Diving doubles recreationally

[ScubaFeenD]

I bet with LP85s, it will be gas.

This is dependent on the person. Perhaps it could be gas, but it might be mdl/ndl too. I did some nice shallow (80ft) dives in palm beach this last march and always called the dive on time not gas, and I was able to do two dives on a set of double Al80s( while still mainting minimum gas reserves).

 

[Rainer]

You might consider, if you are so disposed, to get a "light" set of Al80 doubles for recreational dives, because they arent that much heavier (in total while full) than an HP130 and they allow for redundancy, etc, blah blah blah.

If you need a V-weight for AL80s (i.e. you dive in cold water), then they really aren't that light at all. In fact, they'll weigh about DOUBLE what a single HP130 weighs. That's a lot of extra weight for only about 20cf more gas. For "recreational" dives, I'd usually rather just take a competent teammate along for redundancy.

I do agree, though, there is certainly nothing wrong with using doubles "recreationally". I just don't see much point for myself for most shallow dives. This is especially true for many shore sites. I know Tobin is taking doubles, deco bottles, and a scooter through the surf (I do it at a select few sites, too), but for MANY local shore sites, that just isn't feasible (rocky entries, long walks over rough terrain, etc). Off boats, especially ones that don't pump gas, doubles *are* nicer (again, IMO only!) than multiple singles.

 

[Rhone Man]

There is no free lunch in life.

Doubles are heavier for the same volume, more expensive, and trickier to trim out.
The advantages are increased redundancy, cleaner hose routing, better roll stability, and the fact that you can carry your reserve gas from the first dive into the second dive. (With singles you leave a 1/3 full tank on the boat).

Agree with all of that.

The training for doubles does not have to take a week. Find an active group of GUE divers and/or a GUE instructor. They can square you away in day or two and you can try before you buy.

Not sure it really needs to take any time at all. If you are diving within recreational limits, I'd strap 'em on and go. You are going to be a bit wobbly for your first few dives, but it 'aint rocket science.

 

[Rainer]

Was just addressing your claim that "you will ALWAYS be gas limited with single tank...". As a GUE-trained diver, that just hasn't proved true for me or my teammates. In fact, as I mentioned, it's a rare MDL dive where we are gas limited in a single HP130. Even in smaller singles, we rarely end the dive due to gas limits.

My min gas is a little more conservative than yours. I assume 2 minutes at bottom to take care of air sharing. SCR under stress for both diver is 1. Min gas = 46cf.

But even with your math, it just shows that HP130 is just about balancing NDL and min gas requirement for rec dive. If you take smaller tank, say HP100 or LP85, you are definitely gas limited.

Now, you mentioned 0.75 is terrible SCR. I actually don't know exactly what mine is. I assume it is 0.75. I will need to start keep track of that.

 

[James R]

That may work too if you carefully avoid those who move the tank bands for trim and then adjust the harness to be able to reach the valves and then have to add ankle weights and dive like a seahorse...

While you can find many non-GUE divers that got it right, there is the guarantee that no GUE instructor will encourage or endorse hack jobs.

Oh geez. Man, not only are you drinking the kool-aid, but by reading this it may be your blood-type. I saw on another thread you just took fundies, and I think that's fantastic. However, you may need to get off that little "fresh out of fundies" high-horsie you are sitting on. There are people out in the world with a lot more experience than you have that can move tanks in the bands, adjust their harnesses to make reaching the valves easier if needed, and somehow they manage to stay in a nice horizontal trim. Without ankle weights.

Do you personally know of even any (or even one) non-GUE tec/rec instructors that "encourage or endorse hack jobs?" If your 50-99 dives is correct, I have a hard time believing that you have the first-hand experience to make such a statement.

The comfort factor that Dry_Diver mentioned is greatly enhanced by picking the right tanks for your body style and setting them up correctly. Not every LDS employee has the knowledge/experience to do this. Even fewer understand the concept of a 'balanced rig' that does not turn into a death trap (due to weight) when your primary buoyancy compensator fails.

This I do agree with. I would be surprised if 1 of 20 LDS employees around here have the experience or knowledge to properly set up doubles, a stage bottle, or a BP/W properly, as only a couple are tec divers and even fewer are tec instructors.

 

[Rhone Man]

"I am sure I would need to spend a little (maybe a little more)". This is a huge understatement. You are looking at 2 matching tanks, manifold, bands, double wing, 2 matching regs, maybe a backplate of lighter weight. This can easily run you into $1000 range even if you buy them all used.

Mileage varies. I bought my manifold new (US$275 off Leisurepro), but I bought bands (US$75 off eBay) and tanks (US$100 each in LDS sale) second hand, and managed to assemble my doubles for about $550. Plus a lot of bitching and swearing as I assembled them.

 

[ScubaFeenD]

If you need a V-weight for AL80s (i.e. you dive in cold water), then they really aren't that light at all. In fact, they'll weight about DOUBLE what a single HP130 weights. That's a lot of extra weight for only about 20cf more gas. For "recreational" dives, I'd usually rather just take a competent teammate along for redundancy.

I do agree, though, there is certainly nothing wrong with using doubles "recreationally". I just don't see much point for myself for most shallow dives. This is especially true for many shore sites. I know Tobin is taking doubles, deco bottles, and a scooter through the surf (I do it at a select few sites, too), but for MANY local shore sites, that just isn't feasible (rocky entries, long walks over rough terrain, etc). Off boats, especially ones that don't pump gas, doubles *are* nicer (again, IMO only!) than multiple singles.

Good points for sure. Of course, LP85s are better in terms of storage and with very similar weight characteristics to AL80s. Rainer makes a good point too. If I was doing a lot of surf entries and shore dives I would likely not be diving doubles for my shore entry rec dives, because i dont think there has been one shore dive that I havent fallen while trying to enter the damn water...and the surf wasnt even that bad (easy entries are key here). However, for boat diving (in the NE at least) doubles on a rec dive is pretty nice because there is nothing to change out between dives, and when the boats are really rocking (which they have a tendency to do near me) its just a PITA.

 

[ucfdiver]

The advantages are...snip...cleaner hose routing

How so?

My singles rig


My doubles rig


Everything is within 2-3inches of each other on either rig.

 

[eelnoraa]

Mileage varies. I bought my manifold new (US$275 off Leisurepro), but I bought bands (US$75 off eBay) and tanks (US$100 each in LDS sale) second hand, and managed to assemble my doubles for about $550. Plus a lot of bitching and swearing as I assembled them.

Yes, but you are only counting the tanks themselves. How about a double wing, additional regulator set (1 set at least, possibly 2 if you don't want to break up the single setup).

 

[OldNSalty]

As for cost in my case; I was looking at using my 72's. I would need the bands and the manifold. I might need a new wing but found a plate cheap. I have 4 or 5 regulator sets (I know-I have a problem with old gear).

I still find myself limited by the amount of gas I carry and I was thinking of getting some bigger tanks. Now that I am looking at the cost/benefit I am thinking it might be cheaper to do doubles.

Would 1 or 2 sets of 72's be better then 2 100's or 120's???