BP Wings vs BCD explanation

[SeaJay]

Thanks for chiming in.

I was going to reply to you by PM... I thought it might seem arrogant to do it on the board... And with bp/wing users' reputations being... Well... That they're "abrasive" to say the least, I figured it better to just PM you. However, if y'all will please remark the humility and excuse my gloating, I'll post it here.

It's very flattering that something I wrote helped you to make a decision. That's precisely why I wrote it. With so much BS going around out there (often from the profit-motivated manufacturer or dive shop), someone needed to step up and tell the truth.

Bp/wings aren't for everyone... Neither are Ferraris or Mercedes or big, 4wd sport-utes. Variety is the spice, really... And a bp/wing does have the disadvantage that they need to be assembled and customized by the individual. Thus, they don't make very good rental gear... Which, of course, means that they generally aren't used in basic OW classes.

...So for someone to dive a bp/wing means that they need to somewhere along the line "make the jump" from what they were taught in to something that will serve their needs better. At least, that's my opinion, which isn't shared by all. But I truly think that therein lies the resistance that many people have to bp/wings... And why they're so controversial. The same goes for diving the long hose, or anything else that wasn't taught in the only class that most divers ever take: Basic Open Water. Any other gear configuration is "nonstandard" to those people.

But like you pointed out, RR, assembling your own gear is not without it's advantages. There's a certain pride felt, and you're insured of getting a completely custom rig that's tailored for you in every way. The "understanding" of your gear is unmatched by any "off the shelf" BC. The simplicity of a bp/wing is outstanding, and the stabilty is unmatched. Best of all, they're modular, so you can modify them for any type of diving that you choose. A good bp will stick with you forever, should you choose it to.

...And the performance... Well... Enough's been said on this board to write a book. Of course, not everyone agrees, and there is some truth to the fact that the performance is largely a skill issue. Still, it definitely helps to have the right tool for the job.

Congratulations on your purchase. FredT is a good man, isn't he? Please tell us when you finish your rig. We'd be interested in hearing your reactions - what your impression was of the BC's you dove (please mention brand names if you can) - what your impression was of the "transition" (2-10 dives or so for most people) - and what your impression was once you've got it dialed in and everything adjusted.

...So what do you have invested at this point? $90 or so for the plate? Did it come with the harness? Did you choose the one piece?

Let's see... Hardware... Oxy wing (nice choices, by the way)... You'll have a little over $400 invested in what's arguably the best rig you can buy?

Congratulations on the new gear. We're all envious.

 

[-hh]

SeaJay once bubbled...

Ain't "seeing your profile" great? By far, this has to be the biggest supportive arguement for the use of computers. Is this one of those little black box dealies?

Seeing your profile is IMO usually more useless trivia than anything particularly useful. At least I can donate these profiles to DAN research (not all dataloggers support this).

FWIW, this black box is a "SENSUS PRO". Its better than buying the interface cradle for my dive computer because it stores more hours before its memory rolls over...and it was cheaper too!

Here's the manufacturer's webpage. Ask for one for Christmas ;-)

http://www.reefnet.ca/products/sensus/index.asp

On my website I have a link to a variety of tank specifications... I don't see one with an actual capacity of 78.2 cu ft. Most of them are 77.7 or 77.4 cu. ft... What sort of tank is 78.2 cu ft. at it's working pressure?

The tank was a standard AL80. Normally I just assume ~78ft^3 even though I know that that's not its exact volume.

When you challenged my calculation, I did a quick websearch to find what the exact tank volume value. I was looking for "77-point-something", but this 78.2 value was on the first page I hit, so I assumed that my memory had been faulty, and used it. Oops. Correcting this value lowers the SAC by 0.5%

...My point is... Are you sure that those numbers are correct? If so, they're pretty awesome.

The numbers for calculating SAC aren't that hard. Generally, the only hard part is getting your average depth, and that's delivered here by the datalogger. The calculations for this dive are:

Air Consumed: (tank rating)*(before-after)/(rating pressure)
=(77.7ft^3)*(3100psi-700psi)/(3000psi)
= 62.16ft^3 {Note: psi/psi units cancel out}

Dive Average Depth: 31fsw (per datalogger)
= (31/33+1)atm
= 1.94 ATM

Dive Duration: 89:45 = 89.75 minutes

Surface Equivalent Air Consumed:
= (Air Consumed @ depth) * (Surface ATM)/(Average Depth ATM)
= 62.16 ft^3 * (1 ATM/1.94 ATM)
= 32.05 ft^3 {Note: ATM/ATM units cancel out}

Surface Air Consumption (SAC):
= (Surface Equivalent Air Consumed)/(Dive Duration)
= (32.05 ft^3) / (89.75 minutes)
= 0.357 ft^3/min


FWIW, these numbers still aren't "perfect", because 1 ATM really isn't 33fsw as assumed; the standard works out to 33.23ft. Applying this would again lower the values ever so slightly (0.351)

However, because there's gage calibration errors and resolution limitations within the tank data (air consumed), we're looking at a good example of false precision in our numbers. We generally only had two significant digits in our input values, so our result should only have two S.D's as well...thus, this gets rounded to 0.4 ft^3/min.

(Note: its not 0.36, because the zero is one of the two significant digits)


-hh

 

[-hh]

SeaJay once bubbled...

I agree that most of the time, divers have not maxxed the performance that their gear will deliver; in other words, it's their skills that need the work, not their gear... And so it makes more sense to work on those than go out and buy new gear.

...Of course, conversely, you simply aren't going to develop the skills of horizontal trim and perfect buoyancy if you don't have the tools which support your learning. A bp/wing, a DIR-F class, and lots and lots of practice can be of great use in helping a diver to develop the skills.

Sure, but if you had to pick one (and only one) as the most significdant, would you say that its the BP/W, or the DIR-F class?

IMO, the BP/W can be an enabler, but enablers don't inherently provide direction. Training provides direction.

I see the logic, and I can't say as I disagree.

However, let me point out that with that mentality, you're catering to the lowest common denominator....everyone's always complaining that the mainstream agencies get people through scuba as quickly as possible, and by doing so instill bad habits and problems which must be unlearned later.

...Why not instead cater to the top of the class? Why not teach people the right way from the beginning? Why not encourage them to learn buoyancy and trim in the gear that will enable them to dive for the rest of their lives, at any level they choose?

I guess I haven't expressed myself well enough.

I'm not proposing catering to the lowest common denominator.

Instead, I'm saying that we should recognize what the mainstream is, and while not denying the appropriate opportunities for the 1%ers, recognize the majorian need and tailor the system to provide the "Biggest Bang for the Buck".

This is classical Pareto Principle (aka 80-20 rule), and observation of the reality of diminishing returns.

I'm not saying that there's no place for the 1%ers, but rather that if you expect the majority to be able to benefit, you can't go too far in what they'll say is "wasting their time" by going further than they need. We need to remember that more training doesn't come free.

So let's use the PP to our advantage. We can 'raise the bar' significantly for all divers through a small increase in effort, so the smart thing to do is to grab the proverbial "low hanging fruit" and not worry about the three small apples way at the top of the tree that are usually more trouble than they're worth.

No doubt - perfect examples of this can be seen in the type of gear that newbies are encouraged to purchase, and the fact that they're often taught literally on their knees, on the bottom of a pool. From the outset, bad habits are encouraged.

Sure, but training resources are always finite. Let's say that we can afford 2,000 units of additional training per 100 divers:

How do we best spend them? Here's two options:

Give 100 divers 20 units each.
Give 95 divers 0 units, and give 5 divers 400 units each.
(etc).

FWIW, you can think of the second line here being similar to the status-quo, with the 5 that get the "400 units" as the DIR-F class.

So which is better? Well, the answer really depends on who you are: are you part of the 95, part of the 5, or an outside observer?

For the 95, something is better than nothing, so the first option is best for you.

For the 5, getting 400 is better than 20, so the second option is best for you.

But how about from the perspective of the outside observer? The laws of diminishing returns and the PP say that individually, the most benefit comes from the first part of the effort. As such, the first 20 units provides, say, a 20% benefit, whereas it takes 400 units to get up to a 100% benefit. As such, the system-wide benefit of 2,000 units of training can be spent as:

(100 divers)*(+20%) = 2000% gain
versus:
(95divers)*(0%)+(5 divers)*(+100%) = 0+ 500% = 500% gain

So the collective aggregate would be that the first option is better.

Why not teach them proper control from the outset, while they're still excited and wanting to learn and willing to dedicate themselves to excellence?
...
Man, this isn't about diving... This is about a whole philosophy that seems to permeate our society as of late.

Agreed. The problem here is that you've assumed that people at the onset are interested and willing to learn and dedicate themselves to excellence, and that's unfortunately not the case.

If you ask why people take dive training, the general answer that you'll get is that they want to go have fun in the water. Fun, not excellence.

Some people do embrace the training and take it sincerely, but many others simply look at the OW class as a "Gate" that they have to do but once, and then its behind them. Yeah, I know: a bad attitude. But like it or not, this is the reality of the consumer base.

The whole quality-vs-quantity is a problem for the Industry, because it creates a conflict of interest because the Industry's revenue stream stems from how large the customer base is. It is this motivation to broaden the consumer base that has resulted in the watering down of training, as well as pushing down the minimum age down into children, which IMO is despicably dangerous.

But I digress...to a degree. The reality is that it really doesn't take $5000 worth of dive gear to go have fun diving, no matter how frequently this marketing message is hammered into us.

My underlying message is that we don't have to spend a ton of money to have fun, nor do we have to strive for absolute perfection in performance to enjoy being in the water. If that's how you choose your definition of "fun", that's your personal choice for you personally; it simply doesn't have to also be mine.


-hh

 

[SeaJay]

-hh once bubbled...


Seeing your profile is IMO usually more useless trivia than anything particularly useful.

What? Really? Maaaannn... I thought you and I were totally going to agree on that one. Boy, was I off.

I find it useful in this way: I develop a plan and then go execute it. After the dive, I'm able to see how close I came to the plan. This enables me to "hone" my skills of diving, I believe, so that I can get exactly the results I was looking for. Without being able to see my profile post-dive, I could never really tell how well I did.

I use a Suunto Vyper, and I've used it in guage mode as well as computer mode. I don't much listen to the computer any more, but it's interesting to see how close my own calculations are to the computer's - sorta like having a backup on my wrist.

I also learned the hard way that if my brain and my computer disagree, I need to listen to my brain... Contrary to what your average calculator-weilding student might believe.

Lastly, I've found some "anomolies" in operating the computer... Things that the owner's manual simply doesn't outline well enough... That need to be understood by the diver for safe operation.

In all, the use of a computer on the fly, to me, is now more questionable than it's ever been, but I do quite enjoy the Vyper's excellent depth guage and bottom timer, and logging feature which allows me to see my profile post-dive. I've also remarked on more than one occassion how my "head" numbers and it's NDL numbers are so close. I find it a source of entertainment, when doing those sorts of dives.

 

[-hh]

SeaJay once bubbled...
Seeing your profile is IMO usually more useless trivia than anything particularly useful.


What? Really? Maaaannn... I thought you and I were totally going to agree on that one. Boy, was I off.

Actually, I'm being a bit harsh. I have found it to be useful in certain ways. For example, I look at my profiles for bad habits, such as sawtooth profiles. One bad habit that I have identified this way is post safety stop "dips". Here's an example:

http://tinyurl.com/s2we

Now that I'm watching for this, what I've found is that after I finish my 3-5 minute stop @ 15ft and go to swim over to the boat transom (exit), I tend to swim downwards a little, instead of perfectly horizontal, or progressively shallower. One thing that I have been trying to somewhat counteract this is to pull a one minute stop at 6-7ft.

I find it useful in this way: I develop a plan and then go execute it. After the dive, I'm able to see how close I came to the plan.

Sure. However, a lot of recreational divers don't really have a dive plan in the conventional sense (XX depth for YY duration), so there's no baseline plan for your actual profile to be compared to.


FWIW, when I say "no real plan", I'm referring to the common practice today of having just a general idea, and delegating the task of tracking of Nitrogen on-gassing to the dive computer. Overall, while the flexibility and freedom afforded by this technique is great, it does have its trade-offs. And right or wrong, for better or worse, a heck of a lot of recreational divers dive exactly this way.


-hh

 

[Matthew]

SeaJay once bubbled...

Before you go and chastize me for saying that, note that exactly what I've said differs slightly from your quote.

I have never said that it's impossible to achieve horizontal trim using an off-the-shelf BC. I've said that it's possible, but not not common. Furthermore, I pointed out that I didn't see why someone wouldn't desire to have a rig that was inherently balanced in the first place.

I quoted that verbatim from your article. You are contradicting yourself.

It's not hard to do, and it is very common here. Am I seeing things? Incidentally, does "inherently balanced" mean there are no trim issues? This again seems to contradict some of your previous statements.

That was uncalled for. If we're going to engage in a positive debate (which this seems to be - I am enjoying this) then our words must remain positive. I can't promise that I won't take the occassional cheap shot, but when I do, please point it out and I will apologize. I expect the same from you, and expect that you expect the same from me.

Sorry, Seajay. But you keep repeating questions that have already been answered. You even forget (conveniently) your own words. That’s not conducive to a positive debate. Here you go:

Have you ever dived one?

From a previous post: "Yes. I really liked the way my front and sides were freed of stuff, and the way I didnt feel squeezed when inflating. And as jplacson says, it really looks cool. I found it comfortable, although I felt awkward when I tried to do some of the things we like to do like hovering at an angle, hanging upside down, etc. Maybe it just takes some getting used to. I'd also prefer to be in my bc when waiting to get on a boat in a very rough surface, which situation I often find myself in."

That situation wasn't the sort that I was describing in my original post, however... I was describing the diver who WANTS to maintain horizontal trim, but must fin/scull to do so because his weight/buoyancy is not distributed properly.

That is NOT common. The only ways I can imagine a diver get horizontal using the hands and/or feet is by swimming with the arms in a breaststroke-like motion, or by continuously finning to maintain a horizontal angle of attack, or both. This takes a LOT of effort, is very tiring and defeats the very REASON why divers would WANT to be horizontal – to be more comfortable and to travel UW more efficiently. Even the stupidest diver will realize the futility in a few minutes and would NOT WANT to keep trying. Note that I'm talking here not of minute discrepancies in trim which cause negligible, if any, decreases in efficiency as -hh describes, but of a 45 degree diver who stirs up silt and damages corals as described in your article. Again, the most likely solution is proper amount of weights and/or training and experience.

I suggest that you and your immediate buddies have less of an issue with this for exactly the reason you mentioned: Since you're diving with little exposure protection and little required weight, the forces are reduced. It's much worse as the forces increase. If you need more weight because of thicker exposure protection, the issue moves up from "not a big deal" to "annoying" to "prohibitive."

Not just me and my immediate buddies, but a lot of people who dive in similar conditions. And nobody needs more exposure protection/weight.

Unfortunately, thicker exposure protection (it's noticable in a 3/2 mil), more gear, different tanks or a different number of tanks... All of these things come into play when considering the amount of force at hand.

Unfortunately, for a lot of people, all these things don’t come into play when considering the type of diving they are going to do and the conditions they will dive in. The big majority will probably be diving in a 3/2 and a single aluminum 80 all their lives.

 

[Matthew]

SeaJay once bubbled...

...Because you're weighted according to a set of full lungs. Check the PADI and NAUI ways of achieving proper buoyancy. The GUE method comes up with very similar results.

No, I'm not. With a fully deflated bc I need to fully exhale to be able to descend. I know that almost all training agencies teach the "eye-level" float on the surface as the test for buoyancy. But in my AOW course my instructor tested my ability to stay neutral at 15 ft, to ascend very slowly to the surface, or to hold any depth in between. What's the GUE method?

I asked the "shoot up" question as a reaction to what I believe are exaggerations of the effects of forces affecting buoyancy/trim.

...The REAL question is, "why don't you drop horribly when you DEFLATE your lungs fully?" Well... That's a great question, my friend. If I were to deflate my lungs fully or inflate my lungs fully, then I would definitely rise or fall accordingly. When I'm trimmed underwater, I'm trimmed for somewhere in-between, so that I'm only 4.5 lbs positive or 4.5 lbs negative on an inhale or exhale. This is the method I use to rise or fall in the water column without finning.

...And it will work for anyone who does not negate the result with forcing themselves up or down by finning or sculling.

...So what does that say about your buoyancy? If you aren't rising and falling with each breath, then I suggest that you're doing more finning and sculling that you believe you are.

What I said was "How is it that my body doesn't turn noticeably on my CofG when I breathe? My WHOLE body does rise and sink a few inches, and that's only IF I breathe really slowly, and try to completely inflate/deflate my lungs with each inhale/exhale. And how come that I don't have to keep finning?" OK, that was an understatement. Let me just add, to make my statement more accurate, that I will keep rising until I start exhaling, and keep sinking until I start inhaling (with a few seconds delay of course).

Try it for yourself. The next time you're diving, stop at say, 33 feet, place yourself horizontally, and cross your legs and fold your hands. Now... Hover there like that for one minute, not changing your depth. Now, deflate your lungs a little and fall to 40 feet. Hold it there for one minute. Then inflate your lungs and go to say, 25 feet. Hold it there for one minute.

I predict that you will not be able to accomplish this task. I suggest that the moment that you cross your legs and fold your hands, your body will take another position other than horizontal. I also suggest that you will not be able to control your depth with slight movements in your lungs as I've suggested.

...But that's not a personal attack... It's simply a theory. If you are able to do the above, then it proves beyond a reasonable doubt that you are properly trimmed and buoyanced.

My hands are folded all of the time and crossing my legs doesn't affect my position. The photo I linked to earlier is of very poor quality but it shows my usual stance in the water (before I had 30 dives, in a 3/2 mm, rental Tusa and 8lbs.), which I believe is impossible to maintain if I didn't have my buoyancy "nailed."

I have not tried your test but I do change depth using my lungs, although on a much smaller scale, maybe within a max range of about 5-10 feet, because I'm used to ascending and descending upright. There may also be some safety concerns. But if I'm able to do it (and I believe I can), it still would not matter what type of bc I'm wearing.

For rec. purposes in a warm water setting, I would say that there was an advantage... I don't know exactly how to quantify it, but it's there... Saaaay... 20% more fun? 30%? I can tell you that my SAC is around .50 cft/min for a "normal" working dive... And that I typically get 20% or more bottom time than the other "typical" divers I've seen. Does that satisfy your question?

How can you attribute your 20% improvement solely on your change to a bp/wing set-up? Wouldn't it be more reasonable to consider your entire GUE course (BTW, I honestly enjoyed your narration of your course - IMO you are much better telling stories than doing technical analyses), where your entire configuration was changed, where you learned expert techniques and you became a more efficient and confident diver? Can we not theorize that you will gain nearly, if not the same, improvement given a similar course but using a regular bc?

My last downloaded dive shows a SAC of 0.47 scfm. 59 ft max, 32 ft average, 51 min. 40 sec. We went around a 130-meter long wreck twice.

..."At what cost?" Well... Frankly, the bp/wing doesn't cost any more than the off-the-shelf stuff, although -hh did mention the $200 BC. Unless everyone here is diving the $200 BC, that's not a valid argument.

...The bottom line is that depending on "which" bp/wing and "which" BC you're comparing, and how they were purchased (online, LDS, used, etc.), a true cost analysis is difficult.

I suggest, however, that the costs of both BC's are about the same.

Again I repeat: "Here you can get a decent bc for 8,000 pesos (about $145) and the Halcyon bp/pioneer 27 for 28,000 pesos (about $509)"

"That's an Aquatec, at Nautilus Dive Shop and Sports Center, Pasay Road, Makati City (02)8122848. Very tough bc that's widely used for rentals. I used it many times before I got my own, and it worked well for me. Doesnt look good though, that's why I bought a Seaquest instead. I would NEVER trade a Halcyon, if I had one, for the Aquatec! Zero "cool" points. There's also the Mares Vector Origin (about P9000), and a certain Dacor model (P8,000+) at Scubaworld. Beauchat I think also has a model in this price range, available at Dive Buddies and other dealers. A few years ago the Tusa Liberator (another favorite) sold for only about P6000-7000. I'm not sure how much the newer models cost now but I believe they will be in this range."

You see, the only bc's more expensive than the Halcyon here are some Scubapros. I have yet to check for other available bp/wing setups, though.

You may say that I only speak for the Philippine situation, but believe me when I say that there's a lot of diving going on here (there's ocean everywhere, you're never more than a 2 hour drive away from great dive sites) so you cannot consider us the exception to your generalizations.

 

[Matthew]

A lawyer friend just called asking for advice on what desktop PC's to get for his office. The PCs will be used exclusively for drafting legal documents with a word processor. Shall I advise him to get the newest, fastest Pentium IV? Can anybody perceive a difference in speed between a 500 mhz and a 2.4 ghz machine, when using Microsoft Word? Will a writer given the latter option be more productive, because he has the "right tool?"

 

[SeaJay]

Matthew once bubbled...


I quoted that verbatim from your article. You are contradicting yourself.

No I'm not... And you didn't quote anything from my article. You paraphrased, in your own words... And in doing so, you put words in my mouth.

Please show me a quote where I said that it was impossible to achieve proper trim and buoyancy in a "regular" BC.

It's not hard to do, and it is very common here. Am I seeing things? Incidentally, does "inherently balanced" mean there are no trim issues? This again seems to contradict some of your previous statements.

Not exactly.

I've done my best to explain this to you. If my explanations have not been able to communicate a clear understanding of what I meant by "inherently balanced," then I suggest that you might get a better idea with personal experience than simply taking my word for it.

...Or you can discount my whole article because you cannot understand what I meant. It's up to you - I'm just some guy on the other end of this computer trying to convey his experiences.

Sorry, Seajay. But you keep repeating questions that have already been answered. You even forget (conveniently) your own words. That’s not conducive to a positive debate. Here you go:

I haven't forgotten my own words... And I haven't forgotten that you told me previously of your bp/wing experience.

The reason I asked again was because you weren't very convincing in your answer the first time. Furthermore, your additional questions and comments left me wondering why you didn't already have the answers you were looking for; most people who have had experiences with bp/wings would not complain of "not being able to get into an angled position," or "not being able to float at the surface."

[It] is NOT common [for a diver to scull with his hands/feet.]

Pardon?

That's not what I've seen. Of course, as I suggested to -hh, perhaps your idea of what exactly constitutes "finning" and "sculling" is different from what I consider "finning" and "sculling."

Ask someone to try the exercise of folding their hands, crossing their ankles, and maintaining depth and position in the water column for one minute or more like that. If that can be accomplished, then you're right - there's no "sculling" or "finning" issue there. If they can't... Well... Then some skills problems and possibly some gear configuration issues might be present.

Not just me and my immediate buddies, but a lot of people who dive in similar conditions. And nobody needs more exposure protection/weight.

<shrug> Okay, you win.

I haven't dived with you guys... So I couldn't tell you anything for sure. It was only a suggestion, based on the diving that I consistently see around here, which, incidentally, isn't any different than your own.

I'm not sure why you seem convinced that "your diving" is different than "our diving." Sure, there's probably a few vis differences and salinity differences and gear differences between you and me, and certainly there is between you and other places in the world. But I am amazed that you tend to believe that your diving is somehow "special" or "different." It's simply not.

My point is that there's this vocal minority of people who are saying the same thing that I am... This isn't a conspiracy; you might want to consider what we have to say before discounting it all as, "We're different than you..."

Furthermore, since you have not dived with me, you might want to consider letting go of the myth that I have not dived in many places, in many different environments.

Unfortunately, for a lot of people, all these things don’t come into play when considering the type of diving they are going to do and the conditions they will dive in. The big majority will probably be diving in a 3/2 and a single aluminum 80 all their lives.

Right. And if you reread my post, that's precisely the gear configuration that I dive most often... And let me repeat, "I find a huge advantage to a bp/wing in this gear config."

 

[SeaJay]

Matthew once bubbled...


No, I'm not [adjusted for buoyancy with full lungs]. With a fully deflated bc I need to fully exhale to be able to descend. I know that almost all training agencies teach the "eye-level" float on the surface as the test for buoyancy. But in my AOW course my instructor tested my ability to stay neutral at 15 ft, to ascend very slowly to the surface, or to hold any depth in between. What's the GUE method?

The latter... I'm not sure that I'm understanding what you're saying, however.

The GUE method, the same method that your AOW instructor taught you, gets you effectively the same results; it's simply a matter of how you get them.

MY point was that the lungs are buoyant, and in another post I mentioned that empty to full lungs can have a buoyancy swing of 9lbs or more. Placing a 6lb plate (or in your case, trim weights) can go a long way toward neutralizing the lungs' buoyancy.

If you're looking for a truly balanced rig, then you're going to have to counteract the lungs, or else end up with a "head up" tendency. 6lbs is a nice, even estimate, as the lungs typically rotate somewhere around 6 lbs of buoyancy depending on whether they've got a little or a lot of air in them.

I asked the "shoot up" question as a reaction to what I believe are exaggerations of the effects of forces affecting buoyancy/trim.

Well, in the future, I believe that our conversation would be better without "baited questions." If you'd like to make a point, then feel free to do so.

Did your "baited" ("shoot up") question achieve your desired results?

What I said was "How is it that my body doesn't turn noticeably on my CofG when I breathe? My WHOLE body does rise and sink a few inches, and that's only IF I breathe really slowly, and try to completely inflate/deflate my lungs with each inhale/exhale.

Well, it's got to do with moment arm stuff... Torque and leverage... I'm sure that -hh can give you a scientific explanation.

Believe me, the torque is there... It's just that you apparently aren't sensitive to it. I suggest that this is the case because the forces at work aren't great, and the moment arm isn't long. I believe that you are able to counteract them easily with body movements... So you don't even notice them.

Try the exercise that I mentioned - crossed hands and ankles, horizontal body position and the same depth - for one minute or more. That will show you plainly whether you are properly balanced or not. If you tend to roll over onto your back or go into a "head up" position, or can't maintain depth at all, then there is an issue... Which you are overcoming by sculling, finning, or other body movement.

...And if you're okay with that, then fine. Some of us aren't, as we realize that extra effort equals extra gas consumption - not to mention a problem when diving in really silty or fragile environments.

My hands are folded all of the time and crossing my legs doesn't affect my position. The photo I linked to earlier is of very poor quality but it shows my usual stance in the water (before I had 30 dives, in a 3/2 mm, rental Tusa and 8lbs.), which I believe is impossible to maintain if I didn't have my buoyancy "nailed."

I don't know what to tell you... Perhaps it isn't an issue for you. Perhaps you're different than what so many other people are finding. Perhaps your water has some sort of magical "horizontal" formula in it.

Or, perhaps you've developed the skill set or trimmed yourself out properly. I have never seen you dive, and I couldn't tell you if you have the issue or not.

I'm not exactly sure what you're trying to say... Are you trying to argue with me that you don't have any trim issues? Heck, you win. How am I supposed to know if you have trim issues or not?

Are you trying to argue with me that you don't need a bp/wing to get horizontal? I never claimed otherwise; that is, I agree... Of course you can get horizontal with a "regular" BC.

Are you trying to argue with me that it takes a "tuned" gear configuration to get horizontally trimmed? I don't see how you could argue that - if you're horizontal, then obviously you've developed the trim; which means that you'd be very aware of it, and probably agree with what I was saying. I can't imagine you're trying to take a position that you don't need to be trimmed, or that you don't need to pay any attention to it.

I have not tried your test but I do change depth using my lungs, although on a much smaller scale, maybe within a max range of about 5-10 feet, because I'm used to ascending and descending upright.

Well... Give the test a shot and tell us your results. You may be perfectly trimmed... I couldn't tell you.

Have you debated the horizontal ascent/descent vs. the vertical ascent/descent before? IMHO, there's lots of advantages to the horizontal type...

There may also be some safety concerns. But if I'm able to do it (and I believe I can), it still would not matter what type of bc I'm wearing.

I've done the test lots of times, and I don't exactly agree with you.

While it's true that the BC doesn't really matter to me, the BC's trim and balance does - so I prefer one that's trimmed and balanced. I find better trim and balance in a BC that has a metal plate over my lungs.

...But I'm open to suggestions. I've tried many BC's with many different configurations, but haven't yet found one that has superior trim characteristics to a bp/wing.

IMO you are much better telling stories than doing technical analyses),

Hahahahaaaa!!! Thanks, I guess. I'll have to keep that in mind.