ALISSE - Automatic Liftbag Safety System

[jfc]

Hi everyone,

I woke up tonight at 4am in wonderland with "ALISSE" in my mind. I couldn't sleep until I write this stuff.

Well, ALISSE is what I call an Automatic Liftbag Safety System that could be used while training freediving.

ALISSE is made of a couple of liftbags and bottles of compressed air with a configurable timer countdown.

We could set ALISSE timer to automatically inflate the liftbags after a predefined amount of time. (like Freediver Recovery Vest developed by Terry Maas).

After setting the timer on surface, we drop ALISSE along the rope until it reaches the bottom plate/weight.

Then we do our dive with the usual bodyline attached to the rope and after the predefined time elapsed ALISSE will come up and could bring us to surface in a case of need.

At surface, we just need to empty the liftbags and reset the timer for a new dive.


I think a device like ALISSE as several advantages over a counter-weight system (CWS) or other manual retrieval systems (MRS), such as:

• Transportation: much lighter than CWS
• Configuration: easier to use with the rope than CWS
• Usability: just configure the timer, better than CWS and MRS
• Automatic: it don’t depend on humans to activate as CWS and MRS.
• Safeness: no need to send a heavy weight down as CWS.

Some important factors for such a device to be well accepted by our freediving community would be, i think:

• Pressure Resistance: operation between 100 to 200 meters depth.
• Hydrodynamic: up/down velocity between 1 to 3 meters/second.
• Redudancy: it should have at least two bottles and two liftbags connected to the system, which could also be redundant.
• Autonomie: it should work at least a couple of times without refilling the bottles. (The bottles could be filled/replaced at surface)
• Price: less than 500€.
• Optional accessories: color, backlight, oring for attaching tags, depthmeter, etc…

Imagine ALISSE something like a rugby ball, with a hole in the middle, so that it will always be center with the rope and slide very hydrodynamic. It could be made of two separate parts (each one with a liftbag and bottle) that could be couple together with the rope.


I just leave the following questions:

1. What kind of problems you see with this kind of solution?
2. Is there already any device or similar in the market?
3. Would AIDA or other freediving/apnea federation accept a device like this as a safety standard for competitions and record attempts?

All the best, goodives.


------------------------------
DBS~Freediving
http://www.dbs-freediving.com
Joao Costa
The Freedom of Diving with One Breath

 

[trux]

I think it is not a bad idea, and it certainly deserves some more investingation and testing. The problems I see:

1) Timing may be more critical than at a CB system. CB has relatively constant ascent speed, while a liftbag accelerates on the way up (unless you'd build in some ascent speed control too). A CB system can be released shortly after the diver leaves the bottom plate. At ALISSE you would need to set the trigger to a time time safely long to avoid hitting the ascending diver. That again may be less usefull in case of need.

Also a CB system is triggered from the surface, which on my mind is in fact an advantage, because there may be always unanticipated delays or problems before or during the immersion. It also allows following the diver with a sonar, and releasing the CB when needed, or when it does no more pose a risk to hit the descending (or ascending) diver.

So on my mind, a remote control would be better than a timer.

2) At depths around 100m you would likely need to refill the bottle quite frequently, unless you'd use some sophisticated system that would automatically dose the volume of air going into the lift bag. If you simply open the valve at 100m and let it open till it reaches the surface, the bottle will be empty probably after one or two dives. If you open the valve only for certain defined period of time, you risk malfucntion or insufficient lift.

In general though, I think the idea is good, and has indeed some advantages. What is needed is a prototype, plenty of tests, and probably some improvements. Without being able to demonstrate it successfully live, nobody will tell you whether AIDA would accept it or not.

 

[jfc]

Hi trux,

About your points:

1) I think a liftbag can also have a constant ascend speed with a air escape valve. Although, as you point out, setting the timer is a crucial point.

I also thought of remote control, but i tried to simplify the thing as i think it would be more reliable and cheaper to implement.

2) That's also a great point, will the valve be open until surface or close after an amount of time? I think it could be great to proggrammed the system in those two modes.

By the way, do you see other advantages of such a system instead of a counter-weight and better would buy one if it was already on market?

All the best, goodives.


------------------------------
DBS~Freediving
http://www.dbs-freediving.com
Joao Costa
The Freedom of Diving with One Breath

 

[trux]

Well, a rather big advantage of your system would be that it does not require any tiring manual pulling of a really heavy weight after the use, as it is at a CB system. That's one of the main reasons why a CB is (usually) not used used at every dive, but rather just ready to be activated in case of need. At trainings, and at many competition there is simply not the man power to pull up the weight back after each diver. And a powered lift is rather exceptional. At ALYSSE, it gets activated each time, which is good for safety, though may require bigger spacing of the dives, and frequent changing of the tank, especially at deeper dives.

I'd tell the advantages are as follows:
- compact size, not taking any space on the boat or platform (except of spare tanks)
- activated at each dive
- no manual lifting needed
- no second descent line, which means a) no risk of injury by the descending weight; b) no risk of entangling the two lines (as it happened for example at the accident of Loïc Leferme); and c) more space for safeties, photographers, judges, and onlookers

Disadvantages:
- frequent tank exchange may be needed
- additional delays for checking, programming, and sinking the system before each dive; even longer delays at tank exchange
- more complex than a CB system (it involves battery, electronics, pressure valve, pressure tank, weight, liftbag,...), hence bigger chance of failure
- likely a higher cost than a CB system
- the huge volume of air released underneath the freediver may hinder his ascent - the bubbles may create turbulence, or change the fluidity of his ascent, they can also disturb and disorientate the diver. It can also hinder the safety divers.
- a risk of entangling - the base plate would have to be safely above the entire system, otherwise there is a huge risk freediver's lanyard could get be trapped somewhere
- unlike at a CB system, there is no way to delay, slow down, or interrupt the lift, once it is programmed
- unlike at a CB, there is no way to help manually or speed up in case of need, or in case of dysfunction

Well, that's just a quick list of things that came on my mind in this very moment, but there are certainly many others that I forgot, or simply did not think of.

If you plan selling such system commercially, then it may be rather problematic, and involve unacceptable legal liability. For selling it legally, you would have to pass incredible bureaucratic barriers, and fulfill many standards and homologations. Similarly as in the case of Terry's safety vest, it would take years and hundreds of thousands of Euros to accomplish, and would raise the price many folds. So the only possibility is selling it illegally, which bears even a bigger risk in case of an accident; and the question is whether the potential number of sold devices will pay back the investment.

 

[Jouskari]

I think the best way to increase deep safety at the moment is to put an on-line surface to bottom camera either on a separate line or then thru the competitionline + a CB or Manual recovery system. These camera systems are already commersialy aviailable and proffessionals has used them for years. Today they also provide HD level picture that would also help with judging.

Benefits of this addition:

Immidiate respons to any indication of trouble at the bottom plate (diver confusion or BO at depth or ropes floating around etc.)

Better level of judging as picture quality can be assured all the time.

Readily available and proven concept by proffesionals

Cons:

Prices are 2500 € -> (but perhaps sponsoring could be an option here)