Avelo--I guess there's no need for me to recommend fundies anymore....

[stiebs]

From the FAQ on their website:

The Avelo System’s main component is the Hydrotank, a lean scuba tank with a flexible inner bladder. Compressed air (or another breathing mixture) is stored in the bladder.

 

[wnissen]

From the FAQ on their website:

Wild. They must have some way to reduce the relative pressure to something reasonable for a flexible membrane. Right? Sounds like a great idea, if they can make it as reliable as the conventional alternative.

 

[lowwall]

I did a patent search and didn't come up with anything for Avelo. Its founder, Aviad Cahana, has patents in the field of chemistry, but nothing related to this.

 

[lowwall]

From the FAQ on their website:

It looks like I was wrong. They have a short YouTube intro up and it calls it a bladder.

Still wondering about that second dive. But I guess the idea would be for destination ops to supply these as rentals.

 

[elan]

....i bet that system is really easy to have hydro'd...... once

Fixed that for you

 

[BRT]

I suspect the animation was trying to convey the idea of water entering the outer shell rather than being an accurate rendition of what is occurring within the system.

It's hard to imagine a membrane that can live in saltwater for years, be flexible enough to accommodate several inches of movement and be capable of withstanding 300 bar. That's roughly 100 tons of pressure over an area the size of the base of a scuba tank. A thick enough sheet of Dyneema cloth could theoretically handle the pressure, but how would you go about bonding it to the stub tank (or tank valve)?

Doesn't have to be that strong. Same pressure inside and out. Hydraulic accumulators do it all day long for decades.

 

[lowwall]

Doesn't have to be that strong. Same pressure inside and out. Hydraulic accumulators do it all day long for decades.

I'm trying to visualize this. We've got an outer tank wall inside of which is a big bag containing the breathing gas. Between the bag and the wall (or maybe just between the bag and the bottom of the tank) is a ballast space that is initially filled with gas at the same pressure as the bag?

I really don't see how that would work. What happens when you want to descend? You are going to have to replace what could be several liters of gas compressed to 200 to 300 bar in that ballast space with a fluid. If you dump the gas overboard, it will have the same effect as purging off a quarter of an AL80. You obviously can't boost it back into the breathing bag. And can you imagine forcing dirty lake water or seawater at that pressure through a pump? I guess they could pack a couple of liters of hydraulic fluid in the pump housing, but maintenance would not be trivial.

And what if you pick up a kilo of doubloons or your buddy's dropped weight pouch and try to ascend? Are you really going to have to be willing to give up 10% of your remaining breathing gas (1 liter of gas at tank pressure) to regain neutral buoyancy?

All this leads me to think the ballast area must be at ambient pressure. Or rather, ambient at the depth it last had gas added to it.

Anyway, however it works, I'm starting to warm up to the idea of this as a rental for tropical diving. I like a minimalist setup and this is pretty much just a backplate and harness and tank. No need to pack the BP/W and you can leave your inflator hose behind as well. Not sure how a dive shop could afford a bunch of these things, but I guess the company would lease them rather than force a shop to pay upfront.

I'm not so sure it would work for local diving. How many people own just one tank?

 

[mwerle]

I'm trying to visualize this. We've got an outer tank wall inside of which is a big bag containing the breathing gas. Between the bag and the wall (or maybe just between the bag and the bottom of the tank) is a ballast space that is initially filled with gas at the same pressure as the bag?

No, I imagine the bag to be flush against the inside of the tank when it is filled (could be tricky where the valves are). So the tank takes the pressure, not the bag.

Then when water is pumped in, it compresses the bag (raising the pressure beyond the fill pressure). But again, the bag only presses against the tank and water, so again, no huge pressure gradient as far as the bag is concerned.

There would never be high-pressure, let alone breathable, gas outside the bag. Outside the bag is "contaminated space" - that's where the ballast water goes with all the associated gunk.

And what if you pick up a kilo of doubloons or your buddy's dropped weight pouch and try to ascend? Are you really going to have to be willing to give up 10% of your remaining breathing gas (1 liter of gas at tank pressure) to regain neutral buoyancy?

If you're looking to recover items, you'll be taking lift bags along anyway. In the case of ad-hoc weight pickup, yeah, the question does become on how much buoyancy the device can achieve.

EDIT: But to achieve more positive buoyancy, the ballast water is only expelled. Your remaining air expands the bladder again so no loss of breathing gas.

All this leads me to think the ballast area must be at ambient pressure. Or rather, ambient at the depth it last had gas added to it.

Pretty much.

 

[Vicko]

The concept works it's just pump operated bcd with a lot of advertIsment mumbo jumbo. My only question is how do they find space enough to offset the change in bouyancy from wetsuit compression and gas density in the tank while still having enough tank volume to do a nice dive.

 

[Gone for diving]

It is definitely a bladder inside a tank,
As said above, it's a large hydraulic accumulator, the bladder takes no pressure,
there is more pressure/ water pressure squeezing the air bladder smaller,
(there will be an increase of air pressure, and will need a special gauge, / cuft meter to tell actually tank capacity )
Which crams the air smaller which results in less bouyence,

The inner tank is for sure flexible,
if not it will not work,

I am very interested in the pump,!!

Definitely an interesting idea,