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

[JamesBon92007]

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

That's a very good question! REVAN gave a very good answer explaining how to use your lungs.

There are variables. I learned to dive with a 1/4" farmer john and a steel 72. My weighting goal was to be just slightly negative at the beginning of the dive at around 35-40 feet (typical SoCal beach diving depth). Since 1/4" neoprene is more buoyant and compresses more than 3mm neoprene there is somewhat more variation as depth increases and decreases. If you use an aluminum 80 you will need to add more weight to your belt which makes the situation a bit more complicated because the AL 80 tanks are buoyant when empty while the steel 72s are slightly negative. Now we have to define "empty." Let's assume 500 psi is empty which I think is fairly reasonable by today's standards but let's not forget that the old J-Valves had their reserve set to 300 psi so that assumed you would have less than 300 psi at the end of your dive. Zero psi is more buoyancy than 500 psi. I'm just saying all of this so you realize the various factors involved--it's really not that complicated in practice and, as REVAN explained, is fairly easily controlled by breathing, once you are wearing the correct amount of weight.

The simple answer: estimate how much weight you need and go diving. Decide if you need a pound or two more (or less). Pick up a rock if you need a little more weight. Go diving again and chances are you got it right and won't have to think about it again. Steel is easier than aluminum.

If your dive exceeds 40 feet and your 15 foot safety stop is crucial then hopefully you can have a buddy (wearing a BC) carry a couple of 2 or 3 pound weights just in case you are too buoyant at your safety stop. Or you might need a bigger rock

I have never dove with a BC in California and have done somewhere around 3000 dives here. HOWEVER, there are no delicate coral reefs and I'm not penetrating shipwrecks or cave diving so being a tiny bit off from perfectly neutral is rarely an issue. When I go on dive trips and dive boats BCs are required and I weight myself so that I am just slightly negative at the 15' safety stop with an empty BC.

 

[The Chairman]

The catch is that you need to be able to predict the weight configuration you will need. This only comes from practice, and if the BC is used to habitually avoid the process of practicing accurate weight management predictions, those skills may never be developed.

It's not as hard as you're making it out to be. It's just simple physics and you should have learned this in your OW class. Trim and buoyancy should be the foundation of your class.

 

[REVAN]

It's not as hard as you're making it out to be. It's just simple physics and you should have learned this in your OW class. Trim and buoyancy should be the foundation of your class.

I didn't say that it was hard. It's like riding a bike. It's pretty easy when you know how. It's only hard if you have never learned to do it. Once you know how, it's easy to do and difficult to forget.

A BC is like having training wheels on your bike. It interferes with the feedback loop that is the learning process. It has this illusion of making things easier, while at the same time making it harder to actually learn how to properly ride the bike. I see the BC as having a similar impact on new divers learning weight management skills.

 

[The Chairman]

A BC is like having training wheels on your bike.

We obviously completely disagree on this. That's like saying that a wrench is a like having training wheels and that you should learn how to tighten bolts without it to really learn how to be a mechanic. Or that you should learn how to dive without fins so you'll really learn how to kick. Or you should run without shoes because shoes will hold you back.

One of the attributes that separates man from the other animals is his cunning ability to make and use tools to his benefit. Like a wrench, fins or shoes, we use tools to simplify our lives and to make our fun even more fun. Learn to use the tool: don't abandon it. Think about it, if all you know how to use is a hammer, than the world becomes a nail. For whatever reason, you don't seem to like BCs. That's your own derogative. (See what I did there?) I learned to dive without any buoyancy. In fact, on my first dive, I had a rope that I used to carry the tank on my back. I paid for an AT Pac that very day, so I could have straps. Dove like that for years and years and it didn't make me a better diver. In fact, it made me quit. When I came back to diving and actually got certified, four things had improved greatly. I had an SPG instead of a J-valve. I had a depth gauge instead of a red ribbon. They added an octo and they even added this wonderful device called a BCD. I haven't looked back one bit. Diving without a BC sucks. You can have it.

 

[boulderjohn]

Yes, this is something that is generally not taught.

The use of trim weights us supposed to be part of the PADI OW class now. Studenst view a video clip in which an instructor puts weights up by the student's shoulders, after which he is able to hover in horizontal trim. I will almost guarantee that many and perhaps most instructors are not doing this.

When those standards were announced but not yet implemented, I was teaching two students while we were vacationing in Akumal. The shop we were using allowed me to conduct their OW dives off of their boats. My students were using the shop's gear, which had no trim pockets. I used a bungee system I learned from Pete (formerly NetDoc) to attach trim weights to my students' cam straps. The shop's instructional staff was completely mystified. Why would you do that? Why not just put it all on the belt? When I explained the concept of trim, they clearly had never heard of it. When I told them that they would soon be required to include it in their instruction, they were amazed.

 

[The Chairman]

I teach in tropical waters and usually moving an AL tank way down accomplishes the same thing for me. How does a student know when they are balanced and in trim? They do the blind test. Hover about six inches above the bottom. Got it? All comfy? Now close your eyes and relax. Let your body assume it's natural attitude without you adjusting things subconsciously. Count to ten and open your eyes. Adjust as needed. Once you've achieved 10 seconds, start stretching that out a bit. I can consistently hit a full minute and have done a full five minutes which seemed like an hour. :O Why go through the trouble? The closer you are to being naturally neutral, the less work you have to exert to maintain that. The less work, the less air you'll consume and so forth.

Now, a bit about moving tanks. Aluminum 80s are bassackward. Underwater, you're not shifting weight but rather the buoyancy in the butt of the tank. It's almost always easier to redistribute weights unless you're very close with an AL tank. Steels are straight forward. Slide them to the rear and you'll shift your COG to the rear.

 

[REVAN]

I learned to dive without any buoyancy. In fact, on my first dive, I had a rope that I used to carry the tank on my back. I paid for an AT Pac that very day, so I could have straps. Dove like that for years and years and it didn't make me a better diver.

How can you be so sure that those early diving experiences didn't contribute to making you the better diver that you are today?

I like my analogy better than yours. If you look again more closely I think you'll see, I didn't say that a BC was having training wheels on your kit. I said that it interferes with the feedback loop that is the learning process in a similar way that training wheels interfere with the feedback loop for someone trying to learn to ride a bike. If you can't feel the consequences of mistakes, it's hard to know what you did wrong. (I turned the wheel the wrong way to stay upright, but instead of falling over, the training wheels held the bike up anyway. It must have been okay to do that!)

People would learn weight management more quickly and efficiently if they feel the mistakes immediately and correct them. Once a new diver has a good grasp of things, go right ahead and buy that BCD and learn to use that also. They could even take a specialty course on how to use it to max efficacy.

 

[KatieMac]

.

I didn't say that a BC was having training wheels on your kit. I said that it interferes with the feedback loop that is the learning process in a similar way that training wheels interfere with the feedback loop for someone trying to learn to ride a bike.

Absolutely it was like training wheels for me. Not under water but at the surface. I never would have completed OW without it. To me, getting off the boat without a lifejacket even minutes from shore would have felt like getting off the boat in the middle of the open ocean without a life jacket. I'm not a swimmer. Never have been. As soon as I left the surface the anxiety when away. But I was very happy to have my BC as a security blanket on the surface.

 

[The Chairman]

How can you be so sure that those early diving experiences didn't contribute to making you the better diver that you are today?

I know because I was still kicking the crap out of the bottom.

Once a new diver has a good grasp of things,

Sounds like the same failed argument for teaching tables first. Never letting my students kneel/stand/lie/fin pivot on the bottom does the trick for them. It's my belief that I should train my students with the gear they're most likely to be using. Ergo, I train them on PDCs and BCDs.

People would learn weight management more quickly and efficiently

What's to really learn about 'weight management"? Once you get the weight dialed in, that's a piece of cake. They just need to learn how to breath right. My students learn how to set their BC on descent and then control their depth only by how they breath. In order to graduate from the pool, they have to demonstrate that they can do every skill mid water, can descend to the bottom and ascend to the surface using only their breathing and then there's the weight challenge. After the ascent/descent, I have a row of two pound weights. My students swim over and pick up weights and breath themselves neutral. Men must be able to accommodate 6 pounds and women must handle 4 pounds. No, they don't get to touch their BC... they accomplish this just by altering their breathing patterns. Then they have to drop those weights (two pounds at a time) and still remain neutral. After that, we play a rousing game of underwater jenga with those same weights. Except rather than pulling out elements, we just try to build weight condos. I tell them to blame @Capt Tom McCarthy for that!

 

[boulderjohn]

It's my belief that I should train my students with the gear they're most likely to be using. Ergo, I train them on PDCs and BCDs.

This is a standard concept for good instruction in all activities. I am certified by national organizations to teach two different sports, and my training in each emphasized the concept of making instruction as "gamelike" as possible. In fact, I submitted an article on how to make scuba instruction "gamelike," and PADI has agreed to publish it in its professional journal, probably next year. I start with the most ungamelike of instructional process--teaching on the knees--and go on to show how skill after skill after skill is as a consequence taught incorrectly. (Think, for example, of how regulator recovery instruction on the knees is different from recovering the the regulator in a real dive situation in horizontal trim; the skills are done very differently.)

When I am teaching students who are wearing BCDs, they are learning how to use both the BCD and their lungs at the same time to achieve proper buoyancy and trim. That is how it will be for them on a real dive, and that is how it should be for them during instruction.