Teaching nothing

[L13]

Not sure it's tidal volume so much as basal metabolic rate differences even after adjusting for body size and body composition (a proxy for fitness). Men burn calories faster, and that means we consume oxygen faster.

Actually, air consumption is about CO2 removal, not O2 consumption. Hyperbaric air, let alone nitrox, has way more oxygen than is consumed in each breath. Burning calories(with O2) increases CO2. The increased CO2 drives the need to breath, and therefore gas consumption.

 

[Blackcrusader]

Actually, air consumption is about CO2 removal, not O2 consumption. Hyperbaric air, let alone nitrox, has way more oxygen than is consumed in each breath. Burning calories(with O2) increases CO2. The increased CO2 drives the need to breath, and therefore gas consumption.

So then the divers that move the least need to breathe less, can use inactive breathing techniques to reduce gas consumption.
My dive buddy took this video of me below. Seems I only to breath every 15 seconds or so on slow dives. Now my Lombok extreme fast current dives I did use a lot more gas.

Recently in Bohol I was teamed up with a really nice DM. Some dives we had to finish earlier than I planned as he had used 40 bar more than I had. He said he got cold and chewed up his gas whereas my bulk prosperous lard build up kept me warm. The water temperature was 30c

 

[tursiops]

Again. This is a basic topic which does cover common sense. You are muddying up my discussion of what I'm trying to get across with getting into things beyond basic. If you wish to discuss that, please start your own thread. I'd greatly appreciate it if you'd stop. I know better than to ask the same of the other guy. It is disruptive. Thank you

Report me if you think it is off topic.

 

[Boarderguy]

 

[wetb4igetinthewater]

I have benefitted from most of the commentary fortunately so I am glad I started this thread.

 

[Seaweed Doc]

Not sure if I should hijack this thread or start a new one, but a related question came up in a discussion with an experienced diver who was shaking out her issues with a new combination of gear.

What is trim? I've always thought of it as being sort of equally weighted so that your body is perpendicular to the pull of gravity. That's how we alter trim by moving weights around.

Trim is really being in line with the direction of travel, however, so that you're moving with minimal wasted effort. If you're swimming across a flat bench, or at the same depth along a wall, trim is still perpendicular to the pull of gravity. But if you're ascending from a beach dive and swimming uphill, proper trim is slightly head up. And if you're swimming down the hill at the start of the dive, proper trim is head down. At least relative to a line that is perpendicular to gravity.

At that point, it's technique more than weight position.

And "perpendicular to gravity" is now my favorite phrase. (Level doesn't quite get at it. I live in a 100 year old house. When doing modest remodeling, one hast to choose what exactly you want to level to. The floor? The ceiling? Perpendicular to a wall? Which wall? Level isn't always what my bubble tool in the workshop shows...)

 

[wetb4igetinthewater]

Not sure if I should hijack this thread or start a new one, but a related question came up in a discussion with an experienced diver who was shaking out her issues with a new combination of gear.

Not a hijack (IMHO).

What is trim? I've always thought of it as being sort of equally weighted so that your body is perpendicular to the pull of gravity. That's how we alter trim by moving weights around.

My understand that "trimmed" refers to being at horizontal. Same as you.

Trim is really being in line with the direction of travel, however, so that you're moving with minimal wasted effort. If you're swimming across a flat bench, or at the same depth along a wall, trim is still perpendicular to the pull of gravity. But if you're ascending from a beach dive and swimming uphill, proper trim is slightly head up. And if you're swimming down the hill at the start of the dive, proper trim is head down. At least relative to a line that is perpendicular to gravity.

At that point, it's technique more than weight position.

Not sure if I follow. Finning often masks negative buoyancy, that's how people seahorse through the water. They are finning continuously (burning gas faster).

And "perpendicular to gravity" is now my favorite phrase. (Level doesn't quite get at it. I live in a 100 year old house. When doing modest remodeling, one hast to choose what exactly you want to level to. The floor? The ceiling? Perpendicular to a wall? Which wall? Level isn't always what my bubble tool in the workshop shows...)

Question. Have you had students not get what you meant by trim that you needed to elaborate? Serious question. I think the "perpendicular to gravity" would be a good explanation in open water materials. I like it.

I do wish discussing the difference between center of mass and the center of volume/displacement would be convered in open water. I think it would help tremendously. Unfortunately, there are CDs/ITs that don't know this. I can think of one platinum CD in Thailand off the top of my head.

 

[DiveHewi]

I'm placing this is basic scuba instead of instructor-to-instructor for the reason that I'd like feedback from divers of all levels, from not even certified yet to experienced instructors. This absolutely belongs here in basic scuba as we are talking about open water courses, and there is nothing more basic than that.

Now I do take open water instruction seriously, but still make sure it is fun, and convey concepts in a way that students will remember them.

In my opinion, the most important thing a diver must be able to do is to remain motionless at a fairly constant depth (depending on the length of their breath cycle, they will ascend and descend slightly). But when you really think about it, it is important for a student to do what exactly? That's right! Nothing!


It is my job to first weight my students properly, which as I have said many times includes weight distribution so that the student can float horizontal effortlessly with little change in depth. Second, it is my job to teach my students how to do this (and I'm in the process of ways to improve that).

For students that saw Seinfeld when it aired (US, Gen X and later), I think they'll remember this. What about the idea of doing nothing as to understand what buoyancy control is all about?

I would have to say that OW class, at least back in the day, taught a lot about the physiology of diving and how pressures act upon the body. They also taught about how our equipment functions and, as you said, about the importance of buoyancy control. In our open water sessions, they emphasized a number of basic skills such as mask clearing, regulator retrieval, buddy assist, and a host of other other skills. We were introduced to the idea of discerning between an inconvenience, an urgency, and an emergency. I can't recall now how many skills we were introduced to at the time, but it certainly wasn't limited to buoyancy control. And the stories they shared during surface intervals were priceless!

I think that giving the student a basic foundation in which to build from is the important part. If they understand that they will have to take things a bit slowly at first and practice the fundamentals on their own, they most likely will turn out to be great dive buddies.

 

[Seaweed Doc]

Not sure if I follow. Finning often masks negative buoyancy, that's how people seahorse through the water. They are finning continuously (burning gas faster).

Question. Have you had students not get what you meant by trim that you needed to elaborate? Serious question. I think the "perpendicular to gravity" would be a good explanation in open water materials. I like it.

I'm thinking that your direction of travel is not always perpendicular to gravity. If I'm diving any site with a sloped beach (think Mukilteo, the Alki Coves, etc, not so much Edmonds), on the swim in I'm swimming uphill (so to speak) on the way back to the entry point. I should be swimming parallel to the ground, not perpendicular to gravity.

I quickly made the crappy illustration attached here to try to explain.

On teaching students: No, they get it, but I tend to "teach" trim over a flat bottom, though I evaluate it (and let them know) while swimming up and down hill as well as over a flat spot..

 

[wetb4igetinthewater]

I'm thinking that your direction of travel is not always perpendicular to gravity. If I'm diving any site with a sloped beach (think Mukilteo, the Alki Coves, etc, not so much Edmonds), on the swim in I'm swimming uphill (so to speak) on the way back to the entry point. I should be swimming parallel to the ground, not perpendicular to gravity.

I quickly made the crappy illustration attached here to try to explain.

On teaching students: No, they get it, but I tend to "teach" trim over a flat bottom, though I evaluate it (and let them know) while swimming up and down hill as well as over a flat spot..

Yes, that is true when going up and down slope. Maybe body horizontal/parallel to the relative bottom, regardless of what angle the bottom is? For addressing slopes.

I actually like your picture from Redondo with MAST in there.