Doubles setup recommendation

[Tantram]

Wow, I'm absolutely blown away by the amount of knowledge in this post. I'd like to thank everyone who replied; it has truly been helpful. To some degree even eye-opening. I'm going to contact the instructor and come up with a plan now that I am armed with much more knowledge than I had. I'll circle back and reply with my outcome so that others can benefit if they run into a similar situation.

For those that were asking:
Yes, I have gone through physical therapy for my shoulder. I'm pretty maxed out on how good it will get without surgery. Trying to put off that surgery as long as possible as the recovery time is absurdly long and I've gotten past the 'living with pain' part and now only dealing with limited mobility reaching back. If this ends up being a limiting factor to what I want to accomplish, maybe I'll have to commit to getting it repaired.

In terms of gas I'm used to carrying .. I will adjust gas according to the dive and what my buddies are running. On a shorter shallower dive I'll bring either 2x40's or 2x50's. On longer dives I'll bring 2x80's (I don't like the feel of 2x100s. In order to get good trim they pull on my lower back in a way that's uncomfortable after 30min or so).

 

[Tantram]

Carbondive 300 10ltr twins same weight as 1 10ltr steel

Wow, I've never heard of this. Thank you for pointing it out!

 

[CptTightPants21]

Why? I think fundie also solver gas management for different tank size in a term.

I just don't think it is realistic to assume people show up in fundie with the same type of tanks.

I don't think it's 100% identical tanks, but more similar tanks. A mini set of doubles is a much smaller volume compared to a regular sized set of doubles. A regular set of doubles is at least 50-160% more gas. It's like trying to plan a single tank dive with a group of people and someone plans on just diving with an al40. It throws off calculations, changes the dynamic of the dive, and is just a little bit weird/unexpected.

 

[Ryan Mcshane]

Why? I think fundie also solver gas management for different tank size in a term.

I just don't think it is realistic to assume people show up in fundie with the same type of tanks.

Why complicate things?

All over Europe GUE divers use double 12s. The odd time people will use something bigger for deeper cave. Most dive centres across Europe rent d12s too.

 

[eelnoraa]

Carbondive 300 10ltr twins same weight as 1 10ltr steel

Not so fast. This tank is 21.1lb empty but +7lb empty in water. The effectively the drive is carrying 28.1lb. A LP85 is about 31lb but 0lb empty in water. Diver is carrying 31lb. Not much different is Carbondive 300 10L spec is correct.

The "effective" dry weight of a tank is the dry empty weight + empty buoyancy. Look at this if you want to minimize the weight on land.

 

[Celt]

Wow, I've never heard of this. Thank you for pointing it out!

Should say carbondive 300 bar 6.8ltr twin pack compared to 10ltr steel lp twins would be half the weight

 

[Marie13]

Wow, I've never heard of this. Thank you for pointing it out!

Carbon tanks may not be available for scuba use in the US. I know fire departments use them.

 

[flymolo]

Has anyone suggested double AL80s yet?

 

[Ryan Mcshane]

I’m 5’9 and 12s are perfect for me so I hypothesised that that if you’re 5’7 they will be slightly too long. Body composition like different length arms, legs, muscle change it for different people, and harness adjustment too.

Maybe I’m wrong, are you 5’7, how does it feel for you?

I’m 5’8 and use d12. My 5’2 girlfriend also uses d12. 10s put too much weight high up.

 

[Celt]

Not so fast. This tank is 21.1lb empty but +7lb empty in water. The effectively the drive is carrying 28.1lb. A LP85 is about 31lb but 0lb empty in water. Diver is carrying 31lb. Not much different is Carbondive 300 10L spec is correct.

Carbondive

Not so fast. This tank is 21.1lb empty but +7lb empty in water. The effectively the drive is carrying 28.1lb. A LP85 is about 31lb but 0lb empty in water. Diver is carrying 31lb. Not much different is Carbondive 300 10L spec is correct.

The "effective" dry weight of a tank is the dry empty weight + empty buoyancy. Look at this if you want to minimize the weight on land.

carbondive 300 claim you only have to carry 1-2kg extra, you’ll have to take it up with them