Resort diving - Bring AL19 tank or AL80 bands?

[JohnN]

The lines go through the fuel line. The knots are just to hold it in place

 

[inquis]

If you really want redundancy on a 2-tank charter when they furnish the gas, just take both bottles with you on both dives. Nothing to store/transport. Yes, you'll need rigging for that second bottle (see above pic for an effective and cheap version).

Sling (or ideally sidemount for better streamlining) the second bottle. Rock Bottom reserve in an AL80 is conservatively 1200 psi (600 psi per person) from 90 ft (likely as deep as you'd be on a rec dive), so breath it down to 700 psi on the first dive. (It will be neutral about 650 psi.) A bonus is that you're very unlikely to be the one to turn the dive. In the event of a gas share, you can use the necklaced stage while the OOG diver is on the long hose and has the entire tank on your back. On the second dive, you're on the long hose (back gas), again with an ascent indication of 700 psi. In the event of a gas share, you donate the long hose and switch to the necklaced reg from the stage.

With only 2 second stages in very different positions and frequent checking of SPGs, you shouldn't get mixed up and run out of air by accidentally breathing the same tank twice. Splash with the stage clipped and switch to a bungee underwater for streamlining. Switch back to clipped at the safety stop. Both bottles are always on.

In short, a quick & dirty sidemount -- easier than real sidemount on a boat and with all the gas advantages thereof.

 

[inquis]

In short, a quick & dirty sidemount

I will say that you should have all this sorted in advance of a trip. The crew will not be happy if you're bucking the standard process AND holding things up. The gear config and bottle manipulation is part of any Intro to Tech class, and there are definitely some tricks to work out. Even something as seemingly simple as clipping the stage on takes a bit of doing at first.

EDIT: just saw this, so you should be sorted, but I'll leave the above for the benefit of others.

I’ve done deco dives off full recreational boats with doubles + 3 al80 stages clipped

 

[inquis]

If you really want redundancy on a 2-tank charter when they furnish the gas, just take both bottles with you on both dives.

Ok, another thought... If they'll rent you a pony of some sort (AL19, 30, or 40), I'd say go that route. Taking two AL80s is fairly... bulky.

 

[rjack321]

I’ve done deco dives off full recreational boats with doubles + 3 al80 stages clipped; was no issue at all (just needed a bit more space).

Single rec tank + al30 literally just requires one extra tank holder. Not a big deal at all

Sure so have I. But at a Carribean resort destination you can have DMs that shrug their shoulders and allow "whatever" to DMs who flip out that you want to assemble your own BC. Some places only take you out for a one tank dive and having twice as much gas as every other tourist is going to cause major anxiety that you'll be doing 2 hrs of BT solo when they expect to be back on the dock in 50 minutes. Some panga like boats might not have the tank racks for every client to bring a spare 80 and they'll go ballistic that you're setting a precedent by taking up twice as much space as the other clients.