new setup, 2 first stages vs 2 bottles??

[DaleC]

I am a little envious of a small 140 cuft tank but it would not help me here. In two conversations I have had, shop owners have told me they don't even like the wear and tear HP (3440psi) tanks put on their compressors. They might faint if I wanted a 4500psi fill.
I am considering a smaller compressor down the road but a much smaller unit, to fill Steel 72's (2450psi).

 

[h90]

I am a little envious of a small 140 cuft tank but it would not help me here. In two conversations I have had, shop owners have told me they don't even like the wear and tear HP (3440psi) tanks put on their compressors. They might faint if I wanted a 4500psi fill.
I am considering a smaller compressor down the road but a much smaller unit, to fill Steel 72's (2450psi).

I am used to that....it happens often that DC staff faints when they speak with me But that would be a other topic...

I get that compressor for 1500 Euro (approx 1900 USD) in Austria (and export it to Asia) (which won't you help you much if you are in USA unless you have regular seafreights). It has 4 stages (which I hope will help in compare with the usual 3 stages). I searched the internet and did not find any complains about it. As well I stay at that place max. 1 week per month, so in the average I may fill just 2 bottle per month :depressed:.
So I hope it can do it for a while. I read about people who used it for many years at 232 bar without problems. As well with the warranty laws in Europe I doubt they can sell something that immediately brakes down on high pressure. The safety valve of it is set to 330 bar.
I got told that it is very important to keep it cool. So here at tropic climate I'll run it in a room with air-condition+extra fan.
Please note: that is just what I plan, not a fact that it will work in real life....

 

[Gerbs]

Quick thought... have you considered Double 10L/200-230 bar? (why, yes, some friends are selling theirs due to having gotten themselves 12/200s)

Effectively, at 230 bar you have the same gas as two Al80s, you have redundancy (not just redundant regulators, which should be a minimum standard, but that's another rant) and it's more air than a 15L/300 while being lighter than the two ALs on the surface (and needing less ballast to the tune of 4kg). Also, the valves are easier to reach.

If you don't mind paying more, double 10L/300s are nice (if you can fill them) as for 41kg - same weight as the 200 bar version including ballast (assuming you are diving with 12kg and a steel 12L single now) - you have 5400L of gas.

PM me if you are interested in the Double 10/230s, I can get you in touch with the guys selling (would be new TÜV, galvanised, painted, OXY Clean with serviced valves). I'm based near lake constance in southern Germany, so Austria isn't that far.

If the German shop you are talking about is the one I think (the only people with 15L 300 bar) then be advised that I heard some (so far unsubstantiated) stories regarding tank quality, issues with subsequent hydro testing and rust from people whose opinion I trust. Try Home - DER Onlineshop für Technisches Tauchen for good prices instead.

Gerbs

 

[h90]

Quick thought... have you considered Double 10L/200-230 bar? (why, yes, some friends are selling theirs due to having gotten themselves 12/200s)

Effectively, at 230 bar you have the same gas as two Al80s, you have redundancy (not just redundant regulators, which should be a minimum standard, but that's another rant) and it's more air than a 15L/300 while being lighter than the two ALs on the surface (and needing less ballast to the tune of 4kg). Also, the valves are easier to reach.

If you don't mind paying more, double 10L/300s are nice (if you can fill them) as for 41kg - same weight as the 200 bar version including ballast (assuming you are diving with 12kg and a steel 12L single now) - you have 5400L of gas.

PM me if you are interested in the Double 10/230s, I can get you in touch with the guys selling (would be new TÜV, galvanised, painted, OXY Clean with serviced valves). I'm based near lake constance in southern Germany, so Austria isn't that far.

If the German shop you are talking about is the one I think (the only people with 15L 300 bar) then be advised that I heard some (so far unsubstantiated) stories regarding tank quality, issues with subsequent hydro testing and rust from people whose opinion I trust. Try Home - DER Onlineshop für Technisches Tauchen for good prices instead.

Gerbs

yes with the doubles I am at about 40 kg. While with the 15 L 300 bar I am over 20 kg.....I checked the webpage, but it doesn't has any 300 bar tanks.
Yes I worry a bit why this shop is the only one I can find with 300 bar tanks and why they have no brand name.

 

[Gerbs]

they do have 300 bar tanks (check the second page).

An alternative may also be the Double 7L 300bar.

Here's my calculations based on using 12kg of weights.

12L/220bar: 31kg, 12kg of that lead, 2640L of gas
D7/200bar: 33kg, 12kg of that lead, 3080L of gas
8.5L/220bar: 38kg, 12kg of that lead, 3740L of gas
D7/300bar: 34kg, 9kg of that lead, 3780L of gas
15/300bar: 32kg, 5kg of that lead, 4050L of gas
D10/200bar: 41kg, 11kg of that lead, 4400L of gas
D10/300bar: 41kg, 4kg of that lead, 5400L of gas.

See the attached Spreadsheet for details... (use at own risk!)

Hope that helps!

Gerbs

 

[h90]

they do have 300 bar tanks (check the second page).

An alternative may also be the Double 7L 300bar.

Here's my calculations based on using 12kg of weights.

12L/220bar: 31kg, 12kg of that lead, 2640L of gas
D7/200bar: 33kg, 12kg of that lead, 3080L of gas
8.5L/220bar: 38kg, 12kg of that lead, 3740L of gas
D7/300bar: 34kg, 9kg of that lead, 3780L of gas
15/300bar: 32kg, 5kg of that lead, 4050L of gas
D10/200bar: 41kg, 11kg of that lead, 4400L of gas
D10/300bar: 41kg, 4kg of that lead, 5400L of gas.

See the attached Spreadsheet for details... (use at own risk!)

Hope that helps!

Gerbs

ahhh yes, I looked Mono only.
D7/300 comes close, but I still can not see any advantage of it. Still the 15 Mono looks better on land. In the water I can't tell because never uses a double.
For that Excel sheet, do you have a guide? It looks interesting, but on a quick look I can't figure out what is what.

 

[Gerbs]

There are two sheets.

One sheets compares the weights and the gas quantities of various tanks, as well as how much weight your need based on the valuee of led you are carrying with the mono 12.

The second sheet compares is a list of dives with various deco obligations, and works out based on your air consumption (and your air consumption when stressed (SAC NORM and SAC HIGH) if you have enough gas for the ascend. It also works accelerated deco with O2, as this cuts down on the gas consumption (Shorter Deco times and you are no longer breathing of your back gas).

It will tell you if you can do the dive safely with reserves (X), that one diver (¹) needs a stage or that both divers (²) need stages for decompression if they want to carry the dive out safely.

I'm slipping more and more into technical diving, so it does a lot of stuff for deco. Since there is no deco calculated (it's all from tables, V-Planer or Visual Decompression 3), you can use it to calculate anything, including total time you could spend at this depth as a sum over several dives. So... If you going to be doing three dives of 12 min to 30m (all to NDL), you can enter depth 30 and 12*3+3*2 (assuming 3min to do the ascend, the 3min safety stop will use less gas than the difference between 3 minutes at depth and ascending to the surface. The table will include the last dive's ascend). This will show you that these three dives will all be feasible with all tanks considered, and even on the last dive, you will have enough gas to assist someone else to the surface.

Feel free to mess with the spreadsheet as you see fit - I've worked out the volume of gas used at depth in terms of surface units, then multiplied by SAC at the end.

skype me (gerbs1979) if you want more explanation (I speak english and german)

Gerbs