Dilemma: AL80 vs AL100 ? Costa Rica/Okeanos Aggressor II typical fill pressures you've experienced?

[scubafanatic]

My trip offers standard AL 80's but for a fee can obtain bigger tanks. The 2 bigger tanks in stock are already reserved but the boat can obtain a bigger tank from a land based facility as a special request. I'm not 100% sure if this bigger tank will be a AL 100 or maybe even a steel ? Based on my prior experience years ago in Belize, the steel I got at that time was a LP 95 Faber. The usual bigger tank this boat offers is the AL100, but they only have 2 on board as standard equipment and they are already reserved by other divers so the boat will have to rent a bigger tank (of some kind) from a shore based op.

Does anyone have any experience on the typical fill pressures on this boat ? The AL100 is really only 100 cu. ft if filled to 3300, so I may not really want to mess with this beast of a tank if fills are averaging 3000, as there isn't much of a gap in capacity between an AL 80 @ 3000 vs an AL100 @ 3000. We'll be diving off inflatable RIB/zodiacs, and perching on the edge to ride out to, and back roll off of these RIB/zodiacs, so clambering around/on/off these little rubber boats is more work if I choose the large/heavy AL100...and likely not work the extra work unless the real world gas capacity superiority exists. Also AL100 has more dramatic buoyancy swings from full-to-empty, which is undesirable.

I've dove LP 95's off a Belize liveaboard some years ago, the tank was fine, but it ended up contaminating my reg 1st-stage with rust, which may be hard to avoid given the tropical/humid environment there. But right now I don't know if the boat is even offering this steel tank option, and I'm not sure I'd want a steel tank from there due to the probable lack of inside tank quality control cleanliness.

So, if you were advising me, what would you advise ? (here at home I'm used to diving a variety of HP steels, so I have used bigger/heavier tanks often, my main need for help relates to this boats typical fill pressures that you've experienced in the real world?)

If it turns out, lets say, that the boat averages 3200 psi, then I'd just stick with a slightly overfilled AL80 than cope with an underfilled AL100.

I haven't been on a scuba trip in some years, so I'm a bit rusty, but historically I'd average about 45 min on a AL80 on prior ocean diving trips.

Maybe I can just speak to the crew/tank filler guy and offer a nice tip if he/she makes sure to just 'cave fill' an AL 80 for me ?

Thanks in advance!

 

[Dogbowl]

If you have a little time before your trip, I’d email the Okeanos Aggressor directly and ask/discuss details - my experience is that the captain will respond on turnover days (at least that’s what the Belize Aggressor did - I had a few questions that I wanted the boat crew to respond to). Failing that, head office is quick to respond but may not have the correct answers right away.

My recollection from the BAIV was that our tanks were filled to 3100-3200 consistently, without us asking. It was just the way they did it.

Sorry no experience with the Okeanos Aggressor.

 

[scubafanatic]

If you have a little time before your trip, I’d email the Okeanos Aggressor directly and ask/discuss details - my experience is that the captain will respond on turnover days (at least that’s what the Belize Aggressor did - I had a few questions that I wanted the boat crew to respond to). Failing that, head office is quick to respond but may not have the correct answers right away.

My recollection from the BAIV was that our tanks were filled to 3100-3200 consistently, without us asking. It was just the way they did it.

Sorry no experience with the Okeanos Aggressor.

Hi Dogbowl,

I'd ask the boat directly, but don't want the 'party line' where I'm told what's 'politically correct' or what they think I want to hear, I want the 'secret shopper' version of what to Really expect. I am getting more clarification soon, at least with respect to the type/capacity of tank, as my trip wholesaler is inquiring for me exactly what type of larger tank they can rent for me from their land based shop contact. If it turns out to be a LP steel 95, which is 95 cu. ft. @ 2640 psi, then a 3100-3200 psi fill as you describe would get me to 113 cu. ft-ish, which would be just fine. I'm a bit rusty, and will diving with VERY experienced divers (including a dive shop owner) and I don't want to be the weak link, so I will likely last with them if they have 80 cu ft and I've got 113 cu ft.

A few years ago the Belize Sun Dancer procured me a LP 95 steel from a local land-based dive op so hopefully those are ubiquitous in that region.

As the Aggressor boats are all independent franchises, each boat is free to follow their own individual policy, but I do appreciate you providing your own data point @ 3100-3200 psi.

Historically, it's been my experience boats ignore tank fill ratings and just give everyone the same generic fill, namely the 'universal' 3000 psi AL 80 fill. I'd rather have a slightly overfilled LP 95 steel over an under filled AL100...smaller tank with more gas. The one noteworthy exception was MV SPREE of Texas Flower Gardens fame, where I inspired Captain Frank (Wookie) to upgrade his fill stations to accommodate HP steel fills, for which I was eternally grateful!

I'm a pretty low maintenance diver, but my 3 pet peeves are:
1) short fills
2) timed dives
3) unreasonably conservative depth limits

Thanks!

 

[rongoodman]

I've been on the Okeanos II three times, most recently in May. Each time I had an AL100. The site used to advertise 15L tanks, but that has been changed to reflect what they actually provide. I think the best fill I saw was about 3150, so 95 cf. They request 55 min max dive times and the depth limit of 110 is determined by the 32% fills provided. I'm not large person but I don't find the AL100s to be problematic, although HP 100s are nicer. I don't know what you mean by "dramatic buoyancy swings", since 100 cf of gas weighs the same no matter what kind of tank it's contained in. My chief complaint about the AL100s is that they are heavier but require more lead than the HP 100s, making more work for the panga crew in moving them around.

The crew will bring your rig from the rack in the center to you and assist you into it, the reverse when you come back. A few customers take their rigs off in the water. The only reason I had to stand up prior to entry was to fasten my crotch strap. Many of the dives are deepish and you will be hanging out waiting to see what comes by rather then swimming against a current, so you might find NDLs to be the limiting factor, rather than gas usage. I run my Perdix at 40/85 and occasionally had a minute or so of deco showing when I left the bottom which always cleared before or at the safety stop.

It's a great boat, I'm already planning a return visit for next summer!

 

[scubafanatic]

I've been on the Okeanos II three times, most recently in May. Each time I had an AL100. The site used to advertise 15L tanks, but that has been changed to reflect what they actually provide. I think the best fill I saw was about 3150, so 95 cf. They request 55 min max dive times and the depth limit of 110 is determined by the 32% fills provided. I'm not large person but I don't find the AL100s to be problematic, although HP 100s are nicer. I don't know what you mean by "dramatic buoyancy swings", since 100 cf of gas weighs the same no matter what kind of tank it's contained in. My chief complaint about the AL100s is that they are heavier but require more lead than the HP 100s, making more work for the panga crew in moving them around.

The crew will bring your rig from the rack in the center to you and assist you into it, the reverse when you come back. A few customers take their rigs off in the water. The only reason I had to stand up prior to entry was to fasten my crotch strap. Many of the dives are deepish and you will be hanging out waiting to see what comes by rather then swimming against a current, so you might find NDLs to be the limiting factor, rather than gas usage. I run my Perdix at 40/85 and occasionally had a minute or so of deco showing when I left the bottom which always cleared before or at the safety stop.

It's a great boat, I'm already planning a return visit for next summer!

Hi Ron,

Thanks for the data points and operational details. I've dove pretty much every type/capacity of tank out there at one time or another, and the AL100 is a bit 'tall'...and heavy, so I'm hoping for a LP95 steel, which is shorter. Ideally, HP steels are my favorite, but it's very rare to get a real HP fill, so LP steels are better in the real world. I can live with the 55 min 'limit', given my gas consumption that's about my max endurance anyway, especially if the dives tend to be deepish. I'm OK with not wasting gas fighting a current and don't mind just hanging out to see what comes along. I prefer to re board the skiff with gear-on. I understand they only do 3 - 4 dives daily so NDL's may be somewhat less of a factor compared to the usual 5 dives daily live aboard I'm used to.

Thanks again!

 

[Efka76]

I just came back from liveaboard in Red Sea where i was using AL100 (usually filled in 210 bar). At least for me this tank was not too heave or too big, however, it allowed my to stay underwater more than 55 min.

 

[rongoodman]

I'm assuming your going to Cocos Island? As of March the rangers were still not allowing night dives, so most days are three dives, with four occasionally. Let us know what tank you end up with. I wouldn't be above begging and pleading for an LP 95 myself.

 

[scubadada]

Hi @scubafanatic

I dived Cocos on the Okeanos Aggressor II in March/April 2017 Cocos, March 27-April 5, 2017

Cylinder fills were quite good, average 3220 psi (3100-3350). This would be an average of 83 cf for an AL80 or 97 cf for an AL100. I do not remember anyone diving an AL100 or any size steel tank on my trip. Aggressor does advertise availability of 100s with advance notice and a modest extra cost.

We did 24 dives in 6 1/2 days, including 3 night dives. I would hope some of the night dives would have been replaced by additional dives during the daytime. @rongoodman how many dives did you do on your May trip?

 

[rongoodman]

22, I think.

 

[scubafanatic]

Hi Ron,
Not Cocos but Guanacaste/Bat Islands, so night dives still allowed as no killer Tiger sharks reported there. Once I hear more I'll report what 'larger' tank I'll be issued. Per my latest e-mail update tonight, we're awaiting clarification from the dive op to the boat what's going to be available, then the boat will let us know.