Posted by MHK on January 15, 2001 at 18:22:08:
In Reply to: Re: DIR on the West Coast posted by seahunt on January 15, 2001 at 17:45:29:
Seahunt,
I've written several posts in that past that speak to the very table issue you are talking about.. Let me see if I can sum it up in a brief post but if not I'll expand on this point.. As a side note Dale Sheckler requested that I write an article that addresses the various computer and table models, I've submitted the article and hopefully it will be in the next Calif Diving news as I believe this is a often misunderstood concept..
The overwhelming majority of computer models and tables are all based of the Buhlman modified subset B & C algorithms, absent the Weinke RGBM models, it's a safe bet that any computer you own is based on the Buhlman algorithm. The simple distinction between the variety of computers that provide for varying BT's is the conservation factor applied to the model.. In that same regard the tables follow the same logic. If you compare the U.S. Navy tables you will find extraordinary BT's when compared to the NAUI & PADI tables. This is because the Navy allows for the very fit, young diver's and further allows for a 10% bends factor.. They all have chambers on board so in the Navy's view 10% is acceptable. Even comparing the NAUI -v- PADI tables you'll note varying BT's at the same time and depth. Once again this speaks to the various conservation factors applied.. SO the short answer to your question is that I carry the IANTD tables but more importantly I took teh time to study and learn the algorithms and the variances within the competing models... It's called decompression THEORY for a reason, and that's because it's not an exact science and I err on the side of caution, I build deep stops into my profiles that would cause the computer to on gas when in fact you are off-gasing, I'll bring deco gas if I'm concerned about my projected profiles, but with respect to a average recreational profile the deco gas isn't really necessary.
With respect to the diference between the Buhlamn modified B and C models the only real distinction is that the subset C calculates in REAL time as opposed to PLANNED time and thus allows for the continuous data sampling that you allude to. By understanding the models you can do the same thing...
As to the Steel -v- AL debate that you discuss and attempt to justify, while you attempt to provide solutions that may or may not work I simply avoid the problem in the first place.. DIR is very much about eliminating as many potential problems before they occur as possible rather than attempt to implement emeergency procedures that may or may not work when needed most.
I re-read your post and you refer on several occasions to the *most critical* which is what tables I'm using that work for sport diver's better than the computer. I hope I've directly answered that question about but if you feel compelled to further discuss M-values I'll be happy to expand, but it's the Buhlmand modified subset C that I'm refering to coupled with the incorporation of deep stops...
As to your *perfect example of what I ctriticize DIR for * blah, blah, blah I would add the following, while I've thought some of your comments were less than well thought out I've resisted the temptation to call you silly, I've attempted to continue a dialogue absent any name calling and I would appreciate the same courtesy in return...
We dive doubles when our pre-dive gas management calculations require added gas.. That being said, the increase in mass does increase the coefficient of drag but not to the exponential extent a dragging consoles increases the frontal drag.. Once the slipstream is broken the exponential coefficent decreases proportionately..
Perhaps if you could see the wrist mounting you would understand better.. I use bungie on my depth gauge console and mount it just under my elbow and have never had any problem digging for bugs and to the extent that I did I would simply use the other arm and/or mount the gauge on the other arm, it's simply a problem that doesn't exist and I would add that in my bug hunting efforts I used a 7' hose well before my DIR conversion to allow me to take off the bc and go way back to get some bugs so I believe that I'll take on the best of the holes...
Given that you have never used the console I'm wondering why you believe that because DIR recommends against it's why you believe that this will preclude DIR from mainstream acceptance.. Particulalry since you are arguing in favor of something that you don't even use??????
Later ( I'm leaving the office and can't respond until tomorrow)