Doubles etc.

[damageddiver]

You want to go tech!

http://www.5thd-x.com/videos/TechTeaser.mov

 

[in_cavediver]

My reason for independents vs. manifolded doubles....

With the independent doubles I'd be able to get maximum gas volume out of 4 tanks to do 3 dives in relatively shallow (<100fsw) to get as close to my NDLs as possible. I refer to my gas management post a few pages ago for extended explination.

I may be a bit off, but if you are looking to push the 'NDL' on multiple dives, you'd be far better off taking training to change your limits rather than worrying about the gear configuration to allow it. Think Advanced Nitrox or equivalent intro to tec or decompression class. What you learn will allow you to go deeper longer or to understand how to stay longer shallower.

Pushing NDL's on repetive dives is not a good idea. Having the gear to allow it still doesn't make it a good idea. There are ways with the right training to do those types of dives with a larger margin of safety.

 

[AndrewJD]

With the independent doubles I'd be able to get maximum gas volume out of 4 tanks to do 3 dives in relatively shallow (<100fsw) to get as close to my NDLs as possible. I refer to my gas management post a few pages ago for extended explination.

Ok, your objective is to minimize the amount of gas that you "waste" given the decompression limits of your current training. From an equipment perspective I think that swapping four tanks between three dives is silly. A better way...

Let's say you want to do 3 dives at 100ft for 30min (32% nitrox). I'll assume your SAC is 0.75 (conservitive?). That means you'll need 90cuft of gas at the bottom plus what ever you use on the ascent, I don't know how you ascend, but let's assume 1 minute stops starting at half max depth, so 10cuft*. 100cuft total.

Dive 1: Doubles (190cuft) with a stage (slung 80) (77cuft) of bottom gas. Breath the stage until empty the switch to back gas.

Dive 2: Doubles (170cuft) with another stage (77cuft). Again breath the stage until empty and then switch to back gas.

Dive 3: Doubles (150cuft) with no stage. Backgas the entire dive.

End with 50cuft of gas in your doubles.

With this arrangement, you don't have to worry about screwing with your doubles on the boat, you get your three dives at your NDL limit and you have a huge reliable redundent reserve should a stage fail on any dive or the random solo diver with no air mug you. Also, this configuration will set you up much better as you continue to advance your diving into decompression.

So you'll need, two Aluminum 80s, stage rigging, a doubles wing, a set of bands, a manifold and the third regulator set.

As for additional cost, I think this is a better investment for the long term and the benefit is found in reduced overall risk.

Anyway, good luck with what ever you decide to do.

Jonathan

*Yes, no reserve for his buddy but he is diving solo after all...


P.S. I agree with in_cavediver completely.

 

[limeyx]

Ok, your objective is to minimize the amount of gas that you "waste" given the decompression limits of your current training. From an equipment perspective I think that swapping four tanks between three dives is silly. A better way...
...
So you'll need, two Aluminum 80s, stage rigging, a doubles wing, a set of bands, a manifold and the third regulator set.

As for additional cost, I think this is a better investment for the long term and the benefit is found in reduced overall risk.

Anyway, good luck with what ever you decide to do.

Jonathan

*Yes, no reserve for his buddy but he is diving solo after all...


P.S. I agree with in_cavediver completely.

Stop making so much sense

Acutally, he does have enough rock bottom gas pretty much even though say only 10 is used, in all cases there is plenty spare in the doubles for a buddy.

Using a stage does bring up some more complex issues than just doubles though, so some kind of class/training would probably be in order.

 

[NJScubaDoc]

To be honest I wasn't terribly wild about the tank switching in between dives. I like the plan, especially that it allows the equipment to grow with me as I move forward.

I'm wondering, how cumbersome would the 95 be in comparison to the AL 80? It would be no problem to sell the other two 95's and get 80's, but I'm just wondering if that's necessary. If anything though I'd probably get LP steel 85s instead of the AL 80.

I guess the big decision now is to either go independent or manifolded...and now that I've seen both sides of the spectrum it'll make the decision easier. Thanks for the responses.

 

[AndrewJD]

For stages and deco bottles I'd stick with Luxfer Aluminum 80s and 40s. They have best bouyancy characteristics for the job.

See the 5thD-X technical teaser video a few posts up. The right bottles you can carry as many as you want. The wrong ones and you won't be balanced.

Jonathan

 

[tonka97]

.....
I would advice finding some local people that dive similar ways, and FWIW, independant doubles seem like both a PITA and not an optimal configuration.

Why would independent doubles be a PITA?'

My rig: Necklace mounted back-up regulator always ready on a redundant 80 cf tank.

Plan dive for 1 tank, with 80 cf as back up/emergencies.

This skips problems with the manifold, and valve isolation drills.

 

[fire_diver]

Do you have your independant tanks set up with left and right handed valves? If not, are you able to shut down your left tank in an emergency?

FD

 

[jeckyll]

Why would independent doubles be a PITA?'

My rig: Necklace mounted back-up regulator always ready on a redundant 80 cf tank.

Plan dive for 1 tank, with 80 cf as back up/emergencies.

This skips problems with the manifold, and valve isolation drills.

So really, you've got yourself a 80 cf pony bottle with no secondary 2nd stage on your primary. Seems like a lot of extra gas to carry.

*shrug* Takes all kinds

 

[ianr33]

Do you have your independant tanks set up with left and right handed valves? If not, are you able to shut down your left tank in an emergency?

FD

The beauty of independant doubles is that you do not need to shut down anything in an emergency. Just ascend using the gas in the other tank.

Of course it is more elegant to shut off the valve if you can. I can reach the left valve on independants but it is tough. Another alternative is to turn the left tank around so that the valve faces away from you and the valve knob is facing leftwards. Probably need to reconfigure hoses to do that.

Or you could just dive sidemount then everybody thinks you are cool rather than calling you a stroke