Reasons to take a propulsion/trim/buoyancy class...

[beanojones]

I think you're right; the diver who is perfectly horizontal cannot compensate for not being neutral by swimming up or down. But that also means that the horizontal diver will instantly be AWARE of not being neutral, whereas the head-up diver can swim around negative and not know it, unless he tries to stop.

But someone who is in trim is first stuck on the bottom, and they build in a habit of pushing off the bottom, that makes it so when they finally get neutral one push and off they go to the surface, because a push down when neutral is even more effective than an out of trim kick at sending one to the surface.

At least an out of trim kick has some forward component to it. A push off the bottom only acts to go up.

I think part of what makes this work one way or the other has to do with lung capacity of the student diver. Tiny Japanese lung capacity means that even a deep exhale does not have the ability to stop ascent from a push off, and deep inhale does not have the full capacity to lift the divers in trim off the bottom.

Big American lungs get to come at this differently. In general bigger lunged people 'get' neutral buoyancy quicker because they have a much stronger feedback from the breathing pattern. The degree of "still" necessary for tiny lunged people to get the breathing feedback loop established is significant, and one can see this in the big lung group leaving playing with the inflator behind faster. So for some, the divers start still, and then get feedback that out of trim does not work if they swim try and swim off and up up surfacing.

or as you say:

Trim and buoyancy are intertwined -- UNLESS you are motionless.

So stop is the signal most given to divers in general when training them. They are already neutral, and work themselves out of swimming out of trim from the negative feedback of being sent up if out of trim.

I have played with the walking in trim along the bottom until neutral is established, and getting neutral and working towards trim, and two things jump out at me. One, direct training in the ocean means push-offs, even one finger push-offs can result in injury to diver and sealife. And two, in surge, getting all but the fins off the bottom fast is absolutely necessary for practical reasons. SO still and neutral is the necessary start.

Pools are great. But they are also not part of how many (maybe even most?) people learn to dive.

---------- Post added August 3rd, 2013 at 09:52 AM ----------

Well, duh!
...
It's far easier to do it the right way.
.

Betcha you learn more, and I learn more, if neither one of us assumes we are right, or that there is even a right way, instead of several right ways.

Successful for you I want to hear about because I am always looking to steal new ideas, successful for me is under different parameters, and there are real reasons why parts of the approach you lay out fails to result in positive outcomes in direct to ocean training because it pretty much immediately results in negative feedback, or ingraining bad behaviors.

 

[TSandM]

Well, the definition of confined water is "pool-like" conditions -- so if you are doing your confined water sessions in places with delicate sea life and surge, I don't think that meets the definition.

We don't start our students on the bottom and try to get them neutral. We start them on the surface and let them exhaust air from their BCs until they are underwater. We have VERY few students who push themselves up off the bottom with their hands, and the ones who do are doing so because they AREN'T neutral -- once they get off the bottom, they stop pushing on it. So this whole scenario of a diver getting neutral but giving a push on the bottom and ending up on the surface doesn't make sense to me, because we don't see it happen.

Also, I'm not much bigger than a lot of Asian women, and I can stop an ascent by exhaling . . .

 

[supergaijin]

Japanese lungs are no smaller than any other human of a typical size. I'm sure some Japanese academics exist that would argue that they were 'unique'. I hear Beano spout this so often and it's bollocks IMO and IME working with Japanese guests. Yes, there are some diminutive Japanese women- especially among the elderly. I also know some pretty tiny women in NZ- one girl I remember I shared an apartment with in uni came up to my nipples. I bet she wouldn't need a 15L tank... but ya never know.

While working in Japan it wasn't uncommon for me to have students taller than me (178cm/5'8). This was in a Junior High School. I've met seriously large girls and guys in Japan.... even... one time at the onsen...

I have dived with Japanese with a very good SAC and some with a horrible SAC over 24L/min. I have also dived with a South African 'Hercules' lookalike who breathed not much more than me (8L/min).

AOW PPB courses I have taught with Japanese divers showed that all divers were capable of at least a 3kg/7lb adjustment using lung volume. That includes the stereotypical Japanese-with-gills, starts with 200bar comes up with 210bar diver.

Enough with the Nihon-jinron. It's hogwash.

 

[Imbodie]

An instructor should be able to isolate and focus on your problem areas

As a new instructor... This is my frustration... I can recognize the issues, I just don't know how to translate to an understandable format for my students.

I think I want to take your re-fresher, just to absorb some of that knowledge...

 

[PfcAJ]

The average American female is 5'4''
The average Japanese female is 5'2''

 

[The Chairman]

Can't wait for my course with NetDoc in Key Largo later this month.

I assure you, it will be far more fun than work. Once you get the principles down, the rest is easy tweaking and practicing. This should and will be a painless process for you.

As a new instructor... This is my frustration... I can recognize the issues, I just don't know how to translate to an understandable format for my students.

I think I want to take your re-fresher, just to absorb some of that knowledge...

I have two options for you: bring a student down to the Keys and plan to do a pool session with them and me. I promise to make you look good. Mentoring is the best way to learn how to do this. In fact, I'll make that offer to any instructor and it will cost you nothing. If you don't have an OW student, bring down an AOW student. If you don't have an AOW, bring yourself. If you're teaching status, your class time is on me. I think it's important that all instructors possess this skill and I don't mind sacrificing a day or two getting you up to speed.

Option #2. I hope to be at this upcoming October Mega Dive at Ginnie Springs. You're just around the corner from that event, so come on over and we'll grab a couple of Guinea pigs. It won't take long and you'll have all the tools you need to get your students trim and neutral. BTW, I lived in Trenton back in '63/64 and lived in a house that sits across from a sink hole. It was old then and the house next to it has pretty much imploded the last time I saw it. Lots of fond memories for the year I lived there.

Betcha you learn more, and I learn more, if neither one of us assumes we are right, or that there is even a right way, instead of several right ways.

I've known people to argue with a sign post and take the wrong way home. I'm not open minded enough to follow them in their folly. I have seen more than my share of instructors, both good and not so good. The excellent instructors have always approached problems in a systematic manner, eliminating as many variables as possible. Not so good instructors make excuses why something can't be taught/learned/done. They always make themselves out to have "special circumstances" why things like physics and fluid dynamics simply do not apply to them. Many good (and some great) instructors keep giving them a sign, but they just like to argue I guess. There's a sign for working to establish neutral buoyancy before dealing with trim:

 

[pocky21]

As a new instructor... This is my frustration... I can recognize the issues, I just don't know how to translate to an understandable format for my students.

I think I want to take your re-fresher, just to absorb some of that knowledge...

You're not the only new instructor struggling with that. The canned line given to me was "after 20 something dives you'll figure it out". Thankfully, the learning by mimicry approach has been fairly successful for me, thus avoiding a massive episode of reference quality verbal diarrhea!

I'm in Panama City - if you want to hit up Largo together to run the Netdoc gauntlet, I'll pick you up along the way

 

[The Chairman]

I'm in Panama City - if you want to hit up Largo together to run the Netdoc gauntlet, I'll pick you up along the way

The more the merrier! Just be sure to make sure I'm available with mselenaous. I'm notorious for booking myself in two places on the same day.

 

[guruboy]

If you have proper trim, will you naturally settle in a horizontal position when relaxed? Or does it mean you stay horizontal when relaxed, AFTER you get horizontal?

 

[TSandM]

guruboy, that's a good question, and it depends on the gear you are using.

If you are diving warm water, with minimal exposure protection and an aluminum tank, you may be able to weight yourself and your setup so that you will be roughly stable in any position -- in other words, if you get horizontal, you will stay that way, but if you're standing on your head, you'll stay that way, too. (This can be done fairly easily with sidemount setups, which was one of the joys I discovered when I got to dive one.)

In cold water with steel tanks and a lot more weight, it may not be very easy to achieve that kind of total stability, and you may have to distribute your weights to favor a horizontal position. That would mean that if you were horizontal, you would stay that way, but for example, if you went vertical and head-up, you might tend to fall backwards if you didn't kick to stabilize yourself. (That's my situation with a single tank setup.)