Need help..Tank for my son?

[Landlocked123]

my son has decided to take the plunge and I am extremely excited he will be joining an OW class in July. He is roughly 100 lbs so not the biggest of kids for his age as he is 14. I do not want him to get stuck with an AL80 for the class and because I plan on taking him diving with me whenever we go I am interested in buying a tank for him. What tank should I look into? I have AOW and Ntirox. I dive an HP100 with Pony. The type of diving we will be doing the first years is 30-40 feet max. He is extemely comfortable under the water and my guess is his air consumption would be minimal. What size tank would get him that 30-40 minute dive time ? I would go HP steel but not sure if that would be too heavy for him even with thick expsore. We will be diving in quarries mostly. Any help would be appreciated. Size / weight of tank being the major concern here.

 

[2airishuman]

I don't think a typical BC will accept tanks smaller than 6.7" diameter.

Standard answer is an AL63, 7.25x22", 25 pounds empty, but a little floaty like an AL80. I don't think those are much of an improvement.

You might be able to find a Faber FX-71 (high pressure steel, 6.7"x21", 25 pounds), a little more air, smaller than an AL63, same empty weight as an AL63 but not floaty so that's 2-3 pounds less lead. I don't think they're in production but there might still be some out there.

In older used tanks you could look for an LP72, 6.7"x28", 28 pounds. 4" shorter and 1 pound lighter than an AL80 when empty, not floaty so that's a couple pounds less lead, and the smaller air fill picks up a pound. Still not a big difference.

You might be able to find an old LP53, 22 pounds empty (but a little floaty), 6.7"x24". I think there's a pair of twins of those for sale in the classified section, billed as LP50s.

 

[2airishuman]

First item in the list is, I believe, a pair of LP53s. You would need regular valves instead of the manifold on them now.

For Sale - Doubles, lots of them

I have no connection to the seller and am pointing this out only because they're so unusual.

 

[tbone1004]

make sure you buy him a backplate, depending on his current and expected height, he should be at least 5'4" so a standard plate is fine, Deep Sea Supply would be my recommendation for that, and I would buy it before class. It will save him a LOT of hassle.

You only mention weight, you mention nothing about height. AL80's are very tall tanks, but you can't get them that much lighter overall. They have two things going against them, one is they are fairly heavy on their own, but the other is you need to ADD 4lbs just to offset their buoyancy which is ridiculous.

So, here's what you have to do. Sit him down on some sort of flat surface, table, counter, whatever. Reach back behind his head to wherever is the lowest he is comfortable reaching rememberhing that he has to manipulate a valve back there, and measure the distance from where his hands can still turn a valve to the table.
Scuba Cylinder Specification Chart from Huron Scuba, Ann Arbor Michigan
Go to that chart and go down the list and find a tank that is that same height. Yes there is a standoff from the neck to the valve, but this is OK, you want to be +_2" from the measurement you took above, to the tank height in the chart.

Now for the actual question. The best tank in terms of size, weight, buoyancy is the HP100 or LP72. They are shorter than an AL80, hold more gas, and have beneficial buoyancy characteristics. 8" tanks are not advantageous for size/buoyancy/weight so avoid them, and aluminum just stinks all around for primary tanks.
SCUBA TANK, STEEL 100CF
email him, if he has two, buy them.
Scuba Tanks. Steel high pressure 100 CF with manifold. Pony Bottle
also a good deal, but verify if they're PST or Asahi, if PST buy, if Asahi, they'll be very heavy.
Scuba Tanks Steel 100s
couple others

 

[rivers]

At 14 and roughly 100lbs, he should be alright with an HP100. I weigh about 125, am 5'3" and I dive twin 12s (equivalent to double hp 100s), and sometimes a stage or 2. Let him have a go with your cylinder on land. If he can wander short distances with it on his back, he'll be okay.

 

[Landlocked123]

I appreciate the feedback. I am not sure he will be able to handle the HP100 weight wise. How about an LP72?. He is roughly 5-5 to 5-6. Aren't those substantially lighter and shorter than an HP100? Where can I find one new? Great idea on the backplate. I went to one right after cert calss when I got my OW. Hated the BCD's they had in class.

 

[runsongas]

lp72 is lighter by a few pounds but slightly taller than hp100. you aren't going to be able to find a lp72 or HDG hp100 new. galvanized tanks like that are only available used or very rarely NOS these days.

 

[Landlocked123]

ok so hp100 ... Tonight I will have him try to lift mysetup. That said I dive a steel backplate and STA so we could go aluminum backplate and STA so probably shed 7-8 pounds.. Thanks for the input

 

[uncfnp]

You could start with an HP 80 but at 14 he should be able to handle a 100 and have room to grow.

 

[tbone1004]

LP72's haven't been made in decades, so available used only. They are only a couple of pounds lighter than a HP100, but those deals on the HP100's I linked are pretty good. Don't buy new tanks, colossal waste of money. He's too tall for a HP80 already imho

Don't go to aluminum backplate, remember he still has to carry the lead to get in and out of the water to get neutral. MOST divers are about perfectly weighted with a stainless plate and steel tank. Deep Sea Supply uses an STA-Less design that is very good, so with plastic buckles the rig will be about 4lbs lighter than one with an STA and metal buckles. It would be my first choice. At 5'5" he's fine with a standard sized backplate, and a HP100 will be fine. Total rig weight will be roughly 55lbs, which he should be able to lift. Have him see if he can walk around with your setup. He doesn't have to pick the whole thing up in one go, just be able to walk around and preferably go up a few stairs with it.

Oh, while I understand that this rig will be more than half of his body weight, please remember that I dive regularly with 130lb women that are able to pick up sets of doubles that weigh as much as they do and climb up boat ladders with them with no problem. The line between body weight and strength is anything but linear and the smaller you are, typically the stronger you are in terms of percentage of body weight. 60lbs should not be difficult for him to carry around in a harness. May not be feasible to pick up in front of him to put on a picnic table or truck bed, but he should have no problem walking around with one on his back. Legs should be more than strong enough for that.