Tips on starting diving doubles

[grantmac]

I would not go mucking around with yoke regs on a set of independent right handed valve tanks. That's a recipe for a flooded reg at best.

Seems like you are several upgrades away from doubles.

 

[p_kos]

@tmassey @inquis An explanation for why I planned to do independent doubles rather than using a manifold, is partly because up until now I was not aware manifolds were considered so vastly superior. I'd seen a couple posts on here arguing about independent vs manifolded, and thought they were both considered more or less equally viable, like using a donut vs a U-shaped wing. I had liked the arguments I'd heard about better redundancy in the event of failure, which seem to be overstated from what I'm hearing, and I also liked the fact it seemed easier to travel with. Much like sidemount in that I could use any rental AL 80 with the same setup (different bands, of course, but they're not that expensive). That being said, I don't travel to dive at all currently, so perhaps foolish to be worrying about that now. I'm re-evaluating the manifold issue. I've got a while before I'm actually planning to put all this into practice, so there's time for me to consider what I'm working with and shop around for a manifold/suitable valves.

For further explanation, I don't have any major strength or mobility issues, I'm just on the smaller side and carrying extra weight is something I'd avoid, if that's an option. Hence why I was considering steel 72's for doubles. I can get a fill to about 2800-3000 on them from a local guy (an older and well respected dive operator, who I trust to know what he's doing with such tanks), so I'm honestly probably getting more gas than double AL 80's. Based on what Tmassey said, 72's should be a good fit for me in this use case, but correct me if I'm wrong.

As for wing size...yeah, I may have whiffed it on that one. I bought the 60 pound wing because I was thinking that, as I get more experience and eventually wanna go into tech diving, I can keep using the same wing. I seen people claiming the exact model wing I'll be using (Halycon evolve 60 lbs) is suitable for anything from backmounted 72 doubles to twinset 130's with an AL 80 for stage, so I thought I was "buying once" so to speak. I'll wet test it and see. I'm concerned about the tacoing problem @rongoodman brought up with 72's, so I'll have to see what happens if I use this system in safe, controlled conditions. If it seems like it's tacoing, I'll either switch to larger tanks (like AL 80's) or see if I can trade somebody for a smaller wing. Advice and tips on this would be appreciated. Also, specifically to Tmassey but anyone else feel free to chime in, is the drag difference between 45 lbs and 60 lbs all that? Because if so, that would also be a concern I'd need to consider.

I appreciate all the feedback. The whole point of this post is that I'm very aware I'm relatively new to diving, and didn't want to overlook some obvious mistakes/issues. Thanks again

I have the Halcyon Evolve 60 lbs wing and dive it with twin 72’s no problem. Tacoing not an issue, drag not noticeable at all. Below is a picture my 72’s before I installed the isolator manifold (I had them set up as singles before I found bands for them). I set them up like independent doubles just to see how the tanks and wing would fit together (for the picture only), I would never actually dive them like that. As you can see the wing does not look ridiculously too big for 72’s

 

[SouthernSharktoothDiver]

@p_kos Super helpful! Are those modern bands or vintage? The ones I currently have are vintage, and I'm told the spacing is different, so I'm wondering if that might be an issue I need to correct. No huge deal if so. I got the ones I have cheaply enough that I can probably sell them at no loss and then buy modern bands if needed.

 

[p_kos]

@p_kos Super helpful! Are those modern bands or vintage? The ones I currently have are vintage, and I'm told the spacing is different, so I'm wondering if that might be an issue I need to correct. No huge deal if so. I got the ones I have cheaply enough that I can probably sell them at no loss and then buy modern bands if needed.

My bands are not vintage and I’m not sure if the spacing would be much different. Most vintage bands I’ve seen seem pretty similar, enough so to work with modern manifold dimensions. I had a hard time finding a nice set of bands (some vintage bands are skinny and flimsy looking) until I posted on Scubaboard about it and got these for $75 from one of the members.

 

[SouthernSharktoothDiver]

@p_kos Nice. I got two sets of vintage bands of ebay (4 bands in total) for about the same price, but they're somewhat banged up and I've heard (not certain about this) that they cannot be used with a modern manifold due to spacing issues. If anyone wants to weigh in on that yeah or neigh, feel free.

Also, would it possible for you to measure the distance, valve to valve, on your setup so I can know for certain? If nothing else, I assume different width/dimension of vintage bands exist (not to mention the possibility that the "vintage" on mine is like, 1990 or something similarly new enough to have modern spacing, I don't know their full history)

 

[p_kos]

@p_kos Nice. I got two sets of vintage bands of ebay (4 bands in total) for about the same price, but they're somewhat banged up and I've heard (not certain about this) that they cannot be used with a modern manifold due to spacing issues. If anyone wants to weigh in on that yeah or neigh, feel free.

Also, would it possible for you to measure the distance, valve to valve, on your setup so I can know for certain? If nothing else, I assume different width/dimension of vintage bands exist (not to mention the possibility that the "vintage" on mine is like, 1990 or something similarly new enough to have modern spacing, I don't know their full history)

@p_kos Nice. I got two sets of vintage bands of ebay (4 bands in total) for about the same price, but they're somewhat banged up and I've heard (not certain about this) that they cannot be used with a modern manifold due to spacing issues. If anyone wants to weigh in on that yeah or neigh, feel free.

Also, would it possible for you to measure the distance, valve to valve, on your setup so I can know for certain? If nothing else, I assume different width/dimension of vintage bands exist (not to mention the possibility that the "vintage" on mine is like, 1990 or something similarly new enough to have modern spacing, I don't know their full history)

Valve centre to valve centre is 8.5 inches. The band centre pieces are roughly 2 inches wide.

 

[Nick_Radov]

If you're diving a drysuit or thick wetsuit, you want steel not aluminum doubles.

Please ignore this. A wetsuit with negatively buoyant steel doubles is a deadly combination. For details search for "balanced rig" which has been discussed many times on previous threads.

 

[gordonscuba]

The isolation manifold is one of the best inventions in the history of scuba diving. Deciding not to use one, and showing up to a dive like that, would be a little bit like getting on a plane full of skydivers with a parachute that you knitted yourself at home and packed into a brown paper sack.

 

[SouthernSharktoothDiver]

@Nick_Radov Per my understanding, my rig would be safe so long as I'm positively buoyant, minus any ditchable weight. So, for example, if I'm say, six pounds negative at the start of the dive, neutral at the end, and carrying six pounds of lead, all of which is ditchable, my rig would be safe, correct?

Simplistic example, of course, but the principle holds the same. In practice, I would have more than six pounds of air weight being lost with a twinset, but essentially my point here is that at any point in the dive, I can drop weight to achieve positive buoyancy, and even ignoring that, could in theory swim up just fine even without dropping lead, since the ~12 lbs negative I'd need to be at the start of the dive is manageable by use of fins. This is not even getting into the fact that, in the environment I'm planning to use this system in, I could crawl out if I needed to, or, failing that, drop my whole rig and swim 20-30 feet straight up.

Please let me know if my understanding is flawed here. I've seen several discussions on "balancing" a scuba rig, and many people on here seem to have different opinions of what that term means. I'm not a GUE/DIR/any kind of technical diver myself, I'm just trying to stay at about 30 feet for around two hours at a clip, so some of this stuff is a little above what I'm familiar with. Also worth mentioning I won't be using this in places that don't have a hard bottom (at 30-40 feet, max) which adds to the safety factor. Still, if my understanding is flawed here, do let me know.

@gordonscuba Several other people have already made the point about manifolds. I've said I'm looking into it. Need to put the whole thing together and figure out a few basic issues (such as whether my LP 72's are even appropriately sized for my wing) so that if/when I do buy a manifold, I know the stuff I'm putting it on actually works.

Also, your use of hyperbole doesn't really add to your argument, and in fact makes it less compelling. Independent doubles is not like skydiving with a knitted parachute. Better example, from what I've been told so far, would be to compare it to diving with a parachute made in the 1970's. Not suicidal, or even dangerous, if the thing is well maintained and checked off thoroughly, but perhaps not the wisest course. Also bear in mind, some other people, both in this comment thread and elsewhere on this site that I've seen, would dispute even that, so acting like it's a completely insane idea is rather silly, don't you think?

I acknowledge a manifold would likely be better. I'm just chewing on how best that can be integrated. I'm also, transparently, planning to test independent twins in a safe environment with a buddy nearby. If nothing else, I fail to see the danger of it, and it will be a good learning experience. Not like it'll cost me anything but time, after all.

 

[rjack321]

@Nick_Radov Per my understanding, my rig would be safe so long as I'm positively buoyant, minus any ditchable weight. So, for example, if I'm say, six pounds negative at the start of the dive, neutral at the end, and carrying six pounds of lead, all of which is ditchable, my rig would be safe, correct?

At depth, at the start of a dive, in a wetsuit you will have nothing positive on you at all. Any positiveness of the wetsuit will be completely smushed and gone at 100ft or a little beyond. Depending on the thickness of the wetsuit and the amount of buoyancy lost, and the size of the steel tanks, and the gas in them you *may* be able to swim them up in the event of failure. Or you may be basically pinned to the bottom if you wing is inadequate or fails.

This whole discussion is a giant mess. Invest in a proper class. GUE-F would be a good place to start