Deco penalties

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rjack321:
Most of the cheaper air only computers are still haldane based though. Whether this is the majority of available models, I dunno.

Actually that is not true. Some of the largest manufactures still use Haladine tissue compartments.
 
Rec Diver:
For me a 200' foot dive would require a 27 total minute obligation for decompressing on air. If I were to use 100% oxygen to finish my decompression instead of air I could reduce my total deco time to 16 minutes.

However, your computer shows an interesting situation were doing the, RGBM, deep stops actually adds time to your decompression obligation. It is not just your computer that does this, but so do the others I have witnessed, including my own. I find it interesting that the RGBM deep stop method regarded as being "new science" for deep diving will increase your deco time for a computer diving model. Maybe doing multiple, or extened time, deep stops should be questioned? Though I perform a deep stop it seems that extending the time greater than a minute also increases the decompression time. If you are not diving a computer that is compounding your deco obligation and you are using tables with out the ability to compund tissue compartments, could this lead to a hit.

Its not surprising that haldanian computer will give you penalties for doing deep stops. They don't know anything about bubble growth and offgassing and its tuned so that you create large bubbles and then hang forever shallow to get rid of them in order to reduce your chance of DCS (hence "bend and mend"). It has no idea that you can insert deep stops to encourage offgassing from the free form while deep and prevent large bubbles from forming on the ascent. It always assumes those large bubbles are there because its tuned to ascent rates that create them.
 
rjack321:
Most of the cheaper air only computers are still haldane based though. Whether this is the majority of available models, I dunno.

If you aren't going into deco, the dissolved phase haldane model would dominate -- even if you took a VR3 on a recreational dive the bubble mode code paths aren't going to be very important overall... Doesn't make a whole lot of sense to pack the full bubble model into a dive computer which is intended only for recreational use.
 
Rec Diver:
I have downloaded the recent, 2004, Navy air tables. They are exactly the same as the 1984 air tables. What they have changed is the use of helium, and accelerated decompression. However, there is a different set of tables for that.

I said they were "looking at" updating their tables with bubble models, not that they had published updated tables. The US Navy works at the speed of government on things like this...
 
lamont:
Oh yeah...



Suunto Vypers and such have been using RGBM-modified haldanian models for a long time. Recently the D9 has come out which has deep stops added to it, so it can no longer be considered haldanian or equivalent to the navy tables at all. The v-planner, decoplanner and GAP software packages all have bubble models. Mares and Dacor now have computers with deep stops. The VR3 dive computer uses a bubble model.

The bubble models are computation much harder than haldanian models, which is why you see so many bubble-modified haldanian implementations like the Suuntos, but the trend is clearly towards to the bubble models -- and the higher end trimix tech diving computers are all embrancing the full bubble models.

Although I'm certain this is all just a plot by GI3 to brainwash the entire diving industry, and they're all just going along...

As you have mentioned the basis for these new computer models is still Haladine.

However, I don't think George Irvine has had anything to do with the diving computer industry. Doesn't he still claim that computers will kill you?
 
lamont:
The US Navy works at the speed of government on things like this...

I am really glad because I would rather that they were taking there time Doing It Right than doing it wrong.
 
Rec Diver:
However, your computer shows an interesting situation were doing the, RGBM, deep stops actually adds time to your decompression obligation. It is not just your computer that does this, but so do the others I have witnessed, including my own. I find it interesting that the RGBM deep stop method regarded as being "new science" for deep diving will increase your deco time for a computer diving model. Maybe doing multiple, or extened time, deep stops should be questioned? Though I perform a deep stop it seems that extending the time greater than a minute also increases the decompression time. If you are not diving a computer that is compounding your deco obligation and you are using tables with out the ability to compund tissue compartments, could this lead to a hit.
So you want to question the validilty of deep stops (newer bubble models) because your computer (older Haldane model) still thinks you are on gassing? That is exactly why some people argue that Haldane models are outdated and why most people doing serious deco are using their computer in gauge mode (and following Vplanner tables or similar) or using a computer like the VR3.
 
rjack321:
210 on air? Don't know how to plan you O2 deco time? Shuddder

My thoughts exactly. Just trust your life to that single-gas wrist computer and pray that everything goes right. Heck, I'll toss some O2 in somewhere along the way just to play it safe... :no
 
Rec Diver:
For me a 200' foot dive would require a 27 total minute obligation for decompressing on air. If I were to use 100% oxygen to finish my decompression instead of air I could reduce my total deco time to 16 minutes.

Last 200ft dive I did was a month and a half ago on the Minnedosa (a very, very nice wreck, by the way) in Lake Huron. It was for 25 min bottom time on 18/45 as backgas. Cut table with Deco-planner and used a bottom timer, with a second bottom timer and IANTD's 19/40 Table w/Accelerated Deco as back-up. Deco was 50 mins using 35/25 and 100% O2 for a total run time of 70 min.

You mean to tell me I spent an extra 45 minutes hanging on the up-line I didn't have to? I got to get me one of those computers that will talk me into getting to 20 feet as fast as I can and get me out of the water much quicker - Not!
 
OWSI176288:
I got to get me one of those computers that will talk me into getting to 20 feet as fast as I can and get me out of the water much quicker

You've got it all wrong. You need to get every deco-planner software program you can. Run them all for your planned dive. Then, pick the shortest stop required by each of them at each level. You'll be on your way to really quick ascents! :rofl3:
 
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