High Pressure Fibre Tanks for shore diving???

[undrwater]

The best process I think I have found is to completely gear up at the truck, and walk down to the beach: instead of lugging sets of boxes or tanks up and down the stairs or pathways.

This is how it's typically done in SoCal anyway. Be aware that many of the typical sites have stairways and paths to the entry point (often step and / or long).

 

[teknitroxdiver]

If I do a quick back-of-the-envelope calculation, a tank with "almost" the same capacity as an Al80 but with the size of an Al tank with half the capacity should have a working pressure of around 400 bar.

So I'm wondering: Where do you get a 400 bar fill?

I think this is it: Single Cylinders - CARBONDIVE 300 - Carbon Scuba Tanks, Diving Equipment, Worthington

Roughly 72cf, 5.5" x 23" and 13.8 pounds, if my math is correct.

 

[Storker]

Roughly 72cf, 5.5" x 23" and 13.8 pounds, if my math is correct.

If "roughly" means "about ten percent less than", you're correct. You have to take non-ideality into account when you deal with pressures above some 250 bar. At 300, real capacity is some ten percent less than nominal (water volume times working pressure).

 

[Remy B.]

If I do a quick back-of-the-envelope calculation, a tank with "almost" the same capacity as an Al80 but with the size of an Al tank with half the capacity should have a working pressure of around 400 bar.

So I'm wondering: Where do you get a 400 bar fill?

My tanks don't have the same wall thickness as of a AL-40, they are Steel tanks with Carbon Fiber webbing, so they are thin wall tanks, my tanks are 6.8L X 300 Bar give you 2040L a AL-80 have a capacity of 2200L, if I increase the pressure to 330bar which I do, I get what a AL-80 is.

Techduikshop.nl

These are the best tanks money can buy, weight and size, out performs any other tank.

You can get as well 12L x300 Bar, Worthington tanks, that give you 3600L so if you sling two tanks that is 7200L, it is like carrying 3 1/2 AL-80's, in two tanks, that are a little smaller and are lighter than a AL-80, but that is for more serious Tec diving, and they cost 500eu each.

Techduikshop.nl

 

[Remy B.]

If "roughly" means "about ten percent less than", you're correct. You have to take non-ideality into account when you deal with pressures above some 250 bar. At 300, real capacity is some ten percent less than nominal (water volume times working pressure).

depends how you fill your tanks, for 300bar tanks you want to wait until they cool down and then pumped up again to 350 when it cools down you have 330bar, then you put 10% more in and problem solved, still even if you fill them at 300bar, weight/size ratio it out perform a AL-80

 

[NAM001]

Yeah, I was a volunteer firefighter. The 4500 PSI tanks are used so we can have a smaller and lighter tank for the same given volume of air. Size is a concern when you have to crawl through holes, and weight is important because unlike scuba diving, you have to carry the weight the entire time. When you dive, the tank becomes weightless.

There was a big thread on here about carbon fiber tanks earlier. Basically, if salt water gets under the fibers, it'll ruin the tank, possibly with disastrous results. Because of this, that's why there's only one carbon fiber tank approved for diving (the one mentioned above). Bottom line is do not try using a firefighter's fiber tank for scuba!

Don't forget that a lighter tank (of the same displacement) means that you need more weight on yourself. Of course you can carry weight belts and tanks separately to the shore, you can't carry part of a tank.

I don't know if anyone does this, but could you perhaps use two smaller (regular aluminum or steel) tanks in a doubles setup, carry them down to the beach separate, then put together before you enter the surf? The idea would same amount of air as a AL80, be less weight to carry, but more trips. I'm not sure what's worse for you, the weight or taking extra trips. Just an idea.

Are we talking apples and apples. SBCA tanks I am visioning are full fiber and not fiber reinforced metal tanks. full fiber tanks can not be used for scuba cause they have no weight. full fiber tanks for firemen are used for the reduced weight. I may be confised.

 

[Storker]

depends how you fill your tanks

Yes and no. I use 300 bar tanks. I fill them to 330, and when they've cooled down, they are at ~280. After cooling, I top them up to between 300 and 320, depending on the time of the year (i.e. air temp and water temp). But I can't beat non-ideality. No matter what you do, a 300 bar tank holds 10% less than a 200 or 232 bar tank with the same nominal capacity. And if you overfill a 300 bar tank by 10%, you can do the same with lower pressure tanks.

Comparing apples to apples, you can't beat non-ideality.

 

[tep]

If I do a quick back-of-the-envelope calculation, a tank with "almost" the same capacity as an Al80 but with the size of an Al tank with half the capacity should have a working pressure of around 400 bar.

So I'm wondering: Where do you get a 400 bar fill?

Where do you get a 400BAR regulator or DIN valve?

 

[2airishuman]

The main purpose for wanting a lighter higher pressure tank, is from a SI joint injury thats never been fully resolved, that makes lugging tanks for shore diving more miserable than it already is.

I think you have your answer on carbon fiber tanks.

Let's talk a little about shore diving and gas logistics. Most of my dives are shore dives. I tote my own gas. I have chronic SI joint problems.

Under medical advice I started doing back exercises for my SI joint problems and have progressed to the point where I do deadlifts with a 315 pound barbell, usually twice a week. I started at 75 pounds, took a couple of years to work my way up. Most SI joint problems improve with lower back muscle strength. So my first piece of advice for you is see your doc or your physical therapist and if they concur then get thee to the gym every couple of days.

Typically I shore dive with a steel 120 (high pressure) and make one 75 minute dive rather than two 45 minute dives. If I'm planning a shorter dive I'll use a 72. Longer or deeper dives I add a 40cf stage or a 11 or 19 cf pony, or switch to an HP100 twinset instead of the 120.

Every shore dive has different logistics with the main variables being: horizontal distance to parking, vertical distance to parking, ground conditions, shore conditions, sea conditions, presence of a theft concern, availability of a dock or similar structure, and amount of gas required for the planned dive. If you want to be nice to your back you have to evaluate the dive and have a number of tricks available to try.

I use wheeled carts or wheeled tote boxes for some dives and position cylinders on shore before the dive. This does not work for mud, or stairs.

In rare cases I have used a canoe to bring in cylinders, where there is a nearby landing that has better vehicle access than the dive site.

If access to the site is poor I'll use smaller, lighter cylinders unless the gas requirements of the dive don't permit that.

Depending on the nature of the site I'll assemble my kit at the car or at the dive site, or sometimes half way in between.

Sometimes I have used multiple smaller cylinders. Sometimes it makes sense to throw one or more stage or pony cylinders off a dock or pier and retrieve them after entering the water, to reduce the weight carried during entry. For exiting I may pull them up using a line after or throw them up on the dock before, if the dock is low enough.

Most of my shore dives are solo or with kids. If you dive with a buddy that gives you some additional choices and in particular makes it more practical to don your kit in the water.

 

[Remy B.]

Comparing apples to apples, you can't beat non-ideality.

Still you can't compare a Worthington carbon 300 tank to anything in the market, they out perform anything out there so far I know.