Almost ready to buy 2 Faber galvanized LP 85's - sound right?

[Caveeagle]

Thanks.

I've been renting tanks with over 3000 psi...

Your challenge will be if you go down to W.Palm or the keys for more than 1 day of diving and want to get fills. Many shops won't give you more than 2600 in typical LP tank, (Especially If they don't know you ). ...and won't do a nitrox fill unless your tanks are clean for 100% o2. So if your just dropping down for a two dive trip, you should be fine to fill locally and bring your tanks.

What I have typically done is bring as many pre-filled tanks as I can carry and just rent hp100s locally to avoid dealing with local fill issues.

 

[J322Y]

more than i would pay. no vis and the hydro is out in 8 months (looks like 7/13 to me). you would be looking at roughly another 80 dollars to get that done soon and then you would end up with a set of used painted tanks vs new galvanized tanks. could probably get mirrored valves and an isolator for not much more if you emailed dgx directly and asked. a set of used bands can be found for 60ish. i would go like 420 max on that used set. so with some used bands and maybe a bit more to get mirrored valves and the isolator, probably somewhere around 700 to 720 total vs 630 (550 + 80) for hydro/vis on the used set. i can't remember if dgx states their new tanks come o2 clean, but that might be the case also, which makes paying 550 for those fabers even less attractive.

Thanks.
DGX tanks are O2 clean-nitrox ready.

 

[Caveeagle]

Thanks.
DGX tanks are O2 clean-nitrox ready.

Typically they will be rated for up to 40% as they are sold new. You will need them rated and stickered for 100% if your shop does partial pressure blending. (Vs banked nitrox)

 

[Shotmaster]

I have four Faber LP 95s and 4 AL 80s. I used to dive twin 72s. I switched to twin 80s and thought that setup sucked and then tried the single 95. On cave fill they are over 120. You don't give up much to the HP 100 even if you can't get the over fill. The 95 works for me. Most of my dives are 80-110 feet. I would give them a try, you won't have trouble selling them if you change your mind.

 

[J322Y]

I have four Faber LP 95s and 4 AL 80s. I used to dive twin 72s. I switched to twin 80s and thought that setup sucked and then tried the single 95. On cave fill they are over 120. You don't give up much to the HP 100 even if you can't get the over fill. The 95 works for me. Most of my dives are 80-110 feet. I would give them a try, you won't have trouble selling them if you change your mind.

Thanks Shotmaster. I've enjoyed my dives with LP95's.

Can you guess how much bottom time someone with a low SAC might get with a nitrox cave-filled 95 at 100 ft?

Leisure Pro has a sale on painted 95's with free shipping. $285

 

[tursiops]

Thanks Shotmaster. I've enjoyed my dives with LP95's.

Can you guess how much bottom time someone with a low SAC might get with a nitrox cave-filled 95 at 100 ft?

Leisure Pro has a sale on painted 95's with free shipping. $285

100 ft is 4 ATM. A low SAC might be 0.5 cu ft/min. So, at 100 ft, that is 2 cu ft/min. The nitrox is irrelevant. Cave filled? Call that 3300 psi, so that is 3300/2640*95=119 cu ft. that means 59 minutes, not allowing any time to descend, ascend, or safety stop.It is probably 3 mins to descend at an average of 1 cu ft/min gas use (thus 3 cu ft), and 4 mins to ascend at an average of 1 cu ft/min (thus 4 cu ft), and 3 mins of safety stop at 1.5 ATM so another (say) 2 cu ft, so you need 9 cu ft for the decent and ascent and SS, which leaves 110 cu ft to breath. You don't want to breath the tank empty, so you need to save (say) 10%, thus about 100 cu ft are available to use. That's 50 mins.

Now you know how to make the calculation and can do it yourself, putting in whatever safety factors and assumption you want.

HOWEVER, if you spend 50 mins at 100 ft you WILL have a deco obligation.....so your question ought to be what is your NDL at 100 ft with nitrox, and the answer is something like 30 mins, assuming 32% nitrox and using the first table I looked at. With 30 mins of bottom time, and all the same descent/ascent/SS assumptions as before, you need 69 cu ft to do the dive. You would do fine with an AL80. But what about your buddy? What if he/she needs gas from you? 69 cu ft will not be enough.....

Conclusion: your cave-filled LP95 is unnecessary for that dive. You don't need that much gas. unless there is a problem.

See how complicated this is? See why you need more training? See why just deciding on a tank to buy is not where the crux of the matter is?

I'd recommend you get some serious training on gas usage and planning before going out and buying tanks.

 

[J322Y]

100 ft is 4 ATM. A low SAC might be 0.5 cu ft/min. So, at 100 ft, that is 2 cu ft/min. The nitrox is irrelevant. Cave filled? Call that 3300 psi, so that is 3300/2640*95=119 cu ft. that means 59 minutes, not allowing any time to descend, ascend, or safety stop.It is probably 3 mins to descend at an average of 1 cu ft/min gas use (thus 3 cu ft), and 4 mins to ascend at an average of 1 cu ft/min (thus 4 cu ft), and 3 mins of safety stop at 1.5 ATM so another (say) 2 cu ft, so you need 9 cu ft for the decent and ascent and SS, which leaves 110 cu ft to breath. You don't want to breath the tank empty, so you need to save (say) 10%, thus about 100 cu ft are available to use. That's 50 mins.

Now you know how to make the calculation and can do it yourself, putting in whatever safety factors and assumption you want.

HOWEVER, if you spend 50 mins at 100 ft you WILL have a deco obligation.....so your question ought to be what is your NDL at 100 ft with nitrox, and the answer is something like 30 mins, assuming 32% nitrox and using the first table I looked at. With 30 mins of bottom time, and all the same descent/ascent/SS assumptions as before, you need 69 cu ft to do the dive. You would do fine with an AL80. But what about your buddy? What if he/she needs gas from you? 69 cu ft will not be enough.....

Conclusion: your cave-filled LP95 is unnecessary for that dive. You don't need that much gas. unless there is a problem.

See how complicated this is? See why you need more training? See why just deciding on a tank to buy is not where the crux of the matter is?

I'd recommend you get some serious training on gas usage and planning before going out and buying tanks.

Thanks, I appreciate the help.

 

[Johnoly]

... You don't need that much gas. unless there is a problem.......

Scuba divers and SKY DIVERS have a common saying................

YOU CAN NEVER HAVE TOO MUCH AIR !!

 

[J322Y]

I started this with the intention of making it more convenient to get to nearby springs without the long round trip to/from my LDS each time. I was also tying to anticipate my future needs to maximize the value of a tank purchase. It's becoming clear (thanks to all) that I'm probably not going to figure out my future needs with any accuracy.

At the moment I'm leaning towards one LP95. I like how they feel, can get a few trips to the springs out of a cave fill.

 

[sea_otter]

Nothing wrong with an LP95 if you're happy with the weight and thicker diameter. You can also probably get a used one or two fairly inexpensively.

However, I will add one comment around planning to use the same tank for multiple dives. When it comes to how much gas you need to a do a dive, the most important number is how much does it take to get you and your buddy, sharing from one tank, to the surface at a stressed air consumption rate in the event of an emergency. Even if you don't breathe much, you've gotta account for buddy's breathing rate and how both will increase with stress.

That number is going to vary based upon depth, buddy's gas consumption and diving ability, environmental factors, and planned conservatism, but for me, on an open water dive to 100 ft, it's pretty close to 1000 psi in an LP95. You might finish your first dive with 1800 left in your tank - if 1000 is reserved for the ascent, do you actually have enough to complete a second dive? And if your Florida springs include caverns and overhead environments, even that plan is much too aggressive.

Plan for problems. Finishing a dive with a bit of extra gas in your tank sure beats the alternative.