Technical Bcd question

[aquanuts...]

It's not a matter of questioning things, its a matter of trim. If you are trimed correctly in BP or jacket, they will both float you face down. That is what trim does, it makes you horizontal in the water. When on the surface with a BP, you learn to limit the gas in the bc.

 

[Luc Dupas]

It's not a matter of questioning things, its a matter of trim. If you are trimed correctly in BP or jacket, they will both float you face down. That is what trim does, it makes you horizontal in the water. When on the surface with a BP, you learn to limit the gas in the bc.

Great if it would be that simple!
Indeed, if you're properly trimmed you're floating horizontally underwater.
But at the surface, with your BCD/wing inflated, things might/will be different! If you're floating horizontally at the surface, with a BCD your (heavy) tank will be out of the water and since this tank is not supported anymore by the water (Archimedes Law) your inflated BCD where the inflated bladder is still in the water will ensure you rotate such that your tank is under the water and the inflated bladder/volume is at the surface... so it automatically will ensure that eventually you'll be on your back, or at least not face down in the water.
With an inflated wing, at the surface, both flaps of your wing will be at the surface at both sides of your tank(s) and as such will support your tank thereby preventing that you automatically rotate to your back.
This is where the main difference is between an inflated BCD and an inflated wing... at the surface...

 

[cool_hardware52]

It's not a matter of questioning things, its a matter of trim. If you are trimed correctly in BP or jacket, they will both float you face down. That is what trim does, it makes you horizontal in the water. When on the surface with a BP, you learn to limit the gas in the bc.

I agree. Trim and total weighting. If you are properly weighted in BP&W you only need a very small amount of gas in the wing. This gas will be behind the divers head and shoulders, not down around his waist. How can a small volume of gas up high in a wing force you forward?

If you prefer to dive grossly overweighted, and feel the need to have your bellybutton out of the water at the surface stick with a wrap around jacket........


Tobin

 

[jeffrey-c]

I feel that many of the face up/face down/jacket/BPW arguements are hypothetical and not truly reflective of the reality. Although I'll admit my experience and data set was limited, I've experimented a bit with surface floating in several different jacket BCs as well as a BP/W, and each would tend to slowly put me into a face down position if I was trimmed at anything evenly remotely close to a proper balance at depth. Try this experiment: at the surface, inflate your BC and then go absolutely motionless. No finning, no wiggling hands, nothing - be totally unconsious (this is harder to do than you think). Becoming truly "inert" on the surface without any correction whatsoever, I found that each BC I've tried would eventually roll me into a face down position.

It's a fairly simple matter of physics when one looks at the centers of buoyancy and center of mass for each contributor on a diver (tank, BC, exposure suit, etc.). Jacket BCs may move some of the center of buoyancy forward of a plane defined by the diver's back, but most still seem to have much of their lift coming from the chamber which is still behind that plane.

 

[wallacm]

I agree with the Sherwood, its a great Open Water rig, but once you start doing any more technical diving you will definetly want the BP/W. Once you use it you will never want to dive a jacket again. As far as Halcyon, they are a great company, I have used a BP/W from them a couple times and loved it, but I definetly would look into both Dive Rite and OMS and also Zeagle. All of those companies and I'm sure a few others all make BP/W's. Some people like to mix all of these companies together into their own BP/W, but as far as prices they all seem to be very comparable, usually looking at about 500 bucks or so for a full setup.

 

[cummings66]

with a BCD your (heavy) tank will be out of the water and since this tank is not supported anymore by the water (Archimedes Law) your inflated BCD where the inflated bladder is still in the water will ensure you rotate such that your

No matter what config you choose to dive, your tank will not be out of the water. At most you may find a few inches of it out of the water, the bulk will remain below the water.

No BCD is designed to float you face up, in fact read the manuals and you'll see disclaimers stating that it's not a pfd and not to use it as such. If you end up face up it's luck, you will not be able to do it reliably.

In any event, no BCD is to be used as a PFD, it's not going to work well enough to save your life.

A BP/W is a BCD as is a jacket style. BCD stands for what? As my 4 year old would say, yup, you got it.

 

[hvulin]

Maybe something to try out in a real life situation...
Let's assume you're floating in the water at -5m, doing your safety stop, nicely neutrally trimmed lying horizontally on your belly, face down. Suddenly you feel dizzy, you start losing conscience but you still manage to hit the inflator button to inflate your wing and then the light goes out... you're still there in the water, horizontally, limb, you're still breathing, you don't do anything and your inflated wing will bring you to the surface... You yourself don't do anything, you just let it happen...
Will, at the surface, your inflated wing automatically turn you in a face-out-of-the-water position? Give it a try... you'll be suprised... :14:

if you give it just a puff of air you'll reach the surface and the weight of your body will turn you quite right... if you blow it full somone will have to turn you...

 

[Luc Dupas]

No BCD is designed to float you face up, in fact read the manuals and you'll see disclaimers stating that it's not a pfd and not to use it as such. If you end up face up it's luck, you will not be able to do it reliably

Actually, the good old Scubapro Master Jacket is recognised as a safety/rescue device...

 

[ZzzKing]

If you prefer to dive grossly overweighted, and feel the need to have your bellybutton out of the water at the surface stick with a wrap around jacket........

Come on Tobin. Don't hold back. Tell us what you REALLY think.

 

[cummings66]

I stand corrected, the ScubaPro Master Jacket is recognized as a rescue device.