Carbon Fiber tanks

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Essroc123

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Picton, Ontario Canada
Hi all,

Has anyone out there used carbon fiber tanks for a SCUBA application? If you have used them, how did they work? If not, why not?

I understand that they have some advantages(really lightweight), but also some serious drawbacks as well(large bouyancy swing).

Any thoughts?
 
I wondered the same thing. Figured that they aren't negative to begin with, or very little, things could only get worse. Kinda defeats the purpose when you have to add weight to your belt.
 
The hydro service life of the cylinders are only 15 years as well.
 
Essroc123:
Hi all,

Has anyone out there used carbon fiber tanks for a SCUBA application? If you have used them, how did they work? If not, why not?

I understand that they have some advantages(really lightweight), but also some serious drawbacks as well(large bouyancy swing).

Any thoughts?

Neither hoop wrapped (3HWM) nor Fiber Composite Wrap (3FCM) cylinders are approved by Transport Canada or Department of Transport for underwater use at this time.

These tanks, although light and high pressure, are very expensive. The good ones are 5000 psi and unless they are the latest Luxfer cylinders are required to be hydro tested every three years.

They also do not take abuse very well. The fiberglass/carbon fibre is very suseptible to both abrasion and cutting.

There are some military applications using similar tanks for underwater use and it seems that it is just time before these see civilian use.

But still, they are expensive.
 
Essroc123:
Hi all,

Has anyone out there used carbon fiber tanks for a SCUBA application? If you have used them, how did they work? If not, why not?

I understand that they have some advantages(really lightweight), but also some serious drawbacks as well(large bouyancy swing).

Any thoughts?

The buoyancy swing would be about the same as any tank of comparable internal volume. The problem is that they're very buoyant, and you'd have to carry a lot more weight to compensate.
 
Essroc123:
Hi all,

Has anyone out there used carbon fiber tanks for a SCUBA application? If you have used them, how did they work? If not, why not?

I understand that they have some advantages(really lightweight), but also some serious drawbacks as well(large bouyancy swing).

Any thoughts?

If I understand the information given at http://www.straightshooters.com/pcpitems/cfairtank.html correctly, the tank weighs 12 pounds (probably empty) and holds 88 cubic feet of air at 4500 psi.

That means the internal volume of the tank is 88/300=0.293 cubic feet which would displace 18.8 pounds of sea water. Thus the tank is AT LEAST 7 pounds light empty and (since it holds almost 7 pounds of air full) still light when full.

Since the tank walls have some thickness, the tank would displace more than 18.8 pounds of water. I wouldn't be surprised if it were about 25 pounds, so the empty tank would be about 13 pounds light. By way of comparison, an empty Al80 is about 4 pounds light.
 
The good ones are 5000 psi
:eek:

I am already kinda nervous about having a 3000+ psi bomb(potentially) strapped to my back.

What about other materials? Titanium, really strong, probably expensive as hell. There are other metals out there as well. What about some kind of alloy?
 
When looking for a material to use for tanks, there is a lot to be said for KISS. If not for the cost, I would rather have fe over al anyday. I like the properties of the metal better (steel is FAR more elastic) and especially the weight. Weight on the tank, means none on my belt.

The carbon fiber re-enforced tanks have a porous outside. IOW, you can get salt deposits in places you can't reach. These are very hard to clean. Of course the inner membrane is NOT porous or all hte air would leak out.
 
Essroc123:
:eek:

I am already kinda nervous about having a 3000+ psi bomb(potentially) strapped to my back.
QUOTE]

Us firefighters aren't so concerned with the 5000+ psi bomb strapped to our backs when we go into a raging room full of fire. If those tanks can take that extreme environment, I'm sure they can handle some sea water.
 
I just checked the Luxfer website http://www.luxfercylinders.com/products/scuba/specifications/us_imperial.shtml and they claim to have a Hoop Wrapped 4350psi SCUBA cylinder. Now I don't know if the Gods at TC have approved this puppy but the 106 cu ft weighs in at 34 lbs (Compared to 32 for a AL80) empty. Salt water bouyance is 3lbs positive when empty and about 5 lbs negative when full.

And Pete... Most of these have some expxy sprayed over them so they aren't very porous.... Not as porous as a bad zinc coating anyway :D

Costing arount $300 US. I'd sure be interested in trying one or two....
 
https://www.shearwater.com/products/perdix-ai/

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