SDI DMs and up must demonstrate skills while neutrally buoyant

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Saying that weighting, buoyancy, and trim are not connected is simply not true.
So there I was in the pool, with my new camera in a big metal housing with two strobes and a heavy tray, and my goal was neutral in the water: let go of camera and it does not rise or sink, or flop sideways or roll upside down. The rising/sinking is weighting/buoyancy; the latter is trim. I can choose to adjust the floats and weights so the camera doesn't sink....but that does not mean it won't roll over or flop sideways, depending on where I place the floats and weights. I can put all the weights on once side of the camera, and all the floats on the other....and be neutral......but can't use the camera that way. I can adjust the roll and pitch of the camera by my placement of weights and floats, but that alone does not ensure the camera won't sink or float if I let go of it.

My point is I can be perfectly neutral, or perfectly trimmed, but I want both. They are connected because I WANT them to be, not because any physics demands it.
 
I think a point may be that if you wanted to show students one of them but the others were all messed up, that would be difficult.

Lets talk about how weight distribution affects your natural orientation in the water, while you are massively negative and lying on the pool bottom or plastered to the surface with positive buoyancy, Fail.

Lets talk about bouyancy, while you are canted at a 45 degree angle and occasionally kicking, sending upward, changing your bouyancy, Fail.

It is hard to grab one in the water unless the others are squared away.

I'm glad SDI made this move.
 
I find many newly certified divers are finning throughout their entire dives due to being overweighted and out of trim. One of the things I like about the SSI OW course (yes, I realize this is an SDI thread), is the repeated hovers. Before getting into the water, I ask my students what they think a good diver looks like. It is a great conversation to have that leads to being still, slow, efficient movements, only finning when necessary. And I keep bringing it up before dives and during debriefs.

As I now have classes of two, I like to have them hover often (as I am independent, that means SDI, not SSI - but SDI allows for instructors to add performance requirements, a big plus). I'll just made a fist to signal "stop" and see how they tilt/rotate and address that. I teach them to see about shifting their BCD as needed. I do this often myself as my focus is CC and I shift my rebreather on my back to not rotate.

Students pick this up fairly quick if given the right foundation of proper/as-close-to-minimal weighting with weight distribution to be trim.

And it is not hard to do. But let's be honest, the bar for becoming an instructor is still too low. I'll be convinced otherwise when instructors are required to teach OW NB/T.
 
I find many newly certified divers are finning throughout their entire dives due to being overweighted

Interesting. I have never seen someone finning from being over weighted. That would imply to me that they don't have enough lift available from their BCD. I have definitely never had a student that was so heavily weighted that their BCD did not have enough lift to keep them off the bottom and thus forcing them to fin just to hold their depth.

What I HAVE seen (LOTS) is divers who fin constantly because they are negatively buoyant. But, no matter what their trim or weighting is (unless they are too heavy for the lift of their BCD), they can stop that finning by adding some air to their BCD and getting neutral. Even if they are over weighted.
 
Interesting. I have never seen someone finning from being over weighted. That would imply to me that they don't have enough lift available from their BCD. I have definitely never had a student that was so heavily weighted that their BCD did not have enough lift to keep them off the bottom and thus forcing them to fin just to hold their depth.

What I HAVE seen (LOTS) is divers who fin constantly because they are negatively buoyant. But, no matter what their trim or weighting is (unless they are too heavy for the lift of their BCD), they can stop that finning by adding some air to their BCD and getting neutral. Even if they are over weighted.
You seem to want to have a go at me in this thread, so I'll play along. As we all know, when you are overweighted and neutrally buoyant, any changes in depth result in significant changes in buoyancy (the actual definition as a force).

Therefore, to compensate for this, they remain negatively buoyant. And have short dives.
 
So how do you teach your new OW students the relationship between weighting, buoyancy, and trim?
I'm not a certified instructor; however, I view them as separate but tiered concepts, and the order of understanding is important. Of critical importance, though, is to eliminate the masking effect of propulsion. (I'm assuming a drysuit is NOT involved in any of this, BTW.)
  1. Proper weighting can be directly measured without kicking.
  2. After being weighted correctly, neutral buoyancy can be taught by not kicking. As much flack as the Budda hover gets (or whatever position your body happens to take with legs crossed to prevent kicking), it makes it very obvious that you understand neutral buoyancy when normal breathing has you hanging mid-water in the pool. This includes balancing the air distribution between BC and lungs to achieve that "normal" breathing range. This has little to do with "proper" weighting, requiring only that one is weighted "enough". (Granted, it's easier when properly weighted because buoyancy changes are slower, giving one time to sense/react.)
  3. Finally, the distribution of the weight is adjusted so that rotation is eliminated when physically placed in the desired horizontal trim position by an instructor. Yes, there's discussion about what muscles need to be contracted, core stabilized, head up, torso/knees straight line, etc., but if someone hasn't moved a muscle and rotates fairly quickly when released, that clearly points to weight distribution. Nothing to do with total weight or buoyancy. Once weights are close to correctly positioned, the rotation when released will be slow and can be controlled (either direction) with small positional changes of legs/hands.
If everything is free to be adjusted at once, it's very easy for seahorse trim + kicking + negatively buoyant to perfectly balance out and yield horizontal movement at a constant depth. Indeed, people who care about the reef can make themselves slightly positively buoyant + slightly head down + kicking yielding horizontal movement inches above the reef. (Believe me, when sharp urchins abound where you dive, you quickly learn to respect them!)

Again, this is just how I view things. My OW class (NAUI, late 80s) never even talked about "trim". Hundreds of dives and I never kicked the reef, so I thought I was great. It wasn't until I saw video of myself years later that I realized I was in the slightly kicking down category.

TLDR; My buoyancy control was great, but I was cheating by using propulsion to maintain trim. My opinion is teaching weighting, buoyancy, and trim as separate concepts without the masking effect of propulsion will sort someone out pretty quickly. I know it did for me.
 
How do you separate trim from buoyancy and proper weighting?
Didn't you just answer your own question?
One of the things I like about the SSI OW course (yes, I realize this is an SDI thread), is the repeated hovers
I'd say propulsion is the glue that causes buoyancy & trim to be intertwined. Hovers decouple/separate the concepts.
 
Interesting. I have never seen someone finning from being over weighted. That would imply to me that they don't have enough lift available from their BCD. I have definitely never had a student that was so heavily weighted that their BCD did not have enough lift to keep them off the bottom and thus forcing them to fin just to hold their depth.

What I HAVE seen (LOTS) is divers who fin constantly because they are negatively buoyant. But, no matter what their trim or weighting is (unless they are too heavy for the lift of their BCD), they can stop that finning by adding some air to their BCD and getting neutral. Even if they are over weighted.
Over weighted = negatively buoyant. Implies not enough lift in their BCD or implies they don't know how to use it effectively yet. Finning, sculling to stay off the bottom because they're not properly weighted or using their BCD yep see it all the time.
 
Over weighted = negatively buoyant.
I disagree. I am frequently negatively buoyant during a dive. At other times, I'm positively buoyant. Sometimes I'm even neutrally buoyant. All the while, my weight has not changed.
 
I disagree. I am frequently negatively buoyant during a dive. At other times, I'm positively buoyant. Sometimes I'm even neutrally buoyant. All the while, my weight has not changed.
If you are over weighted you will be negative unless you use your BCD to compensate and yes you can be both negative and positive with the same weight. He implied something different but said the same thing two different ways.
 

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