What tanks should I get?

[nimoh]

Ok so i need to chime in as a newbie. How do I find out buoyancy calcs, sac rates...etc?!?!

to calculate your Surface Air Consumption (SAC) rate, you need to monitor how much gas you use for a particular time at a particular depth. For example, for a portion of your next dive, swim along 33 feet for 10 minutes and make a note of how much gas you use.

Now assuming an aluminum 80 (77 cubic feet actual capacity at 3000psi), you need to find out the cubic feet to psi ratio:

77/3000 = 0.0256667 ft3/psi (note this is fixed for a particular tank, no need to recalculate every time)

Now you need to convert your gas consumption from psi to cubic feet (lets assume you used 500psi):

0.0256667 ft3/psi * 500psi = 12.83335 ft3

Now need to find out how much gas was consumed per minute expressed as ft3/min

12.83335 / 10 = 1.283335 ft3/min

But this was at 2ata, need to convert to surface pressure

1.283335 / 2 = 0.64

SAC rate = 0.64 ft3/min

Now if you want to calculate your consumption rate at 99 feet:

0.64 * 4ata = 2.56 ft3/min

Another option is to take the total amount of gas used on a dive, and use the average depth (luckily my bottom timer gives me my average depth)

The calculations are a lot easier in metric, but unfortunately, I find it rare to find someone using metric in the USA

 

[Drewpy]

Another vote for the HP100..they have been perfect for me! I have PST and like that they are DIN compatible.

 

[Kian]

Thanks everyone for comments, help and thoughts. I don't take anything that anyone has said personally or as an attack on me as a diver.

I don't know how scuba was taught to compare it to how it is taught now. I don't fault my instructor as I think for want i needed to know for my OW class was taught well. I scored high on all knowledge reviews and tests and when it came to applying what i learned and putting it all together to give me a better understanding I found I did with ease.

When it comes to being technical and knowing all the equations for all the theory that goes into diving is kind of unrealistic for a basic OW class don't you think? Isn't that why they have more classes to advance your diving knowledge and skill? That's why I am furthering my education with more classes and reading this forum. When I find a local dive club i'll rely on those people to impart some knowledge on me as well.

Again thanks for all the help!

 

[poomero]

Thanks everyone for all of the input on this.

 

[grf88]

I am about the same size as the OP and I find HP130's to be ideal for the cold water recreational diving that I do. I have H-valves on mine to provide a degree of redundancy.

 

[Bob DBF]

I second the rent different tanks and try them out. Also check what kind of fills you wind up with, a HP tank with 3000 or 3100# is no prize. That is why I got a LP95 for boat trips, that and a good price, where they invariably fill low. Since I dive wet, anything over my HP100 will limit how many dives I can make due to the time it will take to recover on my core temp.

The Faber 72 (3000# steel) is my favorite for hike and dive on the north coast, old school double 72's for a single dive, regular 72 for a short dive and the AL80's when everything else runs out and I still want to dive.

For one tank I would keep the LP95 or go to an LP at 100cuft or better.


Bob
-----------------------------
I may be old, but I’m not dead yet.

 

[rmillner]

I'm really happy with my steel HP100 (PST E7). Never had a problem getting a proper fill in Monterey or the SF Bay area and I typically have them filled with EANx 32.

It feels better trimmed in the water to me than an aluminium LP80. Going dry in Monterey helped air consumption quite a bit - shivering burns a lot of air .

 

[tac747]

I love my steal HP100's. Bouyancy characteristics, trim and weighting have all been easier since going to them. Also I have never gotten a full fill in any shop in monterey with any tank I have used from al80 to hp 130 so i would rather have 3000 to 3100 in a hp100 than the 2600 to 2750 in an al80. Oh I almost forgot...Watch dolphin scuba in Sacramento for sales www.dolphinscuba.com I bought my hp100's with the pro valves (Convertible from yoke to din with an allen wrench) for $269 each last year.

 

[Chuck Tribolet]

Do rent first.

FWIW, Between Adm. Linda and I we have seven HP100s, four HP80s, and one HP120. I use the HP100s, Linda uses an HP100 on the first dive and an HP80 on the second dive. I haven't used the HP120 yet. Why so many tanks? Well, the original plan was to have eight so we could get over a holiday when the dive shops were closed. We got to seven, and I got an opportunity to buy two so we got to nine. Then I got an opportunity to buy a couple out of hydro HP80s for a VERY VERY good price (they passed). Then the HP120 opportunity came along.

Only the first two HP100s were purchased new.

Chuck

 

[FM1520]

I second the rent different tanks and try them out. Also check what kind of fills you wind up with, a HP tank with 3000 or 3100# is no prize.

I second the LP. Getting a good HP fill can be a hassle - thats been my experience. I bought a steel LP 120+ so getting 2600psi is never a problem. Additionally, I rented several different types of tanks which helped me decide what I wanted, when I figured it out I watched craigslist.