A while ago I had the opportunity to do a couple of open water certifications in the Clear Water Scuba Park near Terrell Texas. This was my first time at the scuba park and I did not know what to expect. Getting there was an adventure, but I will leave that adventure for another post. We got to the park around 11am or so and there were already about 100 people at the park. DUI was having one of its dry suit days there and it was quite "festive".
Of course being from the Midwest we were fairly used to diving in cold water so we dove in our regular 7mm wetsuits and did not wear gloves or hoods. The water temperature was aound 65f which was really quite comfortable for a regular Midwest diver. However as we were preparing to enter the water, at least two of the local divers asked us where our gloves and hoods were and offered up their own (thinking that we had forgotten ours).
The one impression I came away with was how absolutely helpful and friendly the local folks were. All in all we had excellent dives and enjoyed our time there. Hopefully we will be able to visit Terrell someday soon.
Saturday, December 30, 2006
Sunday, November 05, 2006
Interesting book.
On Friday afternoon, I spent a few hours with the owner of the local dive store (LDS). I dabble in some web based software and developed a prototype storefront for the LDS so that people can sign up for classes via the Internet. After I spent time at the LDS I decided to go to the local Barnes and Noble to read a few magazines and relax for a while until the rush hour traffic died down.
After I had a great cup of coffee and chocolate cheesecake, I decided to check out some of the new books that are on sale. I picked up a book to scan through, and could literally not put it down. The book had me totally captivated. The author is Eric L Haney and it is called Inside Delta Force. The book is very well written and provides a first person account of Haney's experience inside Delta Force. There was one scene in the book that had me laughing till I had tears in my eyes. Haney's description of his selection interview with the famous Col Beckwith had me in the room there with them almost hearing and seeing the reactions of Haney and Beckwith.
Interestingly enough, I found that I learned a valuable lesson from the book that I applied to my divemaster class today. It was time for us to work on the rescue skills today and I remembered Haney's description of how they were taught to perform a hostage rescue. At first the students were walked through (in slow motion) the steps of clearing a room. Gradually the tempo was increased until the students could do a room clearing at full running speed.
The rescue skill is not all that hard to do, but a lot of students have trouble do a rescue to demonstration level. So what I did was start the candidate divemasters on the shallow end of the pool by talking through the rescue. We broke down the rescue into a number of phases and practiced each phase until the candidates mastered the sub skill. We then ramped up the tempo slowly until the candidates performed the full blown rescue by putting together all the steps. This approach seemed to work well for the candidates and they appeared much more confident in their ability than I have observed with candidates in previous classes.
We will be practicing the rescue skill until the candidates can perform the skill almost by second nature. As I wrote above, the rescue skill is not all that hard to do, but there are a number of things that can (and often do) trip you up.
After I had a great cup of coffee and chocolate cheesecake, I decided to check out some of the new books that are on sale. I picked up a book to scan through, and could literally not put it down. The book had me totally captivated. The author is Eric L Haney and it is called Inside Delta Force. The book is very well written and provides a first person account of Haney's experience inside Delta Force. There was one scene in the book that had me laughing till I had tears in my eyes. Haney's description of his selection interview with the famous Col Beckwith had me in the room there with them almost hearing and seeing the reactions of Haney and Beckwith.
Interestingly enough, I found that I learned a valuable lesson from the book that I applied to my divemaster class today. It was time for us to work on the rescue skills today and I remembered Haney's description of how they were taught to perform a hostage rescue. At first the students were walked through (in slow motion) the steps of clearing a room. Gradually the tempo was increased until the students could do a room clearing at full running speed.
The rescue skill is not all that hard to do, but a lot of students have trouble do a rescue to demonstration level. So what I did was start the candidate divemasters on the shallow end of the pool by talking through the rescue. We broke down the rescue into a number of phases and practiced each phase until the candidates mastered the sub skill. We then ramped up the tempo slowly until the candidates performed the full blown rescue by putting together all the steps. This approach seemed to work well for the candidates and they appeared much more confident in their ability than I have observed with candidates in previous classes.
We will be practicing the rescue skill until the candidates can perform the skill almost by second nature. As I wrote above, the rescue skill is not all that hard to do, but there are a number of things that can (and often do) trip you up.
Saturday, October 28, 2006
Reflection
Yesterday, I had one of those deep and soul searching conversations with a very good friend. We were talking about work, the meaning of life and so on. In the course of the conversation we spoke about what brought us to diving.
In my case, I happened to get into diving by a series of unplanned but fortunate events. I signed up to do the open water class with a number of colleagues at work and just kept on doing classes. For one thing, I really enjoyed being in the water. I feel very comfortable and at home in the water. I think that the reason is that when I was a kid I spent many summer days at the local community pool trying to see how far I could swim underwater. I don't know why I had this desire to swim underwater, but I got fairly good at swimming underwater. However, the idea of SCUBA didn't cross my mind in the least. The closest I got to SCUBA was the fact that there was a small room in the pool complex with the sign "SUB AQUA CLUB" on the door. SCUBA just seemed so far out of reach.
The other factor that caused me to continue the classes was that I found the learning aspect challenging and opened up a whole new world to me. I have always enjoyed science and technology, so when I had to start learning about physiology and physics for diving, I was hooked.
In trying to explain what exactly it was that made me enjoy diving as much as I do, caused me to think about the my motivation and reasons for liking diving. The way I tried to explain it to my friend was to describe a man who walks down the street and unexpectedly finds very valuable article that changes his life. He didn't know the valuable article was there and was not looking for it, but having found it, caused him to experience many new things. I know it is an awkward word picture, but there are elements that are true for me.
My friend's experience was a little different to mine in that she got into diving in a more planned and organized way. She felt that she was not spontaneous enough in her approach to diving. Personally, I don't see her as being all that concrete and structured, but I guess she knows herself best. Everyone is different of course, so I am sure every diver has his or her own story about why they love diving.
The point of this post is that for the first time, I really sat down to think about why I am so passionate about diving and what keeps me so interested in the field.
In my case, I happened to get into diving by a series of unplanned but fortunate events. I signed up to do the open water class with a number of colleagues at work and just kept on doing classes. For one thing, I really enjoyed being in the water. I feel very comfortable and at home in the water. I think that the reason is that when I was a kid I spent many summer days at the local community pool trying to see how far I could swim underwater. I don't know why I had this desire to swim underwater, but I got fairly good at swimming underwater. However, the idea of SCUBA didn't cross my mind in the least. The closest I got to SCUBA was the fact that there was a small room in the pool complex with the sign "SUB AQUA CLUB" on the door. SCUBA just seemed so far out of reach.
The other factor that caused me to continue the classes was that I found the learning aspect challenging and opened up a whole new world to me. I have always enjoyed science and technology, so when I had to start learning about physiology and physics for diving, I was hooked.
In trying to explain what exactly it was that made me enjoy diving as much as I do, caused me to think about the my motivation and reasons for liking diving. The way I tried to explain it to my friend was to describe a man who walks down the street and unexpectedly finds very valuable article that changes his life. He didn't know the valuable article was there and was not looking for it, but having found it, caused him to experience many new things. I know it is an awkward word picture, but there are elements that are true for me.
My friend's experience was a little different to mine in that she got into diving in a more planned and organized way. She felt that she was not spontaneous enough in her approach to diving. Personally, I don't see her as being all that concrete and structured, but I guess she knows herself best. Everyone is different of course, so I am sure every diver has his or her own story about why they love diving.
The point of this post is that for the first time, I really sat down to think about why I am so passionate about diving and what keeps me so interested in the field.
Friday, October 27, 2006
Squeeze the gas
Disclaimer: more dive master physics to follow. May not be suitable for the easily bored ;)
Today, we are going to take a brief look at what happens to a gas when you apply pressure to it.
The first thing to remember is that as the pressure on the gas increases, the volume of the gas will decrease in relation. In SCUBA diving we are very familiar with this from our very first open water classes. Most classes start off by talking about what happens when you take a flexible container of air down to 100 feet or so. Of course as every one probably knows, the air in the container will compress and the container will look like most of the air has been sucked out of it. Of course the air is still there, it is just that is has been compressed (squeezed by the pressure of the water).
Remember that the pressure multiplied by the volume is the same for a given container at any depth.
P1 x V1 = P2 x V2
The pressure multiplied by the volume at the surface will be the same answer as the pressure times volume at depth (for the obvious reason that as the pressure increases, the volume decreases).
Lets do a simple example to demonstrate the relationship and how it is used in dive master physics.
You take a container with the volume of 2 cubic feet (at the surface) to a depth of 66 feet. What will the new volume be.
Remember that 66 feet is equal to 3 atmospheres. So the 2 cubic feet at 66 feet will be compressed by the water pressure so that the gas inside the container will one third of that at the surface - 2 cubic feet divided by 3 (0.67 cu ft)
However, for the dive master exams the examiners try to be a little tricky so you have to read the questions very carefully. For example they might throw in the words "fresh water" into the question, which means you need to use 34 feet instead of 33 feet per atmosphere etc. Be sure to read the questions very carefully.
To make these pressure calculations more challenging, the examiners will ask you to determine what happens to a given volume of gas when you take it from one depth to another. It is not that the work is much harder, it is just that they seem to try to see if you are paying attention.
Lets do an example of a potentially trickier question. Note that we are now starting at depth and not the surface.
You need to take a volume of 20 cu ft from 99 feet to 66 feet in sea water.
First we need to calculate the original pressure at 99 feet - which calculate as 4 ata (p1).
Next we need to calculate the pressure at 66 feet - which is 3 ata (p2).
Remember the formula: p1 x v1 = p2 x v2
We have p1, v1, p2 but not v2. What we need to do is find out what v2 is. So to calculate the new pressure we use a ratio calculation
v2 = p1 / p2 x v1 (the slash is shorthand for divided by)
4 ata / 3 ata x 20 cu ft = 26.67 cu feet.
Of course in the dive master exams they will not give you easy numbers like these, but the principle is the same. Lets do a more realistic example.
15 cubic feet at 105 feet to 41 feet in fresh water.
v1= 15 cu ft
p1 = 105 ft / 34 (3.09 + 1 ata = 4.09 ata)
p2 = 41 ft / 34 (1.2 + 1 ata = 2.2 ata)
So lets plug the numbers into the ratio we used above
v2 = p1 / p2 x v1
v2 = 4.09 ata / 2.2 ata x 15 cu ft = 27.88 cu ft
The calculations are not difficult, but do remember the following key things
Make sure you know whether you are working with fresh water or salt water.
Make sure that you add in the surface atmosphere to get the ata pressure at depth.
Today, we are going to take a brief look at what happens to a gas when you apply pressure to it.
The first thing to remember is that as the pressure on the gas increases, the volume of the gas will decrease in relation. In SCUBA diving we are very familiar with this from our very first open water classes. Most classes start off by talking about what happens when you take a flexible container of air down to 100 feet or so. Of course as every one probably knows, the air in the container will compress and the container will look like most of the air has been sucked out of it. Of course the air is still there, it is just that is has been compressed (squeezed by the pressure of the water).
Remember that the pressure multiplied by the volume is the same for a given container at any depth.
P1 x V1 = P2 x V2
The pressure multiplied by the volume at the surface will be the same answer as the pressure times volume at depth (for the obvious reason that as the pressure increases, the volume decreases).
Lets do a simple example to demonstrate the relationship and how it is used in dive master physics.
You take a container with the volume of 2 cubic feet (at the surface) to a depth of 66 feet. What will the new volume be.
Remember that 66 feet is equal to 3 atmospheres. So the 2 cubic feet at 66 feet will be compressed by the water pressure so that the gas inside the container will one third of that at the surface - 2 cubic feet divided by 3 (0.67 cu ft)
However, for the dive master exams the examiners try to be a little tricky so you have to read the questions very carefully. For example they might throw in the words "fresh water" into the question, which means you need to use 34 feet instead of 33 feet per atmosphere etc. Be sure to read the questions very carefully.
To make these pressure calculations more challenging, the examiners will ask you to determine what happens to a given volume of gas when you take it from one depth to another. It is not that the work is much harder, it is just that they seem to try to see if you are paying attention.
Lets do an example of a potentially trickier question. Note that we are now starting at depth and not the surface.
You need to take a volume of 20 cu ft from 99 feet to 66 feet in sea water.
First we need to calculate the original pressure at 99 feet - which calculate as 4 ata (p1).
Next we need to calculate the pressure at 66 feet - which is 3 ata (p2).
Remember the formula: p1 x v1 = p2 x v2
We have p1, v1, p2 but not v2. What we need to do is find out what v2 is. So to calculate the new pressure we use a ratio calculation
v2 = p1 / p2 x v1 (the slash is shorthand for divided by)
4 ata / 3 ata x 20 cu ft = 26.67 cu feet.
Of course in the dive master exams they will not give you easy numbers like these, but the principle is the same. Lets do a more realistic example.
15 cubic feet at 105 feet to 41 feet in fresh water.
v1= 15 cu ft
p1 = 105 ft / 34 (3.09 + 1 ata = 4.09 ata)
p2 = 41 ft / 34 (1.2 + 1 ata = 2.2 ata)
So lets plug the numbers into the ratio we used above
v2 = p1 / p2 x v1
v2 = 4.09 ata / 2.2 ata x 15 cu ft = 27.88 cu ft
The calculations are not difficult, but do remember the following key things
Make sure you know whether you are working with fresh water or salt water.
Make sure that you add in the surface atmosphere to get the ata pressure at depth.
Tuesday, October 24, 2006
A little off topic
Earlier this week I listened to an interesting podcast on grammar (that statement sounds like a contradiction). What makes the podcast interesting is the way that it is presented. The podcast is called "Grammar Girl's Quick and Dirty Tips for Better Writing". For transcripts and more information take a look at her website. Grammar Girl has a fun and upbeat way of presenting her podcast. She has the wonderful ability to take what could be a dry and boring subject and actually make it interesting and memorable.
I have been listening to the grammar pod casts for a while and have picked up some good ways for remembering some grammar rules. For example, grammar girl gave a very memorable way of how to remember when to use whom (as opposed to who).
I am not sure how other blog writers go about writing their blogs, but as for me I try to make my blog entries interesting and informative, without being too dry. When I started writing this blog, I had a number of funny anecdotes that I wanted share. At first, I thought that the blog would be a good vehicle to sharpen my writing skills and be a place where I could write some of the interesting, and perhaps off-beat things that I notice in my little part of the world.
However, what I found was that I ran out of funny anecdotes and sometimes found it hard to come up with fresh and interesting topics. Last winter I went through a dry patch and had no desire to write blog entries. For one thing, I did not do any open water diving, and for another, just had no inspiration.
One lesson that I learned was that I need to pace myself. Too many blog entries in a short period of time has the effect of causing me to get burned out from writing. Although I really enjoy writing the blog, I find that if this becomes like a job or obligation, then it takes the fun and enjoyment out of it. I want to keep my entries fresh and interesting (at least to me).
So all this rambling brings me back to grammar girl. She mentioned something on her last pod cast about proofreading that actually gave me a fair amount of comfort and relief. Grammar girl wrote "So, given my long history with typos, it has become my belief that it's nearly impossible for someone to accurately proofread their own writing and be consistently successful." I have spent hours reading and re-reading my blog entries to try to catch the dumb typos that I know I make. I often forget to write your and write you etc. What grammar girl wrote helped me understand that I am not alone in the proofreading battle.
The thing is that I don't want to produce a perfect blog entry. That is not my intent at all. My intent is to make sure that I communicate clearly and don't have typos in my post that confuse the meaning of what I am trying to convey. My intention is to have fun with the blog and try to help other divers wherever I can. Hopefully the information I convey from time to time is useful and helpful. I try to walk a fine line between being informative, without giving so much information that it becomes boring.
I have been listening to the grammar pod casts for a while and have picked up some good ways for remembering some grammar rules. For example, grammar girl gave a very memorable way of how to remember when to use whom (as opposed to who).
I am not sure how other blog writers go about writing their blogs, but as for me I try to make my blog entries interesting and informative, without being too dry. When I started writing this blog, I had a number of funny anecdotes that I wanted share. At first, I thought that the blog would be a good vehicle to sharpen my writing skills and be a place where I could write some of the interesting, and perhaps off-beat things that I notice in my little part of the world.
However, what I found was that I ran out of funny anecdotes and sometimes found it hard to come up with fresh and interesting topics. Last winter I went through a dry patch and had no desire to write blog entries. For one thing, I did not do any open water diving, and for another, just had no inspiration.
One lesson that I learned was that I need to pace myself. Too many blog entries in a short period of time has the effect of causing me to get burned out from writing. Although I really enjoy writing the blog, I find that if this becomes like a job or obligation, then it takes the fun and enjoyment out of it. I want to keep my entries fresh and interesting (at least to me).
So all this rambling brings me back to grammar girl. She mentioned something on her last pod cast about proofreading that actually gave me a fair amount of comfort and relief. Grammar girl wrote "So, given my long history with typos, it has become my belief that it's nearly impossible for someone to accurately proofread their own writing and be consistently successful." I have spent hours reading and re-reading my blog entries to try to catch the dumb typos that I know I make. I often forget to write your and write you etc. What grammar girl wrote helped me understand that I am not alone in the proofreading battle.
The thing is that I don't want to produce a perfect blog entry. That is not my intent at all. My intent is to make sure that I communicate clearly and don't have typos in my post that confuse the meaning of what I am trying to convey. My intention is to have fun with the blog and try to help other divers wherever I can. Hopefully the information I convey from time to time is useful and helpful. I try to walk a fine line between being informative, without giving so much information that it becomes boring.
Monday, October 23, 2006
can you handle the pressure?
Disclaimer: these posts might not be suitable for people who have physica-o-phobia ;)
This is the next installment in the series on dive master physics. Today, I am going to write about how calculate pressure per at specific depths. There are some important things to remember when working with pressure. There are two types of pressure that is referred. There is absolute (ATA) and gauge pressure. The two very similar and it is very easy to confuse. Be very careful when reading the question to ensure that you know whether you are working with ATA or gauge.
The easiest way to remember the difference between the two is to think about what a gauge is. The gauge pressure is what you see on the pressure gauge. The other takes ambient (surrounding pressure) into account. So when the question asks you to determine ATA remember to always add in the ambient air pressure at sea level. Lets do a simple example to demonstrate the difference.
How much ata pressure is at 90 feet/30 meters?
90 feet divided by 33 = 2.73 atm + 1 atm = 3.73 ata
30 meters divided by 10 = 3 atm + 1 atm = 4 ata
Note that you always add the ambient pressure of 1 atm to the answer to calculate the ata pressure. So when you see "ata" think "add 1 atmosphere".
Gauge pressure is the same except that you don't add the 1 atm. The answer is what you see on the gauge. So when you see gauge - think what I see on the gauge.
Some other things to remember:
33 feet / 10 meters of sea water = 1 atm
34 feet / 10.3 meters of fresh water = 1 atm
Lets do another example.
What are the gauge and absolute pressures 67 feet / 22 meters in fresh water?
First calculate the atmospheres at depth
67 feet / 34 = 1.97 ata
22 meters / 10.3 = 2.14 ata
Remember that gauge pressure is what you see on the gauge so therefore the gauge pressures those we have just calculated.
To calculate the absolute pressure (ata) remember to add 1 atmosphere (the effect of the air column on the water). There the absolute pressures are
1.97 + 1 atm = 2.97 ata
2.14 + 1 atm = 3.14 ata
To add a little complication to the matter, the questions sometimes ask you to determine the psi or kg/cm2.
To do that you need to remember that 1 atm is equal to 14.7 psi (pounds per square inch) and 1.03 kg/cm2.
Imperial: 2.97 ata x 14.7 psi = 43.66 psia (pounds per square inch atmosphere)
Metric: 3.14 ata x 1.03 kg/cm2 = 3.23 kg/cm2
This is the next installment in the series on dive master physics. Today, I am going to write about how calculate pressure per at specific depths. There are some important things to remember when working with pressure. There are two types of pressure that is referred. There is absolute (ATA) and gauge pressure. The two very similar and it is very easy to confuse. Be very careful when reading the question to ensure that you know whether you are working with ATA or gauge.
The easiest way to remember the difference between the two is to think about what a gauge is. The gauge pressure is what you see on the pressure gauge. The other takes ambient (surrounding pressure) into account. So when the question asks you to determine ATA remember to always add in the ambient air pressure at sea level. Lets do a simple example to demonstrate the difference.
How much ata pressure is at 90 feet/30 meters?
90 feet divided by 33 = 2.73 atm + 1 atm = 3.73 ata
30 meters divided by 10 = 3 atm + 1 atm = 4 ata
Note that you always add the ambient pressure of 1 atm to the answer to calculate the ata pressure. So when you see "ata" think "add 1 atmosphere".
Gauge pressure is the same except that you don't add the 1 atm. The answer is what you see on the gauge. So when you see gauge - think what I see on the gauge.
Some other things to remember:
33 feet / 10 meters of sea water = 1 atm
34 feet / 10.3 meters of fresh water = 1 atm
Lets do another example.
What are the gauge and absolute pressures 67 feet / 22 meters in fresh water?
First calculate the atmospheres at depth
67 feet / 34 = 1.97 ata
22 meters / 10.3 = 2.14 ata
Remember that gauge pressure is what you see on the gauge so therefore the gauge pressures those we have just calculated.
To calculate the absolute pressure (ata) remember to add 1 atmosphere (the effect of the air column on the water). There the absolute pressures are
1.97 + 1 atm = 2.97 ata
2.14 + 1 atm = 3.14 ata
To add a little complication to the matter, the questions sometimes ask you to determine the psi or kg/cm2.
To do that you need to remember that 1 atm is equal to 14.7 psi (pounds per square inch) and 1.03 kg/cm2.
Imperial: 2.97 ata x 14.7 psi = 43.66 psia (pounds per square inch atmosphere)
Metric: 3.14 ata x 1.03 kg/cm2 = 3.23 kg/cm2
Saturday, October 21, 2006
Water weighs how much?
Yesterday, I bumped into one of the dive master candidates who recently completed his dive master classes. He was having all kinds of problems with the physics portion of the course and was lamenting his travails in trying to pass the exams. We will be getting together next week sometime to work on his physics and try to get him over the hurdle.
In the interim, I am going to review some of the most salient points in the physics for dive masters. What I would like to do is boil the issues down to the most critical ones. My intention is not to cover the entire physics portion, but to go over the parts that most students seem to have problems with. If anyone is interested in learning more about dive physics, physiology, equipment, I would highly recommend the PADI encyclopedia of recreational diving. There is a printed version and a version that you can install on your computer that includes videos etc. Again, the ERD is highly recommended.
So, why do we need to know how much water weighs? After all we are not going to haul water around.
Just about everyone knows that things seem to weigh less when submerged in water. So what is the reason and why is this important.
Water has the odd effect that it "pushes things up" to the extent that you are "pushing" water away for an object. For example if you put a SCUBA tank weighing approximately 40 pounds in the water it may feel like it only weighs a fraction of the actual weight. The reason is that the SCUBA tank displaces (pushes water away) to make place for the object.
So to determine how much the SCUBA tank weighs (or seems to weigh) in water, you have to know how much water has been displaced (pushed away). The amount is called the displacement volume. For example if the object we are putting in the water is one foot by one foot by one foot (a cube) then we know that the displacement volume is 1 cubic foot.
Next we need to know how much a cubic foot of water weighs. For example one cubic foot of sea water weighs 64 lbs and one cubic foot of fresh water weighs 62.4 lbs.
Now that we know how much the water "pushes back" we can determine what the effect of the push back is on the object we are putting in the water. Lets say the 1 cubic foot object weighs 100 lbs on the surface, we can find out how much the object will appear to weigh in the water. So the apparent weight is 100 lbs - 64 lbs = 36lbs.
This means that the effect of the sea water "pushing back" on the object will make it seem to only weigh 36 lbs.
Does this make sense?
Say for example you were asked by a friend to recover this 1 cubic foot object from the local quarry that you dive in. To do this, you will need to know how much lift you need to use to lift the object (how large a lift bag to use).
Right now the object is negatively buoyant by 36 lbs. Therefore we need to add extra lift to the object of at least 36 lbs to make it neutrally buoyant. To lift the object we will have to use a little more lift to make it positively buoyant to make it rise to the surface.
So we must again ask ourselves how much does water weigh to find out how much water we must displace (push away) to cause lift of 36 lbs. We know that 1 cubic foot of sea water weighs 64 lbs, so to displace 36 lbs we have to displace 36 divided by 64 which is approximately 0.56 cubic feet. So to make the object neutrally buoyant, we need a lift bag that can be inflated with at least 0.56 cubic feet of air. In other words we need to displace at least 0.56 cubic feet of sea water to provide enough lift to make the object neutrally buoyant.
I hope that this is fairly straight forward. I tried to boil the issues down to the most essential in calculating displacement and how much lift is needed.
Lets do another example for practice.
Lets say you need to recover a motorboat engine that weighs 400 lbs. The engine displaces 3 cubic foot of water.
So lets see what we know. The engine displaces 3 cubic feet of water and the weight of the displaced water is: 3 cubic feet x 64 lbs = 192 lbs. To find out what the apparent weight is we subtract the weight of the displaced water from the weight of the engine: 400 lbs - 192 lbs = 208 lbs. In other words the object appears to only weigh 208 in the water (or: it is negatively buoyant by 208 lbs).
Next we need to determine what size lift bag we need to lift the engine. Since we need to provide at least 208 lbs lift we need to displace 208 lbs of sea water: 208 lbs divided by 64 lbs = 3.25 cubic feet.
In the interim, I am going to review some of the most salient points in the physics for dive masters. What I would like to do is boil the issues down to the most critical ones. My intention is not to cover the entire physics portion, but to go over the parts that most students seem to have problems with. If anyone is interested in learning more about dive physics, physiology, equipment, I would highly recommend the PADI encyclopedia of recreational diving. There is a printed version and a version that you can install on your computer that includes videos etc. Again, the ERD is highly recommended.
So, why do we need to know how much water weighs? After all we are not going to haul water around.
Just about everyone knows that things seem to weigh less when submerged in water. So what is the reason and why is this important.
Water has the odd effect that it "pushes things up" to the extent that you are "pushing" water away for an object. For example if you put a SCUBA tank weighing approximately 40 pounds in the water it may feel like it only weighs a fraction of the actual weight. The reason is that the SCUBA tank displaces (pushes water away) to make place for the object.
So to determine how much the SCUBA tank weighs (or seems to weigh) in water, you have to know how much water has been displaced (pushed away). The amount is called the displacement volume. For example if the object we are putting in the water is one foot by one foot by one foot (a cube) then we know that the displacement volume is 1 cubic foot.
Next we need to know how much a cubic foot of water weighs. For example one cubic foot of sea water weighs 64 lbs and one cubic foot of fresh water weighs 62.4 lbs.
Now that we know how much the water "pushes back" we can determine what the effect of the push back is on the object we are putting in the water. Lets say the 1 cubic foot object weighs 100 lbs on the surface, we can find out how much the object will appear to weigh in the water. So the apparent weight is 100 lbs - 64 lbs = 36lbs.
This means that the effect of the sea water "pushing back" on the object will make it seem to only weigh 36 lbs.
Does this make sense?
Say for example you were asked by a friend to recover this 1 cubic foot object from the local quarry that you dive in. To do this, you will need to know how much lift you need to use to lift the object (how large a lift bag to use).
Right now the object is negatively buoyant by 36 lbs. Therefore we need to add extra lift to the object of at least 36 lbs to make it neutrally buoyant. To lift the object we will have to use a little more lift to make it positively buoyant to make it rise to the surface.
So we must again ask ourselves how much does water weigh to find out how much water we must displace (push away) to cause lift of 36 lbs. We know that 1 cubic foot of sea water weighs 64 lbs, so to displace 36 lbs we have to displace 36 divided by 64 which is approximately 0.56 cubic feet. So to make the object neutrally buoyant, we need a lift bag that can be inflated with at least 0.56 cubic feet of air. In other words we need to displace at least 0.56 cubic feet of sea water to provide enough lift to make the object neutrally buoyant.
I hope that this is fairly straight forward. I tried to boil the issues down to the most essential in calculating displacement and how much lift is needed.
Lets do another example for practice.
Lets say you need to recover a motorboat engine that weighs 400 lbs. The engine displaces 3 cubic foot of water.
So lets see what we know. The engine displaces 3 cubic feet of water and the weight of the displaced water is: 3 cubic feet x 64 lbs = 192 lbs. To find out what the apparent weight is we subtract the weight of the displaced water from the weight of the engine: 400 lbs - 192 lbs = 208 lbs. In other words the object appears to only weigh 208 in the water (or: it is negatively buoyant by 208 lbs).
Next we need to determine what size lift bag we need to lift the engine. Since we need to provide at least 208 lbs lift we need to displace 208 lbs of sea water: 208 lbs divided by 64 lbs = 3.25 cubic feet.
Sunday, October 15, 2006
Contemplation
As I write this post, I am sitting at the local lake that we do all our dive training in. A kind soul as left a wireless port open for us to use and fortunately I able to get Internet access here.The weather turned out to be fairly nice for this time of the year and right now it is sunny with a light cool breeze. The air temp is probably around 50f or so, and that is the best it has been all week. I didnt plan on coming out to the lake today, but was talked into it by a dive buddy who has an out of town friend visiting.
The out-of-towner have never used a drysuit and and has also not experienced our bracing temperatures at this time of the year. So I duly brought out my drysuit, thermal underwear etc. and help my dive buddy and her friend get set up etc. I think the out-of-towner will either love the cold water or hate it. I guess there is no real way to prepare someone for the cold bracing water. So far they seem be having a good time. They came back for extra weight, since the out-of-towner could not descend. I think it might be a case of the breathing too hard, but, but I got him squared away with an additional 6lb.
It is so serene out here. I lit a large fire and we are going to grill some meat when they come out of the lake. Even though the conditions are not ideal by a long shot, it is still good for the soul be out here, enjoying a late fall day.
The lake is placid surrounded by trees on all sides. The leaves have started to change color and there is an explosion of color all around us. In the lake there are three dive flags reflecting the warm afternoon glow and a few pontoons around with some fisherman trying to coax a few fish to take their bait.
What an excellent day this has turned out to be.
The out-of-towner have never used a drysuit and and has also not experienced our bracing temperatures at this time of the year. So I duly brought out my drysuit, thermal underwear etc. and help my dive buddy and her friend get set up etc. I think the out-of-towner will either love the cold water or hate it. I guess there is no real way to prepare someone for the cold bracing water. So far they seem be having a good time. They came back for extra weight, since the out-of-towner could not descend. I think it might be a case of the breathing too hard, but, but I got him squared away with an additional 6lb.
It is so serene out here. I lit a large fire and we are going to grill some meat when they come out of the lake. Even though the conditions are not ideal by a long shot, it is still good for the soul be out here, enjoying a late fall day.
The lake is placid surrounded by trees on all sides. The leaves have started to change color and there is an explosion of color all around us. In the lake there are three dive flags reflecting the warm afternoon glow and a few pontoons around with some fisherman trying to coax a few fish to take their bait.
What an excellent day this has turned out to be.
Tuesday, October 10, 2006
Stingray City
The Sydney Morning Herald reports that tourism to the world famous Stingray City has dropped by at least 40%.
"Watersport operators on the Grand Cayman Island in the Caribbean, are
reporting a drop in tourist numbers of up to 40 per cent with many locals
attributing the decline to the death of Steve Irwin (Sydney
Morning Herald)"
In August of this year (2006), I was fortunate enough to visit Stingray City. I was able to be the first one off the boat and got to spend at least 10 minutes with the Stingrays on my own while waiting for the rest of the divers. It was one of the most memorable experiences of all my dives. The Stingrays were so graceful and gentle and the visibility was excellent since no-one had kicked up any sand as yet.
As the dive progressed, the dive master started to hand feed the Stingrays and the other divers started to touch and pet the Stingrays. Personally, I do not like to touch the marine life so I just observed spellbound.
Like all things in this world, perception is almost as important as fact. The fact is that one is more likely to be injured by all kinds of things than being injured by a Stingray. What happened to Steve Irwin was a complete freak accident. However, I do understand the apprehension of casual divers and snorkelers toward Stingrays.
On the one hand, I am opposed to hand feeding the Stingrays, but on the other hand, Stingray City was one of my most memorable dives. I am a little conflicted about the interaction with the Stingrays in Grand Cayman, but since they have been doing Stingray City dives, there has been an excellent safety record.
The bottom line: lets continue to dive safely and responsibly, taking all reasonable precautions, but let us not stop enjoying the wonders of the sea because of one isolated incident.
Sunday, October 08, 2006
Last open water class for the season
This past weekend, I conducted two open water classes at the local spring-fed lake. The visibility was the best that I have seen all year and the water temp was on the cool side, but not too bad. I actually managed to enjoy the dives. Once you get used to the cooler water (let's say south of 60f) its not all that bad. I know that folks who are used to the 80f plus temps of the warmer climates will probably think that I have lost my mind, but I find the colder water oddly comforting. I cannot explain it, but I actually enjoy the sensation of the cold water against my skin. I suppose it is a matter of mind over matter.
The students did exceptionally well. I was one happy instructor. Even though the water was cold for the students, and the weather not too great, they did not complain and completed the certification dives and I believe had some fun along the way.
Today, as we came out of the water after the fourth certification dive, I noticed that the wind had picked up significantly and it looked like it might rain. So I asked the students if they would be willing to go over to a local Perkins restaurant to have some hot chocolate and complete the paper work. Everyone thought that it would be a good idea to go, so after packing up all the gear we headed over to the Perkins in a long convoy of vehicles.
What I did not consider was that the after-church lunch-time crowd would be there too. The manager was quite grumpy and was rather unfriendly and brisk. I did not really care for his attitude. No matter what I asked him, he would shake his head and come up with with a reason why what I was asking for would be a major inconvenience for him. Too bad, since I have taken a number of groups there before.
However, for the future, I have found a much better option. One of the students suggested that we go down to the local Target store and sit in the cafeteria to do the paper work. I was disappointed since I wanted to drink something hot (like hot chocolate) and wanted to buy everyone a round of hot drinks. In any event, we convoyed to the local Target and I was very happy and surprised to see a Starbucks inside the store, co-located with the cafeteria. I could not have been happier. We got to have a round of lovely hot drinks while I signed logbooks etc. We had a great time chatting, drinking our hot drinks and getting to know each other a little better.
What a wonderful way to end the open water diving season!
The students did exceptionally well. I was one happy instructor. Even though the water was cold for the students, and the weather not too great, they did not complain and completed the certification dives and I believe had some fun along the way.
Today, as we came out of the water after the fourth certification dive, I noticed that the wind had picked up significantly and it looked like it might rain. So I asked the students if they would be willing to go over to a local Perkins restaurant to have some hot chocolate and complete the paper work. Everyone thought that it would be a good idea to go, so after packing up all the gear we headed over to the Perkins in a long convoy of vehicles.
What I did not consider was that the after-church lunch-time crowd would be there too. The manager was quite grumpy and was rather unfriendly and brisk. I did not really care for his attitude. No matter what I asked him, he would shake his head and come up with with a reason why what I was asking for would be a major inconvenience for him. Too bad, since I have taken a number of groups there before.
However, for the future, I have found a much better option. One of the students suggested that we go down to the local Target store and sit in the cafeteria to do the paper work. I was disappointed since I wanted to drink something hot (like hot chocolate) and wanted to buy everyone a round of hot drinks. In any event, we convoyed to the local Target and I was very happy and surprised to see a Starbucks inside the store, co-located with the cafeteria. I could not have been happier. We got to have a round of lovely hot drinks while I signed logbooks etc. We had a great time chatting, drinking our hot drinks and getting to know each other a little better.
What a wonderful way to end the open water diving season!
Tuesday, October 03, 2006
Divemaster fun
There are two students in my current divemaster class. They are naturals in the pools and it has been a lot of fun working with them on the various skills that we have cover. Last night, I sprang a surprise on them. I have a non-diving friend who was visiting me and I suggested to him that he accompanies me to class and be a discover scuba student for the evening.
The two candidate divemasters had to walk my friend though all the steps of setting up the gear. He didn't have to set up any of the gear himself, but just had to watch and learn. The candidates did a fantastic job. One of the candidates has a great way of explaining concepts in every day terms and makes even seemingly complex things seem easy and understandable. They seemed to really enjoy the unexpected challenge.
The advantage that I could see was that they had an actual person to demonstrate the skill to which probably made it more realistic for them. In any event, they will make excellent instructors one day.
The two candidate divemasters had to walk my friend though all the steps of setting up the gear. He didn't have to set up any of the gear himself, but just had to watch and learn. The candidates did a fantastic job. One of the candidates has a great way of explaining concepts in every day terms and makes even seemingly complex things seem easy and understandable. They seemed to really enjoy the unexpected challenge.
The advantage that I could see was that they had an actual person to demonstrate the skill to which probably made it more realistic for them. In any event, they will make excellent instructors one day.
Friday, September 29, 2006
Caught rather than taught?
There are two course directors that teach at the same store as I do. The senior of the two course directors has been teaching for many years and has encyclopedic knowledge of dive theory, local dive sites, people in the industry etc. He is really one of a kind. However, the senior course director (SCD) has not taught confined water skills in any of the classes that I have attended so far. The two course directors divided up the work and each chose to teach a different component of the IDC (instructor development course).
The course director that taught me most of what I know about instructing is excellent and I have written previously about how I still feel like a student around him. However with SCD, I have not really built up that kind of relationship and was a little curious about what his teaching skills would be like in the pool.
In the current IDC that is being held, SCD is the only course director since the other CD has work commitments that prevented him from attending. So last week, I got to work with SCD in the pool and I must say I enjoyed the experience. His style is unique to him of course (like everyone), but I both found that I learned some new ways of explaining the same skills and also found that I found his style familiar. By being familiar, I mean that I could identify with how he was conducting the class and found that even though we were taught by different people in different generations, there were enough similarities that I felt that we were on the same page every step of the way.
The casual observer might say that since we are both certified by the same agency one could suspect or expect that we would be on the same page. But I would counter that although we are expected to perform up to the same minimum certification, there is a huge component of "stuff" that is only "caught" rather than "taught". This intangible quality could variously be referred to as culture, oral learning, affective behavior, etc. I am not a trained educator, but I know that in any organization there are written and unwritten rules, procedures and methods. The same could be said of how one conducts SCUBA instruction.
Sometimes as instructors we convey just as much by our behavior, dress, demeanor, enthusiasm, professionalism, patience, etc. as we do by the actual content of the lectures. This is obvious stuff really, but as instructors we need to always pay attention to the intangible aspects of working with students - for example by trying to get them to be as passionate as we are about diving. (ok - I made a big assumption about passion here, but I sincerely hope that each and every instructor is passionate about diving and has not lost the fire and passion for diving.)
The course director that taught me most of what I know about instructing is excellent and I have written previously about how I still feel like a student around him. However with SCD, I have not really built up that kind of relationship and was a little curious about what his teaching skills would be like in the pool.
In the current IDC that is being held, SCD is the only course director since the other CD has work commitments that prevented him from attending. So last week, I got to work with SCD in the pool and I must say I enjoyed the experience. His style is unique to him of course (like everyone), but I both found that I learned some new ways of explaining the same skills and also found that I found his style familiar. By being familiar, I mean that I could identify with how he was conducting the class and found that even though we were taught by different people in different generations, there were enough similarities that I felt that we were on the same page every step of the way.
The casual observer might say that since we are both certified by the same agency one could suspect or expect that we would be on the same page. But I would counter that although we are expected to perform up to the same minimum certification, there is a huge component of "stuff" that is only "caught" rather than "taught". This intangible quality could variously be referred to as culture, oral learning, affective behavior, etc. I am not a trained educator, but I know that in any organization there are written and unwritten rules, procedures and methods. The same could be said of how one conducts SCUBA instruction.
Sometimes as instructors we convey just as much by our behavior, dress, demeanor, enthusiasm, professionalism, patience, etc. as we do by the actual content of the lectures. This is obvious stuff really, but as instructors we need to always pay attention to the intangible aspects of working with students - for example by trying to get them to be as passionate as we are about diving. (ok - I made a big assumption about passion here, but I sincerely hope that each and every instructor is passionate about diving and has not lost the fire and passion for diving.)
Friday, September 15, 2006
The small things matter too
This coming weekend, my diving buddy and I are going to be teaching an advanced open water class. The class consists of some classroom presentations, and two days of diving. There are two required components - navigation and deep. The other three components are up to the discretion of the instructor. However at the local dive store (LDS) that I teach at, we all teach the same optional components for the advanced class. The advantage is that everyone is on the same page and it makes logistics etc. easier.
One of the modules that we will be teaching this weekend is naturalist. The aim of this component is to expose the students to the various types of animals and plants they might encounter in the various types of diving they will be doing in the future. From my own perspective, I can attest to the fact that I have enjoyed my diving a lot more since I have started to pay a lot more attention to the various species of plants and animals on dives.
My diving buddy, the navigating phenom (NP) is an avid photographer and videographer. He has a keen eye for detail and manages to get spectacular shots on just about every dive. The secret is that he knows the habitat and habits of the various species. This knowledge enables him to find the various animals in areas that most other divers just swim over. A lot of divers just zoom over a dive site and mainly want to see all the big animals. On a lot of dives, these "speedy" divers will miss the most beautiful and interesting animals right under their noses.
In our class room session last night, we tried to encourage the students to spend the time to learn what the various species look like in the places where they will be diving. We showed them some of the video that NP shot on one of our dive trips and I think we managed to get the point across that it is not always the whale shark or giant grouper that makes for an interesting dive.
One of the modules that we will be teaching this weekend is naturalist. The aim of this component is to expose the students to the various types of animals and plants they might encounter in the various types of diving they will be doing in the future. From my own perspective, I can attest to the fact that I have enjoyed my diving a lot more since I have started to pay a lot more attention to the various species of plants and animals on dives.
My diving buddy, the navigating phenom (NP) is an avid photographer and videographer. He has a keen eye for detail and manages to get spectacular shots on just about every dive. The secret is that he knows the habitat and habits of the various species. This knowledge enables him to find the various animals in areas that most other divers just swim over. A lot of divers just zoom over a dive site and mainly want to see all the big animals. On a lot of dives, these "speedy" divers will miss the most beautiful and interesting animals right under their noses.
In our class room session last night, we tried to encourage the students to spend the time to learn what the various species look like in the places where they will be diving. We showed them some of the video that NP shot on one of our dive trips and I think we managed to get the point across that it is not always the whale shark or giant grouper that makes for an interesting dive.
Monday, September 11, 2006
Forever friends
Last weekend I took a dive trip to a neighboring state to attend an annual event that is organized by one of the long-time instructors at the local dive store (LDS) that I teach at. I have been aware of the trip for a number of years now, but until this last weekend, I have not been able to make it. Every year something came up and I could not go.
This year, I decided at the very last moment to go to the annual event and the weekend turned out to be a lot of fun. The weather was so-so, a little on the cold side and rainy off and on. The water temperature was actually warmer than the air temperature so it was comfortable and easy diving.
The event was basically a treasure hunt. We had to hunt for specially marked objects. The numbers on the objects were entered into a prize drawing. The prize drawing was held on Saturday evening, and some people actually came away with some very nice items.
I am reminded of something a one of the candidate dive masters mentioned a few weeks ago. He was reflecting on the fact that on his last dive trip, the people he met were from many different walks of life, yet he found it easy to relate to all the participants. The folks I met over the weekend were from many different walks of life, but we had a wonderful time recounting old dive stories, and watching videos from various dive trips. To me, it was almost like visiting family.
On every dive trip that I have gone, I have met some very nice people (without exception). On these trips I have met retired people, young couples, professional people, etc. No matter what walk of life people came from, I immediately felt at home talking to people about their favorite dives, the new piece of camera equipment and so on. In some cases I believe that I have made life-long friends.
This year, I decided at the very last moment to go to the annual event and the weekend turned out to be a lot of fun. The weather was so-so, a little on the cold side and rainy off and on. The water temperature was actually warmer than the air temperature so it was comfortable and easy diving.
The event was basically a treasure hunt. We had to hunt for specially marked objects. The numbers on the objects were entered into a prize drawing. The prize drawing was held on Saturday evening, and some people actually came away with some very nice items.
I am reminded of something a one of the candidate dive masters mentioned a few weeks ago. He was reflecting on the fact that on his last dive trip, the people he met were from many different walks of life, yet he found it easy to relate to all the participants. The folks I met over the weekend were from many different walks of life, but we had a wonderful time recounting old dive stories, and watching videos from various dive trips. To me, it was almost like visiting family.
On every dive trip that I have gone, I have met some very nice people (without exception). On these trips I have met retired people, young couples, professional people, etc. No matter what walk of life people came from, I immediately felt at home talking to people about their favorite dives, the new piece of camera equipment and so on. In some cases I believe that I have made life-long friends.
Thursday, September 07, 2006
Equipment challenge
One of the "intangible" type skills we try to impart to the candidate divemasters is to be ready to deal with situations that are unusual or that they have not encountered before. The thinking is that there will be times that you have to deal with unusual challenges - both in-water and on the surface. We try to prepare the candidates to be ready to think on their feet to be able to deal with a wide variety of equipment problems, and problems that divers might have etc.
One of the candidate divemasters was faced with an equipment problem that took me by surprise. We were in the deep end of the pool and the candidates were being evaluated on the various skills that they have to perform (up to demonstration quality), The particular skill that the candidates were working on was the scuba unit remove and replace.
The last candidate went through the paces to remove his scuba unit, and when he had the scuba unit in front of him, I noticed that something looked strange and I could not quite understand what I was seeing. He had the mouthpiece of the second stage in his mouth, but the second stage was laying on the floor of the pool. Somehow the mouthpiece became detached from the second stage. The thing was that I was so focused on evaluating his performance of the skill that I could not immediately figure out what the heck was going on with the black thing in his mouth!
The most surprising thing was that he sat there totally calm and confident going through the paces of starting to replace his scuba unit. Almost at the same moment the course director (CD) and I realized what was happening and raced over to the candidate to assist him in case he panicked and shot to the surface. Incidentally we teach our students to solve problems underwater and not to bolt to the surface immediately when faced with challenges. The candidate was remarkably calm under the circumstances and did not panic or bolt to the surface. He calmly spat out the mouthpiece, took CD's alternate airsource and completed the skill.
CD and I were very impressed!
Once the candidate had repaired his equipment, he performed the skill again and scored very well. CD said that he had seen this kind of thing before, but I must admit I have never seen a mouthpiece detach from the the second stage underwater.
One of the candidate divemasters was faced with an equipment problem that took me by surprise. We were in the deep end of the pool and the candidates were being evaluated on the various skills that they have to perform (up to demonstration quality), The particular skill that the candidates were working on was the scuba unit remove and replace.
The last candidate went through the paces to remove his scuba unit, and when he had the scuba unit in front of him, I noticed that something looked strange and I could not quite understand what I was seeing. He had the mouthpiece of the second stage in his mouth, but the second stage was laying on the floor of the pool. Somehow the mouthpiece became detached from the second stage. The thing was that I was so focused on evaluating his performance of the skill that I could not immediately figure out what the heck was going on with the black thing in his mouth!
The most surprising thing was that he sat there totally calm and confident going through the paces of starting to replace his scuba unit. Almost at the same moment the course director (CD) and I realized what was happening and raced over to the candidate to assist him in case he panicked and shot to the surface. Incidentally we teach our students to solve problems underwater and not to bolt to the surface immediately when faced with challenges. The candidate was remarkably calm under the circumstances and did not panic or bolt to the surface. He calmly spat out the mouthpiece, took CD's alternate airsource and completed the skill.
CD and I were very impressed!
Once the candidate had repaired his equipment, he performed the skill again and scored very well. CD said that he had seen this kind of thing before, but I must admit I have never seen a mouthpiece detach from the the second stage underwater.
Monday, September 04, 2006
Sunday, September 03, 2006
Podcasts
Podcasts have been around for a while now and I have been listening to a number of SCUBA related podcasts. The client that I use to search for and play podcasts is Apple's iTunes. I really like using iTunes even though my personal computer is not an Apple and I don't have an iPod.
Recently I ran a search on iTunes to see how many SCUBA related podcasts were available and was surprised to see that there were 24 different SCUBA related podcasts that were found in the search. I cannot vouch for the content or quality of many of the podcasts, but I will be researching the various podcasts in the months to come. I do however regularly listen to Bottom Time Radio and Pod Diver Radio. Willy Volk from Divester contributed to some of the early Bottom Time Radio and it was great to be able to hear Willy's voice, after reading so much of what he writes.
Hal Watts was interviewed on Bottom Time Radio show number 15. Hal is one of the icons and fathers of the SCUBA diving industry. An interesting tidbit from the podcast is that Hal is the originator of the very well known phrase "Plan your dive, dive your plan".
As I wrote previously, I feel it is important to stay current with new information and developments in the industry. There are many avenues that the information is available - magazines, books, trade events etc. Podcasts are a new and very exciting avenue that one can catch up on new developments. The great thing about podcasting is that regular guys who love the sport decide to put their own time and talent into making the podcasts.
A heartfelt thanks to the folks who do such a great job of putting so many great shows together.
Recently I ran a search on iTunes to see how many SCUBA related podcasts were available and was surprised to see that there were 24 different SCUBA related podcasts that were found in the search. I cannot vouch for the content or quality of many of the podcasts, but I will be researching the various podcasts in the months to come. I do however regularly listen to Bottom Time Radio and Pod Diver Radio. Willy Volk from Divester contributed to some of the early Bottom Time Radio and it was great to be able to hear Willy's voice, after reading so much of what he writes.
Hal Watts was interviewed on Bottom Time Radio show number 15. Hal is one of the icons and fathers of the SCUBA diving industry. An interesting tidbit from the podcast is that Hal is the originator of the very well known phrase "Plan your dive, dive your plan".
As I wrote previously, I feel it is important to stay current with new information and developments in the industry. There are many avenues that the information is available - magazines, books, trade events etc. Podcasts are a new and very exciting avenue that one can catch up on new developments. The great thing about podcasting is that regular guys who love the sport decide to put their own time and talent into making the podcasts.
A heartfelt thanks to the folks who do such a great job of putting so many great shows together.
Wednesday, August 30, 2006
Right hand release?
Last night, I had to buddy up with one of the candidate dive masters so that she could do her skills for evaluation. The first skill that the dive masters were being evaluated on is the buddy check. The course director (CD) wanted me to get my gear setup so that there were a number of things wrong with the gear. The idea is that the dive masters must become accustomed to what new divers can do to mess up their gear (and hopefully they will catch those things before the divers enter the water).
What CD wanted me to do was cross over the shoulder harnesses, and reverse my weight belt so that I had a left hand release on the buckle.
Unfortunately my candidate dive master buddy did not follow the slate and tried to do the buddy check from memory using the method I described in a previous post. If she had used the slate she probably would have caught the weight belt problem.
The problem with divers (myself included) is that we become complacent and do things almost automatically - especially when we set up our gear. The issue that we try to get across to the candidate dive masters is that the divers that they will be working with might be new divers who can and will do things to their gear that an experienced diver will not do. For example in just about every class that I teach to new divers, one student will set up the first stage backwards on the tank valve and when they open the tank valve the escaping air makes an impressive hissing sound that often intimidates the new diver.
No matter how carefully you brief the new divers beforehand they can and do forget details. Sometimes it is information overload, sometimes it is anxiety, sometimes it might even be some physical challenge like being hard of hearing. Whatever the reason, we have to prepare the candidate dive masters to be ready to catch these kind of problems.
What CD wanted me to do was cross over the shoulder harnesses, and reverse my weight belt so that I had a left hand release on the buckle.
Unfortunately my candidate dive master buddy did not follow the slate and tried to do the buddy check from memory using the method I described in a previous post. If she had used the slate she probably would have caught the weight belt problem.
The problem with divers (myself included) is that we become complacent and do things almost automatically - especially when we set up our gear. The issue that we try to get across to the candidate dive masters is that the divers that they will be working with might be new divers who can and will do things to their gear that an experienced diver will not do. For example in just about every class that I teach to new divers, one student will set up the first stage backwards on the tank valve and when they open the tank valve the escaping air makes an impressive hissing sound that often intimidates the new diver.
No matter how carefully you brief the new divers beforehand they can and do forget details. Sometimes it is information overload, sometimes it is anxiety, sometimes it might even be some physical challenge like being hard of hearing. Whatever the reason, we have to prepare the candidate dive masters to be ready to catch these kind of problems.
Sunday, August 27, 2006
What exactly is BWRAF?
Firstly, I think I should start with an admission. When I created this blog, I was hard pressed to come up with a suitable name. I wanted to use something that I could easily remember and that was SCUBA related. Eventually I decided to use the term "BWRAF". I guess I did not think about it too much since I assumed that BWRAF is only a user name and no one would really care too much about what user name I selected.
However, I have noticed a pattern in my blog tracking statistics that a fair percentage of the searches that find my blog are related to what "BWRAF" is. So I think it might be a good idea to define what BWRAF stands for and how to use BWRAF to do a good buddy check.
There are many ways to remember what the order of letters etc. The one that we use where I teach is "Begin With Review And Friend". Whatever method you use is fine as long as you don't forget one of the steps. Below, is a method of training students to use BWRAF to do a buddy check (source: PADI divemaster slate).
B (BCD)
W (Weights)
R (Releases)
A (Air)
F (Final check - OK)
Disclaimer: The information above is for educational purposes only. Please do not undertake any SCUBA related activities without the proper training and certification.
However, I have noticed a pattern in my blog tracking statistics that a fair percentage of the searches that find my blog are related to what "BWRAF" is. So I think it might be a good idea to define what BWRAF stands for and how to use BWRAF to do a good buddy check.
There are many ways to remember what the order of letters etc. The one that we use where I teach is "Begin With Review And Friend". Whatever method you use is fine as long as you don't forget one of the steps. Below, is a method of training students to use BWRAF to do a buddy check (source: PADI divemaster slate).
B (BCD)
BCD secure and functioning properly?
Low pressure inflator attached?
Appropriately filled for entry?
Buddy familiar with operation?
Tank secure?
W (Weights)
Amount of weight appropriate?
System free and clear for emergency release?
R (Releases)
All buckles and releases functional?
Locate releases without looking?
Buddy familiar with operation?
A (Air)
Sufficient for dive?
Valve turned on all the way? (remember to turn a quarter turn back from all open)
Alternate air source properly located?
Familiar with buddy's alternate air source?
Air pressure on which to turn dive? (when to return back)
F (Final check - OK)
General check of buddy - nothing odd or out of place?
Prepare to enter water
Disclaimer: The information above is for educational purposes only. Please do not undertake any SCUBA related activities without the proper training and certification.
Saturday, August 26, 2006
Cameras
Its been about eight months since I acquired my first underwater camera. The camera that I purchased is the Sealife DC500. For my experience level (novice) I think that the camera was a good choice. The camera does everything I need it to do and is fairly easy to use. I have had some problems with the camera, but the company that sells the camera in the USA was very responsive and helpful with my camera trouble.
The problem is that now I am starting to look at more advanced cameras with more features. On the one hand I like the simplicity and easy of use of my DC500. On the other hand, I found that my DC500 tends to take pictures that seem to be a little on the cold side (more blue than necessary). So far I have not had problems with pictures since I use photo editing software and can correct most of the blue problems. I don't really like doing too much editing on the photos. As long as I can bring out the colors and brightness of the scene as naturally as possible, then I am quite content. I don't like going to the extreme of making the scene something it never was (for example introducing subjects that were not there etc.). If I can correct for some of the camera and lens issue with the software, then I think it is worth the effort.
My diving buddy, the Navigating Phenom who is a very good photographer (mostly video), but he had a very nice digital still camera as well. His camera is a little older than mine, but it seems that his camera takes more lifelike pictures than mine does. Of course NP would say that it is all in the hands of the operator, and I think that might be partly true, but I do think that his camera captures more colors.
So now I have started looking at other cameras. A while ago I created a blogroll link to Kona Hawaii Scuba Diver's Blog. The pics on his blog are gorgeous. Steve uses an Olympus SP-350. I know that the photographer's skill makes a huge difference and I fully acknowledge that he has a great eye for composition etc. But I do think that the colors and clarity of the shots are just great. The price of the camera is also quite reasonable compared to other cameras that I have looked at.
Another example of excellent pictures is Dany Weiberg's gallery on Pbase. His images are breathtaking. On his personal website he mentions that he uses a Fuji S2 pro camera.
The choices are overwhelming. I guess one should not chase features, but work on developing technique etc. It still is nice to look at what other people are doing and try to get better at photography.
I think I have been bitten by the photography bug!
The problem is that now I am starting to look at more advanced cameras with more features. On the one hand I like the simplicity and easy of use of my DC500. On the other hand, I found that my DC500 tends to take pictures that seem to be a little on the cold side (more blue than necessary). So far I have not had problems with pictures since I use photo editing software and can correct most of the blue problems. I don't really like doing too much editing on the photos. As long as I can bring out the colors and brightness of the scene as naturally as possible, then I am quite content. I don't like going to the extreme of making the scene something it never was (for example introducing subjects that were not there etc.). If I can correct for some of the camera and lens issue with the software, then I think it is worth the effort.
My diving buddy, the Navigating Phenom who is a very good photographer (mostly video), but he had a very nice digital still camera as well. His camera is a little older than mine, but it seems that his camera takes more lifelike pictures than mine does. Of course NP would say that it is all in the hands of the operator, and I think that might be partly true, but I do think that his camera captures more colors.
So now I have started looking at other cameras. A while ago I created a blogroll link to Kona Hawaii Scuba Diver's Blog. The pics on his blog are gorgeous. Steve uses an Olympus SP-350. I know that the photographer's skill makes a huge difference and I fully acknowledge that he has a great eye for composition etc. But I do think that the colors and clarity of the shots are just great. The price of the camera is also quite reasonable compared to other cameras that I have looked at.
Another example of excellent pictures is Dany Weiberg's gallery on Pbase. His images are breathtaking. On his personal website he mentions that he uses a Fuji S2 pro camera.
The choices are overwhelming. I guess one should not chase features, but work on developing technique etc. It still is nice to look at what other people are doing and try to get better at photography.
I think I have been bitten by the photography bug!
Tuesday, August 22, 2006
Diving with the candidate divemasters
Last week, the instructor who really taught me most of what I know about diving and instructing called me and asked if I would be interested in helping with the pool sessions for the divemaster class. Of course, I jumped at the chance.
It is an interesting experience working with my instructor (who is also our course director) as a colleague and not as a student. For the sake of simplicity, I will refer to my instructor as CD for the rest of this entry. I still feel like a student when I am around CD and I guess that will be so for some time to come. The great thing about working with CD is that he is so good at what he does and I find myself always learning when I dive with him.
The one area that CD excels in is paying attention to detail. I tend to be a big picture kind of person and find that I don't always drill down to the nitty-gritty detail of things. However in working with CD, I have learned to pay very close attention to every skill and subskill that the students perform. It is part of the training to have the students flub on a specific skill to see if the candidates pick up on the mistake, but he is a stickler for detail which makes his students stickler for detail too.
Previously I wrote about how I felt that my training was more intense when I did my divemaster class. Having worked with the new batch of divemaster candidates, I guess I still feel that way. I remember how picky CD was about the most minute aspect of every skill. I am glad that he set such a high standard for us. The current class is much smaller than the class I attended so I am sure that the smaller class size allows for a more informal class situation.
It is an interesting experience working with my instructor (who is also our course director) as a colleague and not as a student. For the sake of simplicity, I will refer to my instructor as CD for the rest of this entry. I still feel like a student when I am around CD and I guess that will be so for some time to come. The great thing about working with CD is that he is so good at what he does and I find myself always learning when I dive with him.
The one area that CD excels in is paying attention to detail. I tend to be a big picture kind of person and find that I don't always drill down to the nitty-gritty detail of things. However in working with CD, I have learned to pay very close attention to every skill and subskill that the students perform. It is part of the training to have the students flub on a specific skill to see if the candidates pick up on the mistake, but he is a stickler for detail which makes his students stickler for detail too.
Previously I wrote about how I felt that my training was more intense when I did my divemaster class. Having worked with the new batch of divemaster candidates, I guess I still feel that way. I remember how picky CD was about the most minute aspect of every skill. I am glad that he set such a high standard for us. The current class is much smaller than the class I attended so I am sure that the smaller class size allows for a more informal class situation.
Wednesday, August 16, 2006
Did you check your air pressure?
Recently, I had the occasion to be diving with a very professional dive shop in Grand Cayman. The dive masters were first class and the diving was superb. The dive that I was almost ecstatic about was Trinity Caves. I guess it was just one of the those days where everything coincides and you have a wonderful dive. Trinity caves was just one of those places that I fell in love with. The fish were large and plentiful, the views were phenomenal, the viz was great etc., etc.
It was interesting to be diving with no responsibilities and under the guidance of the dive master. The dive masters, as I wrote previously were top notch. However, the problem for me was that I had a hard time switching gears from the usual instructor mode that I am in to the happy holiday maker mode. At one point the dive masters went around check people's gear, and asking if we had checked our air pressures etc. It was an interesting experience being on the other side of the table so to speak.
The dive masters impressed me with their attention to detail. The dive briefings were thorough and the dive plans were followed to the letter. The emphasis is on safety and I was impressed that they insisted that everyone do a 5 minute safety stop after every dive, since some of our dives were a little on the deep side (nothing over 100 though),
Good on you folks at Divetech.
It was interesting to be diving with no responsibilities and under the guidance of the dive master. The dive masters, as I wrote previously were top notch. However, the problem for me was that I had a hard time switching gears from the usual instructor mode that I am in to the happy holiday maker mode. At one point the dive masters went around check people's gear, and asking if we had checked our air pressures etc. It was an interesting experience being on the other side of the table so to speak.
The dive masters impressed me with their attention to detail. The dive briefings were thorough and the dive plans were followed to the letter. The emphasis is on safety and I was impressed that they insisted that everyone do a 5 minute safety stop after every dive, since some of our dives were a little on the deep side (nothing over 100 though),
Good on you folks at Divetech.
Saturday, June 24, 2006
Supersized
One day this week I received a phone call from my friend the Navigating Phenom (NP) with news that he received a coupon for discount at a local sporting goods store that is now selling SCUBA gear. So today NP , Mrs NP and I duly paid a visit to the sporting goods super store.
I was very surprised by the large selection of high quality SCUBA gear on display. The staff were very knowledgeable and most helpful. I realize that today was their "launch party", but I think they are doing everything right.
In the metro area that I live in there are at least twelve SCUBA stores. So far the SCUBA stores were spread out throughout the metro area with each store basically servicing a region of the metro. With the advent of the superstore selling a large range of SCUBA gear I think there is bound to be a shakeup in the status quo. One could probably compare it to the way Walmart, Target etc. changed the retail landscape from mom and pop stores to superstores.
I am all for supporting the local dive stores (LDS), since I derive some income from instructing from the one of the local dive stores in my area. At the same time I think that competition is good for the local SCUBA scene. In the SCUBA business relationships are very important. The superstores are good at selling on price, but I think that the LDS can handily beat the superstores on building relationships with customers.
For us to survive and thrive we will have to adapt to change and get better at what we do.
I was very surprised by the large selection of high quality SCUBA gear on display. The staff were very knowledgeable and most helpful. I realize that today was their "launch party", but I think they are doing everything right.
In the metro area that I live in there are at least twelve SCUBA stores. So far the SCUBA stores were spread out throughout the metro area with each store basically servicing a region of the metro. With the advent of the superstore selling a large range of SCUBA gear I think there is bound to be a shakeup in the status quo. One could probably compare it to the way Walmart, Target etc. changed the retail landscape from mom and pop stores to superstores.
I am all for supporting the local dive stores (LDS), since I derive some income from instructing from the one of the local dive stores in my area. At the same time I think that competition is good for the local SCUBA scene. In the SCUBA business relationships are very important. The superstores are good at selling on price, but I think that the LDS can handily beat the superstores on building relationships with customers.
For us to survive and thrive we will have to adapt to change and get better at what we do.
Wednesday, June 21, 2006
It's back
About a month ago, my new camera started acting up. Apparently this specific model has had some teething problems and after a few emails, the manufacturer suggested that I send back the camera for repairs. So I duly sent the camera back the manufacturer via Fedex. After about four weeks a UPS note appeared on my door that I had a parcel from the manufacturer. I was very pleased, except that I missed the UPS guy. I tried rescheduling and after much going back and forth I was able to schedule the delivery for a day when I knew I would be at home.
So today, the camera was delivered by UPS (I remain in awe of UPS and Fedex in terms of efficiency, but will leave that for another post). I realized once again (not that I needed confirmation) that I am a complete gadget geek. I could not wait to open the parcel and get the camera out and start playing with it. Obviously I had to see whether the problem that I had was resolved. Fortunately it was, but strangely I could find no note from the manufacturer about the resolution to the problem. Too bad - I would have liked to know what happened.
I can't wait to go diving to try out the camera again. It is almost as much fun as when I first bought the camera.
Apparently, there is a medical term for what afflicts me and so many of my friends. It is called neophilla. I first learned of this term in an excellent podcast that I regularly watch called Geek Brief. According to an article that Cali from GeekBrief referenced "Neophiliacs are people who love everything new or novel". The article goes on to say
This is all a little tongue in cheek, but I must admit that I do enjoy new technology. I don't think that I am a total first adoptor or pursue technology for the sake of technology, but I sure am grateful to be alive in a time of great technological developments.
So today, the camera was delivered by UPS (I remain in awe of UPS and Fedex in terms of efficiency, but will leave that for another post). I realized once again (not that I needed confirmation) that I am a complete gadget geek. I could not wait to open the parcel and get the camera out and start playing with it. Obviously I had to see whether the problem that I had was resolved. Fortunately it was, but strangely I could find no note from the manufacturer about the resolution to the problem. Too bad - I would have liked to know what happened.
I can't wait to go diving to try out the camera again. It is almost as much fun as when I first bought the camera.
Apparently, there is a medical term for what afflicts me and so many of my friends. It is called neophilla. I first learned of this term in an excellent podcast that I regularly watch called Geek Brief. According to an article that Cali from GeekBrief referenced "Neophiliacs are people who love everything new or novel". The article goes on to say
And now a team of researchers have provided these consumers with just about the greatest excuse ever for justifying their expensive compulsion to buy the newest and coolest. They can't help themselves. It turns out some people may, in fact, be more genetically predisposed than others to wanting the newest toys, gadgets and fashions.
In scientific mumbo jumbo, it seems that genetic differences mean that people produce different variations of a mitochondrial enzyme called monoamine oxidase A. That’s according to research from the Yamagata University School of Medicine in Japan, which was recently published in the scientific journal Psychiatric Genetics and mentioned in the New Scientist magazine. (source: http://www.medialifemagazine.com/artman/publish/article_5439.asp)
This is all a little tongue in cheek, but I must admit that I do enjoy new technology. I don't think that I am a total first adoptor or pursue technology for the sake of technology, but I sure am grateful to be alive in a time of great technological developments.
Monday, June 19, 2006
Reflection
A few months ago I wrote about a staff instructor class that I was taking. The class eventually ended a few weeks ago and I thought that I would like to write some of my reflections and thoughts on the class. Just to fill in those who might not be familiar with what a staff instructor is, please click on this link to a description.
The first thought that springs to mind about the class is how different it was to be an evaluator of presentations. When I completed my instructor training, I remember the presentations to have been judged very strictly. I suppose most will have the same feeling of things being more difficult in "their day".
The second reflection is how much I enjoyed watching the instructor candidates develop and grow in their confidence and ability.
The third reflection is how my own instruction has improved. Every time you teach something you learn it again. It is commonly believed that to really learn something you should teach it.
If one wants to be good at anything one should keep growing and developing. To be a good instructor takes more than just great personality and people skills. I think it takes work, preparation and dedication. In my opinion, a good instructor makes the material come alive and makes the difficult material look easy. A good instructor will find a way of unpacking the theory so that the students not only learn it, but understand why it is important and are able to apply it. I am not a trained educator, but I believe that the better prepared and trained I am, the easier it is for me to present the class and the more the students enjoy the class.
Even though I am glad that the course is over, I feel a little empty at the same time. My dive buddy (the Navigating Phenom) completed the staff instructor class with me. NP suggested that we staff the next IDC (Instructor Development Course) so that we can apply what we learned and keep developing our skills. Perhaps focusing only on the students success and not being concerned about passing the SI course will make the IDC a lot of fun. I dove with the dive master candidates a few weeks ago (they are the ones who will be doing the next IDC) and found them to be a great bunch of people. I will write more on my adventures with the next IDC as things get started in few month's time.
Thanks to our course directors for a good class.
The first thought that springs to mind about the class is how different it was to be an evaluator of presentations. When I completed my instructor training, I remember the presentations to have been judged very strictly. I suppose most will have the same feeling of things being more difficult in "their day".
The second reflection is how much I enjoyed watching the instructor candidates develop and grow in their confidence and ability.
The third reflection is how my own instruction has improved. Every time you teach something you learn it again. It is commonly believed that to really learn something you should teach it.
If one wants to be good at anything one should keep growing and developing. To be a good instructor takes more than just great personality and people skills. I think it takes work, preparation and dedication. In my opinion, a good instructor makes the material come alive and makes the difficult material look easy. A good instructor will find a way of unpacking the theory so that the students not only learn it, but understand why it is important and are able to apply it. I am not a trained educator, but I believe that the better prepared and trained I am, the easier it is for me to present the class and the more the students enjoy the class.
Even though I am glad that the course is over, I feel a little empty at the same time. My dive buddy (the Navigating Phenom) completed the staff instructor class with me. NP suggested that we staff the next IDC (Instructor Development Course) so that we can apply what we learned and keep developing our skills. Perhaps focusing only on the students success and not being concerned about passing the SI course will make the IDC a lot of fun. I dove with the dive master candidates a few weeks ago (they are the ones who will be doing the next IDC) and found them to be a great bunch of people. I will write more on my adventures with the next IDC as things get started in few month's time.
Thanks to our course directors for a good class.
Sunday, June 18, 2006
Go free little fishy
Its been a while since I did open water certification dives. Last weekend I was able to work with another instructor and we had two groups of eight students to run through the certification dives.
We had a great time at the lake, except that the visibility was really poor this year. The visibility has been going down every year for a number of years. I think there are a number of factors that influence the visibility in our lake, but two of the contenders are - fertilizer and apparently the stocking of trout in the lake. The trout, I am told, eat the organisms that keep the algae in check. Who know what the actual cause is of the algae - I just know that at this rate we will not be able to use that particular lake for certification dives much longer.
One of the students in the morning class had an interesting surprise for us. He is a marine biology expert and decided that he wanted to release a sunfish that he had raised from a tiny newborn. He received the tiny sunfish from the local Department of Natural Resources in 1999 and kept the fish as an experiment. I am not sure what the experiment entailed, but he told us that he did not want to name the fish since he did not want to become too attached to the fish.
The marine biology expert brought the fish to the lake in a large plastic bucket and when it was time to release the fish we all gathered around the expert in the water (all of us in our full scuba gear). He tilted the bucket so that some of the lake water entered the bucket and held the bucket at an angle so that the fish could swim out if it wanted to. However the fish seemed confused and did not rush out. In fact it backed up a little and it seemed like he just wanted to stay with what was familiar. Eventually he swam a little forward and then back again. He did this a number of times (all the divers were loudly cheering the fish on by this time). Eventually the little fish swam off lazily to the loud cheers of all the students.
The release of the little sun fish was a unique experience for all of us. What a nice way to end a class.
We had a great time at the lake, except that the visibility was really poor this year. The visibility has been going down every year for a number of years. I think there are a number of factors that influence the visibility in our lake, but two of the contenders are - fertilizer and apparently the stocking of trout in the lake. The trout, I am told, eat the organisms that keep the algae in check. Who know what the actual cause is of the algae - I just know that at this rate we will not be able to use that particular lake for certification dives much longer.
One of the students in the morning class had an interesting surprise for us. He is a marine biology expert and decided that he wanted to release a sunfish that he had raised from a tiny newborn. He received the tiny sunfish from the local Department of Natural Resources in 1999 and kept the fish as an experiment. I am not sure what the experiment entailed, but he told us that he did not want to name the fish since he did not want to become too attached to the fish.
The marine biology expert brought the fish to the lake in a large plastic bucket and when it was time to release the fish we all gathered around the expert in the water (all of us in our full scuba gear). He tilted the bucket so that some of the lake water entered the bucket and held the bucket at an angle so that the fish could swim out if it wanted to. However the fish seemed confused and did not rush out. In fact it backed up a little and it seemed like he just wanted to stay with what was familiar. Eventually he swam a little forward and then back again. He did this a number of times (all the divers were loudly cheering the fish on by this time). Eventually the little fish swam off lazily to the loud cheers of all the students.
The release of the little sun fish was a unique experience for all of us. What a nice way to end a class.
Tuesday, March 14, 2006
You want me to do what?
As many know, SCUBA divers have their own unique way of communicating while submerged. We use various hand signals to communicate with one another. In every open water class that I teach we review the various hand signals that I will be using in the pool to make sure that everyone knows what I am trying to convey. Usually everyone is very well prepared by the time they attend class from watching the video or DVD and reading the course work.
Recently, I noticed that the WRSTC (World Recreational Scuba Training Council) has issued guidelines on standardized hand signals. Most major training organizations are represented on the council which means that the hand signal standard will probably become the “gold standard”. Having a united council deciding on common hand signals is a very positive step in my opinion.
The council has put together a very good document in a PDF format that describes the signal and includes pictures of the various signals.
Recently, I noticed that the WRSTC (World Recreational Scuba Training Council) has issued guidelines on standardized hand signals. Most major training organizations are represented on the council which means that the hand signal standard will probably become the “gold standard”. Having a united council deciding on common hand signals is a very positive step in my opinion.
The council has put together a very good document in a PDF format that describes the signal and includes pictures of the various signals.
Subscribe to:
Posts (Atom)
