Doubles...

[Dan Gibson]

Why, are you looking for a set of 104s?

JImC, where are you finding LP104s?

 

[PerroneFord]

Why, are you looking for a set of 104s?

Possibly. I have a set of 108s in mind for right now, but I could be convinved otherwise depending on cost.

 

[Dan Gibson]

You might have to get in line, but it might be possible if the other people pass. pm me for details if you are interested.

Possibly. I have a set of 108s in mind for right now, but I could be convinved otherwise depending on cost.

 

[mart1]

Even if you breath less than everyone, its the guy with the smallest tanks that restricts the dive.

If you breathe less than everyone else, you should have the biggest tanks.Sounds strange, but it's true.
And my advise would be to get into doubles as soon as possible, never mind Doing It wRong.

ciao, mart

 

[xiSkiGuy]

If you breathe less than everyone else, you should have the biggest tanks.Sounds strange, but it's true.
And my advise would be to get into doubles as soon as possible, never mind Doing It wRong.

ciao, mart

Huh? :06:

 

[matt t.]

Huh? :06:

At least this time he didn't recommend the double bladder wing

 

[Meng_Tze]

To answer that I'll have to get into a bit more of a discution about thirds. So here goes:

Basic idea of gas management. Allways have enough gas to get you and your buddy out. In caves this means 1/3rds for an outflowing cave. 1/3rd in, 1/3rd out, 1/3rd for buddy.

Senario #1, no tank size matching:
Lets call the cave a squair profile to 102ffw (4ATA) and ignore deco.
Diver 1: double 100's filled to 3400psi. SAC rate on this dive is 0.5cf/min.
Diver 2: double 130's filled to 3400psi. SAC rate on this dive is 0.75cf/min.

Doing 3rds without regard to size matching:
Diver 1: 1100psi (64cf) third, 2300 turn
Diver 2: 1100psi (83cf) third, 2300 turn

They dive into the cave and exactly at 28 minutes, diver 2 hits his turn (2300psi) and diver 1 has used 56cf and has 2440psi (141cf) left. Diver 2's back gas is instantly vaporizes. Diver 1 and diver 2 need 147cf to get out, they have 141cf left. You will note the rounding up here, if they dove to true thirds instead of rounding up to the next 100psi they would be worse off.

So, you have to limit the penetration to the smallest 1/3rd on the team. In this case, diver2 must use 64cf for his third. Diver 1 does nothing, Diver2 must recalculate his third.

Diver 2: 800psi (64cf), turn 2600psi.

Same dive, except dive2 turns the dive at 21 minutes and both divers survive.

Agreed, the trick is not to 'count' on SCR's. Use them as a guide to relate to time. When things happen, or you get cold or whatever..... SCR (DCR actually) get higher. You can also not account for the actual profile of the cave itself. Bottom line:the smallest volume of gas determines the 1/3 of volume used before turning.

I say this with the caveat that no-one should try this (overhead environments with rule of 1/3's) without proper training!

 

[PerroneFord]

You might have to get in line, but it might be possible if the other people pass. pm me for details if you are interested.

Given my experience last night with twin95s, I think I had best leave the 104s alone for a while! Those twin AL80s, and a pair of 72s are starting to look a LOT more attractive!