Matthew once bubbled...
I am not talking of trim problems. I am contesting your often repeated statement that "jacket-style BC's do not allow a diver to easily stay in this position without constantly swimming or "sculling" with the hands and feet."
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 regularly see this being proven wrong, Seajay, by perhaps more than a thousand divers to date. That includes myself when I only had about 20+ dives, wearing a rental Tusa Imprex bc, 3/2 mm wetsuit, 8 lbs. on the waist, no trim weights anywhere. And I don't fin to keep my position.
...And I hear that regularly as well, by divers who simply don't realize that they do it. The only way to demonstrate this is to take someone out and dive with them, which you and I could not possibly do because of distance.
...I'm not saying that YOU don't have good buoyancy and trim. Frankly, I've never seen you dive, so you very well could. It's just not what I've consistently seen, even from those who claim to have thier trim and buoyancy nailed.
Remember, I, too, thought that my trim and buoyancy were nailed until I saw for myself exactly what "nailed" meant.
Let me repeat what I said a few posts back since your memory doesnt seem to go that far back:
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.
"Let me point out that problems in maintaining UW position/balance is not always a trim problem. It rarely is, especially in a country like the Philippines where almost all diving is done with thin wetsuits, single aluminum 80 tanks and very little weight. It is usually just a newbie problem (usually due to wearing too much weight and consequently, having too much air in the bc thus pushing the diver into a vertical position) which never fails to resolve after gaining a few more dives, especially with instructor intervention. It is the resolution of problems like this that result to significant improvements in air consumption. xxx
I don't believe its even an issue since here, divers using trim weights seem to be the exception. I have never seen ankle weights on tank valves. Some, including myself, bother with the placement of weights on the belt and nothing else. But I assure you that we can effortlessly maintain a horizontal position or any position we desire."
Fair enough. I've never dived the Phillippines... Although I'm convinced that their water is no different from ours.
FYI, I've spent quite a bit of time in tropical waters; I don't do cold, and I don't do dry. My typical exposure protection is a 3/2 O'Neill one-piece.
...And I'm not alone. Many of us who dive this configuration have found an advantage to a bp/wing, and/or the trim offered by a device that gets some of the weight off of your hips and onto your back.
Have you ever dived one?
I can tell you that I have dived one. I own one, in fact. Furthermore, I've dived many different BC's, including the "cheap Tusa" that you quote.
Imagine, Seajay, a diver in a 45 degree angle. What would happen if he sculls with the hands? Would he achieve a horizontal position? NO. Would sculling push his upper body/head UPward? YES. What would happen if he sculls with his feet? Would he gain a horizontal position? NO. Would he be swimming up? YES.
What then, is a diver in a 45 degree angle, who sculls with his hands and feet, trying to achieve? A horizontal position? NO. Most likely, he is trying to:
1. keep from sinking,
2. maintain his depth, or
3. maintain his 45 degree, head-up position because he is not comfortable in a horizontal position (common among new divers).
Now, would you consider this a trim issue? NO. An equipment configuration issue? NO. A skills/training deficiency? YES.
Hm.
Well, I can certainly see your point... It's logical and clear. I agree that the situation you describe is a skill issue.
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.
The solution? Weights on the tank valve? NO. A bp/wing set-up? NO. Learn bouyancy control? YES! Determine the correct (minimal)amount of weight? YES! Do more dives, gain more confidence and be more relaxed? YES!
Agreed that in the situation you describe, that would be the solution.
Yes, the forces at work aren't that great. That's why there's no need to fin to keep horizontal. Add lots of air to the bc and lots of weight on the belt (hey, those are 2 pounders, 2 on each side) and the increased forces WILL be a big issue. But WHY would I do that? We dive in warm water that very few divers, use more than 12 pounds.
Fair enough. And I agree that if the diver typically wears less than 12 pounds, the forces would not be that great. That wouldn't negate them fully, but that would mean that the "torque" wasn't all that bad.
...Which in my book says that the extra movement required to stay horizontal "wouldn't be that bad," either. It still would not negate it fully, however, and if the diver chooses at some point to dive with more exposure protection and/or more weight, then the issue "WOULD be that bad."
I was wrong in adopting your green/orange dots/arrows. As I said, I was trying to show the distance between the downward pull of the weights and the lift of the bc. And I based the shape of the bc aircell on what I believe is the shape of the majority of modern bc's. I believe the distribution of air was increased under the arms and around the waist in most modern bc designs precisely to minimize the distance we're talking about.
I agree. It's an improvement.
...What I believe would be an even better improvement would be to focus both the weight and the air cell on the diver's back, however... Not at the diver's waist. The reason would be that it's the diver's lungs which are consistently changing in buoyancy and volume. If the weight and buoyancy are brought together at the diver's waist such as you're suggesting, then as the diver inflates/deflates his lungs, it changes both his buoyancy and his trim. If the weight and buoyancy are brought together a little further up (closer to the back) then when the diver inflates/deflates his lungs, it changes his buoyancy only, but does not effect his trim.
It's for this reason why manufacturers have begun to place trim pockets on many "better" off-the-shelf BC's... To more closely emulate what a bp/wing has already, by design.
So you considered the lungs in your illustrations? You may have done so, but it is not apparent.
Of course.
Of course, it's only an educated guess, with some testing behind it... But yes, it's a fairly good representation of where the CofB would be, considering the lungs.
I've been doing this long before I heard of DIR. I learned it by emulating my instructor and other divers. Its flattering to know, though, that the technique is used by the experts.
Yes... You SHOULD be flattered. A horizontal position makes tons of sense on many levels.
I have not done any research. What I say are not theories, but are what I actually see being done around me and by myself.
Okay.
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."
You say you cannot be horizontal in a bc without sculling, finning or trimming, based on three PADI classes, 130 specific "testing" dives, 250 "other" dives, several research books, and a GUE class. I can show it can be done in one (1) dive.
-hh mentioned that the less weight and buoyancy you have, the lower the forces... He said that they could both "go to zero." I agree with that.
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.
For reference, I personally dive with 12 lbs of total ballast in salt water in a 3/2 mil wetsuit, and I can feel the "torque" that a badly trimmed BC offers.
...But I also can accept the notion that that hasn't been your experience. I suggest that you take more variety in your samples, but hey, if it works for you, then fine.
...But I respect that what works for you, works. I have tried other ways, and found other things that work better for me. I believe that if you tried them, you'd agree, but you disagree, without having tried anything else. If you're happy with that, then fine.
You say "do it with a $200 Tusa," and I say, "do it with an old-fashioned backplate." Either way, I agree that "the latest and greatest" isn't usually of benefit to the diver.
