doubles besides AL 80's when diving wet...

[Icarusflies]

Hello All;

I want to dive doubles for extended bottom time. I ll be diving wet in summer so besides AL 80's (not a lot of gas when used in 2 tank dives) what would be a good tank capacity to stay in the safe side...I am concerned about the negative bouyancy of steel tanks when diving wet.

Thanks;

 

[Jim Lapenta]

Steel 72's or lp 85's. I can swim up my rig with either when diving wet doubled up. Phil at Divesports was also running a deal on lp77's. TDL had some steel 80's that were meant to replace the al with about the same buoyancy characteristics although they may be out of them. If you are looking at a large single pumped lp 95's give alot of gas. What I use anyway. I know of others who use single 120's.

 

[Wildcard]

If twin 80s are not enough air to hit NDLs then you have bigger problems. If your only goal is more air then think about a single larger tank. Not sure about your dive set up but a single steel 100 with a 3mm suit should get rid of almost all of the rest of your weights.
Maybe you can clairify what your goal is here.

 

[Icarusflies]

Thank you Jimlap but what I am looing for is for more gas in doubles that is why I was thinking about double AL 100 (very heavy tho) or go for steel doubles 100 or more but then I ll be way negative diving wet....do you guys dive stell double diving wet?

 

[Icarusflies]

Wildcard, my goal is to have more air in both of my to tank dives without switching tanks...in other works my doubles should last two dive...forgive my ignorance about doubles but that is why I am asking to more experienced divers.

 

[pickens_46929]

Yep, steel LP 85's... make sure you get the one's that are neutrally buoyant when empty as there are some that are slightly negative... then use an aluminum or kydex backplate vs. stainless...

Tech Diving Limited's chart is a good resource for tank info, not to mention they are a good place to get gear.

But if you're looking simply to save from changing over tanks during the surface interval, a large single works well too.

What is your typical profile? (depth and time)

I use an HP 120 and can get two decent recreational dives out of the tank without switching over.

 

[Wildcard]

Before you rush out and buy them try to rent or borrow a similar set up. I think you will find it's far easer to change out a tank than to lug two around all the time.

 

[Icarusflies]

Yesterday I did the tortuga for 39 min at 105'' and then we did the anothrer wreck at 60' for 49 min (Nitrox)....in these 2 dives I used 153 cuf of gas...so I could not have done it with double AL80's (not enough margin)

 

[ianr33]

Yesterday I did the tortuga for 39 min at 105'' and then we did the anothrer wreck at 60' for 49 min (Nitrox)....in these 2 dives I used 153 cuf of gas...so I could not have done it with double AL80's (not enough margin)

The way I would do that would be to use the existing double 80's and sling another 80 on the first dive.Breathe off the stage first. On the second dive use the (full or almost) doubles. Downside is that you are dragging a lot of tanks around for an NDL dive.

Alternative would be 2 single steel tanks.A 95 with a good fill will have quite a bit more gas than an 80.Use one on each dive. You would have enough gas but obviously would lose the redundancy

 

[Icarusflies]

Thanks for the idea Ianr33...yes, it souds like a lot of drag but if only used in deepest NDL dives its an option....is it possible to dissasembe the doubles from the back plate and assemble a single tank with an adaptor all in the SI....it sounds like a lot of work but this would only be done in few dives that require a lot of gas...just an idea...let me know what you think