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Finless: You couldn't invent him...
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OK, here is my dilemma. I currently dive twin 10s + 3 ltr for accelerated deco and I am at the stage on some dives where I would feel happier having a bit more gas in reserve OR to use (esp the deco gas).

Naturally the obvious choice is to get 12s + a 5 or 7 HOWEVER to complicate matters - I really really really want an Inspiration but can't afford one for at least a year.

It was suggested to me (admittedly after some beers) that I should stick with the 10s and get two sideslung 7s. The benefit being that when I get my Inspiration I will be able to utilise the 7s.

I will be doing at least the normoxic trimix course asap.

2 * 10s and 2 * 7s - would it work?? I can't see why it wouldn't.

Any comments appreciated.
 

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<font color='#32CD32'>I know plenty of people that dive that config.

Works very well for them.

I only use 12s instead of 10s because my RMV is higher than theirs.

Juz
 

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<font color='#000080'>Hi

Won't you need 2 x 7's anyway if you do the 32%/80% deco gas combination?

Andy
 

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Finless: You couldn't invent him...
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[b said:
Quote[/b] (wetlettuce @ Feb. 20 2004,13:01)]Hi

Won't you need 2 x 7's anyway if you do the 32%/80% deco gas combination?

Andy
Andy,

I have absolutely no idea - haven't done the course yet  
.

If I am using a normoxic mix I thought I would only need two gas mixes (surface to bottom and back + a deco?) - although I suppose I could have weeker deco mix for the deeper stops ??

Rgds
Bryan
 

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The problem is there is no one single perfect combination of cylinders for all dives.

It sounds like 2x10 + 3 is fine for most of your 'intermediate' diving, i.e up to 30m. This is exactly what I use in this range. Deeper than that you can switch to one or two 7l stages for deco and travel.

Unless your SAC is very high or you want to jump to significantly deeper depths (not a good idea anyway) then I would start off with just adding 1x7 stage, then possibly another as your diving progresses.

I'm not a big fan of changing everything in one go.
 

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Finless: You couldn't invent him...
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[b said:
Quote[/b] (Mark Powell @ Feb. 20 2004,13:06)]The problem is there is no one single perfect combination of cylinders for all dives.

It sounds like 2x10 + 3 is fine for most of your 'intermediate' diving, i.e up to 30m. This is exactly what I use in this range. Deeper than that you can switch to one or two 7l stages for deco and travel.

Unless your SAC is very high or you want to jump to significantly deeper depths (not a good idea anyway) then I would start off with just adding 1x7 stage, then possibly another as your diving progresses.

I'm not a big fan of changing everything in one go.
I'm with you there.

I'm currently using the set up down to 40 mtrs OK but that is my realistic limit to get a decent bottom time. In fact I am prepared to do a longer deco stop than I can achieve with this set up.

I think, so far, the limiting factor on what to do/use is going to be the amount of time I am prepared to hang around on deco stops.
 

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A short fat well off crap cave diver. Likes wrecks
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[b said:
Quote[/b] (Finless @ Feb. 20 2004,13:05)]
[b said:
Quote[/b] (wetlettuce @ Feb. 20 2004,13:01)]Hi

Won't you need 2 x 7's anyway if you do the 32%/80% deco gas combination?

Andy
Andy,

I have absolutely no idea - haven't done the course yet  
.

If I am using a normoxic mix I thought I would only need two gas mixes (surface to bottom and back + a deco?) - although I suppose I could have weeker deco mix for the deeper stops ??

Rgds
Bryan
The highley controversial dodgy diving method thats about as non DIR as a Mares Hub is to use your back gas to the max and have all your redundancy in your stages.

I do this on deep dives 60m+ to max the bottom time. Leaving the bottom on 40bar at 70m would normaly be suicide but I just stick the 32% in at 40m with 20bar left in my twin set and head for home. God forbid I should have a big loss of back gas at the end of the dive with low tank presure I would get as high as I could and stick the 32% in. On a survivable PP02 0f 2.0 I only have to get to 53m

OBVIOUSLY this is a OW no overhead environment dive and you stay well away form entanglement issues in the last third of the bottom time.

To be honist on a dive like this I would lower the 02 to 30% so I could get on it deeper or carry a bail out to first stop depth pony bottle of bottom mix and I would be running a sub 25m EAD for clear thinking.

This is definatly NOT rule of thirds and dont put it on your TDI exam paper or you WILL fail  



The question is is it any worse than diving independants with diferent gas mix in each tank?

Not IMHO

ATB

Mark Chase
 

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I'm a pig on gas. On a good day my SCR can be 21 L. On a crazy day, as high as 28L.... I used 2X 12L back and 2X 10L stages. Planning certain dives 60sh was hard especially when applying the rule of thirds on the travel and back. That wasn't the greatest for me, and X2 for deco gas was even a greater pain in the a55.

Now I have 2 X 12's for stages and 2 X 16 L for back. I don't mind having extra gas but if I run short - that would be bad.

Lawrence
 

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if you wan to make dives up to 7o meter range with a rpm of 17 to 20 you need 2X 15 and two 12 litre stages plus an extra 12 litre dnagling in 6 meters for safety nothing less !
 

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<font color='#000F22'>You don't need to use twin 7L's. I have a secondhand 10L O2 clean for 32% a 7L for 80% and twin 12L's for backgas. This was a trimix setup that I bought, (not done my ticket yet). Just using it for ERD air dives.
 
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