meters	3 bar
30 meters	4 bar
40 meters	5 bar

So why is it important to know the pressure underwater? For one, when diving with enriched air, the pressure is needed to calculate the partial pressure.
An understanding of pressure , together with gas compression, is also needed to better understand the changes in buoyancy when changing diving depth.

Gas compression

Gas compression is very convenient in diving. It makes that you can stay underwater as long as you do. By compressing air into your tank you can take air with you to stay underwater for a long time. How does that work?

Boyle's law
Boyle's law states that at any given temperature the product of the pressure and the volume of a certain amount of gas, is constant:

P1*V1 = P2*V2 = constant 

So let´s say your underwater at 10 meters and the air in your BCD is has a volume of say 9 liters. When you descend to 20 meters, the water pressure will increase from 2 bar to three. The air pressure in your BCD will take on the same pressure. This pressure will make the volume of the air in your BCD change from 9 liters to 6 liters. 

The other way around, when you go to the surface the water pressure will decrease from 2 to 1 bar and the volume in you BCD will increase to 18 liters.

Boyle´s law can be corrected for temperature influences. This results in the combined gas law:

P1*V1/T1 = P2*V2/T2 = constant

Because when diving, temperature differences aren't that big (unless you pass through a thermocline), I will explain the temperature influence with an example of filling your tank.

You might have noticed that after you've fill your tank at the dive center, your tank feels a bit hot. Let's say that you filled your tank to 200 bar. 

Then later on when you have set up your gear to go diving and check your air supply, you might notice that your tank has cooled and when you check your air supply you will notice that you have less than 200 bar in your tank.

That is the temperature effect working. The volume of your tank is still the same, the temperature has dropped a bit, so only the pressure can decrease to make the formula work.

Pressure, compression and buoyancy

So when you change depth, the water pressure changes and the volume of air in your BCD changes with it. These changes have a direct influence on your buoyancy. Your buoyancy is dependent on your weight and volume. As your weight doesn't change when you change depth, only the air volume in your suit and BCD has an influence on your buoyancy.
When you go deeper the volume in your CD will decrease, as will your buoyancy. That is why you will have to add air to your BCD to compensate for the volume lost by the pressure. Also, when you go up, you'll have to release some air, otherwise your buoyancy will be too positive and you will shoot to the surface, with all risks that come with that....


Relates subjects:
Physics in diving (1): Buoyancy

Physics in diving (1): Buoyancy

Why does a piece of wood float and does a rock sink? Why does a steel rod sink but will a steel hull boat float? Why do I go down when I deflate my BCD and do I go up when I inflate it?


It's all about buoyancy.........

Archimedes

But what is buoyancy exactly? Legend says that when Archimedes took a bath he discovered the buoyancy principle. He then jumped out of the bathtub and ran into the street shouting "Eureka!!!". Afterwards it was stated as: "Any object, fully or partially immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object".

That, of course, is a very nice statement, but how does it work?

When a stone is submerged in a fluid, the buoyacy force (Fb) on the object can be calculated by multiplying the volume of the object by the density of the fluid and the gravitational force is the weight of the object:

Fb = Vo*ρf and Fg = Mo

But you know the volume and the mass of the stone, so you can also calculate the density of the stone by dividing the mass of the stone by it's volume. When comparing the density of the object and that of the fluid, there are three different states of buoyancy:

1. Positive buoyancy; The density of the fluid is higher than that of the object. This will result in the object ascending and finally surfacing.
2. Negative buoyancy; The density of the object is higher than that of the fluid. This will result in the object sinking to the bottom.
3. Neutral buoyancy; Here the density of the object and fluid are equal. The object will hover. This is the buoyancy state of a diver tries to maintain.

Diving and buoyancy

So there are three things influencing the buoyancy of an object, or a diver. These are the density of the water you dive in and your weight and volume, including your dive gear. 


Salt water has a higher density than sweet water, so a diver has a higher buoyancy in salt water than in sweet water. So in general, in salt water you need to add more weight than in sweet water.


If you have a positive buoyancy you can ad some weight to put on some extra pieces to your belt or in your BCD. If you alreaydy have a negative buoyancy you can increase your volume by wearing a thicker suit. Never just inflate your BCD to add volume, you'll need that when you underwater!

You might have noticed that when you get deeper underwater, your buancy tends to become negative; you feel like you are dragged down. This will be discussed in my next entry on pressure and (air) compression


Related subjects:
Physics in diving (2): Underwater pressure and gas compression

 

Started diving... And blogging

In spring 2009 I got the opportunity to do a Padi Open Water course with my company. And while I was in the water for most of my life (competitive swimming, water polo), this sport or hobby looked like it was made for me.

So after four nights of theory lessons with repeatedly setting up the diving gear and four practice rounds in the pool, at june 6th we were finally ready to go into open water (Lake Oostvoorne).

I was a little bit anxious about that first open water dive, but after a minute or two, I was already getting really comforable under water. 
Although we didn't get to see too much of wildlife, it still made me want to see more.
Me and 11 of my collegues made it through the exercises and as a bonus, we all became a member of the dive team until the end of the year.

And because of the dives I made with the dive team in mostly Lake Grevelingen, I am now so hooked that I am aiming for the Master Scuba Diver Rating.

Follow me in my quest to get that rating and in all my other diving experiences.

Want to read this page in another laguage? Check below...