Small integrated SCUBA outfit

[a64pilot]

Even properly weighted a bcd or wing is nice.
No matter what your going to end a dive significantly more buoyant than you started it, back in the 70’s when I started diving with a tank and plastic back plate, we started the dive overweighted and usually picked up a rock or something to carry around towards the end of the dive.

The first BC’s were May west WWII pilots emergency life preservers, and the pioneer cave divers back in the day would use all sorts of things to achieve neutral buoyancy because trim is way more important in cave diving as you can’t kick to maintain buoyancy or you will silt up the cave and lose visibility.

I’ve not seen these 20 cu ft tanks you guys are talking about, smallest I’ve used we’re aluminum 40’s for deco, but would be good for what your discussing, they are pretty available used.
The standard aluminum 80’s used price used to be $100 if it had a fresh hydro, so used bottles are a good value.

If I wanted a tiny bottle, I think I’d go this route, higher pressure steel tanks are much smaller and lighter than aluminum and usually don’t have as much buoyancy change as aluminum tanks
https://www.divegearexpress.com/fabe...xoC75MQAvD_BwE

[Jammer]

Originally Posted by a64pilot

If I wanted a tiny bottle, I think I’d go this route, higher pressure steel tanks are much smaller and lighter than aluminum and usually don’t have as much buoyancy change as aluminum tanks
https://www.divegearexpress.com/fabe...xoC75MQAvD_BwE

[/quote]


The buoyancy change is the same regardless of cylinder wall material as it is simply due to the mass of the gas that is used during the course of the dive.


The FX-23 in your link is widely used as a rebreather bottle and not much as a stage or pony cylinder. They are 3442 PSI and getting them filled to that pressure is problematic in tropical areas where high pressure steel cylinders are not common. They are quite negative.



For smaller cylinders the better choices are low pressure 50 cubic foot steel cylinders (LP50s), or aluminum cylinders in 19 or 40 cubic feet (AL19 or AL40). AL30s are available but are an unusual size with a thin used market which complicates both buying and selling.


I have an AL19 stage and the whole thing with valve, regulator, mini SPG, and stage straps is six pounds negative when full, five pounds negative when nearly empty.


At shallow depths typical of anchor and prop checks most people can get around 15 minutes out of an AL19 if they use nearly all the air in the cylinder rather than leaving a reserve for safety.



A fact to consider is that many divers consider around 10-12 cubic feet to be the minimum safe reserve at the end of the dive. This corresponds to 500 PSI on a typical full size AL80 dive cylinder.



You would want to choose the best size based on space required and how long you want the air to last.

[akopac]

I’ve had a small tank and regulator for years on board for that purpose. Only used it twice but was really handy. Only used it for anchor. I’d like to make a hookah rig from an oil-less compressor for cleaning the bottom and prop though.

[JC Reefer]

These integrated packs seem really expensive for what we are looking for

[WSMFP]

Originally Posted by JC Reefer

These integrated packs seem really expensive for what we are looking for

They are. You can get a travel BC for a fraction of the price and it won't take up much more space when stored.