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Discussion Starter · #1 ·
Hi All

I am selling off my old steel stages from my OC days, & replacing them with ali's.

I'm trying to make up my mind what size ali's toget.

Option 1.
3 x 7 litre stages, allowing a bailout bottom mix, a 'travel' mix & a rich deco mix.
Also allows me to leave the deeper bottom mix stage behind when doing 'recreational' diving.

Option 2.
1 x 7l stage, 1 x 12l stage . Bottom mix in the 7l, mid range mix (50%) in the 12, transitin from bottom mix to deco later (21m) longer deco schedule on the 50%

Option 3.
2 x 12l stages
Similar plan to 2. But additional gas would cope with deeper dives.

The down side is hefting 12l stages is a pain in the recreational range (down to 40m). The advantage that it is one less cylinder to clean every year (the cleaning bill is begining to bug me). The three 7's are more likely to result in a better deco schedule. I have dived in team bailout before now. However currently most of my buddies are on OC so team bailout is not really an option, however the shorter dive times normally reduce this as a serious issue.

I look forward to your views -

Gareth
 

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Team Peanut Butter
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I use 3 7s I carry one with air or 32ish% if i am diving shallow I also run my suit of this, for deeper dives I carry one 7 with 20/35 and one with 80% (suit run of seperate 1litre) however now that i have worked the maths on this the 20/30 would not get me back to 10metres if I asume a SAC of 30 litres a minute and have to do the deco for a sixty metre dive. My thoughts are I should change the 80% to 50% and replace the other 7 with an ally 11litre as the other option would be carry all three7s and this would be totaly over the top for a 60metre dive.
 

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A short fat well off crap cave diver. Likes wrecks
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Hi Gareth

I assume your going CCR?

Do you dive all tanks left or do you dive left right?

By 12s? I asume you mean Ali80s (11. somethings I believe)

If you dive left right there is a small problem in that an Ali 80 full of Trimix is floaty as hell and a 80 full of 50% sinks. End result is your off balance. Same problem but worse using two steel 10s

So I run a steel 10 of 18/45 which just about floats and a Ali 80 of 50%. This way I trim out nicely.


Three Ali 7's is an efficient way to get out of the water but I just try and avoid diving more than two tanks if i can help it. Some Ali7's are fantastic to trim and others are apparently rubbish. So if you decide on that then find out which is which.
 

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East coast, think I dive there !
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I dive two Ali 80s left and right and as Mark has pointed out the bottom mix is floaty but I have not found this to be a problem with my trim. Some people add a weight on the end but I haven't found it necessary.

I would rather dive two 80s than three 7s but I do have a 7 for shallow stuff as well.
 

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I'd get 2 80s, and then get a small tank for shallow long stuff. Carrying an 80 on 40m dives isn't a problem for me, and is what I have done on recent dives. If the bottom time gets big on 40m dives then just add an AL40 or 7 of rich deco mix and you're off.

7s are nice, but I find that more than 2 stages and you start getting into special procedures and significant bulk. More than one on each side I find cumbersome and relies on team identifying regs etc to make sure they're safe to breathe if you're in crap viz or where there's loads of tanks going on.

It also depends what maximum depth you want to be rigged up for. If you've got a couple of 80s and a 7 then you could have enough gas for some big dives, plus the flexibility of different sizes when required.

I haven't had a balance problem with AL80s of nitrox or rich trimix, even blown to 210. You can rig them slightly differently to make them do what you want them to.

Digs.
 

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A short fat well off crap cave diver. Likes wrecks
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I haven't had a balance problem with AL80s of nitrox or rich trimix, even blown to 210. You can rig them slightly differently to make them do what you want them to.

Digs.

How?

Id be interested to know as i found two 80s blown to 220bar one with 18/45 and the other with 50% had me all over the place.

The ali 80 with 50% in was 3lb negative and the one with 18/45 in was a couple of pounds positive so I hade about a 2Kg off balance going on



Steel 10 floating arse up. Ali 80 flat on the bottom




ATB

Mark Chase
 

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East coast, think I dive there !
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Might have to do with what reg you have, mine are Poseidon Deeps and are quite heavy first stages, Also took me quite a while to get them to sit right by altering the rig, there clipped on to my waist on short tails. They were a pain in the arse to start with but once altered are spot on.
 

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Discussion Starter · #8 ·
Thanks for the answers so far.

Yes I am CCR - I've been very 'good' & waited until I did my CCR mix ticket, prior to pushing my CCR diving beyond 40 - 45m.

Prior to this all my mix stuff had been on OC.

This year I'm switching 100% for all my pleasure diving to CCR, including the deep stuff.

I habitually carry rich right, lean left.

I guess I'm really rigging to dive to 60m, I can't see me pushing beyond 70m (although I have one dive planned for this later in the year).

This is begining to look like two 80's, which will mean I'm carrying bigger stages than when I did most of my OC diving :) .

Also carrying a 80 around as a bailout cylinder for 30-40m dives seems a bit excessive.

One of the problems is that significantly longer bottom times are so easily done on CCR that the 'illusion' that you are removing cylinders (equipment & weight) when on CCR rather than OC is unfounded when you start analysing what you actually need to get you out of the water when it all goes t**'s up.

It also appears to me that 50% appears to have become the CCR 'standard' rich mix for bailout. Which appears to cope with the compramise of only carrying two stages, of which one has to be safe to breath as a bottom mix.

If there are 'problem' ali80's out there can you tell me which ones to avoid?

Gareth
 

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A short fat well off crap cave diver. Likes wrecks
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15,343 Posts
Thanks for the answers so far.

Yes I am CCR - I've been very 'good' & waited until I did my CCR mix ticket, prior to pushing my CCR diving beyond 40 - 45m.

Prior to this all my mix stuff had been on OC.

This year I'm switching 100% for all my pleasure diving to CCR, including the deep stuff.

I habitually carry rich right, lean left.

I guess I'm really rigging to dive to 60m, I can't see me pushing beyond 70m (although I have one dive planned for this later in the year).

This is begining to look like two 80's, which will mean I'm carrying bigger stages than when I did most of my OC diving :) .

Also carrying a 80 around as a bailout cylinder for 30-40m dives seems a bit excessive.

One of the problems is that significantly longer bottom times are so easily done on CCR that the 'illusion' that you are removing cylinders (equipment & weight) when on CCR rather than OC is unfounded when you start analysing what you actually need to get you out of the water when it all goes t**'s up.

It also appears to me that 50% appears to have become the CCR 'standard' rich mix for bailout. Which appears to cope with the compramise of only carrying two stages, of which one has to be safe to breath as a bottom mix.

If there are 'problem' ali80's out there can you tell me which ones to avoid?

Gareth

There are no problem 80s I am aware of only problem 7s.

botom mix to 50% is a smart move from PP Nitrogen spike and deco. On biger dives a drop tank of 80-100 on the boats not a bad idea also. Dont plan it in, just have it in reserve.

If left right id definatly "try before you buy" on the two 80s front. You can see how the steel 10 is floating up in fresh water in the pic above and you are no doubt aware of how floaty 80s are so imagine what its like full of mix and in the moare floaty salt water.

There are no regs on these tanks

The people i know diving two 80s have them both rigged on the left and they use the floaty mix tank to suport the sinky 50% tank. Then they trim out using a canister torch on the opposit hip.


If you wre down Kent way you would be welcome to try my ones. There are usualy some freindly DIR divers up arround Stony who would lend you a couple of 80s but be sure you have them full, not with 160 bar in. An 80 with 16 in is a diferent animal to one with 220 in.

ATB

Mark Chase
 
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