Independent Doubles!

[DaleC]

A few questions if you don't mind!

I was told by one of my LDS guys to install a 7' hose on my primary reg, which has my dive computer attached, a small SPG and the low pressure hose for the bc. Now he said in an OOA situation for a buddy, to remove my primary reg from my mouth with the 7' hose and pass it to my buddy, and for me to switch to the regulator on the 2nd tank. I was wondering your thoughts on that?

I won't tell you how to dive but I will describe what I do:

I put the longhose on the right post. This avoids confusion with others who are diving longhose set ups and the hoses will be the correct length for routing that way.

I don't use an AI dive computer so no comment there.

Learning how to donate with a longhose in an OOA, the drills, not trapping the longhose etc... are all covered elsewhere on SB in very good detail, just use the search function. I could type for hours and not cover it all (and others have already done a stellar job of it).

A fact one must consider with ID's is that for half the dive you are on the back up reg (left post). For me this is always the first half of a dive where there is less chance of an OOA but still, should an OOA diver need air my longhose would at that time be clipped off on the right chest D ring. For that reason I secure the clip to my primary reg with either an O ring or thin piece of bicycle tubing. Worse case scenario I, or someone else, could just pull the reg free from the D ring without unclipping.

Another question, what about an octo, Is anyone still diving with an octo on one reg? I hear so much different opinion's about the octo. Its just gonna confuse you, why need it... Just curious what you guys think, or is it just better to use the two regs?

I just have two regs, one on each post/tank. Here are the scenarios:
Solo - I experience a failure with one tank. Switch regs and begin ascent.
Buddied - Buddy experiences a failure. I donate the longhose and we begin ascent.
In the OW setting I plan for one failure. With that in mind there is no need for an extra reg attached to one of the tanks.

Another question. And I may need to be pointed in the right directions. I was thinking since my dive computer is air integrated and is on the left post, I would start on the left side for 1000 psi, then switch to the right and use that till it reaches 2000 psi and switch back to the left side for the last 1000 psi. Always keeping 1000 psi in each tank at the end of the dive. So I was wondering what everyone else is doing as far as gas usage?

Lots of debate on reg switching. First I would suggest you do your own homework in regards to what reserve gas levels you will need for your dives - don't use someone elses model. Here's the link to Lamonts rock bottom page: Rock Bottom and Gas Management for Recreational Divers
From there one must decide how important gas preservation is for the dives they are doing. If max capacity is a factor most divers switch every 500psi or so. That way they have max gas in either tank should a failure occur. If max capacity is not a factor (direct ascent possible with rock botton reserves) then reg switches don't need to be so frequent. I often just do one reg switch in a dive. Descend on left post to 1000 or 1500psi, switch, right post to 1000 or 1500psi, begin ascent.

 

[Atomic_Diver]

I have dove independant doubles once before (AL 80's) from what I remeber when I did a dive on the Spiegel Grove (2 dives) I breathed down 1/3rd of one tank, and 2/3rds of the other so that at the end of the first dive there was the equlivent of 1 AL 80 left of the 2 tanks combined to use on dive 2, that or you could use half of 1, and half of the other...

 

[TheBigPhillyFish]

Ok the rig is set-up, had about 1 1/2 hour pool time with it to place everything where I thought it was comfortable, and nothing was in the way, everything was easily accessible. I am sure once I start diving a few times, I may want to change things a little here and there. I also practiced plenty of regulator switching drills, and didn't have any issues. I will say, I do prefer diving with two tanks versus single tanks, trim and buoyancy is is so much easier and more comfortable. I have attached some photos of the set-up, if anyone notices anything that I should look at, or maybe something that could be different, let me know.

Also I figured run the primary regulator for first part of dive and run down 1000 psi, switch over to secondary regulator and run down to 2000 psi and switch back to primary regulator for another 1000 psi. This leaves 1/3rd in each tank (1000 psi) in each tanks, which if fine for down to 100'. Any depth beyond 100' I have calculated to leave an extra 200 psi for a total of 1200 psi per cylinder. The 1200 psi in each cylinder will cover anything within recreational limits after 100'. If I do anything deeper then 140' I will re-calculate for the depth, but I have no intentions of getting that deep with this rig, just yet. Not till I have had sufficient time to become a custom to the set-up.

Leave any comments or concerns about the rig! Thanks all for the input and feedback.

 

[kanonfodr]

A quick question about your gas limits: What if you were to lose a tank @ 100 feet and you only have 1000 PSI left in your good tank, and your buddy just went OOA?? Unless you are a very light breather, you may not have enough gas to make it up safely.

Peace,
Greg

 

[ianr33]

Just a couple of points.
1) Probably a good idea to start breathing the long hose as you suggest as the start of a dive is when many problems will happen. Dont see any point changing from the secondary reg at 2000 psi. At that point both tanks are at the same pressure.Why bother changing? Why not breathe that tank down to 1500 before switching?

2)IF the secondary reg is on a necklaced bungee that means you can not donate the reg in your mouth. Consider having the long hose reg which will be clipped off on a breakaway attachment.

What are those nasty things on the bottom of your tanks?

 

[ianr33]

A quick question about your gas limits: What if you were to lose a tank @ 100 feet and you only have 1000 PSI left in your good tank, and your buddy just went OOA?? Unless you are a very light breather, you may not have enough gas to make it up safely.

Peace,
Greg

That would be 2 failures. Nobody plans for 2 failures.

(I dont dive with people that "just" go OOA )

 

[Atomic_Diver]

same situation, but you have deco to do now what...one thing learned over the years is to do the best you can to prepare for the worst...

 

[DaleC]

A quick question about your gas limits: What if you were to lose a tank @ 100 feet and you only have 1000 PSI left in your good tank, and your buddy just went OOA?? Unless you are a very light breather, you may not have enough gas to make it up safely.

Peace,
Greg

What if you are at 100 feet with manifolded doubles and your primary regulator free flows (so you shut down the right post) and your buddy goes OOA?

same situation, but you have deco to do now what...one thing learned over the years is to do the best you can to prepare for the worst...

Ones at the end of a rec dive, their buddy goes OOA and they suddenly find themselves in deco??? I don't know what passes for dive planning these days but you guys better be careful.

 

[StreetDoctor]

That would be 2 failures. Nobody plans for 2 failures.

(I dont dive with people that "just" go OOA )

I believe in the GUE Tech 1 manual you are trained to be able to handle up to 3 failures.

 

[DaleC]

Leave any comments or concerns about the rig! Thanks all for the input and feedback.

Looking at the rig I see some dangly bits I wouldn't have etc... but I'll comment on some glaring concerns I would think more about:

1. Two spgs on the left post? I know one's a computer but either one trusts their gear or they don't. If you have two on the left, why not two on the right etc... If you like the computer I would consider losing the one on the shoulder.

2. The reg hoses. As predicted, putting the backup on the right post leaves a big loop when it is bungied around the neck. Try looking in the mirror with the hose on each post and see the difference. The coiled up longhose may not deploy that easily (I don't know as I have never tried it that way?) but it would certainly be impossible to restow in that position. One side effect is that you will be unable to do regular donation drills that way and thus be rusty with an important skill. Also, if you lose your primary it could fall behind you and become trapped behind the wing somewhere. With the traditional longhose routing, if you drop the reg, it is easily recovered. And, as noted before, you need a tear away on the reg clip or it could be dangerously trapped in an unplanned OOA.

3. Wing inflator on left post. The problem here is that traditionally the left post in more prone to failure so the primary bouyancy device is put on the right post. In the pic above it wouldn't matter as your valves are backwards anyways but everybody is going to assume it's on the right.

4. Don't like that left post valve (but you already know that). If you are going to dive it long term splurge for the lefty.

5. Overall, too many modifications. That might sound funny from me but I do believe that a rig with too many mods will confuse everbody around you. I had to look for a long time to figure it out myself. If you recall the description about my rig I say it looks and acts exactly like a manifolded doubles rig except for the removal of the isolator (and an extra spg).

Anyways it's your rig. Rather than criticise outright I'd rather try to help you fine tune it (as it seems your set on diving it). If you want some more thoughts on the little dangly bits let me know but I didn't want to overwhelm you so that you wouldn't think about the bigger issues.

I would like a pic of how the mounting system works though, if you don't mind.

Good luck,
Dale.