What are your thoughts about our constant buoyancy BCD ?

[lmarks]

We have developed a BCD that does not change buoyancy with depth. This prevents runaway ascents and descents. With it you do not have to inflate and deflate the BCD during a dive. It allows the diver to precisely compensate for overweighting and the compensation is fixed regardless of depth. Details are at Home. We have not yet commercialized this technology and would like to get feedback from divers before doing so. Do you think this would be a useful feature ? Are there disadvantages we may not have thought of ?

 

[TracyN]

That's a very novel concept. However it sounds like a gear solution to a skills problem. I'll give you guys props for ingenuity though.

 

[flots am]

We have developed a BCD that does not change buoyancy with depth. This prevents runaway ascents and descents. With it you do not have to inflate and deflate the BCD during a dive. It allows the diver to precisely compensate for overweighting and the compensation is fixed regardless of depth. Details are at Home. We have not yet commercialized this technology and would like to get feedback from divers before doing so. Do you think this would be a useful feature ? Are there disadvantages we may not have thought of ?

Someone invents this every few years, but it has never become popular (or gone into production, as far as I know).

Why would someone want one of these, instead of being properly weighted?

flots.

 

[g1138]

I'm a little confused over the process and explanation.
I think I see a flaw, if you add your high pressure air at depth to compensate for negative buoyancy, that's a certain volume of air that will expand on ascent.
It shouldn't matter if you add air at high pressure or low pressure at depth, because it is the volume of air that gives you your buoyancy characteristics.

Can you explain in more depth how this system solves runaway ascents?
Is your bladder a rigid container?

Will this compensate adequately for wetsuit bouyancy characterisitcs? Say a 3mm with +6lbs buoyancy or a 12mm two piece suit with +30lbs buoyancy?

 

[Dirty-Dog]

As above, I think it's a gear solution to a skills problem. Further...

With the ABCD, the diver experience only a 3 lb increase in lift, which can easily be compensated for by shifting the tidal volume when breathing, something the diver does instinctively.

is utter nonsense. Divers, most especially NEW divers (the market your product is clearly aimed at) most certainly do not adjust their tidal volume instinctively. If anything, the accelerated ascent will lead to the new diver increasing their rate and depth of respiration, increasing the problem. This can be corrected by training and experience, but it will never be an instinct.

 

[raftingtigger]

Very interesting idea, but is useless if there is no high pressure gas available (eg. OOA, LPI failure). Even a tiny leak would render this system useless, which is not the case with a conventional BCD.

 

[lmarks]

The device uses a bladder that does not inflate at all until about 3 atm pressure. It's pressure volume characteristic is such that it changes only about 3 lb in buoyancy from 96 feet to the surface. Thus, it is essentially rigid with constant volume. In answer to your other question, the device will not compensate for changes in buoyancy due to wet suit compression. In actual diving with a 3 mm full suit we found that you can go from 40' to the surface without having to let out air.

---------- Post added August 14th, 2014 at 02:47 PM ----------

I hope this is not utter nonsense after 5 years of development and testing!

You may find it interesting to look at our web site Home where the technology is explained. The buoyancy change with this device during a recreational dive is small enough that the diver can control buoyancy by shifting the tidal volume. Air does not have to be put into the bladder or expelled from the bladder after an initial adjustment.
I think it is is especially useful for technical divers because they often carry equipment that varies in buoyancy, so it is not possible to know how to weight oneself precisely before getting in the water. Th constant buoyancy BCD solves this problem as it is essentially applying "negative weight" which does not vary with depth.

 

[PACKRMAN]

How do you inflate at the surface?

 

[lmarks]

It has a conventional power inflator with which you can inflate the bladder at the surface. Because it runs at higher than ambient pressure, the diver can not inflate it by breathing into. Thus, a low pressure backup system is provided.

---------- Post added August 14th, 2014 at 02:54 PM ----------

Interesting comment and a problem we have given considerable thought to. There are 4 bladders. If any one of them should develop a leak, it becomes sealed off from the other 3 which continue functioning normally.

---------- Post added August 14th, 2014 at 03:02 PM ----------

Good point. But with changes in wetsuits and equipment, one can not always weight oneself accurately before entering the water. With this device you can make an educated guess as to how much weight you should use then add a couple of pounds. Any overweighting can be compensated for by adding a fixed volume of air to the constant buoyancy BCD.

 

[flots am]

The device uses a bladder that does not inflate at all until about 3 atm pressure. It's pressure volume characteristic is such that it changes only about 3 lb in buoyancy from 96 feet to the surface. Thus, it is essentially rigid with constant volume. In answer to your other question, the device will not compensate for changes in buoyancy due to wet suit compression. In actual diving with a 3 mm full suit we found that you can go from 40' to the surface without having to let out air.

You lost me. If it has constant volume, then it has constant buoyancy. That doesn't seem useful.

While it's true that a 3mm suit doesn't change buoyancy much, the world is not just 3mm suits. Many people wear 5 or more, which definitely changes buoyancy.

The device uses a bladder that does not inflate at all until about 3 atm pressure.

The buoyancy (and pressure) change is greatest in the shallower depths. At 3ATM, buoyancy changes are minimal and your device would have no real purpose.

I'm still not certain what this is supposed to do or why and I have read your web page.

flots.