Fiberglass Tanks

[BobArnold8265]

Hi,

I remember reading a year ago or so about fiberglass tanks. Have these been developed any further and are they going to be available to the general public anytime in the future ?? Sure would be nice to have a light weigh tank !!!

Bob

[comet24]

What would be the buoyancy of such a tank. Might be light but if you have to add weight to compensate whats the point.

[Charlotte Smith]

My motto is "if it ain't broke ....don't fix it" I am comfortable with my gear and know all about it , and being comfortable is one of my top priorities....but that's just me...

[ScubaToys Larry]

We fill SCBA tanks for fire departments all the time - and they are 4500 psi, and much lighter - but as the other poster pointed out - it would mean adding a lot of additional weight to your belt to compensate. Really a lot of folks lean toward heavier tanks - steel, or neutral al instead of lighter.

And the cost of the carbon fiber tanks is a bit much - in the $500 price range, and if you bang them on a rock, you can cut the fibers and that makes the tank useless....

[Iceman]

If you do a bit of research you can find those cylinders available to anyone who can pony up the cash. But, as posted, they are expensive; compared to metal cylinders they are fragile; they work at much higher pressures than scuba cylinders; you would need to add more weight to your rig to offset them.

Why then, you ask, are they used? Because they reduce the amount of weight a firefighter has to carry while working. It is worth the money to achieve the lighter weight, decreased workload and increased safety, for them.

[cummings66]

Here's a thread from a couple months ago with some links and specs in it.
Carbon Fiber?

[sudnit5]

The fire department that I work with sometimes said that they have some fiberglass tanks. They also said that they paid about $650.00 each for them. It serves a great purpose for them because it is so light, but not so good for SCUBA diving.

[in_cavediver]

Here's the real problem with composite tanks - the buoyancy characteristics suck. The problem is for a given tank size, you displace X amount of water. Your tank (empty) is either positive, neutral or negative. If its positive, like composites, you add lead to get neutral. If its neutral, you stay the same. If negative - remove lead.

In all of this, assume empty tank since the wieght of air shouldn't be used in determining your wieghting. (air is used and its weight decreases during dive).

Now, why is composite so bad - lets assume the composite tank is 80% the volume of a Al 80. Composite weighs 8lbs, Al weighs 30lbs. (numbers are close but not exact). Even with the 30lb tank weight, AL tank needs 4lbs of lead since its positive 4 lbs when empty. This means the composite needs 80% of 34lbs or 27lbs. Its weighs 8 so you have to add 19lbs of lead to your belt just for the tank. (Al tank needed 4lbs for the tank).

If you take your average 7mm wet suit in freshwater, you may carry 35-40lbs of lead with composite tank.

[cummings66]

Originally Posted by in_cavediver

Now, why is composite so bad - lets assume the composite tank is 80% the volume of a Al 80. Composite weighs 8lbs, Al weighs 30lbs. (numbers are close but not exact). Even with the 30lb tank weight, AL tank needs 4lbs of lead since its positive 4 lbs when empty.

You didn't read the link I made did you? If you had you'd see the buoyancy characteristics are not as bad as you painted. I won't make any assumptions here, I'll post the link and compare the two.

Consider like vs like here. Follow this link. http://www.luxfercylinders.com/produ...imperial.shtml

You will note that it is 1.26 lbs positive at the end of a dive, you get more air and are less positive with it than an empty al80. It's a no brainer, the composite s85w is less weight than an AL80, has more air then an AL80 and has less lead needed to make it neutral compared to an AL80. It's better than an AL80 if you consider buoyancy characteristics.

Now look at the S106w, you get 27.8 cf more air, it's 2 lbs heavier than an AL80 and needs one lb less lead than an AL80. What's wrong with that one?

Composites drawbacks are two. They won't last as long and they cost much more than steel tanks. Buoyancy characteristics are not their failing, in fact they're not far from ideal.

My examples are real world facts as attested to by the links from Luxfer.

[in_cavediver]

Originally Posted by cummings66

You didn't read the link I made did you? If you had you'd see the buoyancy characteristics are not as bad as you painted. I won't make any assumptions here, I'll post the link and compare the two.

Consider like vs like here. Follow this link. http://www.luxfercylinders.com/produ...imperial.shtml

You will note that it is 1.26 lbs positive at the end of a dive, you get more air and are less positive with it than an empty al80. It's a no brainer, the composite s85w is less weight than an AL80, has more air then an AL80 and has less lead needed to make it neutral compared to an AL80. It's better than an AL80 if you consider buoyancy characteristics.

Now look at the S106w, you get 27.8 cf more air, it's 2 lbs heavier than an AL80 and needs one lb less lead than an AL80. What's wrong with that one?

Composites drawbacks are two. They won't last as long and they cost much more than steel tanks. Buoyancy characteristics are not their failing, in fact they're not far from ideal.

My examples are real world facts as attested to by the links from Luxfer.

Your right, my data was for older composite tanks, much like the Fire service SCBA which are very light. The new luxfers look like nice tanks with MUCH better characteristics. The question is what is the true advantage for going composite? The luxfers are more like steels in characteristics which is good (even a bit smaller in size and overall weight) but do the disadvantages of very high pressure and the limited life span doom them?