Interesting approach to automatic Buoyancy at DEMA

[tridacna]

Aviad Cahana, CEO Avelo, will be teaching the courses Sept 13-17. I'm sorry I could not do those dates.

They have a presence at DEMA. And they’re doing a seminar.

 

[iliketopetsharks]

After reading a lot on this board, i finally registered for the purpose of venting about this contraption...(pun intended)

It just seems inherently unsafe:
Basically "inverting" the way buoyancy control works (bcd inflates to change the density of the diver as a whole, "avelo" changes the mass) seems interesting.
Ditching the weights and utilizing seawater as ballast, like a submarine, surely sounds cool.

But guess what: a submarine has several independent ballast and trim chambers with dozens of fail-safes. And even if everything fails, it can stay underwater for months by generating oxygen through electrolysis, a diver can't.

How long does it take to purge all of the ballast water? 60 secs? Through a single tiny solenoid?
How long does it take a diver to get rid of his/her lead? 2-3 secs, it's one of the first things you learn

Also: seawater, possibly contaminated with sand or other particles, and high-pressure pumps, solenoids and a flexible membrane rubbing against a carbon fibre shell sounds like a recipe for disaster...
Sure, bcds, regulators and drysuits have a lot of valves too, but they only regulate the flow of perfectly clean and dry air/breathing gas, not nasty seawater...

Don't get me wrong: innovation and new technologies are great, IF the benefits outweigh the risks and costs. Which is not the case with that thing IMO.

Oh and saying; "horseshoe inflators evolved to jackets, which evolved to wings, who knows what comes next?" is not well thought out. The shape changed, but the working principle stayed the same: a bag filled with air. There are reasons why certain things don't change: because they just work.

 

[iliketopetsharks]

And like many others said before: it's a technological overkill solution to a skill problem: IF you're properly weighted, maintaining neutral buoyancy isn't that difficult.
I think scuba diving is a privilege, and therefore you should learn these skills before wreaking havoc on reefs...

 

[lowwall]

How long does it take to purge all of the ballast water? 60 secs? Through a single tiny solenoid?
How long does it take a diver to get rid of his/her lead? 2-3 secs, it's one of the first things you learn.

I'm dubious about this for a few reasons, but this particular criticism does not appear warranted. The pump is only for adding ballast water. To remove water, you open a valve in the water section of the tank. The air pressure inside the bladder will cause it to expand pushing out the ballast water through the valve.

Even if the ballast valve somehow fails closed, the diver is left neutral, not overweight. Maybe not ideal on the surface, but it does come with an SMB for that issue.

 

[inquis]

bcd inflates to change the density of the diver as a whole, "avelo" changes the mass

They both change density (ratio of mass to volume). BCD changes volume, and Avelo changes mass.

How long does it take to purge all of the ballast water? 60 secs?

I expect a purge is very quick with a quarter ton (or more) per square inch of pressure pushing the water out.

 

[iliketopetsharks]

I'm dubious about this for a few reasons, but this particular criticism does not appear warranted. The pump is only for adding ballast water. To remove water, you open a valve in the water section of the tank. The air pressure inside the bladder will cause it to expand pushing out the ballast water through the valve.

Even if the ballast valve somehow fails closed, the diver is left neutral, not overweight. Maybe not ideal on the surface, but it does come with an SMB for that issue.

Yes, purging is mechanical, but still: achieving positive buoyancy is slower than with a BCD.
If you ditch your lead, you should be pretty much neutrally buoyant too, and with a BCD, an emergency buoyant ascent is very simple and a basic skill.

The FAQ on the Avelo website is a bit strange, here's a direct quote:
"BCDs can (and do) tear"

What?? I mean, yes, they CAN, but when's the last time that happened? BCDs aren't made out of old chewing gums!
Also that's why inflating your BCD until the safety valve releases is part of every pre-dive check...

 

[inquis]

Tearing is not the only way a BC can be rendered inoperative.

I'm also pretty sure lead will be required for anything more than a 3mm wetsuit -- the range of compensation isn't terribly large. (ETA: in which case, dropping would be an option.)

 

[iliketopetsharks]

Tearing is not the only way a BC can be rendered inoperative. I'm also pretty sure lead will be required for anything more than a 3mm wetsuit -- the range of compensation isn't terribly large.

Yes, but for the very, very, very rare case your BCD completely fails, you can ditch your lead and become neutrally or slightly positively (cylinder) buoyant. And yeah, in the end you probably still need lead.

They both change density (ratio of mass to volume). BCD changes volume, and Avelo changes mass.

I expect a purge is very quick with a quarter ton (or more) per square inch of pressure pushing the water out.

You're absolutely correct, so yes, BCDs control volume, Avelo mass.

That's what's fishy: i can't find any info on how long it takes to purge all the ballast on their website... sus!

 

[inquis]

for the very, very, very rare case your BCD completely fails, you can ditch your lead and become neutrally or slightly positively (cylinder) buoyant

The last time my BC failed (inflator elbow came off) while diving an AL80 & 3mm wetsuit, I became positively buoyant by taking a breath. Being properly weighted is a useful thing. Hopefully the Avelo training will incorporate that concept.

 

[L13]

That's what's fishy: i can't find any info on how long it takes to purge all the ballast on their website... sus!

If you are in any way close to neutral, there is no need to purge all the ballast. Just a little makes you positive.

In the type of diving it is designed for (single tank, no BC, no dry suit), there is no sudden loss of buoyancy that need a sudden loss of weight.

The main risk is actually a sudden loss of weight or the ability to add weight if the water valve or pump fails. and corking to the surface.

In normal operation buoyancy due to breathing down tanks or wet suit decompression occurs slow enough for the pump, and there are no sudden buoyancy adds other than accidentally dropped weights.

I actually like its design, it just isn't useful for the type of diving I do (dry suit, side mount, etc.). For warm water single tank diving, it sounds great.