Doubles w/o manifold...

[oversea]

Oversea, how tall are you? Those 119's are kind of stubby and might be a bit nose heavy for you if doubles up. 45# wings are on the limit i reckon for those tanks, dive-rite suggests that the trek wing (45#) can be used with double 119's, but i would think its tighter than using lighter doubles. As for regs, you need an independant 1st stage and 2nd stage on each valve, be it independant or manifolded doubles, dont put more than one 2nd on a 1st stage as you would with a singles set up, it isnt needed, but you cant get away with only one 1st stage (that is one of your redundancies) between both valves if that was what i thought i was reading into the question.

Whats the downside to doubling up my aluminum 80's and keeping the steels to shallower single tank dives?

 

[MSilvia]

I currently dive with double 80s, and a 45# wing should be more than enough with them, it would also be a much safer rig to dive in a wetsuit than the double steels, as you could still swim them to the surface with minimal difficulty if you had a wing failure. That would still leave you with a pair of 119s, which would give you greater capacity for diving singles. As far as regs go, you can just add a 1st stage to what you already have, and switch one of your seconds over to it.

As for the gas management thing with doubles, assuming you're using the 80s, and that 3000psi is full capacity, you know you've used up a full tank's worth when you hit 1500psi. So long as you're at the surface with at least that much, you know you have at least half of your gas left.

 

[MSilvia]

Whats the downside to doubling up my aluminum 80's and keeping the steels to shallower single tank dives?

You might make other single tank divers jealous.

 

[oversea]

I currently dive with double 80s, and a 45# wing should be more than enough with them, it would also be a much safer rig to dive in a wetsuit than the double steels, as you could still swim them to the surface with minimal difficulty if you had a wing failure. That would still leave you with a pair of 119s, which would give you greater capacity for diving singles. As far as regs go, you can just add a 1st stage to what you already have, and switch one of your seconds over to it.

As for the gas management thing with doubles, assuming you're using the 80s, and that 3000psi is full capacity, you know you've used up a full tank's worth when you hit 1500psi. So long as you're at the surface with at least that much, you know you have at least half of your gas left.

Its that simple? I posed this question because once I get the steel tanks, I just don't think I would use them much. If they were doubled up now I would.

What criteria determines the need for doubles other than say redundency? It seems part of gear selection these days is trying to not look like the new guy but also not look stupid. I'm fine with diving the 119 and a pony, but doubles had been suggested for numerous reasons, but most have been some sort of a preference other than need.

 

[simbrooks]

Its that simple? I posed this question because once I get the steel tanks, I just don't think I would use them much. If they were doubled up now I would.

What criteria determines the need for doubles other than say redundency? It seems part of gear selection these days is trying to not look like the new guy but also not look stupid. I'm fine with diving the 119 and a pony, but doubles had been suggested for numerous reasons, but most have been some sort of a preference other than need.

Its mostly a need rather than a preference. That is needing the gas, with backup, redundancy, no immeadiate access to surface air (hard or soft ceilings - ie cave/wreck or deco). Given the option i like my doubles, but there are many dives i would seriously wonder about taking them on where long hikes are to be expected or if a single tank would fill the need.

It is fairly simple, but you need time to work on/with them, a good mentor is helpful to get the most out of such equipment.

 

[MSilvia]

What criteria determines the need for doubles other than say redundency?

Basicly what simbrooks said is right on. I didn't bother with doubles until I started doing deco and diving past 130' (soft ceiling), and had to be able to manage problems without surfacing. Doubles gave me both the added capacity to stay at depth longer, and the ability to isolate and switch regs if I have a serious malfunction.

Prior to that, I used a stage-mounted pony bottle as an emergency backup. In either case, you need an additional reg.

It seems part of gear selection these days is trying to not look like the new guy but also not look stupid. I'm fine with diving the 119 and a pony, but doubles had been suggested for numerous reasons, but most have been some sort of a preference other than need.

IMHO, the diver who looks the least stupid is the one who's diving skillfully and using the equipment that's right for the job. Since you aren't planning overhead or deco diving, I think you'll get more mileage out of a pair of single 119s and an AL40 (which shouldn't make you any less stable) for emergency use. Think about it... that's 39cf more available gas on your back (rock bottom calculations aside) per dive, and you can use the same AL40 on both dives assuming you won't have to use any of it. 39cf+40cf is more gas than an AL80 holds anyhow (just over 77cf), and you won't have to abort dive #2 if you use some of the extra back gas to extend your bottom time. Given the kind of diving you're doing, that makes more sense to me.

 

[oversea]

IMHO, the diver who looks the least stupid is the one who's diving skillfully and using the equipment that's right for the job. Since you aren't planning overhead or deco diving, I think you'll get more mileage out of a pair of single 119s and an AL40 (which shouldn't make you any less stable) for emergency use. Think about it... that's 39cf more available gas on your back (rock bottom calculations aside) per dive, and you can use the same AL40 on both dives assuming you won't have to use any of it. 39cf+40cf is more gas than an AL80 holds anyhow (just over 77cf), and you won't have to abort dive #2 if you use some of the extra back gas to extend your bottom time. Given the kind of diving you're doing, that makes more sense to me.

I agree, this brings me back to where I was originally and feel as though I have a grip on what I was doing. As far as the balance when using a pony, does it seem to throw you off? Will I need to offset some of my weight to compensate?

Also, what is meant by side mounting?

 

[simbrooks]

I agree, this brings me back to where I was originally and feel as though I have a grip on what I was doing. As far as the balance when using a pony, does it seem to throw you off? Will I need to offset some of my weight to compensate?

Also, what is meant by side mounting?

That sometimes is the nature of research, but at least you have asked the questions and learnt something new today! Everyone was in that boat of not knowing about doubles etc at one time or another, if it looks like its best to go pony, then thats your call, but at least you looked into it. Not sure about weighting etc, but ponies arent that heavy, mount them upside down to the side of your tank for best effect, plenty of products out there.

Side mounting is a whole different thing in terms of rigging than back mounting independant doubles. Its mostly used for caves where you will have restrictions or a low ceiling (where you cant get back mounted tanks through) and you can offload your tanks one at a time to get through or keep gliding along without the same chance of getting snagged up in those two cases, respectively. Go here for more info, you clip your tanks off your chest d-rings at the neck of the tank and the base of the tank to an extension of whatever BP/BC you are wearing, same gas management principles apply as mentioned in the last 50+ posts

 

[MSilvia]

As far as the balance when using a pony, does it seem to throw you off? Will I need to offset some of my weight to compensate?

Since the 40cf aluminium tanks are close to neutrally bouyant, you should be able to add or remove one without it having any substantial effect on your bouyancy. If you use a steel bottle you'll need to make adjustments.

Also, what is meant by side mounting?

Side mounting is a diving configuration where you have one independant tank on each side, so you can get through tight overhead restrictions in caves, etc.

This is a picture of a sidemount configuration:
http://www.advanceddivermagazine.com/images/Armadillo/ArmadilloBret.jpg

With regard to pony bottles, side mounting or sling mounting are terms I've sometimes heard used to describe a stage mount setup... like tech divers use for stage and deco bottles. Personally, I prefer stage mounting to any of the devices that mount a pony to a tank on your back. It's quite comfortable, and more out of the way than you might believe. I've tried it both ways, and have no intention of ever going back to a tank mount of any sort. That of course is a matter of preference, but FWIW stage mounting is usually cheaper too.

Here's a page describing how to rig a bottle this way:
http://www.mikey.net/scuba/gear/stages.html

Here's a picture of one in use:
http://www.thedecostop.com/photopost/data/2/359scubacop-med.jpg

 

[oversea]

Since the 40cf aluminium tanks are close to neutrally bouyant, you should be able to add or remove one without it having any substantial effect on your bouyancy. If you use a steel bottle you'll need to make adjustments.


Side mounting is a diving configuration where you have one independant tank on each side, so you can get through tight overhead restrictions in caves, etc.

This is a picture of a sidemount configuration:
http://www.advanceddivermagazine.com/images/Armadillo/ArmadilloBret.jpg

With regard to pony bottles, side mounting or sling mounting are terms I've sometimes heard used to describe a stage mount setup... like tech divers use for stage and deco bottles. Personally, I prefer stage mounting to any of the devices that mount a pony to a tank on your back. It's quite comfortable, and more out of the way than you might believe. I've tried it both ways, and have no intention of ever going back to a tank mount of any sort. That of course is a matter of preference, but FWIW stage mounting is usually cheaper too.

Here's a page describing how to rig a bottle this way:
http://www.mikey.net/scuba/gear/stages.html

Here's a picture of one in use:
http://www.thedecostop.com/photopost/data/2/359scubacop-med.jpg

I was actually intending on using a neck ring W/ clip and clip/band clamp at the bottom of the pony and clip the whole assembly off of my bp, like the way oms shows their stage or argon rigging. I don't really like the pony tamers, etc. seems to be way too much crap involved.