RGBM vs traditional decompression calculations

[gregtaffet]

I am trying to figure out whether RGBM is really better than the traditional decompression calculations. Does anyone have a link to any of the research or have any experiance with the differenct methods.
I would also appreciate any recommendation to more conservative computers. I am at a stage of life where I have decided to switch from being a more agressive diver to being more conservative.

 

[wedivebc]

I am trying to figure out whether RGBM is really better than the traditional decompression calculations. Does anyone have a link to any of the research or have any experiance with the differenct methods.
I would also appreciate any recommendation to more conservative computers. I am at a stage of life where I have decided to switch from being a more agressive diver to being more conservative.

If conservatism is your goal the RGBM model in probably not for you. If you are doing no-deco dives then RGBM will give you a ascent limit sooner than Buhlmann. For deep long (deco) dives RGBM may get you out sooner depending on what parameters and gas selections you use but for straight minimum deco dives I would stay away from it.
The algorithm Suunto claims is RGBM is not and will result is quite conservative profiles.

 

[tgsmith]

Define "traditional." There's a couple other algorithims that came before RGBM.

I'm assuming you mean the Navy Tables/Haldanian vs bubble models, but I don't know anyone that runs Navy tables unless it's on some submersible backup tables in their pocket. I also assume that you're interested in RGBM because of deep-stops, which there's some studies on showing it's effectiveness. RGBM is not the only model crediting deep stops.

For instance, in V-Planner you can run either VPM or VPM-B. From what I've read, VPM-B is VPM but with padded time at the shallow stops for extra insurance. I leave V-Planner select which one automatically based on it's criteria for each specific dive, and it always chooses VPM-B(I'm diving OC nitrox/air with ~30min BT's above 200ft). The Variable Permeability Model(I think) credits deep-stops, and from what I've seen V-Planner is without doubt the most popular decompression planning software.

Another example is the algorithim used by Oceanic(and it's sister companies) on it's computers. I think it's called the Rogers. It's liberal in no-decompression diving, but ridiculously conservative on repetitive decompression dives.

On the Dive Rite computers you can choose how conservative you want it to be. They run a variation of Buhlmann.

Most conservative thing to do would be just run tables. Nothing more conservative for planning your schedule based on a depth you weren't at for more than a few minutes...a computer will ride the curve, naturally meaning that you're pushing it.

I know I didn't answer all your questions directly, but hopefully gave you some info to go off of. Sounds like VPM-B on +5 conservatism might be what you're looking for.

EDIT: Went into V-Planner to run some tables as an example to you. Found out that it's VPM-B or VPM-B/E(padded shallow stops) that you can run. It also won't start making a difference till you hit about 100 minutes of deco.

V-Planner:
http://www.hhssoftware.com/v-planner/index_gs.html

 

[rongoodman]

If you want a relatively inexpensive computer that tries to account for micro-bubbles, the Aladin Tec 2G has the option for extra deep stops. I don't know of any dive computer, which runs true RGBM, and only the Liquivison has the horsepower to run VPM-B.

 

[Shearwater]

I don't know of any dive computer, which runs true RGBM, and only the Liquivison has the horsepower to run VPM-B.

The Explorer runs RGBM. As far as I know, any of the other RGBM computers only include some parts of RGBM.

The Shearwater Pursuit can easily run VPM-B. We chose not to.

Bruce

 

[Kern]

I'm assuming you mean the Navy Tables/Haldanian vs bubble models, but I don't know anyone that runs Navy tables unless it's on some submersible backup tables in their pocket. I also assume that you're interested in RGBM because of deep-stops, which there's some studies on showing it's effectiveness. RGBM is not the only model crediting deep stops.

For instance, in V-Planner you can run either VPM or VPM-B. From what I've read, VPM-B is VPM but with padded time at the shallow stops for extra insurance. I leave V-Planner select which one automatically based on it's criteria for each specific dive, and it always chooses VPM-B(I'm diving OC nitrox/air with ~30min BT's above 200ft). The Variable Permeability Model(I think) credits deep-stops, and from what I've seen V-Planner is without doubt the most popular decompression planning software.

Bubble models like VPM/RGBM don't really give credit for deep stops. Deeper stops are inherent in the algorithms. If the deco for a particular dive doesn't require a deeper stop, a fully iterative version of either won't throw in a Pile stop at half your maximum depth. It'll just give you a deco curve based on the assumptions of the bubble model being used.

Another example is the algorithim used by Oceanic(and it's sister companies) on it's computers. I think it's called the Rogers. It's liberal in no-decompression diving, but ridiculously conservative on repetitive decompression dives.

Pelagic/Oceanic/Arise computers are based on the same algorithm as the PADI RDP.
The not so RGBM from Suunto/Mares/etc. is usually far more conservative than the Pelagics' for multi dive, multi day scenarios. Especially if you break any of their golden rules.