>I currently use twin 10ltr 300bar steel tanks, manifolded and adopting 
>"Hogarthian" principles (ie long hose, no stuffing etc) and use a 10 ltr 
>300bar steel tank for EAN80 from 9m upwards.
     
Are you diving solo or with a Buddy, does your buddy have exactly the same 
configuration

>The diving I do of this nature is always when exploring wrecks. Up till this 
>point in time I have always dived rule of thirds on my twinset and 50% + 15bar 
>EAN80 reserve.
     
     
Rule of thirds works and is there for a very good reason, you are at the 
maximum point of penetration, and you have a catastrophic failure, and you 
lose your back gas (assuming you have no additional stages) you must now 
exit using your buddies gas. And remember both your gas consumption and 
your buddies is going to be much higher because of the stress.


>Given the separate deco gas source I now use (as opposed to just having a 
>twinset of air) I believe I am quite safe to breath my air down to 50% (150 
>bar) before beginning my ascent. I have run many dive profiles etc with 
>ProPlanner and everytime I have enough air to deco should the EAN80 fail.
     
Remember your buddy, and dissimilar breathing rates. The dive should be 
turned when the heaviest breather reaches thirds in his/her supply. Thirds 
applies to penetration (wreck or cave) and not open water. If open water 
you must have enough gas for you and your buddy to reach your deco stop.

If you lose both back gas and deco you are in the shot, but you should 
still have enough gas in the team to reach your high O2 stops. You would 
then require additional emergency procedures to indicate to your surface 
cover that you require more gas.

     
>The tables I have cut and take down are for single depth only. So if I should 
>briefly journey to say 50m then spend the rest of the dive at 35m I have to 
>assume a square 50m profile for the deco schedule I then execute. Nothing new 
>with that I know. 
     
>So far so good. But given I am going to dive to 50% reserve on my bottom 
>time, it is possible on the above profile that I could leave myself with 
>insufficient air in an EAN80 failure to complete the air deco schedule. 
>Albeit that the longer deco is due to briefly visiting 50m and not therefore 
>actually essential, however apart from taking down my notebook PC I'm not 
>sure how to get round this without compromising my safety margin which is 
>allowing for one reg failure in my configuration.
     
When cutting the Proplanner tables are you using a safety factor, if you know 
you are going to follow a particular profile, remove the safety factor, the 
time spent at shallower depth is your safety factor.
     

Andy

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