LP85 or Al80?

[legrandorange]

Hey you guys,
I typically dive for scientific purposes (my university and research team has our own compressor and rather large collection of Al80s and HP100s) and am curious about the benefits of getting my own LP85 rather than an Al80 for some pleasure diving. When not diving for research, I borrow one or two of the 80s and will usually stick to around 60, 70fsw and rarely will go deeper than 80fsw. Would the tank size of the LP85 really be that much of a step up from Al80?

Thanks in advance for any help you guys!

 

[HowardE]

For gas supply, or so that you can drop weight off your belt? Both are certainly an advantage. There's no downside to more gas if you ask me.

 

[redacted]

The LP85 is actually 82+change with the + rating. If you loose the + rating, it is then a bit smaller capacity than an AL80. But it does have more favorable buoyancy characteristics and there is always the possibility of an overfill. But it is really hard to beat that HP 100 for capacity, size, and buoyancy. Everything but price.

And for low cost and ease of fill and maintenance and AL 80 ain't bad.

 

[halocline]

The LP85 is neutral empty, which is pretty nice for some diving conditions, and it's 7" instead of 7.25 for the AL80. It does feel different on your back, but with only 5 cft for than an AL80, you have decide if that's worth it. You could try a LP72, which is also neutral empty and smaller diameter (6.9"). You could probably find one for $40-50. If you love diving with it but want more gas, the LP85 will be pretty similar.

 

[ToddK]

I would only dive an Al 80 in California as a last resort. A steel LP85 weighs about the same amount as an Al 80, but is neutrally buoyant vs an Al80 being +4 pounds buoyant. The Al80 just translates to more weight on your weight belt.

Scuba Cylinder Specifications from Tech Diving Limited - 928-855-9400

 

[legrandorange]

Would you guys say I should go for a US Divers steel 72 that has current hydro and VIP for $60? Would I see a large step down in air quantity from the Al80 or would it be, for all intents and purposes, the same (for a single pleasure dive here and there)?

 

[Jeff Toorish]

Just so you are clear, AL80s actually have a capacity of 77.4 cubic feet of air. So an LP85 is a bit more. I own 6 AL80s and if I had to do it over again, I would switch to LP85s. Their buoyancy characteristics are better and, frankly, I like that fact that I can overfill them if necessary.

Jeff

 

[halocline]

Would you guys say I should go for a US Divers steel 72 that has current hydro and VIP for $60? Would I see a large step down in air quantity from the Al80 or would it be, for all intents and purposes, the same (for a single pleasure dive here and there)?

I would, as long as the tank is galvanized. The trick to getting longer dives out of the LP72 is to get just a slight overfill to about 2700, at which point they hold 77 cft, just like an AL80 at 3000. (service pressure is 2475 w/plus rating)

LP72s are nice and compact, very easy to move around with, you get to take 4 lbs less on your belt, and you actually might save a little energy over diving with a AL80, so if you had a few cft less of gas, you might be able to do roughly the same dive as an AL80. That's just a guess, but there might be some validity to it. The LP72s are also substantially lighter on land; to me, that's enough reason to use them for most of my local diving. They also make good small doubles if you ever have any desire to get into that.

 

[rstofer]

Would you guys say I should go for a US Divers steel 72 that has current hydro and VIP for $60?

Absolutely! I paid $60 and I still had to pay for the VIP and hydro. But it's a pretty nice old tank and I'm looking for another.

Richard

 

[WD8CDH]

$60 is a very good price for a steel 72, especially if it is galvanized.

For a new tank, the LP85 is the closest in physical size modern tank to the venerable old steel 72. It's only 1/10" larger in diameter and just barely longer. Due to slightly thicker walls, the LP85 has slightly better buoyancy for most people, at least if not diving without a suit. They also have a slightly higher fill pressure so it's like a LP72 with a "legal" overfill. IMHO, either is a step up from an AL80 and they are my 2 favorite LP tanks for singles.

Still, I prefer HP steel tanks over LP steel tanks. The FX71 (actually closer to 72CF at rated fill) is a super nice compact tank and only 6.74" diameter. For more capacity, I usually recommend skipping the HP80 except for short divers and would go directly to the HP100. Slightly smaller than an AL 80 and with better buoyancy. If under-fills are common, an HP100 will still hold as much air as an AL80 if filled to 2640psi.