How to configure twin 7's?

[Justin Owen]

Hi guys, continuing the earlier posts regarding redundancy, I think i'm going to go for the twin-7's route, but need to know the best way of configuring the equipment. I'm not going to be diving extremely deep, and i'm not going to be doing speciality stuff like wreck penetrations or cave diving...

My present thoughts are:

Twin 7's (manifolded) mounted on my Buddy CommandoTD
My current 1st stage/DV (ATX40) on the right cylinder with my suit inflator.
A new ATX40 1st stage with my current AAS (ATX40), BCD inflator and pressure guage on the left cylinder.

As I see it I would have basically the same kit configuration as I have now - but with the redundancy/extra air i need to do the slightly more challenging dives (upto 30m).

I would plan to upgrade to a wing at some point in the near future also (those who told me only six months ago to get a wing to start with   )

Is there anything inherently wrong with this configuration? As I see it i get the benefits mentioned above, and my buddies/club members will be seeing a configuration they're used to dealing with.

While i'm thinking about it - if you have to isolate the left cylinder and call the dive, how do you know how much air you have available for your ascent/deco? Simply that you were already carefully monitoring your air supply???

Thoughts appreciated.

[abucksdiver]

<font color='#000080'>I thought a manifold allowed you to isolate one cylinder but to still use its regs/gauges/inflators?

(Only a numpty single cylinder diver, so I don't know for sure....)

abucksdiver

[Justin Owen]

From my researh (Dom's website - again!) you isolate the regs and not the &quot;cylinder&quot; as such? That way you can use the contents of both cylinders off a single reg even when the other is isolated?

The situation i was thinking of was a burst hose/o-ring that meant the reg had to be isolated - if it's the one with the guage on you have no way of reading your contents...? I'm still learning - i too am currently a single cylinder numpty diver!

[Chris Hall]

<font color='#728FCE'>This was the type of configeration used by a lot of people before wings became popular &amp; without a manifold.

I am looking into putting twin 7l on a Commando TD, had to get rid of the wing and twin 10s as they were to heavy. I have dived with 2x12l on this jacket and it handled it well. With the manifold, get used to using it in the pool and going through shut down drills and then go diving.

Send me a PM and we can compare notes and have a dive.

[daz]

Just my thoughts...

Twin 7's (232 or 300s) &nbsp;just out of interest.

I tend to use my suit more than my wing so I bring my suit inflator off the same post as my spare reg and my jacket off the post with my primary. &nbsp; Throughout the dive I am effectively using both 1st stages so hopefully if one fails I would spot it reasonably quickly.

There was another reason why I set mine up like this, but I can't for the life of me remember what it was &nbsp;

I only have a guage on one post and in the event of having to shutdown then I would know I had enough air in the remaining cylinder for the ascent and safety stop for the following reason.

Plan the dive as if you had a single 7, &nbsp;What is the minimum amount of air in that 7 for you to ascend and do a safety stop ? &nbsp; Lets say after all the calcs it equates to 560l (80 bar ) &nbsp;then you should plan to finish your dive and start your ascent when your guage registers 80bar. &nbsp;If one side goes TU after that you still have enough in the remaining cylinder. &nbsp;(This is based on you having to isolate at the manifold not the post and assuming one side is completely unavailable).

Hope that is clear, &nbsp;sorry if it is a bit rushed.

Daz

[MartinS]

One other thing to remember - Apeks regs can't be swapped from right to left-handed, so you'll need to bring your secondary reg behind your neck and on a necklace/bungy under your chin. This may mean you'll need a longer hose, and some may say you should have a longer hose for your primary anyway, but I don't and it works fine for me - in an OOA situation, pass primary reg to buddy and breathe from reg under chin (which is close to hand and easily reached).
HTH
Martin

[Justin Owen]

Hi Martin,

As my AAS (octopus) is mounted on the left side of the 1st stage, it could still be routed to the left couldn't it? Why would it need to be routed behind my neck? (Unless i did want to necklace it).

At present my config is totally &quot;BSAC&quot;, not saying it's the best way of doing it but we're all drilled at moment to look for octopus on left...

[Dominic]

Originally Posted by [b

Quote[/b] ]A new ATX40 1st stage

I hate to be pedantic, but there's no such thing - the ATX range are modified TX second stages. The first stages remain the same, either DS4 or DST.

I personally recommend you get the DS4, which is the non-turret version. You don't need the swivel on a twinset.

Your described hose routing is pretty much the same as mine, only I have my LP hoses the other way around, with the wing on the main and the drysuit on the left. Mainly because I put more air into the suit on descent than the wing, so it spreads the load a bit.

(There's also the DIR argument that if you've handed over your main and the backup doesn't work, you can breathe off the wing inflator if it's on the right post...)

[Dominic]

Originally Posted by [b

Quote[/b] ]Why would it need to be routed behind my neck?

Because it's a twinset. It's there for redundancy. That means you have to be able to breathe off BOTH cylinders. You have to configure your DVs so you can breathe off both of them.

A single + octopus rig has two DVs. One is yours, the other is for your buddy if something goes wrong.

On a twinset, you have two DVs. One is yours, the other IS ALSO YOURS if something goes wrong. If you can't breathe off your backup DV, you might just as well use a single 15 instead. Less to go wrong, and its cheaper too!

That's why the long hose is so popular - you can have your backup under your chin where it's dead convienient for YOU, your primary is in your mouth, dead convenient for YOU, and yet you still have a DV that's convenient for your buddy without having to have more than two DVs

[Justin Owen]

A whole hour and a half! What took you so long Dom? &nbsp;

OK, I understand the thinking and you're probably right - it's just that it doesn't seem too much of a hindrance to me to take my octopus from the left where it's clipped to my BCD and stick it in my mouth. That could of course change at 30m - especially as i've never had it happen to me before - so hard to say. I take on board what you're saying though.

So with a DS4, the best way of routing my AAS would be to the right and then under my chin... What about the length of hose? My AAS hose is pretty long, couldn't that be an issue...?