How much more down time??

[captain]

Geez, after 3 pages of useful responses, nobody answered the original question, which was really quite simple. You will get ~ 25% more down time if nothing else changes by going to a HP100 because you are now have an extra 20 ft3 of air. If you could stay down for 30 minutes w/ an 80, you can now stay 37.5 minutes.

Double 100's will give you 2.5X more air than a single 80, but you can't really plan 2.5X more down time as you could be exceeding your NDL on a dive of that length and a different set of dive planning rules are needed.

John

You need to learn how to calculate your SAC, do it and get your own answer as to how much gas will be needed for a dive to a particular depth and time. It will also show if you are improving your air comsumption.

 

[OldNSalty]

Geez, after 3 pages of useful responses, nobody answered the original question, which was really quite simple. You will get ~ 25% more down time if nothing else changes by going to a HP100 because you are now have an extra 20 ft3 of air. If you could stay down for 30 minutes w/ an 80, you can now stay 37.5 minutes.

Double 100's will give you 2.5X more air than a single 80, but you can't really plan 2.5X more down time as you could be exceeding your NDL on a dive of that length and a different set of dive planning rules are needed.

John

Actually, this was answered in the first reply-except with more accurate math.

 

[9supratt4]

Is the deal you're talking about $500 for the two tanks, manifold, and bands? Can you post some particulars, like what are the markings on the tanks, what kind of manifold is it, price, etc? If you do that, we can offer opinions about how a good a deal it is. It might not be such a good deal, in which case you can move on and shop for the best possible tank for you.

If you were to go to doubles, you'd have to get another reg set and a larger wing, at a minimum. If you're not a drysuit diver, you'd probably want to get one of those too before diving steel doubles, especially in cold water. That's because you'll be down there much longer getting colder, and you would be wise to have some redundant buoyancy with the steel doubles, which the drysuit provides. It's not an absolute rule, but I think you'll find very few NJ ocean divers in doubles wearing a wetsuit. (Just a guess)

They are 2 Steel HP 100's in great shape!! They are out of hydro. Not sure what bands they have, but they do have a 300 Bar manifold.

 

[Splash-X]

I will probably be doing some wreck diving off of NJ which is between 100-130 ft., but that's probably the deepest.

With those depths you're going to start to run short on NDL bottom time before you run out of gas.

Moving to 100cuft - 120cuft tanks will give you more gas but wont always extend your bottom time.

 

[letterboy]

I think it should not be just giving the OP an anwser, but giving them the anwser then making sure they have enough information to make a EDUCATED decision. telling him he would get 25% more time is ok. But giving them our opinions on purchasing gear and how fast he should move into doubles etc is also part of ensuring a SAFE decision is made.

SB is a great place to learn, there are times when you shouldn't just give the 25% more anwser to a poster.

 

[Atomic_Diver]

9superratt4- you know that 300bar most likly means Din type regulator right?

as for sac rate, a 100 cu ft (AL filled to 3000psi) at 130' would last me: 47mins (without reserve), or 41 mins with 500psi when i surfaced, but i did not count my deco stops that i would have to do since i over stayed my NDL limit (10mins) by over 30mins (on air), so now i would have to do deco stops (on air), and assuming your not Nitrox certified (to give you a mix with an EAD of 110'), or Deco procedures certified (so that you would know how to safley cunduct Decompression stops/dives) you would most certinatly get bent, and most likely a Emergancy Decompression stop at 15' for 15 mins like your RDP says and from what you learned in your O/W class would not cut it...

 

[Scared Silly]

They are 2 Steel HP 100's in great shape!! They are out of hydro. Not sure what bands they have, but they do have a 300 Bar manifold.

If out of hydro I would not pay $500. In hydro with a couple of years to go may be.

Hmm, I wonder if these might some old PST with the 7/8" thread instead of the more common 3/4" thread. If so make if you are going to break them down, make sure that you can get plugs for the where the isolators goes or have other valves that will work (Finding 7/8 valves is not too hard but might take a bit of looking).

As said, as a 300 bar manifold you will have to convert your regs to din or find other valves such as 200 bar pro valves which can be used with DIN or Yoke.

 

[spectrum]

Geez, after 3 pages of useful responses, nobody answered the original question, which was really quite simple. You will get ~ 25% more down time if nothing else changes by going to a HP100 because you are now have an extra 20 ft3 of air. If you could stay down for 30 minutes w/ an 80, you can now stay 37.5 minutes.

I guess I gave the OP the benefit of the doubt on that most basic analysis.

If you want to put a fine point on it consider this. The diver will be reserving nearly 25% or 20 CF of the AL80 for contingency leaving a little over 60 CF for the dive. In terms of effect on the dive going to the 100 adds more like 1/3 to the air available to plan for the dive.

If the dive profile remains the same then the answer is in time. If the dives become different the time answer lies in the planned profile and divers SAC rate.

Pete

 

[halocline]

They are 2 Steel HP 100's in great shape!! They are out of hydro.

Faber? PST? Worthington? It makes a difference. The 300 bar manifold is not my favorite, but others might like it. The 200 bar ones are convertible valves, which is nice, and are actually a little stronger because the recess area is not as deep and there's more metal on them to protect them in case of a fall or whack from something. There's basically no difference in pressure capacity; they can both handle HP fills easily.

 

[9supratt4]

9superratt4- you know that 300bar most likly means Din type regulator right?

as for sac rate, a 100 cu ft (AL filled to 3000psi) at 130' would last me: 47mins (without reserve), or 41 mins with 500psi when i surfaced, but i did not count my deco stops that i would have to do since i over stayed my NDL limit (10mins) by over 30mins (on air), so now i would have to do deco stops (on air), and assuming your not Nitrox certified (to give you a mix with an EAD of 110'), or Deco procedures certified (so that you would know how to safley cunduct Decompression stops/dives) you would most certinatly get bent, and most likely a Emergancy Decompression stop at 15' for 15 mins like your RDP says and from what you learned in your O/W class would not cut it...

Yes I am aware I would need to change my regs to DIN. I was planning on doing that anyway. I am not yet Nitrox certified....I plan on doing that this winter, since it's all classroom work. I am aware of the very short NDL on deep dives and I would be sure to plan and dive a Non-Deco dive, even if I have enough air to go longer. It's not worth the possibility of getting bent as well as losing the rest of the day because of having to deco.

If out of hydro I would not pay $500. In hydro with a couple of years to go may be.

Hmm, I wonder if these might some old PST with the 7/8" thread instead of the more common 3/4" thread. If so make if you are going to break them down, make sure that you can get plugs for the where the isolators goes or have other valves that will work (Finding 7/8 valves is not too hard but might take a bit of looking).

As said, as a 300 bar manifold you will have to convert your regs to din or find other valves such as 200 bar pro valves which can be used with DIN or Yoke.

That I would have to find out. I just bought 2 HP Steel 80's from the same guy for my girlfriend and they passed hydro and the shop said the insides looked "Awesome."

But I will definitely try to find out the size of the valves.