3-part series on teaching neutrally buoyant and trimmed

[wetb4igetinthewater]

The 3-part series I wrote and submitted to SDI now has been fully published. Links to the SDI blog posts provided in my blog.

Teaching Neutrally buoyant and trimmed

Comments welcome. This is intended for instructors, yet-to-be certified divers, and certified divers alike.

 

[johndiver999]

The third text:

Quick Review
At this time, I would like to repeat the definition of proper weighting from the first blog post: Proper weighting is the minimum amount of weight needed to keep a diver at their safety stop (5 m or 15 feet) with an empty BCD/wing, and a nearly empty cylinder (50 bar or 500 psi). If the diver is wearing a dry suit, then the dry suit has the bare minimum amount of gas to keep the diver sufficiently warm. And not a gram or ounce more. A diver then rises and falls with just normal breathing.


Can't agree with this for several reasons.

First, a diver will have a lot of expansion in a wetsuit from 15 to 3 feet. That means they may not be able to easily control or suspend their final ascent (for example- say a boat comes over their head with props turning).

Second, how is a diver supposed to deploy and hold an smb and keep it vertical if they can not have a few lbs of negative buoyancy at their disposal?

Third: Telling openwater divers that they are diving improperly if they have literally one gram of excess lead on their belt (or air in their BC) is counter productive and ridiculous.

Proper weighting involves getting the weight close, it is ridiculous to play a game of trying to minimize the weight to the level of a gram, an ounce, a pound and possibly a kilo.

 

[wetb4igetinthewater]

The third text:

Quick Review
At this time, I would like to repeat the definition of proper weighting from the first blog post: Proper weighting is the minimum amount of weight needed to keep a diver at their safety stop (5 m or 15 feet) with an empty BCD/wing, and a nearly empty cylinder (50 bar or 500 psi). If the diver is wearing a dry suit, then the dry suit has the bare minimum amount of gas to keep the diver sufficiently warm. And not a gram or ounce more. A diver then rises and falls with just normal breathing.

Can't agree with this for several reasons.

First, a diver will have a lot of expansion in a wetsuit from 15 to 3 feet. That means they may not be able to easily control or suspend their final ascent (for example- say a boat comes over their head with props turning).

Easy, kick down. Even when vertical, ones arms provide enough propulsion to descend.

Second, how is a diver supposed to deploy and hold an smb and keep it vertical if they can not have a few lbs of negative buoyancy at their disposal?

Easy, orally inflate, hold one's breath, then release. This is taught in GUE fundies.

Third: Telling openwater divers that they are diving improperly if they have literally one gram of excess lead on their belt (or air in their BC) is counter productive and ridiculous.

Proper weighting involves getting the weight close, it is ridiculous to play a game of trying to minimize the weight to the level of a gram, an ounce, a pound and possibly a kilo.

I never imagined that people would take things so literally. Given how much the lungs can compensate, getting in the ballpark within a 1 lb is all that is intended. Do I intend for divers to cut weights to trim off some grams? Of course not. Are they going to do this test with exactly the SAME amount of gas in their cylinder? 500, 600, whatever, close enough.

I'm amazed you have this interpretation.

 

[johndiver999]

Perhaps you don't understand my comment about an smb. The question is not how to inflate it, but rather how to hold a reel or spool or sting and apply sufficient downward force on the smb for an extended period of time, which is necessary to make the smb stand up and actually function as an effective marker while at a Safety stop or deco.

If you did not intend to indicate that the metric was to be in grams, then I don't think you should have explicitly said that. When someone says that a quantity needs to be measured to a precision of plus or minus one gram, it is not unreasonable for some people to read that in a literal manner.

This is more than semantics, just look at the exhaustive thread about the guy (a certified DM) who F-ed up in a shallow cave, presumably because he did not recognize the problems with trying to "play games" and minimize to the n-th degree his ability to carry minimal ballast.

 

[wetb4igetinthewater]

Perhaps you don't understand my comment about an smb. The question is not how to inflate it, but rather how to hold a reel or spool or sting and apply sufficient downward force on the smb for an extended period of time, which is necessary to make the smb stand up and actually function as an effective marker while at a Safety stop or deco.

How much force is really needed here? A pound or two? Is every diver draining their tank so much? So here's the thing. I believe that divers are not stupid. I believe that they should not be taught to the lowest common denominator. I believe that divers should be taught to think about the impact of configuration changes.

Try descending to 20 feet if that is such a concern or add whatever weight you've determined is necessary. Maybe clip on a weight to your spool so that it floats in front of you. But ultimately, use the grey matter between your ears.

If you did not intend to indicate that the metric was to be in grams, then I don't think you should have explicitly said that. When someone says that a quantity needs to be measured to a precision of plus or minus one gram, it is not unreasonable for some people to read that in a literal manner.

Again, I don't expect people to be that stupid. I've never had a student who would be so literal but would understand the gist of what I'm getting at.

This is more than semantics, just look at the exhaustive thread about the guy (a certified DM) who F-ed up in a shallow cave, presumably because he did not recognize the problems with trying to "play games" and minimize to the n-th degree his ability to carry minimal ballast.

No need to comment further.

 

[johndiver999]

How much force is really needed here? A pound or two? Is every diver draining their tank so much? .

So now you seem to be indicating that the diver obviously needs to have around 2 lbs of extra weight for the smb, is that your point?

The smb should be deployable in an emergency situation. That emergency might very well involve a diver who has drained their tank too far trying to find say, an ascent line or anchor line and then gives up and has to ascend in the open water and perform the safety stop with a very, low tank, maybe only 200 lbs while drifting away from the boat. This is the EXACT scenario where an smb could be really important.

It could be very important that they perform the stop because they stayed longer underwater (searching for the anchor line) and the drifting away behind the boat aspect should be easy to understand.

BTW, I can hang for about one minute on 50 psi in an aluminum, 80 tank, so a diver might well want to hang for 3-4 minutes with just 200 psi. The diving (weighting) configuration should be robust enough to handle undesirable, yet foreseeable contingencies.

To say that: "hey most people aren't really going to use all the air in their tank anyway" is not "using a whole lot of gray matter". That is exactly what you are supposed to have a reserve for!

 

[wetb4igetinthewater]

So now you seem to be indicating that the diver obviously needs to have around 2 lbs of extra weight for the smb, is that your point?

No it isn't. The point is that the weight for the DSMB should be determined separately. If you don't then there are easy ways to compensate: more reserve or going deeper. I'm not looking to address poorly trained divers who don't pay attention to their gas. That's why I teach min gas in open water.

The smb should be deployable in an emergency situation. That emergency might very well involve a diver who has drained their tank too far trying to find say, an ascent line or anchor line and then gives up and has to ascend in the open water and perform the safety stop with a very, low tank, maybe only 200 lbs while drifting away from the boat. This is the EXACT scenario where an smb could be really important.

It could be very important that they perform the stop because they stayed longer underwater (searching for the anchor line) and the drifting away behind the boat aspect should be easy to understand.

That's a scenario where so many things went wrong, I'm not even going to address it.

BTW, I can hang for about one minute on 50 psi in an aluminum, 80 tank, so a diver might well want to hang for 3-4 minutes with just 200 psi. The diving (weighting) configuration should be robust enough to handle undesirable, yet foreseeable contingencies.

Not an issue with properly trained divers.

To say that: "hey most people aren't really going to use all the air in their tank anyway" is not "using a whole lot of gray matter". That is exactly what you are supposed to have a reserve for!

You are not understanding, but that's okay. I'm not going to address poorly trained divers who don't think.

 

[Brett Hatch]

Hi Kosta, I read these 3 articles and enjoyed them. My OW course was not taught this way, and I won't say not-nice things about my instructors or my instruction (both were good!). But had I been taught this way, I think I would have picked things up much more quickly and more comfortably. And who knows, maybe the one student who felt so nervous and out of control that they never made it out of the pool and into open water, would be diving today.

If I ever decide to give teaching SCUBA a shot, I would strive to teach the way I actually dive: in a Hogarthian BP/W, properly weighted, neutrally buoyant and in trim. And would look to these articles for pointers on bringing students up to speed. Thanks

 

[wetb4igetinthewater]

Hi Kosta, I read these 3 articles and enjoyed them. My OW course was not taught this way, and I won't say not-nice things about my instructors or my instruction (both were good!). But had I been taught this way, I think I would have picked things up much more quickly and more comfortably. And who knows, maybe the one student who felt so nervous and out of control that they never made it out of the pool and into open water, would be diving today.

If I ever decide to give teaching SCUBA a shot, I would strive to teach the way I actually dive: in a Hogarthian BP/W, properly weighted, neutrally buoyant and in trim. And would look to these articles for pointers on bringing students up to speed. Thanks

Besides some minor tweaking the fundamental ideas of each article are consolidated from a number of instructors. By listening to others and experimenting has made a dramatic change in my retention rate. Next is my DSMB doc.