- Reaction score
- Shelby Township, MI USA
- # of dives
- 500 - 999
Diving singles, I would allow trim and body geometry to determine whether I used 120 or 130s: would you do better with a shorter tank or with a longer tank? With doubles, I really, really like my 120s because of my long torso, and I can tell the difference in resistance with the larger diameter tanks.
Just a follow up with this. I did three dive trips last weekend, each with a different set of doubles. I used double HP130’s, double HP120’s , and double LP85’s. If you’re not familiar with them, HP120s are about the longest tanks out there, HP 130s are roughly the same length as AL80’s, and the 85s are in between, but closer to the 120s. If you want more detailed information, check out this link of scuba tank specifications. (The guy who made it is a genius. )
For me, a guy who is 6‘2“ with a long torso, the HP 130s were very difficult. In addition to being very heavy, they are also, for me, quite short; and like most dive boat benches, there is a groove that the tanks drop down into, so the bottom of the tank is below the level of the bench. That made it almost impossible for me to get up off the bench: I didn’t have the ab strength to be able to bend forward! I did not have that problem with either the 85s or the 120s, even though the 120s are not that far off weight wise: because the tanks were up higher, I was actually sitting up straight, and managing the tanks were no problem. But the 130s forced me to be hunched backwards, and I just could not overcome that without either extreme effort or help from a dive master.
Again, these are doubles, not singles, which really lock you into the bench every which way. Plus, they weigh more than twice as much as a single tank. So maybe none of that is quite the same for a single tank diver. But my point is: the geometry and weight distribution of a scuba tank quite possibly makes more of a difference than its capacity. It pays big dividends to pay attention to more than just the capacity number. Depending on your strength and geometry, a long and skinny HP120 may be way more useful even though it’s smaller (and even then less than 10% smaller). Or just as possible, a short tank, despite its extra wideness and unwieldiness, might make the difference between properly fitting on your back or not.
Just be aware of these issues, and how each person changes the requirements. Which makes it very difficult to go off of someone else’s recommendation and experience, unless you very much understand how their shape, strength and capabilities compare to yours. And really check out the specifications for any tank before you make any assumptions about its usefulness. (Like I said, the guy who made that list is a genius. All kidding aside, there’s a reason that having a list of tank specifications at your fingertips is so useful.)