large_diver
Contributor
A few thoughts...
One thing to be careful about -- weight on dry land vs. buoyancy. AL tanks weigh more on dry land than steels (assuming same volume), but are actually less negatively buoyant in the water than steels.....
A brief list comparing the three main tank types --
HP Steel Tanks:
- Smaller in size, weigh less, and have more negative bouyancy than an Aluminum tank of the same capacity. Steel is stronger than AL -- therefore you use less metal and can pump the tank up to greater pressures, resulting in more volume and less weight
- Some shops/resorts can't fill HP tanks to capacity, negating the lower "weight per volume" advantage.
- With most HP tanks, you need to use a DIN fitting on your reg.
- Steels can rust
- HPs are generally lighter and smaller than LP tanks holding the same gas volume
LP Steel Tanks:
- Heavier and physically larger than HPs
- Generally less negative bouyancy than HP; more than AL
- Lower pressure rating = easier to get complete fill
- Yoke or DIN
- Steels can rust
Aluminum Tanks:
- AL -- generally heavier than steels (although LP and AL are somewhat close)
- Neutral bouyancy when full; positive when empty
- Yoke or DIN
- Cheapest tanks (much cheaper than steels of equal volume)
- AL only avail. in 80CF or smaller these days -- if you want more capacity in a single tank, need to use steel
And regarding the "don't use steel with a wetsuit" comment.....as with anything else, I think it depends. The issue here is that steel tanks are negatively buoyant (although some LP steels are close to neutral when empty). As mentioned above, wetsuits lose buoyancy as you go deeper. If you don't have any ditchable weight and are diving wet and steels (no ditchable weight -- more likely in a double tank scenario), you will have to work pretty hard to swim up from depth......and if you have a BC failure -- could be a problem. I dive single steels with a wetsuit and don't view this as a big issue -- of course, I still have a bunch of ditchable weight. My steel tank also represents a relatively small precentage of the "weight" I carry. For a smaller human.....this might be an issue. Also an issue = Doubles (again -- too much "weight tied up in not-easily-ditchable tanks).
Hope this is helpful.
One thing to be careful about -- weight on dry land vs. buoyancy. AL tanks weigh more on dry land than steels (assuming same volume), but are actually less negatively buoyant in the water than steels.....
A brief list comparing the three main tank types --
HP Steel Tanks:
- Smaller in size, weigh less, and have more negative bouyancy than an Aluminum tank of the same capacity. Steel is stronger than AL -- therefore you use less metal and can pump the tank up to greater pressures, resulting in more volume and less weight
- Some shops/resorts can't fill HP tanks to capacity, negating the lower "weight per volume" advantage.
- With most HP tanks, you need to use a DIN fitting on your reg.
- Steels can rust
- HPs are generally lighter and smaller than LP tanks holding the same gas volume
LP Steel Tanks:
- Heavier and physically larger than HPs
- Generally less negative bouyancy than HP; more than AL
- Lower pressure rating = easier to get complete fill
- Yoke or DIN
- Steels can rust
Aluminum Tanks:
- AL -- generally heavier than steels (although LP and AL are somewhat close)
- Neutral bouyancy when full; positive when empty
- Yoke or DIN
- Cheapest tanks (much cheaper than steels of equal volume)
- AL only avail. in 80CF or smaller these days -- if you want more capacity in a single tank, need to use steel
And regarding the "don't use steel with a wetsuit" comment.....as with anything else, I think it depends. The issue here is that steel tanks are negatively buoyant (although some LP steels are close to neutral when empty). As mentioned above, wetsuits lose buoyancy as you go deeper. If you don't have any ditchable weight and are diving wet and steels (no ditchable weight -- more likely in a double tank scenario), you will have to work pretty hard to swim up from depth......and if you have a BC failure -- could be a problem. I dive single steels with a wetsuit and don't view this as a big issue -- of course, I still have a bunch of ditchable weight. My steel tank also represents a relatively small precentage of the "weight" I carry. For a smaller human.....this might be an issue. Also an issue = Doubles (again -- too much "weight tied up in not-easily-ditchable tanks).
Hope this is helpful.
