High Pressure Fibre Tanks for shore diving???

[Basking Ridge Diver]

Another good (and economical) tank option for beach diving is an old steel 72. They're about the same buoyancy as a HP100 as far as weighting, relatively inexpensive, readily available, and it's easy to get good fills (and with basic care will last almost forever). They're smaller diameter than an Al80, HP80 or HP100, so do well getting out through moderate surf too. Low pressure 85s are another good choice, about the same form factor as an Al80 or HP100 (and about the same buoyancy as a HP100), but pricier.

In my world LP 72 and LP 85s are the best choices - and the fact that I fill them make it even better...
LP 72 at 3000 psi is about 95 cu ft.
LP 85 at 3300 psi is about 106 cu ft.

 

[geoff w]

In my world LP 72 and LP 85s are the best choices - and the fact that I fill them make it even better...
LP 72 at 3000 psi is about 95 cu ft.
LP 85 at 3300 psi is about 106 cu ft.

I forgot to mention, dry weight of a HP80 is the lightest (metal) tank option, and coupled with most negatively buoyant means lowest total weight you wear, carry or haul to the dive site, and back when you're tired and everything is wet. LP 72s are pretty light (dry weight), followed by LP 85s

 

[Remy B.]

Remy, what is the buoyancy (not weight) of the 12L carbondive full and empty? I have not been able to find that information anywhere.

Guy
Look at it this way, the bouyancy characteristics of a Carbon 12L is like the Al-80 just add 1.5Kg, for the Carbon 6.8L is like a AL-40 just add 1.5Kg

Carbon 12L
Single Cylinders - CARBONDIVE 300 - Carbon Scuba Tanks, Diving Equipment, Worthington

Carbon 6.8L
Single Cylinders - CARBONDIVE 300 - Carbon Scuba Tanks, Diving Equipment, Worthington

Storker
I don't know what are the tank characteristics from your buddy's but it is not that much extra weight you have to strap on, for sure I don't think they are using Carbondive tanks.

And regarding backmount, imaging using a double backmount Carbon 6.8L, the advantages beside weight reduction and size, is streamlining = less effort to displace your self in the water, you are much more streamlined with smaller tanks that have the same capacity as a Al-80, and you fit easier in constrained spaces, like cave diving or wreck penetration.

I keep sustaining that these Carbondive tanks are the best money can buy and out perform anything out there.

 

[rodrico99]

Hi, Rod here in Northern Ca.

I have been shore diving for the past 10 years with HP Steel 130's and a dry suite. My over all weight remains the same whether I dive with an aluminum 80 or a steel 130. I E ( it takes the same amount of weight to sink a dry suite no matter what tank I'm sporting)
Your situation will be the same, Go with the biggest heaviest tank you can find, and take off the same corresponding amount of lead. More bottom time, same weight. no downside

 

[guyharrisonphoto]

Looking at the carbon 12L tank, my calcs are as follows:

Carbondive 12 L

10.9 kg empty

Bouyancy 1.5 KG

So12.4 KG to make the tank neutral, or 27.3 pounds

At 232 Bar (3400psi) capacity equals a steel HP 100, which is 34 pounds

At 300 bar (4350) capacity equals a steel 120, which is 39 pounds

So carbondive saves 7 to 12 pounds

That is a significant weight savings on your back, especially compared to the steel hp 120

 

[undrwater]

Looking at the carbon 12L tank, my calcs are as follows:

Carbondive 12 L

10.9 kg empty

Bouyancy 1.5 KG

So12.4 KG to make the tank neutral, or 27.3 pounds

At 232 Bar (3400psi) capacity equals a steel HP 100, which is 34 pounds

At 300 bar (4350) capacity equals a steel 120, which is 39 pounds

So carbondive saves 7 to 12 pounds

That is a significant weight savings on your back, especially compared to the steel hp 120

You may have included it in there, but I didn't see it. Did they have a buoyancy swing? I see the 1.5k, is that full or empty?

 

[BRT]

You may have included it in there, but I didn't see it. Did they have a buoyancy swing? I see the 1.5k, is that full or empty?

Buoyancy swing is the air in the tank.

 

[guyharrisonphoto]

I assumed like BRT that it was empty as that is the only meaningful number, but you're right his answer did not say for sure.

Remy, can you clarify that this is the positive buoyancy when the tank is empty?

 

[Remy B.]

Correct it is for when the bottles are empty, you need to add 1.5kg per tank in order to be neutral.

Two weeks ago I got my bottles very empty which I normally always leave at 70 to 100bar, With 15 Bar per tank I was struggling to not pop to the surface at the end of the dive, I think that with 2 Kg I shall be neutral and with 3 Kg more comfortable, which ends up to 1.5Kg per tank.

 

[Storker]

At 232 Bar (3400psi) capacity equals a steel HP 100, which is 34 pounds

At 300 bar (4350) capacity equals a steel 120, which is 39 pounds

A 12L 232 bar Faber (~95 cuf) weighs 14kg, or 31# and is slightly (about 0.5kg) negative when empty.
A 12L 300 bar Faber (~115 cuf) weighs18kg, or 39# and is about 3-3.5kg negative when empty.
And a pair of 7L 300 bar Fabers (~135 cuf) weighs 20-22kg and is some 4kg negative when empty.

Carbondive saves 7 to 12 pounds

That is a significant weight savings on your back

And if you were correctly weighted with a - or a pair of - steel tank(s), the same 7 to 12 pounds have to be added to your belt. Everybody's MMV, but I prefer carrying that weight on my back rather than around my waist. Now if you want ~neutral or perhaps even positively buoyant tanks, as I have the impression that some SM guys might want, that's another story.