Aluminium 100's, Steels, and Breath Control...

[scrubbo]

So... I'm a big guy, and I've been an air hog ever since I started diving. And my Fiancee just started diving herself, and already she's using way less air than me. (She's on Dive 15, I'm on dive 80ish)

She has recently purchased everything except for her tanks from the LDS and ScubaToys, and is really enjoying diving. Today (after I convinced her not to swim like a madwoman at full speed... I couldn't tow the dive flag fast enough to keep up with her) she and did a dive at 15-30ft (lake diving, ain't it grand?) for 68 minutes. We both had AL80's. She had 3100 PSI, I had 3000. At the end of the dive, I had 600 PSI and she had 1200. Obviously I'm sucking gas quite a bit faster. 2400 PSI vs. 1900 PSI used is a pretty big difference. And I was working on my breathing on this trip. When I'm not paying attention to my breathing, I suck air like crazy. Slow, deep breaths was what I did.

So since she hasn't gotten tanks yet, I was thinking of giving her my old tanks and trying to up the cf of air I carry to try and try and equalize our bottom times. Of course, going on trips we'll always be using the AL80's that every outfit uses, but there's enough local lake diving and she's shown enough interest (We've gone every weekend for the last 4 weeks and she did the OW class for a month before that) for me to think that tanks are worth getting for her.

So, that means either AL100's or Steel. I know steel has a much more negative boyancy. Diving in the lakes, I don't think it'll be a big deal as being well weighted at the surface makes me a couple of pounds heavy at 30 ft. Diving the deeper quarrys and great lakes, however, makes steel tanks more worriesome. I have my dry suit rating and own a drysuit and even enjoy diving in it (I like the boyancy control with the DS better than with a BCD, really.) so it's really not a problem. If my BCD goes down, I can michelin man it enough to get off the bottom.

However, the AL 100's are cheaper, and the boyancy characteristics looked closer to what I'm used to on a tank (even if they're heavier to lug around.) But it looks like to get the extra CU out of it, you need to be over the standard filling PSI. 3300 PSI instead of 3000PSI. Do most LDSs fill tanks that need a higher pressure? I'm just worried that most of the places I run into will only fill to 3000 PSI and if so, will the added cost and effort really give much more air?

Does anybody run AL100s?

 

[jonnythan]

No one I know who has bought Al 100s has been happy with them.

The PST E7-100 and E8-130 are great tanks.. particularly the former.

 

[ScubaSarus]

The steel 98's or 100 are great tanks and providing you use or will require some weights you should have no problem with buoyancy. If you are in warm water were you use no wetsuit and need no weights then the tank can be too negative to use safely.

 

[spectrum]

I get from your post that you're OK with the offset between her usage and yours. Odds are it's phyisiology and there's nothing you're going to do about it. The gap may close but genrally women will do better on air consumprion.

AL-100, IMO that's just plain evil. I would think that when diving in Wisconsin you will have enough exposure protection that even the residual wetsuit bouyancy on a fairly deep dive will leave you fine with something like a PST E7-100. Do watch the specs since there are some cylinders that are exceptionaly heavy.

The lower mass when you drop some of the ballast will help close the consumption gap.

Can you get good fills? "Usually" I''d say. We're diving 4 E7-80s and usually get nice fills. There are some shops that just pump them hot and that's it. We can't always wait for cooling and a top-off. Then again I see plenty of AL-80 buddies show up with 2700, 2600 PSI so it's all relative. Nearly any shop is banking air above 3000 so it's usually available. Even with a short fill an E7-100 will give you an edge. At 3000 PSI you have 87 CF if I remember right. Remember that if you give her your AL-80s she only has 77.4 CF on a perfect fill.

Do your homework and you should improve your situation.

Pete

 

[Firefyter]

No one I know who has bought Al 100s has been happy with them.

The PST E7-100 and E8-130 are great tanks.. particularly the former.

There are several of us around here who dive AL100's, and like them just fine. I've always been happy with them, and so have my friends. With that being said, the PST's are a better tank. The only drawbacks to the PST's are price and availability. If money isn't an object, and you don't mind waiting to get them, I'd go with the PST's strictly for the better bouyancy characteristics.

 

[jonnythan]

There are several of us around here who dive AL100's, and like them just fine. I've always been happy with them, and so have my friends. With that being said, the PST's are a better tank. The only drawbacks to the PST's are price and availability. If money isn't an object, and you don't mind waiting to get them, I'd go with the PST's strictly for the better bouyancy characteristics.

That's OK... I don't know you

 

[PerroneFord]

Something to consider....

How is your bouyancy/trim, and how are you rigged? One thing that really causes issues is poor trim. If you're swimming with your feet down, you're causing a HUGE amount of work and drag for yourself and that will bring your consumption up. Also, if you are overweighted and swimming with a bunch of air in your BC, and stuff dragging all around and not streamlined, you'll increase drag and burn more air.

Not to say you'll be able to match your fiancee, but you might improve your diving if you haven't worked on these things already. And you might find your change to a 100cuft tank will bring you even or even make her the limiting factor.

As a quick aside, I'd be careful at this point of ending dives with 500-600 psi. Should something happen, you're cutting things awfully close. Just my opinion.

 

[alibee]

Spectrum, I think that we're both okay with the offset between our usage -- I'm not one to risk my honey's life just because I want more bottom time, so hopefully he feels no guilt. (Although we've now discussed having a little piggy in scuba gear as our wedding cake topper... air hog! )

Perrone, re: your concern -- our dive was, at its deepest, around 28' today; we spent the last 10 minutes of the dive where he ended w/600 psi at 5-8'. (Yay shallow fresh water lakes!) We were mostly trying to avoid a long surface swim in the windy, wavy lake. In any other conditions, I don't think we'd push it that far.

 

[Wreck]

What is your's and your fiance's SAC? It will get better down to a point. Cold water runs mine up a bit above normal, no matter whether I'm warm or comfortably cool. More dives will make you more relaxed.

Is your goal to really maximize your bottom time more or just to match up air consumption? It seems like the former. If that's the case, I'd recommend 100+ cf. 130's are nice if the weight isn't an issue for warm water diving (are you going to carry your tanks south, or rent 80's on location?). If you can't get a good fill, 130's become 113's at 3,000 PSI, and 97's @ 2600 PSI

Using a DS as a BCD..... I've been forced into a situation where that would have caused me to get bent. Personal preference for some, but not for me.

 

[Charlie99]

We both had AL80's. She had 3100 PSI, I had 3000. At the end of the dive, I had 600 PSI and she had 1200. Obviously I'm sucking gas quite a bit faster. 2400 PSI vs. 1900 PSI used is a pretty big difference. And I was working on my breathing on this trip.

2400psi vs 1900psi used isn't really all that big a difference in SAC. Since her SAC is lower, that's a good excuse to have her tow the flag.

If your local diving is shallow lakes, then the tanks you already have should be fine.

If you're just using this as an excuse to buy some more gear, then the HP100 tanks look pretty nice. Just be forewarned that once your fiance sees high much lighter it is, that she'll be out looking for an HP80 tank