Doubling AL80's, bad idea?

[dhampton82]

I do most of my diving in the springs here in florida.....alot more sooner when I move out to the caves.......

Oh yea, and I will be going to either a 5mil or 7 mil suit.

72 degrees is just tooooo cold for me!

 

[utdivermatt]

Arent there still alot of problems using a smaller set of doubles like steph is talking about? Especially if you have a buddy with bigger tanks. If say I was diving doubled lp 104s (somethign I hope to be doign soon), and my buddy has a set of 72's. Doesnt this throw all kinds of crazy kinks into gas planning? Wouldnt my buddy need enough air to support me and them getting out of a cave? So therefore wouldnt both turn pressures be based on when both could breath off the smaller tanks? Seems like it presents alot of problems with the management issue. I dont know how much cave diving training goes into issues like this, but it makes sense to me that small doubles present a problem with buddies that have larger tanks. Im not a cave diver (yet), so please dont attack me if the logic is flawed

 

[MilitantMedic]

You pretty much nailed the basics of Rock Bottom, look at http://www.direxplorers.com/new-dir-articles/1376-rock-bottom.html for more info.

 

[mike_s]

There are several different types of steel 72's out there as well. I have a set of 2475psi 72's made by Norris in the 1970's. Although I haven't tested them they feel slightly negative. I think Faber and PST make 72's as well in 3300psi and 3442 versions.

There are some 72's that are 2250psi also. (which if you overfill them by 10%, gets you 2475's. I'm not sure if thats the same type 2475's you refer to. I'm guessing you dont' find many 72's with a 10% "+" (plus) rating anymore since the tanks are so old...

Arent there still alot of problems using a smaller set of doubles like steph is talking about? Especially if you have a buddy with bigger tanks. If say I was diving doubled lp 104s (somethign I hope to be doign soon), and my buddy has a set of 72's. Doesnt this throw all kinds of crazy kinks into gas planning? Wouldnt my buddy need enough air to support me and them getting out of a cave? So therefore wouldnt both turn pressures be based on when both could breath off the smaller tanks? Seems like it presents alot of problems with the management issue. I dont know how much cave diving training goes into issues like this, but it makes sense to me that small doubles present a problem with buddies that have larger tanks. Im not a cave diver (yet), so please dont attack me if the logic is flawed

several valid points you got there Matt. I don't know what the "cave diver rules" are. But I think you've got many variables like this regardless of the diving type. (although most standard recreational diving you don't have to worry about the marins of difference in air usage as much when doing more "normal" inshore diving.

 

[SeanQ]

There are some 72's that are 2250psi also. (which if you overfill them by 10%, gets you 2475's. I'm not sure if thats the same type 2475's you refer to. I'm guessing you dont' find many 72's with a 10% "+" (plus) rating anymore since the tanks are so old...

That's right. They're 2250 +10%. These tanks were coated in black vinyl which I peeled off to reveal a galvanized finish.

 

[UP4AIR]

I prefer to look at diving as a "What If " type of thing. In other words ...I'm diving my Lp 120 and my BC fails...go to my drysuit inflation. I'm diving my Lp120 and my BC fails along with my drysuit...go to my dual bladder. I'm diving my Lp120 and my BC (both bladders) fail and my drysuit fails....it wasn't my day to dive.

I think that if one keeps in mind the saying "One is none and two is one" as it applies to our equipment, then we can minimize our risk. If you want to double up Al 80's then prepare your configuration to do so. If you want to double up steels...then prepare your configuration to do so. Each equipment configuration has a time and place and no configuration lends itself to all diving conditions.

Most importantly.....diving is still a dangerous venture. Last I checked no human is able to breath water. Prepare your gear and yourself to what you are about to undertake and you can minimize your risk.

 

[utdivermatt]

You pretty much nailed the basics of Rock Bottom, look at http://www.direxplorers.com/new-dir-articles/1376-rock-bottom.html for more info.

Yay! Im finally starting to think like a tech diver!

 

[Adobo]

Yay! Im finally starting to think like a tech diver!

The notion of rock bottom or proper gas planning in general is not unique to tech/overhead diving. Perhaps you just had the good sense to think through some of the what ifs.

 

[TSandM]

utdivermatt, you do your gas management based on the consumption of the diver with the highest rate. And when DIR teams do bigger dives, they generally standardize to the same tanks.

But when you are LEARNING to dive doubles and you are a very small person, like me, starting out with a small set of tanks makes the physical stress of lugging them around and getting them on and off much easier.

 

[terrasmak]

In a 3 mm neoprene drysuit I wear 12 lbs of lead with an AL 80 tank. Not what I would consider a big sacrifice. I might even get away with the same lead if I doubled 2 AL 80s because of the weight of the manifold, bands, and such. But I have not seriously looked at it yet. I might next summer if I do Tech 1. It depends on my objectives.
.

I actually use 3 pounds less with my alum doubles than i do with a single alum tank. Its not my STA causing that either its less than a pound .