HP119 vs AL80?

[novasquid]

I did my OW dives with AL80 tanks and all the rec diving I've done up to today (about 15 dives) have been with AL80 tanks.

I'm about to purchase some HP119's and was wondering what to expect in comparison to the AL80's that I'm used to. I know it's about 9lbs heavier, steel, 8" diameter and a few inches shorter. But never having dove with one, I have no idea what to expect in the water. My reasons for going with 119's is the higher air capacity and the need for less weights in the BCD.

I'll be using a cressi travelight BCD, which secures an AL80 pretty well given the soft back. The 119 will be solely for freshwater rec diving. Will the 119's be fine Or should I stick with AL80's for now?

 

[doctormike]

I bought two HP 119s about two years ago, and I doubled them up last season. I love them, they trim out great, and since I'm a big guy, I really appreciate the extra gas capacity.

As you mentioned, these are 8 inch diameter tanks, as opposed to 7.25 inch diameter that you would find on an AL80 or even a steel HP 120. This would only be an issue on a dive boat with those wells that hold the tanks, but up here (NYC area) we don't really have that - tanks just get bungeed to the rail. Since many people are diving doubles or rebreathers, there isn't a lot of use for the wells that you see on Caribbean dive boats that basically just take people with single AL80s. If you are just using them for quarry diving, then that also wouldn't be an issue. Don't know if you would need longer cam bands or if your current BC will hold these tanks.

I also really appreciate the extra negative buoyancy on the tank, since I am diving in a dry suit. On the other hand, you said that you would only be diving in freshwater with them, so that would be less of an issue. Are you diving dry? How much weight do you need to add with your current exposure suit in fresh water? I don't know how close you are to the Virginia coast, but you may at some point end up using them in the ocean as well, so the extra negative buoyancy would be more helpful there.

Then there is the whole "ditchable weight" controversy. Plenty of threads on that here, but you may end up with no ditchable weight if you are diving wet in fresh water, depending on your particular circumstances. I don't have ditchable weight myself, but something to consider.

One potential issue is that they are much shorter than the HP 120s. I'm 6'2", and it does mean that I have to squat down a bit on a dive boat bench to suit up, but this quickly became a non-issue as I got used to them. If it's a big problem, you could always bring along a piece of wood to sit them on while donning them and taking them off after the dive, but I didn't find that necessary.

They are also very heavy out of the water (especially once they are doubled up!), but I have been able to manage them so far. Some people with back issues might prefer another solution. I don't know much about the Cressi BCD, if there is some sort of limit to how much tank weight it can handle out of the water on a long hike to the shore, but hey... there's a reason to get that BP/W you are going to end up with sooner or later!

 

[chrpai]

I'm going to try to keep this short.

There are potential advantages and disadvantages to a steel tank. But to understand these from both an academic and practical perspective you are probably going to need to get some dives in first. As a beginning diver, there is a good chance that you are still over weighted with poor trim and buoyancy control. It's not your fault, it's just how the system seems to fail us over and over.

I would get a bunch of dives in an AL80 and with the help of a mentor or instructor (e.g. peak performancy buoyancy) shed that weight and work on getting a nice stable platform... be able to hold a hover in a perfect horizontal position without any hand of foot sculling. At the same time work on getting SAC rate down. For example a new diver might consume 1 SCF/min where after some experience that might be .75 or .5. You may have no idea what an SFCM is yet and you need to know this to be able to do gas planning for a dive and know how much gas is enough.

Once you are in this position you can then evaluate the different tanks that are available to you and try them out. If an LP95 is too short for you and it makes you head heavy, you'll know it because you'll know what stable platform feels like. If a certain tank takes 6lbs off your belt but you only had 4lbs on your belt, you'll know it overweights you because you know what perfect weighting feels like. If a certain tank rides just right and gives you just the right amount of gas without killing your back, you'll know it.

If you don't know what this feels like, you could just make the problem worse.

 

[elan]

its hard to give any advise without knowing your height and exposure protection.
HP119 is shorter and less buoyant. If you are tall and need little weight it can present a problem with the trim if you want to keep the valve reachable.
You might not have enough weight to move around to trim them.
If you are around 6ft Check LP85 and HP130/LP104/LP108

An option in the middle would be LP95 by faber as they are more positive and add you possibility to add trim weight

 

[novasquid]

my wife is 5'2 and i'm 5'7", with 7mm wetsuits and AL80s, she needs 20lbs and i need 15lbs of weights to get us sinking. given that the HP119 is 9lbs more negatively buoyant than the AL80 when full, that means we can shed ~10lbs each (rounding up). so we're taking roughly 10lbs off our BCD and throwing it onto our backs. theoretically, i'm worried that the extra tank weight may cause rolling issues from side to side.

we plan to take the PPB class soon too, so that should help.

 

[chrpai]

given that the HP119 is 9lbs more negatively buoyant than the AL80 when full, that means we can shed ~10lbs each (rounding up). so we're taking roughly 10lbs off our BCD and throwing it onto our backs. theoretically, i'm worried that the extra tank weight may cause rolling issues from side to side.

You don't weight yourself based on a full tank, you weight yourself based on a (nearly) empty tank. A Catalina AL80 is +4LB when empty. A PST E8-119 is -2LB when empty. This means you can shed 6lbs not 10lbs. The full tank buoyancy is important to understand in terms of knowing how much lift your BCD needs to have. Your BCD needs to be able to offset the weight of the gas in the tank when full and the loss of buoyancy in your wetsuit caused by compression at depth.

Again, as a new diver, you probably are over weighted as it is. So you'd go about shedding 10lbs and be OK and think you understand what you just did when in fact you went about it all wrong.

As for the stability issues, it's not just bank but also pitch. But if you aren't already diving with good trim then you won't know what it feels like and how to judge the difference.

This is a perfect example of why I think you should build more knowledge and experience using the gear you have now before spending money and selecting what could be the wrong tank for you.