decompression isses

hookah diving systems produce compressed air on the surface and pump it down to the divers. With SCUBA tanks, the air is compressed on the surface while the tank is being filled. Regardless of where or when the air is compressed, it is still compressed air and it is still being breathed at depth. Therefore it is important to know the same risks and gas laws that apply to SCUBA diving also apply to hookah diving. However, generally you won't go much deeper than say 50 feet on hookah so the issue of decompression is moot at that depth

 

Its not the deco-issue of joels post.
I dont think it is working propperly deeper then 15 - 20 feet. The intermediate pressure from the 1st stage should be around 10 bar/ata higher than the surrounding pressure. if its too high your reg usually freefloats, if too low you gotta suck more. Especially if you have an unballanced 1st stage. going to 100 ft with the divesled you have a surrounding pr of 4 ata, so you need an intermediate pressure of 14 ata.
As your first stage is at the surface it only has 10.
As the density increases also 4x you may have on top quite some air-turbulences in a 100+ hose. pls correct me if I am wrong and made a thinking mistake.
cheers

Rhoody

 

When you go to 10 m you must have at least 2 bar at 20 m 3 bar at 30 m 4bar and so on.

So you always get up nitrogin into your tissues, no matter what equipment you use.

Greetings J.diver

 

It does not matter where you get the air from, you will have the same saturation.. Our body is not interestet what is the airsource. The gas we breath will be compressed at depth and the N2 saturation is the same with Scuba and Hookah. Hookah is not extending the max bottom-times of recreational diving.

The reason why we my dive longer is simple that with Hookah you don't run out of air cause we have a endless supply. Most divers run "low on air with a normal (12l/3000cft) Tank before they reach the non-deco-limit. With hookah you don't have to think about you air-consumption even you have long decompression-stops

cheers

Rhoody

 

Air Supply

When using a scuba tank on the surface supplying air to a diver through a 100foot hose my personal experience has shown very little difference than having the tank on your back. Much of this has to do with equipment quality: using quality air hose with 300 psi working pressure, 1200 psi burst pressure, a balanced first stage of good branding, etc.... evens out the playing field breathing wise.

I have also found that even without a pressure guage the same low on air indicators still apply. I know exactly when I have to surface and make a tank change as soon as my intake of air becomes more labored but I have never ever found a situation when I didn't have more than enough air in reserve in the 100 foot of hose itself (even thought the tank was empty) to make it to the surface with air to spare. Remember 100 foot of hose holds alot of air.
I also know how much time I have been underwater and depending on depth I am more cognizant after about an hour under.

 

PhDiver, if I calculate the "lots of reserve air" in a 100 feet long hose with an inner diameter of only a few mm, then I can't be very happy with the amount of 'reserve air' for ending my dive ! Your tank was empty at start of your ascend as you said.
Take 1,5 or 2 liter of volume which your longs will have to 'refill' at each normal breath (some however 'refill' much more volume, so also air !).
That hose contains air with a pressure of about 10 bar (1th stage at surface) at the beginning of your ascend, assuming that the 100 feet hose provided the air to also a dive-depth of 100 feet. But at that beginning you also need more air (still 4 bar waterpressure on your lungs).
Or do you use a much bigger diameter for the hose to your 2nd stage ? :D
The remark of Rhoody seems to me very valid: For most of the used 2nd stage regulator sytems your breating resistance will increase enormously with the fast dropping pressure in the hose between 1th and 2nd stage.
But I think I made a reading mistake and that you are talking about the amount of reserve air in a 100 feet hose when diving at only 30 feet or even less. Am I right ?

 

Reserve air

At 100 feet the hose would be absolutely vertical to the surface and obviously this is not realistic, practical or even possible unless you are sitting on the bottom directly under the sled.. Generally you will be diving around 60 feet and less comfortably in terms of ease of movement. Much of this kind of diving has a common sense approach to it. You keep a watch on your depth and your time. Simple as that as it is with any dive whether with tanks or hookah.

Personally, I have never had any out of air scenarios with hose. With the majority of the dives I have always been able to surface with normalcy with still about 300 to 500psi in the tank. Not to be conceited but after so many years diving I know my air consumption and can stretch a tank beyond that of most all divers. This is also a fact for most all instructors as they have to have excellent air management and can usually stretch a tanks way beyond that of most social divers as well. As for the few times I did run low on air with only the reserve in the hose yes you are correct that scenario occured at about the 30 foot area but there were still plenty of breadths left. You are welcome to try it. I have a couple of sets of 100 foot hose ready to use. You can try it on the surface first. OPen the tank and let the hose fill with air, then close it off and see. Then you can try it at various depths.

 

You are right what my question was about, Roddy, and I agree to the rest of yours post and the others, related to the physics.
Thats why I was asking if I missed something.

@PhDiver, to answer your first question (if divers are interested)
In my opinion this device is something for "DSD" or bubble maker only, even when I strongly doubt PADI - or any other organization - would allow you to do something like a DSD with it.

Beside that I think this device is somehow dangerous. Don't want to be offending to you - but you have been asking for response and by following your argumentation, I have to say it might be not the device itself, more likely its the way you're explained how you're already or would like to handle it.

As a dive operator you can get in big trouble - IMHO. No insurance will pay this - not any insurance your customers might have, nore a private or business insurance you might got.

Profs won't go for it - IMVHO. As a UW-photographer I would go for a rebreather first, before I would like to get wired or "hosed" and of course I wouldn't like to ascend for changing tanks, because I think its unhealthy - beside that, I don't want and it makes no sense to me, staying much longer than 70 minutes underwater. And reaching this 70 minutes is not a problem of how big is the tank, its a problem of the depth or the diveplan. After 75 mins in 15 m you reach deco anyway (does my Suunto divemanger say)

A (girl)friend of mine asked me sometime ago about nitrox: "why I should use nitrox for being able to stay 70 minutes down there, when I start to freeze after 45 minutes?" (5mm) Hm, that are women - they have air much more then you, but gets cold feet. But in no way a bad question.

In a 3mm suite I need usually ~ 2 Kg lead (in asia - 3Kg if the suite is new). One for the suite, two for avoiding the emptied tank will pull me to the surface. In a 3mm I get cold latest after ~ 60 min. Even when I need 2 Kgs less with this device, coz I don't wear a tank, why should I (carry to asia) and wear a more or less uncomfortable, stiff 5 or 7mm just for staying some dozen minutes longer (see some other needs at the bottom), when I need 3 or even 5 Kgs lead more, just for compensate the buoyancy of those suites then?
Guess I'll win nothing with this device.

And last but not least: why I should stay 3-4 hours at the same place?

Three hours at one one place / sanctuary? Hm, you are not a photographer, right? The batteries of the flashlights and cameras needs to be loaded, the memory card to be emptied which might have to be done after ~ 100 shots, which easily can be taken in 50 minutes. Latter can be avoid by going for i.g. 4Gb cards, but still the batteries are a problem.
I guess UW-filmer have similar needs.
And for sure I won't go back down there after 20 minutes SI. After 90 minutes I need a pee, some cigarettes & coffee and some energy in form of warm food, my girlfriend at least a kiss

Hope you get the picture - I wouldn't spend to much money in it, if I would be you.

 

Dive Sled

I appreciate the comments. I didn't build the dive sled to make a business venture out of. I built it for myself and if anyone else is interested would build for them as well. It is no more than a poor mans "Brownies Third Lung". Nothing more nothing less

I have had years of enjoyment with the Dive Sled mostly for sightseeing, lobstering and some spearfishing. I don't know diddly about photography so don't use it for that. I can tow it around effortlessly on the surface and cover large areas that are not possible on scuba with one tank. It is comfortable for me to use and depending on my weight ,the shape I am in, what I might be wearinf and carrying I will alterthe amount of weight.

I have used the sled with many newbies to the underwater world. And yes they have NEVER gone underwater before...so sue me!!! We go down with two hoses (no more than 50 feet) and they stick by me and in EVERY INSTANCE have had the greatest experience that actually sold them on scuba diving. I am very conscience about their air consumption and time so we always surface with plenty still left in the tank. I also have my own hose that typically will generally have almost twice as much left so buddy breathing is always an option. These things are carefully covered in the pre dive instruction.

In any event I have no doubt that when I start using mine in the santuaries there will many who will be curious about it. If and when thqt time comes I will be very happy to let anyone try it. Including you Joe

thanks