Steel doubles in the tropics

[Ed Palma]

There's someone around here selling 2 72cf steel tanks for just about the equivalent of $100 for both. I'm thinking of getting them to complete a set of banded doubles. Will the negative buoyancy be too much? How about for single tank use if dubs will be too negative.

Here's the other pertinent data:

Locale: Warm tropical water diving.

Exposure: Neoprene shorts - for non-overhead environments
Full 3 mm wetsuit for limited wreck penetration

Harness: Have both an aluminum and stainless backplate.

Diver data: 5'6", around 150 lbs.

Single tank wing lift: 30lbs

Currently, for my open water dives, I'm in neoprene shorts, hood and vest, 5lb stainless plate, 30lb wing, using an al80. I use 2 lbs of lead, just to offset any post-dive floatiness. Never tried dubs before, but I was thinking that steels might make me a tad negative (though not to a degree that I can swim up, i think). Redundant buoyancy is in the form of a SMB.

To summarize my questions:
1. is $100 okay for 2 old 72cf (LP) tanks? (Assuming it passes hydro and viz)
2. are steels to negative for tropical salt water diving?

 

[kanonfodr]

Hi Ed!

1.) I have never heard of LP72s going bad, so your money will be well spent. If they are out of hydro and viz, I'd ask less but that's just me.

2.) Maybe. I just did my first doubles dives, HP100s on an aluminum backplate wearing 3mm of neoprene all around. The only lead I added was a 2lb weight on the backside of the crotch strap, more for balancing the rig than actually weighting me down but I should do a proper weight check. If you are heavy, even with no lead, you can always bump up the exposure protection.

The rub is this: doubles are pretty controversial since they are very personal. Everyone loves their setup the best. Adding a manifold and bands will increase your tendency to be head-heavy, don't know if that is an issue for you or not.

End result: If you got the money to do it, go for it. Just make sure you are using the correct wing for those tanks (you need a doubles wing, period) and prepare to take some time getting used to them. I am already in love with my dubs, even if they are a giant pain on land. Underwater they are very stable from side to side, and while I have a head-down tendency I'm sure it will soon correct itself with practice.

Peace,
Greg

 

[Ed Palma]

Thanks No worries, forgot to add that getting a doubles wing was also part of the equation.

 

[Gilldiver]

Fairly soon there will be posts here saying "No steel doubles with wet suits" but that is ignorance, it should be "don't use some steel doubles with wet suits."

If you have galvanized vintage steel 72's from the 60's or 70's they make very sweet doubles with excellent buoyancy. Fully dressed out, regs, bc, etc., they should be very close to neutral at 300-500 psi. In warm water, you can dive these without a weight belt in a T-shirt and may find that at the end of the dive you just don't have much, if any, air in your BC.

There are some things to look out for:
72's with a 3/4" valve thread are preferred by most
Some 72's have a resin coating on the inside which can cause problems at many LDS's
Some 72's are not galvanized and only have a resin like paint on the outside. These can usually be told by the rust on the exterior.

See if you can buy them "on condition of passing vis and hydro" that should take care of all of the above.

Most vintage manifolds have only 1 regulator post, a J-valve, and no isolator. There is one type of manifold that was made by Sherwood that has 2 posts, no J-valve, and no isolator. But, if you want to use a modern 2 post manifold with an isolator, any modern manifold will fit. But you may need to have a custom set of bands made up.

Here is my set after being repainted:

By the way, the oldest 72 I have is from 1960 and there is no reason my grandson/daughter will not be diving it.

 

[Scott L]

Why are doubled AL80's not in consideration?

 

[RJP]

Why are doubled AL80's not in consideration?

"There's someone around here selling 2 72cf steel tanks for just about the equivalent of $100 for both"

 

[Scott L]

"There's someone around here selling 2 72cf steel tanks for just about the equivalent of $100 for both"

AL80's could be acquired for a similar price resulting in the most appropriate configeration IMO. I have doubled LP85's listed here and TDS which I would breakup selling valve (Halcyon) and bands (Highland)...

 

[halocline]

Steel 72s won't be too negative. As Gilldiver said, they're pretty close to neutral empty with hardware; mine are slightly positive empty w/single valve. They have a nice advantage over AL80s in that a doubles set is about 10 lbs lighter, and does not require the 5-6 lbs of lead to compensate for positive buoyancy. (with bands/manifold)

So that's at least 15 lbs less land weight. If you can get 2700 PSI fills, you'll have the same amount of gas. They're also nice and compact.

 

[Jim Lapenta]

Let's see find two al80's for 100 total. Use them for 5,10,15 years if you are lucky since some places will not hydro al tanks older than 15 yrs. At least up this way. Empty they are 8lbs positive(4lbs each). need to add lead with a 3 mil suit. oh and 3000psi fill pressure. Hot fill will drop that to 2700-2800 by the time you hit the water.
Dbl steel 72's. Use them until you die then hand them down to your kids who will hand them down to theirs. I have two from the 50's that still pass hydro. Empty they are nearly neutral at surface. Dump 8lbs of lead off the belt. With my 3 mil and steel plate I need no extra lead and can still swim them up from depth. 2250 fill pressure with plus takes em to 2475. Easy to always get a full fill and if you are like me and take em to 2700-2800 you now have an 81 cu ft tank with none of the downsides of aluminum.

72's are sweet tanks for single tank diving and make an even better set of beginner doubles. I;d like to get another set at some point to go with my 85's and the 95's I've yet to put together. Two sets of 72's would easily get me thru a weekend of OW check outs or any course I teach that does not require a deep dive. For AOW I use one set of 85's, a set of 72's and an extra 80 for the rescue/assist scenario. I would never take an al tank over steel if I could help it. Too many pro's and the cost analysis over time makes it a no brainer.

 

[Scott L]

Fair enough...