Deco Habitat Design

Hey there

I am a tec/cave diver based in South Africa, we are currrently exploring a system at 125m/410ft and to say the least, the deco is becoming a real PITA.

I am looking for some advise, technical designs, practical tips on: firstly how to design/build the habitat (I am leaning towards using a water tank) and secondly on how to install/fix it to the bottom etc. Advise on overall design and smaller things like seating position (and the like) would be really welcome.

The habitat is to be simple (also read: cost is an issue:smt045) no comms etc required and divers will stay on their rebreathers. It has to fit 2-3 divers - purpose is merely to find a warmer/dryer place.

Habitat to be fixed, i.e there is no need to hoist up/and down in water collumn.

All advise and ideas would be really appreaciated.

Regards Dries

I have seen several. Most are "pinned" to the ceiling by the buoyancy of the gas in the habitat. They also are some type of water tight container, like large amimal watering troughs, large chemical containers, or something like a swimming pool liner, stretched over a frame.

I'd like to hear more about your So African cave :D




Brett Hemphill built a neat habitat recently with seating, you may want to see if you can get his designs.

Hey Dries, Howzit??

These guys should be able to help you out: Wet Mules Their contact page is here

They are currently diving the Pearse Resurgance each year pushing further and further - 194m (636ft) so far and they use habitats for deco to escape the really cold water.

Heres a promo video they did, you can see the habitats really well at about 3:50 into it, details of the seats they built etc are visible as well.

This video is just about the habitats - it shows each of the 4 they use in the Pearse and how they're fixed in position etc.

Give them a shout and i'm sure they'll help you out!

For anyone else interested in the Pearse dive there is a downloadable 3D flythrough available on this page quite amazing what they have done so far.

Here is a pic of KUR's small Habitat that is installed in Madison Blue

http://www.cavediver.net/forum/galle...1/dsc_6799.jpg

If Chris, Shannon or any of the other members from the OCDA check this out, they can probably give you some ideas on the one they have constructed here in one of our local Missouri caves.

We used the designs from the Pearse Resurgence project for habitats built out of 250 and 350 gallon juice containers. They can be purchased cheap here, usually 75-125 USD and you just cut the top off. They come with a plastic pallet on the bottom and they are enclosed with a tubular metal cage. Not sure how the metal will hold up over time, but for the price, its not a big issue. Two people can easily move it around.

Brett Hemphill and Andy Pitkin came up with valve designs so the containers could vent without "burping" from the bottom - otherwise, the noise level is very annoying after a while. The containers have a threaded fitting at the bottom used to drain the tank and you can install pvc pipe and valves to allow it to drain. Andy used a simple downspout that can be adjusted to vary the water level in the tank and direct the exhaust away from the sides. It is self adjusting so once it is set, you don't have to do anything more. Brett's uses a valve you can access from the inside to adjust the gas flowing out. It requires periodic adjustment based on breathing rate, but worked fine and gave us something to do while decompressing.

Brett built triangular supports in diagonal corners with seats that can be removed. That the picture that Billy posted above. It got you fully out of the water, but the seats were a little unstable and we had to have a ladder to get up inside. But it was very comfortable once we got inside. His was a 350 gallon tank with a little more headroom. Andy used 2x4's as seats, which put you more in the water, but was still comfortable and very simple to install.

Both were pinned to the ceiling using natural buoyancy. Finding a good, flat place is critical. If the ceiling is very irregular, it is very difficult to get it leveled out. Of course we've only done this twice, but the containers are awkward to deal with underwater. One location was flat and installation was a breeze. The other had scallops in the ceiling and took a while to get it level and stable.

You'll want plenty of loops around the bottom of the habitat to hang tanks and stuff.

Thanks for the replies so far. :clapper

One of our problems are that the cave entrance sits @ 12m and then enters open water. We will accordingly have to fix the habitat to the floor or to the sides of the open hole, an old quarry - Asbestos mine.

The cave/mine is well know (Komati Springs) was though to have been explored to its end. We however managed, a year or two ago, to break a metal door open (at 108m) with some crow bars and brute force. This door led to new passages at 108m and 125m which we are in the process of exploring.

Thanks Dries

how deep is the open water section? any way to anchor that habitat down to some huge boulders using chains? those water tote should have somewhere around 1000kg uplift (250 gal ones). If not you will need to suspend it down from some huge surface buoys or on at each corner, the water totes might work for that as well if they have the steel cage, hang some weights on each, lets say 300kg each corner and hang the habitat on those weights as well. Sounds like some real fun

I have limited experience with habitats, but my experience with installing the current one in Roubidoux tells me that trying to affix one of these to the floor would be a major undertaking. The lift force of a filled habitat is huge.

Here's a few pics of our install. Due to the small opening into the spring, we had to assemble the habitat inside. Some pics show the aluminum panels on the ground. The inside is lined with a "huge bag" - kind of like an upside down above ground swimming pool. Seats are wooden. All probably more than you're wanting to do, but maybe this all helps some.

http://www.picturetrail.com/sfx/album/view/18244407

Our previous habitat was a simple box frame made of square tubing. Then a thick liner (bag) was filled inside the framing. It was light weight and probably low cost. But again the lift force when it was filled was huge.

If there is anywhere somewhat near your spring entrance where the ceiling rises to at least 25 ft, that would be best. Deco at 30' in a dry habitat would be fine.

Mike Poucher summarized what we've been doing very eloquently.

Here is a French page on deco habitats:
http://www.plongeesout.com/articles%...gruissanot.htm

And the Google translation:
http://translate.google.com/translat...520douchet.htm

This has a lot more information about securing the habitat if you don't have a roof to put it under. When you calculate the forces involved, you realize you have to take the tie-down system very seriously.

Andy

Quote:

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Originally Posted by billyf

Here is a pic of KUR's small Habitat that is installed in Madison Blue

http://www.cavediver.net/forum/galle...1/dsc_6799.jpg

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Thanks Billy - I managed to source two of these - for free (Thanks Steven:clapper) We'll start playing with these and once we have patted the technique down, we'lll try something bigger - I found a very nice 2250l horizontal water tank (about $700) that would be perfect.

Natuarally just propping the habitat up against the roof is 1st price, but I think it is not going to be possible (will look for a spot - but the entrance to the cave might be to deep.

The open hole is between 35m and 50 deep so the bottom might not work (also a lot of silt) - we might be able to drill into the shear cliff sides and attach anchor bolts, We will also look for big boulders.

Any advise on what tyype of ropes cables, chains, attachment points, etc that we can use.

Also any other tips, warnings on handling the crates in open water?

Regards Dries

Quote:

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Originally Posted by Dive Africa

...The open hole is between 35m and 50 deep so the bottom might not work (also a lot of silt) - we might be able to drill into the shear cliff sides and attach anchor bolts, We will also look for big boulders.

Any advise on what tyype of ropes cables, chains, attachment points, etc that we can use.

Also any other tips, warnings on handling the crates in open water?

Regards Dries

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One problem attaching it to a wall would be uneven tension on the hold down lines. You may have to reinforce the sides of the habitat so it won't collapse from the uneven loading.

Be really sure it is secure, because if it comes loose on deco, whoever is in it will get a very fast ride to the surface.. It it hits another diver on the way up, they will be hurt as well.

If you are in that deep of water,I suggest a open bell with a winch and anchor, you can winch it down to depth, then let it come up as you do.

These used to be lying around the Gulf used a few years ago, I dont know if any are still around. This is good for a picture, but the price is crazy. If you weld, these aren't hard to make.

http://www.ebay.com/itm/NAUTILIS-2-M...item4aaca12dcf

Quote:

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Originally Posted by Dive Africa

Also any other tips, warnings on handling the crates in open water?

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Once you get things in place all will "look" good, then you start filling with air and things can unravel in a hurry. Lots of uncertainty when you start filling so be careful and make sure everyone is out of the way and paying attention.

Quote:

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Originally Posted by Dive Africa

Any advise on what type of ropes cables, chains, attachment points, etc that we can use.

Also any other tips, warnings on handling the crates in open water?

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If you plan to anchor one to the floor, I would go with good tubular webbing, or chains for strength. A come along system, or the cam bands for tying down loads should work for making it adjustable. I think you may have to reinforce the cage to take the strain. The crate was pretty easy to handle in the water. It floated nicely on top while we got in and attached a lift bag, and then turned it over to make it sink. The plastic pallet took a little while to fill with water - I would drill a few more holes to make it fill quicker next time around. We were able to swim it in relativily easy with no flow in Alachua, but in Madison, with the flow (and the flow was not high by any means!) it was more of a challenge. We swam it in part way, but as the passage got lower, we didn't have clearance for the lift bag, sowe ended up rolling it along the floor to get it in place (all sand and rubble).

It might be wise to use spreader bars, or a platform or a simple steel cross a few feet below the cage to allow to chain the cage to it in all corners straight down. from there on you can go to a single point of attachment in the center down to the anchor. This will avoid the cage from deforming at the rim since you don't have any horizontal forces. If you run any of the chains that attach to the cage in an angle you will need to reinforce around the rim. It might come in handy as a platform to stand on as well.

Quote:

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Originally Posted by Dive Africa

Thanks Billy - I managed to source two of these - for free (Thanks Steven:clapper) We'll start playing with these and once we have patted the technique down, we'lll try something bigger - I found a very nice 2250l horizontal water tank (about $700) that would be perfect.

Natuarally just propping the habitat up against the roof is 1st price, but I think it is not going to be possible (will look for a spot - but the entrance to the cave might be to deep.

The open hole is between 35m and 50 deep so the bottom might not work (also a lot of silt) - we might be able to drill into the shear cliff sides and attach anchor bolts, We will also look for big boulders.

Any advise on what tyype of ropes cables, chains, attachment points, etc that we can use.

Also any other tips, warnings on handling the crates in open water?

Regards Dries

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And lastly, don't forget to take pictures and write up your experience so we can learn from it too!

Good luck.

Quote:

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Originally Posted by huxley

It might be wise to use spreader bars, or a platform or a simple steel cross a few feet below the cage to allow to chain the cage to it in all corners straight down. from there on you can go to a single point of attachment in the center down to the anchor. This will avoid the cage from deforming at the rim since you don't have any horizontal forces. If you run any of the chains that attach to the cage in an angle you will need to reinforce around the rim. It might come in handy as a platform to stand on as well.

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But what if they have to attach it to the wall?

I would attach the platform with 4 individual chains to the wall, lets say 30' below the platform with individual length chains so the platform would be leveled. Picture mountaineering if they hang a platform off a cliff on a single anchor point in the wall, now turn this picture around and you have the floating platform. My biggest concern would be to pull one of the boulders out of the side wall of the quarry. keep in mind you are applying a couple 1000's pound of force, that might loosen something up and now what, you either go up or that whole thing goes down if the boulder is big enough that you are attached to. It depends on the local conditions but sounds like it is safer to look for the big on on the ground and use it as a counter weight, its not going anywhere neither down or up unless it is too small.
If chain wraps around the rock are done right so that they can only tighten up ( lets say couple loops at the corners of the rock that get combined to a single attachment point for the up chain) this should be foul proof. Just keep in mind the rock might move a little while you fill up the habitat.
Second bet would be drill holes and use expansion bolts, but make sure you have plenty, while the bolt might hold couple thousand pounds the rock might not.

Quote:

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Originally Posted by fw

but what if they have to attach it to the wall?

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"superglue"

Quote:

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Originally Posted by huxley

I would attach the platform with 4 individual chains to the wall, lets say 30' below the platform with individual length chains so the platform would be leveled. Picture mountaineering if they hang a platform off a cliff on a single anchor point in the wall, now turn this picture around and you have the floating platform. My biggest concern would be to pull one of the boulders out of the side wall of the quarry. keep in mind you are applying a couple 1000's pound of force, that might loosen something up and now what, you either go up or that whole thing goes down if the boulder is big enough that you are attached to. It depends on the local conditions but sounds like it is safer to look for the big on on the ground and use it as a counter weight, its not going anywhere neither down or up unless it is too small.
If chain wraps around the rock are done right so that they can only tighten up ( lets say couple loops at the corners of the rock that get combined to a single attachment point for the up chain) this should be foul proof. Just keep in mind the rock might move a little while you fill up the habitat.
Second bet would be drill holes and use expansion bolts, but make sure you have plenty, while the bolt might hold couple thousand pounds the rock might not.

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That should work, but I think Mike is right, ropes are easier to adjust.

I am currently thinking the best method might be a combination of heavy duty ratchet straps and chains. I.e use the ratchet traps to adjust the length and ones you are satisfied, then fix length of chain and then remove the ratchet strap, but we'll see.