Constant volume or regulated BCs?

[fledder]

Hi all, I'm curious about what attempts have been made to reduce or eliminate the change in air buoyancy as a function of depth.

I've found just about all there is to find on the internet about the Dacor Nautilus CVS, which seems to be the only example of such a thing. Basically, it works similar to a submarine's ballast tank: a rigid tank that gives about 60 lbs (!) of buoyancy when empty, and which the diver floods with water to decrease its buoyancy when diving. It also has a regulator to keep the air space in the tank pressurized to nearly the same pressure as the outside environment. While it's a neat idea, it looks cumbersome and seems to have its own set of problems. Not surprisingly, there are very few left and almost none in use.

There was another thread here about someone who had tried to make a similarly depth-invariant buoyancy system and was soliciting feedback in 2014; he certainly got a lot of feedback, mostly negative. He didn't seem to explain it very well at first, so it's hard to say what the technology was, especially since the website he gave seems to be gone. From what I can tell it was pretty complex, with membranes and valves and all sorts of components.

I was even curious enough to dive into some extraordinarily dry patents on the subject. There's one from 1973 that looks neat, but I can find no other evidence of its existence. The Dacor Nautilus shows up there, as well as the other person from the thread in 2014, and a few others, but I found precious little else on what seems like a reasonable problem to solve.

Is it just a problem nobody has been able to solve economically, or is it a problem that doesn't need solving? I can hear it already... "gear solution to a training problem"... but I remember a similar attitude towards computers when I started diving, which has since softened or even reversed.

So has anyone ever heard of such a thing beyond the examples I've already found?

 

[msinc]

I have never heard or seen anything like it. I am relatively new although I have always been interested in diving gear and how it works and have followed diving equipment for quite some time now. Interesting, and I am sure there are some divers out there that would like to try it. Me personally, I guess I am lucky in that I seem to have caught on to buoyancy adjustment pretty quickly. One thing I do that makes it a lot easier for me to "feel" what is going on is to not try to get to the bottom asap, like some divers do. I find that if I go down slow and make a lot of little corrections I have way less trouble adjusting my buoyancy and getting it right on the money.
It seems like where many divers have trouble is when it is time to come back up...what I see is they tend to get going too fast and then over correct to slow down and end up sinking again. I am sure something that would positively help stop this would be a welcome addition to some divers gear bag.

 

[tursiops]

It might be helpful to a very few divers; diving more and getting some decent instruction and practice would likely be even more helpful to that small market.

 

[Bob DBF]

In my case, using a 7mm wetsuit, I would have to correct for buoyancy change in the wetsuit whether I was using a rigid BC or my wing, so there would be no advantage. Also 60# of lift is overkill for my gear and dives.

I could see limited use for those not using thermal protection but as stated above, 60# of lift is a lot, and a rigid unit would take up more room than a wing of the same buoyancy for anything less than maximum lift.


Bob

 

[boulderjohn]

I see two obstacles for this to be successful:

1. It is pretty darn easy to adjust the buoyancy of a conventional BCD/wing, so there is no great need driving innovation.
2. Buoyancy is NOT constant. As you dive, you eliminate air, which changes your weight. Your constant buoyancy system would have to be adjustable, which makes it no different from a conventional BCD.

 

[fledder]

I see two obstacles for this to be successful:

1. It is pretty darn easy to adjust the buoyancy of a conventional BCD/wing, so there is no great need driving innovation.
2. Buoyancy is NOT constant. As you dive, you eliminate air, which changes your weight. Your constant buoyancy system would have to be adjustable, which makes it no different from a conventional BCD.

Fair enough. I felt like it was an obvious enough problem and that there must be more than just the Dacor Nautilus, but it's starting to look like that was the only one that ever tried.

 

[Bierstadt]

Interesting. I would liken this to the race to create the first airplanes, which were initial failures in large part due to the belief that airplanes needed to be inherently sable to avoid crashing. Enter the Wright brothers, who accepted inherent instability and the need to actually fly the aircraft in exchange for far less weight and complexity. I can see the value in constant volume tanks, but not for a scuba diver. Too much complexity, too much additional weight and drag and expense for the benefits it has over bladders and lungs. I am more surprised that a commercial model was built and sold than I am that there has only been one. Still, neat find.

 

[Eric Sedletzky]

With all the computer technology out there in this day and age, automatic neutral buoyancy wouldn’t be that hard to come up with. It would be like cruise control on your BC. Or a dial-a-depth, you turn a knob for the depth you want and the BC automatically does whatever it has to to get you there and then keep you there, until you dial another depth and then the BC gets to work again.
The problem is it would be very expensive, potentially complex, possibly difficult to maintain, might need to be serviced fairly often, the computer and servos and other parts could be sensitive to shock and rough handling, might be hard to calibrate, etc.
Also, the diving community is very small, and I don’t think there would be enough overall sales to support the product and pay for all the R&D.

BC’s are a very simple thing and are easy to use. As they are now they don’t really require much in the way of service except for good rinsing after diving and maybe a inflator lube or a few O-rings once every decade or so.
Also, an automatic BC still wouldn’t decide how much weight a diver carries, the diver does. An automatic BC might have a lot of difficulty trying to keep up with the wild weight swings of a grossly overweighted diver. I would be more concerned about the current epidemic and culture of overweighting in the dive industry that seems to be currently going on.
Once that problem is resolved then the BC part of diving is a breeze. An automatic BC at that point would just be a solution looking for a problem.

 

[RainPilot]

This is the one I remember reading abut, seems like it has gone away...

SUBA

 

[fledder]

This is the one I remember reading abut, seems like it has gone away...

SUBA

Very interesting, thanks! I hadn't found that one in the wild. It's interesting to me that they tried to go directly to an automatic depth controller instead of just adjustable maintained buoyancy. It also looks to have been pretty super expensive...