Portable Lightweight Decompression Habitat

[Joshua Smith]

Very cool idea!

http://newswatch.nationalgeographic.com ... t-is-born/

[DiveZen]

Cool! White Arrow makes one for cave diving (simpler). I've not used it, but it looked cool.

http://www.nick-toussaint.com/sump_diver/wa_habitat

[Joshua Smith]

Cool! White Arrow makes one for cave diving (simpler). I've not used it, but it looked cool.

http://www.nick-toussaint.com/sump_diver/wa_habitat

Yes, I've seen a few different cave habitats, but never one for open water. I'm really intrigued by the idea. Those last few deco stops just freaking kill me, on deep dives. The idea of getting out of the water, even partially, and maybe even having a snack and...wow, maybe even a hot cup of coffee?....is really amazing.

[diverden]

So, I've been thinking about this and have "run the numbers." A 3 ft diameter sphere of gas (cozy!) is going to displace about 900 lbs of seawater. How is this "Portable" and "Lightweight" ? It obviously assumes you have something like a 1200 lb block of concrete with a chain on it where you want to use it.

Discuss.

(Assumptions:
the formula for the volume of a sphere is correct,
that the weight of seawater is about 64 lbs/ft^3,
the anchor 1/3 "heavier" than what it's holding down,
diameter of 3 ft is for the minimum imaginable size of a sphere for 2 people,
is one where you can barely touch the other side of it)

[diverden]

So, I've been thinking about this and have "run the numbers." A 3 ft diameter sphere of gas (cozy!) is going to displace about 900 lbs of seawater. How is this "Portable" and "Lightweight" ? It obviously assumes you have something like a 1200 lb block of concrete with a chain on it where you want to use it.

Discuss.

(Assumptions:
the formula for the volume of a sphere is correct,
that the weight of seawater is about 64 lbs/ft^3,
the anchor 1/3 "heavier" than what it's holding down,
diameter of 3 ft is for the minimum imaginable size of a sphere for 2 people,
is one where you can barely touch the other side of it)

Ok, after about 1 minute of thought, I realized that you could conceivably get away with half of a sphere... 450 lbs of upward force. Still seems to be the most challenging part of the problem where there is not already a hearty mooring buoy/block of concrete/professionally installed anchor.

[Joshua Smith]

So, I've been thinking about this and have "run the numbers." A 3 ft diameter sphere of gas (cozy!) is going to displace about 900 lbs of seawater. How is this "Portable" and "Lightweight" ? It obviously assumes you have something like a 1200 lb block of concrete with a chain on it where you want to use it.

Discuss.

(Assumptions:
the formula for the volume of a sphere is correct,
that the weight of seawater is about 64 lbs/ft^3,
the anchor 1/3 "heavier" than what it's holding down,
diameter of 3 ft is for the minimum imaginable size of a sphere for 2 people,
is one where you can barely touch the other side of it)

Ok, after about 1 minute of thought, I realized that you could conceivably get away with half of a sphere... 450 lbs of upward force. Still seems to be the most challenging part of the problem where there is not already a hearty mooring buoy/block of concrete/professionally installed anchor.

I'm not as good at the math as you, but when I said "portable" and "Lightweight" I was talking about the equipment as it sits, out of the water. I've seen pictures of a few habitats that used giant plastic tanks- the kind you might use to store water or gasoline underground- and were inflated and "stuck" to the ceilings of caves. This one breaks down to a single bag about the size of one person's luggage, if I read it right.

[CaptnJack]

How do you anchor it to the bottom yet drift?

I have a very large PVC bag which could be setup as a habitat. Tobin set it to me a couple years ago, they normally hold his garnet media. Its pallet sized 4x44 roughly - just not needed so far, or more work than its worth for the dive.

[Joshua Smith]

How do you anchor it to the bottom yet drift?

[sarcasm]Well, my theory is that you anchor it to the bottom, and just expect that everything will work out in some magical fashion.[/sarcasm]

And, perhaps, people might look at this idea and adapt it to their needs. I've been trying to think of a way to rig this up to our floating deco station all day.

[CaptnJack]

How do you anchor it to the bottom yet drift?

[sarcasm]Well, my theory is that you anchor it to the bottom, and just expect that everything will work out in some magical fashion.[/sarcasm]

And, perhaps, people might look at this idea and adapt it to their needs. I've been trying to think of a way to rig this up to our floating deco station all day.

couple of engine blocks?

[diverden]

Magic is fine for no-deco dives

[diverden]

Also good to know: you probably want to start by filling the bubble up with O2 but after people have been exhaling and off-gassing into it, you don't really know what you're breathing. All your deco is still on the loop. I still agree that it would be nice to have a seat, take off the mask and hood, take a break and drink something warm, and enjoy a quick deco snack.

[kdupreez]

Thats pretty neat! anchoring is for sure a challenge with that much lift force.

Doing support dives for a team and having something like that would be awesome!!

You can order Jimmy Johns too!

The advantage the WKKP (and other cave diving) guys have is a fairly solid rock surface roof so they literally use huge water drum, turn it upside down, bolt some seats on it and fill it with air and wedge it on the cave roof..

We dont have the luxery of installing "semi permanent" habitats though..would be nice to have mooring blocks maybe? Then a portable habitat like this would be very viable!

A few interresting things they do is use long hoses on the dedicated habitat deco tanks. they can completely remove gear, sit down, eat, drink, chat, etc.. That would be nice!!

\

[selkie]

Way back in the day.

Many commercial diving operations hung a inverted T shaped bar for divers to stand on while doing deco. We were all vigorously warned to never sit on the bar because it could impede circulation and thus impede off gassing.

Habitats that are not vented or monitored can kill. Commercial divers normally do not remove their helmets except in a bell with a monitored environment.

In the commercial world this is most common in temporary welding habitats. Welding habitats are normally filled with argon however divers exhaust gas can raise oxygen levels to the point were the habitat explodes.

[CaptnJack]

When you're breathing 100% O2 the gas in the habitat has plenty of O2 (from the air or 32% it was filled with and 100% exhalations) Not sure about CO2 accumulation however, I'd have to do the math.

For the 2 dives I've considered a habitat on, doing a shorter BT was a better option than the effort to rig it.

[diverden]

When you're breathing 100% O2 the gas in the habitat has plenty of O2 (from the air or 32% it was filled with and 100% exhalations) Not sure about CO2 accumulation however, I'd have to do the math.

For the 2 dives I've considered a habitat on, doing a shorter BT was a better option than the effort to rig it.

... and the loss of O2 due to metabolism. ~= .6 l/m/person

[CaptnJack]

When you're breathing 100% O2 the gas in the habitat has plenty of O2 (from the air or 32% it was filled with and 100% exhalations) Not sure about CO2 accumulation however, I'd have to do the math.

For the 2 dives I've considered a habitat on, doing a shorter BT was a better option than the effort to rig it.

... and the loss of O2 due to metabolism. ~= .6 l/m/person

Breathing 100%, your exhalations have more than enough. I don't know anyone using habitats any deeper than 20ft anyway

[diverden]

Breathing 100%, your exhalations have more than enough. I don't know anyone using habitats any deeper than 20ft anyway

So what would you say you were breathing, during your decompression?

[CaptnJack]

Breathing 100%, your exhalations have more than enough. I don't know anyone using habitats any deeper than 20ft anyway

So what would you say you were breathing, during your decompression?

Just take the reg out to talk and eat. I wouldn't sit there for extended periods of time breathing the habitat's gas. I just wouldn't be paranoid that the gas in the habitat wouldn't support life.

[diverden]

Ok, yeah. I thought you were suggesting to deco on the habitat gas. We're on the same page

[kdupreez]

typically diving habitats you breathe regs, cause there is no gas circulation, CO2 is a big issue.

thr wkpp support divers hang tons of deco gas and use 7ft hoses on the deco tanks outside the habitat, they take all gear off except drysuit and the watch movies on iPads and eat like BBQ chicken and drink Gatorade etc..

i stayed at Mark Messermiths house a while back when teaching fundies in florida and he had tons of awesome info on the new WKPP habitats and these are like Stylin!! compared to old upside down troffs.

that would be nice on a tec dive up here.. spare suit heater batteries, food, drink, etc.. nice!!

[Joshua Smith]

How do you anchor it to the bottom yet drift?

[sarcasm]Well, my theory is that you anchor it to the bottom, and just expect that everything will work out in some magical fashion.[/sarcasm]

And, perhaps, people might look at this idea and adapt it to their needs. I've been trying to think of a way to rig this up to our floating deco station all day.

couple of engine blocks?

Point taken, of course. Still, it might work well in a lake, for instance- or anywhere not current sensitive- engine blocks and all. What about fixing something under a boat, maybe?