15L (100cf) on liveaboard

[kommisarrex]

I'm doing a liveaboard in Egypt in June (South Red Sea) and they offer 15L tanks in addition to the 12L if you let them know in advance. Any reason not to get the bigger tank for the week?

For background, I've only dived 12L (80s in the U.S.) before, so I don't know how much my trim will be impacted. I'm not an air hog, but don't sip either (6ft, 185lbs). I'd like to be comfortable, but the idea of 20% more air seems pretty good.

 

[Wookie]

My opinion. Worth every penny.

Unless you are an air hog, you don't need the gas. You're going to be N2 limited (on air) or bottom time limited (on nitrox) on day 2 anyway, if you do all 5 a day. Go with what you are used to.

 

[BoltSnap]

They are talking about Steel 12L and 15L tanks most likely. Both are heavier than the AL80 tank. Depending on their pressure, they both will have more air capacity at either 207Bar or 232Bar than the AL80/207Bar you are used to in the US.

12L: will have 88cf at 207Bar and 98cf at 232Bar

15L: 110cf/207Bar and 123cf/232Bar

I'd go for the 15L tank for sure.

 

[admikar]

More gas never hurts, but you need to consider your weighting too.

 

[Diving Dubai]

Generally the steel cylinders in hotter climbs are the "lighter weight" variant to allow for thin exposure suits

As a guide (which does not negate a proper weight check) the buoyancy characteristics are roughly as follows

12L in lbs & (kgs)

Full -7.65 (-3.47) Empty -0.5 (-0.24)

15L

Full -15.58 (-7.07) Empty -6.52 (-2.96)

Personally I prefer to dive a 15L, my wife dives a 12L. While you may well surface well above the minimum gas, it gives you options especially if you hit current. You have the benefit of knowing that you have excess gas to burn, without worrying that you may have to end the dive earlier than others.

Obviously your choice is also impacted by the amount of lead you carry as standard. Give that the difference between an Al 80 and steel 15 could be -10lbs

 

[Steelyeyes]

When we dove Wakatobi and the Pelagian I opted for 15l tanks. Our dives ran an average of 70 minutes. I became a fan. We were on EAN 32 the whole time.

 

[kommisarrex]

Just heard from the dive boat operator that they use aluminum 15L. Wasn't sure on buoyancy characteristics. Guess I'll find out...

 

[Centrals]

12L and 15L tank should be the standard in all liveaboards.

 

[Neilwood]

I did a liveaboard last year to the Red Sea and took the option of 15L tanks and was glad I did. Trim wise was no great issue compared to the steel 12s I had used in the UK.

Small extra cost but meant that I (6'3 and fairly large) could get close to the dive times of the others in the group (most of whom had a huge number of dives).