AL tanks and diving wet

[crofrog]

An AL100, which I use, is going to be more positive at the end than the 80.

Probably not should be about the same.

 

[azstinger11]

I have only 4 AL80s since selling my 2 steel tanks years ago. I dive wet in Nova Scotia and use 40 pounds with my 7 mil farmer john. No problems in my 17 years diving. Dealing with an AL tank that may have less than 500 PSI near the end of a dive should be no problem for anyone except maybe a newly certified diver.

40lbs ?!? I think I re-herniated a disk just reading that.

 

[GDHLEWIS]

Wet suits and AL tanks all the time. Just get used to weighting a little heavier at the beginning of the dive compared to after

 

[inquis]

An AL100, which I use, is going to be more positive at the end than the 80.

Actually, the AL100 is about 1.5 lbs less positive. At 500 psi, Luxfer buoyancies are +3.4 lb (AL80) and +1.9 lb (AL100).

 

[Bob DBF]

I've been told, mostly on this board, that aluminum tanks are not really suitable for diving with a wetsuit, especially in colder water.

Less than optimal is more like it. Not only do you carry 5# more lead, the tanks are heavier, so it's more weight to lug to the water. I did it for quite a while because of cost, but I was young and strong.

 

[Brett Hatch]

See here for a list of common tank specs: Updated SCUBA tank specifications list -- in PDF and spreadsheet

A Luxfer 80 is a typical AL80, which weighs 31.4 lbs on the surface, and 4.4 lbs positively buoyant. Since it takes about 4.4 lbs of lead to make it neutral, the net weight on the surface is about 36 lbs. A hot-dip galvanized Faber 100 is a typical HP100, which weighs 34 lbs on the surface, and is .6 lbs negatively buoyant. So to make it neutral, you can shave half a pound of lead off, making its overall dry weight about 33.5 lbs

The AL80 requires about 5 lbs more lead, as discussed above, but the fact that it is lighter in the first place offsets this downside somewhat. Overall the HP100 gives you 25% more gas, while weighing 2 - 2.5lbs less walking around on the surface.

All things considered, in cold water, I call it a win for the HP100 tanks, whether you're diving a thick wetsuit or a drysuit. The main upside is the extra gas. For a shallow dive where gas isn't a big deal, sure I'll use an AL80 and slap on a bit more lead.

 

[Bob DBF]

. I dive wet in Nova Scotia and use 40 pounds with my 7 mil farmer john.

40lbs ?!? I think I re-herniated a disk just reading that.

I dove the NorCal coast with a 7mil Farmer John with 38# until I could afford a BP/W and got rid of the jacket which had 6# of buoyancy, and got the weight off my belt. That's why I liked freediving, it was a lighter walk to the beach.

 

[Searcaigh]

Diving with a 6lb backplate in seawater.

3mm suit: 2lbs on a camband at the bottom of an AL80
5mm suit: 4lbs on a camband at the bottom of an AL80

 

[Cthippo]

So that kind of confirms what I suspected. Steels are better with thick wetsuits, but an AL can be made to work, so if the price is right...

 

[TMHeimer]

40lbs ?!? I think I re-herniated a disk just reading that.

Not at all unheard of. People vary. An instructor at our shop uses 38 with the 7 mil as did Bob DBF in this thread before he dumped the jacket. Another instructor I know at a different shop says he uses only 22 pounds with the same suit. The amount of weight you need to descend while wearing a 7 mil suit is the same whether it is in the form of lead, metal or anything else that is negatively buoyant.