What are your thoughts about our constant buoyancy BCD ?

[drbill]

As a working videographer, I don't see any benefit to this system. I overweight myself intentionally and frequently purge my wing so I can be stable on the bottom and film. With the surge on last night's dive I would probably have needed an extra 50 lbs to be stable!

 

[NAM001]

The difference is ths you can vary the buoyancy. His bladder may change 5% from depth change wherer the capped pvc will change none. The bcd would change perhaps 3-400%. If teh thing changes volumn when 200psi or greater is applied then the 60psi change from 130' to the surface will not result in a change. Therefore the volumn is constant with its lift factor. If your reg is 25 heavy. then you use this thing for comping of say 20# and use your wing for the rest. 5# of lift may shange 10 percent at depth... thats only 1/2 #. Much easier to control than the 10% change in a wing with 25 lift in it. I used the capped pvc to counter the no air buoyancy of gear The opvc tubes were replacements for thicker wetsuit buoyancy.

It still doesn't make any sense. How is this different from diving with a 1' section of PVC pipe with endcaps glued on each end?

All I have so far is that if you become negative when you descend, this thing fixes it somehow, and then doesn't change buoyancy, even though your wetsuit will and your tank will, but somehow you're still neutral.

It's either smoke and mirrors or the OP needs to figure out how to explain it better.

---------- Post added August 22nd, 2014 at 05:25 PM ----------

You cant alter the lift on a sealed piece of pvc.

I'm really confused by this.

Your statement: "Since it does not change volume with ascent, the diver remains neutral as he/she rises" doesn't seem to make any sense.

If your BC doesn't change volume on ascent, how is it different than diving with a sealed piece of PVC pipe, or even better, not being overweighted in the first place?

flots.

 

[eelnoraa]

If it is the way you explain it, I actually think it is a good idea if the execution is good and reliable. Basically a BC that does NOT change its lift (or volumn) with depth. But diver can still change its lift (or volumn) at will, ie for compensating suit buoyancy or gas weight. Now I want to see the implementation.

 

[NAM001]

The static lift is tha same as static weight. no one thinks a thing about putting on 10# of lead. However no one thinks about putting on 30# of static lift till the need for it is through. The situation that caused me to play sith this was a sive on a wreck. starting at the keel on the port side and going to the keel on thestb side by going over the ship. up 40 ft and back down 40 ft. this mans contraption would allow you to do this without havng to vent or repressurize the bc or wing to the extent one would have to do this with ont his device. You set the static amount of lift at depth and then you run with say 20% of the air in the wing as you would otherwise have to do. depth changes have n much less effect . You dont use this to counter the effects of air expansion of wet suit compression or sir consumption per se' ,,, it is to counter the changing effects of the air in the bcd or wing because of depth effects. . The gas in the bcd still expands and compresses the same way but there is much less of it to happen to,,, reducing the blow and venting of the wing thus making the buoyancy more consistant. if the device has 8# lift at 100 ft it also has 8# lift at safety stop, no venting on the way up. When you use this without teh aditional bcd or wing. you find that as you assend the lift ramains constant and only changes from suit squeeze. The bubble in the wing is not there to get bigger and ascelerate the ascent rate. So imagine you have one of these. you junp in set it for neutral with full gear and and air. You just go down,,, you dont have to keep adjusting the system cause the lift is static and does not suffer compresson from deeper depths.

Yes there are a lot of things to learn and work out with this,,, expecially if the DIR arena gets involved. Habits and traditions are hard to break. If for instance his idea was to have a bladder installed inside a dry suit to use in event of a suit flood. We all would be having the same type of discussions. I wonder how much opposition the horse colar folks had when the bcd came out???? His concepts are good however like many have said,,, there may be too many failure points to be practical,,, given the level of care and maintenance by most divers to their gear.

If it is the way you explain it, I actually think it is a good idea if the execution is good and reliable. Basically a BC that does NOT change its lift (or volumn) with depth. But diver can still change its lift (or volumn) at will, ie for compensating suit buoyancy or gas weight. Now I want to see the implementation.

 

[flots am]

The difference is ths you can vary the buoyancy. His bladder may change 5% from depth change wherer the capped pvc will change none. The bcd would change perhaps 3-400%. If teh thing changes volumn when 200psi or greater is applied then the 60psi change from 130' to the surface will not result in a change. Therefore the volumn is constant with its lift factor. If your reg is 25 heavy. then you use this thing for comping of say 20# and use your wing for the rest. 5# of lift may shange 10 percent at depth... thats only 1/2 #. Much easier to control than the 10% change in a wing with 25 lift in it. I used the capped pvc to counter the no air buoyancy of gear The opvc tubes were replacements for thicker wetsuit buoyancy.

It's not compensating for wetsuit compression, since wetsuits can vary in buoyancy from "a lot" to "almost nothing" as you descend.

It's not compensating for air used from the tank, since that requires periodic adjustments as the tank(s) become more buoyant.

The only thing I've been able to figure out so far is that it's to compensate for diving overweighted, which is a planning issue, not something that should require another gadget.

Is there something I'm missing here?

You dont use this to counter the effects of air expansion of wet suit compression or sir consumption per se' ,,, it is to counter the changing effects of the air in the bcd or wing because of depth effects.

There is very little change in air volume or buoyancy in the BC or wetsuit at normal recreational depths or below. The majority of change occurs shallower. And even if it did, how is it better than just adding or venting a little air?

flots.

 

[TN-Steve]

Is this going to be packaged with the Dive-Guard?

 

[NAM001]

flots i agree with you, this is not an auto pilot device. its an adjustable static buoyancy device.

I see it in use as combination with the wing or bcd. the unit for a amount of static buoyancy and the wing for the dymanic adjustments. Under current phylosophy you are not missing anything. And i see this having a purpose of suplimenting or sharing the wing duties to minimise the air volumn in the wing that can (IE) change with depth.

With your socond comment . yuou are correct again nowever teh greater change at shallower depths would not be felt to the same degree with the static lift. instead of having 15# of variable lift you sould have say 10 fixed and 5 variable. Here is perhaps a more visual example. you dive in both fresh and salt water. you would rig for salt water and take the same rig in fresh no plate or weighting changes you just inflate the fixed buoyancy to comp for salt to fresh change. Go to a more buoyant suit.,,, deflate the static lift a bit. This now allows you to use say a 10-15# wing (smaller) resulting in a more distributed air bubble in the wing and allowing to hold trim better as result of a less moving bubble.

It's not compensating for wetsuit compression, since wetsuits can vary in buoyancy from "a lot" to "almost nothing" as you descend.

It's not compensating for air used from the tank, since that requires periodic adjustments as the tank(s) become more buoyant.

The only thing I've been able to figure out so far is that it's to compensate for diving overweighted, which is a planning issue, not something that should require another gadget.

Is there something I'm missing here?



There is very little change in air volume or buoyancy in the BC or wetsuit at normal recreational depths or below. The majority of change occurs shallower. And even if it did, how is it better than just adding or venting a little air?

flots.

 

[kr2y5]

We have not yet commercialized this technology and would like to get feedback from divers before doing so.

Well, there are no pictures of a real physical unit anywhere to be found on the website... building an actual prototype can go a long way towards commercializing a new technology.

 

[KeithG]

A... I overweight myself intentionally and frequently purge my wing so I can be stable on the bottom and film. With the surge on last night's dive I would probably have needed an extra 50 lbs to be stable!

Just to be clear, you meant 50 LBs of negative weight...
I personally possess the 50Lbs, but it is primarily comprised of bioprene. Mostly very buoyant material. Not all that advantageous for photo ops.

I thought this thread could use a small level of additional entertainment as many of the contributors are being way too serious.

Discuss...

 

[Storker]

this is not an auto pilot device. its an adjustable static buoyancy device.

I see it in use as combination with the wing or bcd. the unit for a amount of static buoyancy and the wing for the dymanic adjustments.

In that case, I personally would have absolutely no need for it. I need a bit of air in my wing at the start of my dive, but towards the end - especially if it's a long dive and I'm approaching 50 bar tank pressure - I have absolutely no air in my wing, and I'm pretty shrink-wrapped inside my DS.

What use is a fixed buoyancy device then? And if I change undergarments, DS type or tank size, I'll just check my log and adjust my weighting accordingly.