Let's discuss peoples over-reliance on BC's and over-weighting.

[BoltSnap]

Check back in the posts. I'm just laughing at those who think "good divers" somehow magically defeat physics. Sillyness.

Got it, you were saying it "tongue-in-cheek." I missed that

 

[Chip Elliott]

As someone in the learning phase, I read this discussion somewhat like this: if you are a really good driver you don't need seat belts.

 

[tbone1004]

Please excuse my ignorance but how can you compensate for buoyancy loss due to wetsuit compression underwater if you aren't using a BC or a drysuit, wetsuit only? If the diver who isn't using a BC starts as neutrally buoyant at the beginning of the dive, how do they stay neutrally buoyant at depth without a BC?

What Jim failed to mention in that post is that those using thick wetsuits would weight themselves for specific depths. I.e. I'm using a 1/4" wetsuit and planning to dive to 80ft, so I need 10lbs, but the second dive is only going to be to 40ft so I need 16lbs and they would change their weight belt for each dive. They didn't "hover" the whole time, instead they were swimming down from the surface and if they went much deeper than planned they would have to swim back up. They had a fairly narrow range depending on the thickness of the suit that they could use their lungs to offset the tank and the suit. The range of depth is inversely proportional to the thickness of the suit *i.e. the thinner the suit the wider the depth range*. Using LP72's any normal sized human being has enough lung capacity to offset the tank and if diving properly weighted with no exposure suit can theoretically hover throughout the whole dive. Put a 3mm shorty on them and they may struggle with a full tank at depth, but after the first few hundred psi is consumed it should stabilize. Diving looked a bit different back then, so it's wrong to compare what was done in the 50's and 60's with today because the reality is you can't "hover" with a 7mm wetsuit on and a steel 100 without a BC for the duration of the dive regardless of depth unless you have superhuman lungs and then CO2 retention would be a real concern.

Someone already hit the point of why buoyancy control isn't pushed so hard in the basic class.. Time. Since time is $$, you can't teach a proper basic scuba course imho for $300 over two weekends. It's not enough time in the water. Unfortunately our industry relies on high turnover of these types of courses to fund the innovation for those of us that actually stick with the sport. Pros and cons. Back in the day when BC's didn't exist, SPG's were more expensive than full regulator sets, and you cut your own wetsuit from a sheet of rubber with a pattern, there weren't a lot of divers and therefor little monetary incentive to invest in innovation for new gear. Now there is huge incentive to develop new gear from the money available but with that comes less intense and in depth courses because you have to churn out new divers. Huge part of why I don't teach for a dive shop. Also a huge part of why I advocate for those that are serious about diving to take something like GUE Fundies ASAP after open water instead of getting time in the water to get comfortable. I'm also a musician and the saying "practice makes perfect" is complete bullsh!t. Practice makes Permanent! Only perfect practice makes perfect.

Principles of learning - Wikipedia
read up.
Important laws for this discussion.
Primacy-what you learn first sticks
Exercise-practice makes permanent
Intensity-what is beaten into you stays with you

Taking something like fundies or whatever AG is calling his equivalent these days, or whatever a good local instructor is going to teach minimizes the effect of the Law of Primacy from any bad habits you picked up in OW by overlaying it with the Laws of Exercise and Intensity. Note this isn't necessarily saying your OW instructor was a bad instructor, though I would argue most of them aren't really what I would call "good divers", it is simply the way the industry has decided training is going to be conducted to make money and if you want to overcome that, you have to be proactive with it. Sucks, but is what it is. Controversial I know, but I never claimed to be politically correct....

 

[Killerflyingbugs]

When did this become a BC no BC discussion? My intent seems to have been missed.

 

[BRT]

As someone in the learning phase, I read this discussion somewhat like this: if you are a really good driver you don't need seat belts.

Except that if you are a good enough driver and are lucky you really won't need seat belts. Variable flotation is needed every dive.

 

[Nemrod]

The idea that divers today have that one cannot dive without a BC and have reasonably neutral buoyancy is wrong. Even in a 1/4 suit it is doable. But the tanks we used (use) are not super negative, the good old steel LP 72 was very neutral. Yes, after suit compression in the first 20 feet or so, the idea was to be initially slightly negative, midway through the dive buoyancy would be close to neutral and by the end of the dive (and the J valve was pulled) we would be slightly positive. Since nobody did so called safety stops, nobody cared and besides that, I can hold a safety stop if only a few pounds positive. Once on the surface being positive assisted swimming back to shore or remaining for pick up. Some used an inflatable vest (usually army surplus) for extra buoyancy. There was always the ability to drop lead in an emergency.

It is just a skill, anyone can learn it, and it takes the right equipment as well. For one thing, the genuine Rubatex G231 suits we had did not have the huge shift some of these suits today have. And we simply did not wear as much exposure wear as people do today. Learning to do all this was part of the class which also explains why SCUBA courses in the 60s often lasted weeks.

And it is true, the heavier the exposure gear, the more challenging it becomes. You set up for the depth. You swim down, swim around and then swim back up. Nothing to it. And, yes, one must learn to use breathing control to assist. Learning these skills at a basic level would certainly go a long way towards producing more skilled open water divers.

N

 

[TMHeimer]

I've never dived without a BC, but would imagine a way to help counter the effect of wetsuit compression at depth would be to breathe with lungs always 2/3 full (as opposed of course to holding breath).

 

[dumpsterDiver]

The answer to the basic question is that too many students never learn to really swim with fins. Their equalization skills are weak. If you take a freediver and teach him to use scuba, they will flip over, assume a head down position and kick down. These types of people will not want or need excess lead at all. They are used to kicking down the first 20 feet.

This is beyond the capability of many students, for a variety of reasons. So they are taught to float on the surface in a heads up position after entering the water, they are taught to press the down button and begin to sink feet first.

In all honesty, this is an easier and safer means to manage new divers and it makes equalization easier and less likely to cause injury - so there are reasons for it. However, divers have trouble getting the last bit of air out of their BC and suit and they often have nervous feet, all of which work together to prevent an easy, feet first decent.

So... they are often overweighted to simplify the descent process. In reality, a feet first descent should be doable without excess lead, because the diver is starting with a heavy, filled tank and should be 5 or 8 lbs negative when they vent all the air from their gear. But we still see instructors over weighting their students.

Once they are put in this over weighted state, then they are going to be dependent on the BC to a larger degree than if they carried a little less lead.

And one trick to diving without a BC is to wear too little lead, swim down hard and suit compression will take over after a certain depth. When you are ready to ascend (if there is no rope to climb) you grab a 6 or 8lb rock and kick up. You carry the rock until you reach the surface and then drop it.

A useful "trick" to consider if you ever lose a weightbelt at depth and can not recover it.

 

[BRT]

The answer to the basic question is that too many students never learn to really swim with fins. Their equalization skills are weak. If you take a freediver and teach him to use scuba, they will flip over, assume a head down position and kick down. These types of people will not want or need excess lead at all. They are used to kicking down the first 20 feet.

This is beyond the capability of many students, for a variety of reasons. So they are taught to float on the surface in a heads up position after entering the water, they are taught to press the down button and begin to sink feet first.

In all honesty, this is an easier and safer means to manage new divers and it makes equalization easier and less likely to cause injury - so there are reasons for it. However, divers have trouble getting the last bit of air out of their BC and suit and they often have nervous feet, all of which work together to prevent an easy, feet first decent.

So... they are often overweighted to simplify the descent process. In reality, a feet first descent should be doable without excess lead, because the diver is starting with a heavy, filled tank and should be 5 or 8 lbs negative when they vent all the air from their gear. But we still see instructors over weighting their students.

Once they are put in this over weighted state, then they are going to be dependent on the BC to a larger degree than if they carried a little less lead.

And one trick to diving without a BC is to wear too little lead, swim down hard and suit compression will take over after a certain depth. When you are ready to ascend (if there is no rope to climb) you grab a 6 or 8lb rock and kick up. You carry the rock until you reach the surface and then drop it.

A useful "trick" to consider if you ever lose a weightbelt at depth and can not recover it.

I've done it when divemasters insisted I didn't need THAT much lead. Not really ideal in a coral environment without a lot of heavy rocks loose on the bottom. You have to start looking early.

 

[KeithG]

This whole concept is easy (at least for those peeps that are not expert divers. Take the millennial point of view:
- lead weight is the elevator down button
- your bcd is the elevator up button

Next topic!
When do we get to see the big fish?