"Correct Weighting" Identified as #1 Needed Improvement in SCUBA Diving

[Aqua-Andy]

After many years of teaching OW, watching others teach OW, and then experimenting with different approaches, I am quite convinced that the primary cause of overweighting is the continued teaching of OW classes to students who are on their knees while learning basic skills.

For those who don't know, a number of years ago I experimented with teaching students while neutrally buoyant and in horizontal trim rather than on their knees. I convened a number of like-minded people, and we submitted an article on this to PADI. PADI agreed to publish it in a reduced form (it was a very long article), and Karl Shreeves of PADI and I worked on the final wording. the article was published in PADI's professional journal, The Undersea Journal. After that, PADI obviously experimented on their own, for two years later they began to advocate our approach as the best way to teach. Unfortunately, they still allowed the traditional approach on the knees, and that is still what most instructors do.

Before the article was published, I was asked to pose for pictures comparing the two methodologies. I did the pictures for neutral instruction first, weighted the way i always was in pool instruction--about 6 pounds overweighted so that I can better control students in an emergency. Then I posed for the pictures while kneeling, something I had not done for years. I couldn't do it. I had to double my weight in order to stay firmly planted on my knees to the degree that I needed in order to perform the skills.

I have since watched other instructors teaching their OW classes on the knees, and I would say that in order to get the students to kneel comfortably and stably, the students must be at least 10 pounds overweighted, and it is frequently more. The students learn that that is the weight they need to dive, when it is actually only the weight they need to kneel on the bottom of a pool.

Would it be possible to post the article you wrote? It sounds like it would be an interesting read.

 

[REVAN]

I'm pretty sure you'll violate standards for every agency by teaching it this way.

This is a man-made concern, a rules issue. If the rules are changed, the problem magically disappears.

After many years of teaching OW, watching others teach OW, and then experimenting with different approaches, I am quite convinced that the primary cause of overweighting is the continued teaching of OW classes to students who are on their knees while learning basic skills.

I think you are absolutely right about this, and I'd like to add a couple thoughts:

First, if the class were taught without a BC, it could not be taught kneeling on the bottom. The divers would be too close to neutral for that to be viable.
Second, although it adds more equipment and skills which will add to the length and cost of the class as compared to a basic OW structure which parses the BCD out into a specialty course, this teaching method you describe should also adequately address the need for better weighting skills. It comes down to the cost barrier for entry.

One method involves a shorter less expensive class that teaches divers to dive successfully with a $50 back plate in a shorter and less expensive OW class. Upon graduation, this diver will have the basic skills required to either add a BCD and figure it out, or they can take a specialty course and accelerate the learning process. The other method takes a more involved and costly OW class where the student learns to dive with a $500 BCD system.

I'm thinking the first method could attract more new divers as the initial barriers are lower, and the end result if they continue to dive can easily track to the same conclusion as the path with a more intense barrier. I'm thinking the method of initial instruction without a BC may be like adding a catalyst to accelerate a chemical reaction, allowing it to happen without requiring the initial barrier energy that is normally required to make it happen. It could be a good thing. However, simply taking the the class off the bottom is, I think, another viable method to reaching better weighting skills.

 

[Gr8WyattWhale]

So the goal is to be just slightly negative at the surface?
I'm a beginner but I want to practice excellent techniques and become a master

 

[Stoo]

All you need to do is look at any given group of recreational divers and a small percentage of them will be dangerously over-weighted. I blame instructors... let's face it, it's easier (i.e. more time-effective) to slap a few extra pounds on a student, rather than teach them proper technique for descending. This may be fine as long as it gets "corrected" but since courses are so "condensed" now, there really isn't time to do this. Instructors need to get it right from day one.

When over-weighting become "normal", it effects the new diver's ability to do "anything" right... trim is off, air consumption is horrible, buoyancy skills are much harder to master. General comfort is at risk and makes for a less-than-awesome experience in the water.

I am just back from a trip south and two of the eight people on our boat were massively over-weighted. The PADI DM got all excited when she worked with those two and was able to reduce their lead by 2 pounds each. What they needed to do was reduce the weight by more like 10 pounds, but it's a start.

Obviously we aren't all built the same and technique can only go so far. With a 3mm suit and 1/3mm hooded vest, I wear 6 pounds (although my camera is maybe 4 pounds negative. When I see a "husky" diver with a 30# belt and a 3mm shorty, it makes my head explode...

 

[KatieMac]

it's easier (i.e. more time-effective) to slap a few extra pounds on a student, rather than teach them proper technique for descending.

So I should thank my instructor then! My very first dive, I had 12lbs, then 10, then 8 and on my 4th dive it was 6. 6 proved to be too challenging for me though but he was prepared and had an extra weight.

 

[Stoo]

So I should thank my instructor then! My very first dive, I had 12lbs, then 10, then 8 and on my 4th dive it was 6. 6 proved to be too challenging for me though but he was prepared and had an extra weight.

You should! He done good!

 

[REVAN]

So the goal is to be just slightly negative at the surface?
I'm a beginner but I want to practice excellent techniques and become a master

The method I use is to dial my weighting in to be neutral with shallow breathing at my safety stop and with an empty tank (and empty BC if I'm using one). This situation will minimize the amount/size of compressible gas-bubble volume the diver will be carrying during the dive and therefore minimize the diver's buoyancy instability effect.

Edit - The "shallow breathing" is an important detail. The buoyancy difference between shallow breathing and full-lung breathing can easily exceed 4 pounds. For me, it's about 6 pounds. For perspective, this is bigger than the amount of weight shift in a standard AL80 scuba tank between full and empty states which is how I can maintain neutral buoyancy throughout the dive without the aid of an external BCD.

 

[boulderjohn]

Would it be possible to post the article you wrote? It sounds like it would be an interesting read.

I will try to find it when I have more time.

 

[boulderjohn]

his is because BCDs are unstable. The more air in the BC the more unstable it is. Also, the more shallow you are the worse it will be, so deco and safety stops are especially bad. If you have a lot of air in it, you will have to constantly fight its instability adding and removing air from the BCD.

Sorry for hijacking the thread. I was rising/dropping more than I wanted on safety stops last week. I wasn't inflating/deflating though. But the rest of the dive I was neutrally bouyant. Is this because I'm overweighted a bit?

As Revan said, the more you are overweighted, the more air you have in the BCD. Each extra pound requires about 15 fluid ounces of air volume to compensate. That air will expand or contract with changes in depth. The closer you are to the surface, the more significant the changes. When you are at safety stop depth, that air is expanding and contracting far, far more quickly than it does at depth. I used to require DM candidates to calculate the change in gas volume between the bottom of the 11-foot swimming pool we use for instruction (at our altitude) and the surface, and the increase in volume is about 40%. At depth on a dive, that much difference in depth would make very little difference.

What that means is that at depth in a dive, you can overcome small changes in BCD volume with your breathing, but at safety stop level, if you have a lot of air in the BCD, it is much harder to overcome those volume changes with the volume changes in your chest.

 

[boulderjohn]

First, if the class were taught without a BC, it could not be taught kneeling on the bottom.

Actually, it can.

When we wrote the aforementioned article, one of our co-writers was famed dive historian Dr. Sam Miller. His primary role in our group was to try to determine when teaching on the knees started. Dr. Miller was one of the earliest instructors who is still around to talk about it. He had a lot of trouble finding information about it. We concluded that teaching instruction on the knees started with the very earliest instruction, before there was any kind of buoyancy device--not even a wet suit. It was very easy to have students kneel while showing them how to clear a mask, etc. It became the norm so much that people began to think eventually that it was required.