Tips on starting diving doubles

[SouthernSharktoothDiver]

Hey everybody,
So, I've been looking into diving doubles, picked up a backplate and wing on the marketplace here (thanks, Dan Bartus), and as I'm putting all my kit together, I wanna stop and make sure I'm not making any obvious or potentially dangerous mistakes.

My current intended setup (open to changing it) is to use a 60 lbs Apeks wing, aluminum backplate (SS would probably be better, but I might wanna travel with this at some point, and I don't need more backplate rn), wetsuit ranging from 3mm to 7mm semidry depending on water temps. For tanks, I had figured on using a set of lp steel 72's, as I'm not the strongest person around, so I'm taking the advice I've seen from some california shore divers and trying these, since they're lighter than say, double Lp 108's, but still give you a lot more air than just an al 80 or even an HP 130. I'm planning on setting them up as independent twins, most because I just don't see the need for a manifold in my current style of diving, and it represents an additional cost/failure point vs the redundancy of two, completely independent regs.

For my dive profile, I'll be taking these in shallow water (30 feet, usually), so NDL isn't a concern, and I'm definitely not going into deco (I also run my dive computer rather conservatively, so definitely not risking deco). It's a hard bottom, no drop offs past maybe 45 feet (and even that's rare). I will be carrying an SMB which can be used as redundant lift if needed, and in theory my dive buddy will be around (at least early on when we're working out the kinks, we'll probably use a tether, because the water is rather dark.) Additionally, it is entirely pausible to just crawl up the bank and out of the water at the dive sites I'm planning to go to (I've done it before just to avoid the surface swim), so overall, while I definitely don't wanna screw up the buoyancy/weighting, overloading is a concern I think I'm accounted for.

So, any tips/warnings? I'm somewhat concerned about the amount of lead I'll need to carry, hence another reason I wanna use the 72's, since as I understand, they're a little less floaty at the end than the Al 80's, while not being so negative that I would risk overloading my buoyancy, since I don't dive dry.

 

[steinbil]

I'm planning on setting them up as independent twins, most because I just don't see the need for a manifold in my current style of diving, and it represents an additional cost/failure point vs the redundancy of two, completely independent regs.

IMO, the argument of a failure point is greatly exaggerated, and the advantage of having full access to all of the gas in both bottles even with failures heavily outweighs it. On top of that, you save having to manage two independent gas sources, so you can focus on your dive - meaning it's much less error prone and takes less effort. Just get a manifold.

 

[halocline]

I’ve used backmounted LP72s, and they’re nice tanks for doubles. But….BM independent doubles are pretty much out of the mainstream for a few reasons. I would either go with a manifold or change gears and go side mount.

Finding a manifold and a set of bands won’t be expensive. There are lots of used ones around. And forget about the ‘extra failure point’ idea; manifolded doubles have been proven rock solid safe for decades. You can read endless hours about the theoretical safety factors, but the bottom line is that through many thousands of successful technical dives, there is no evidence at all that independent BM is safer, and plenty of indications that it could be less safe. SM is a different story, but that’s a whole different style of diving with pluses and minuses like anything else. Probably more expensive to get started on, too.

Unless you have LP 72s already, I would consider just using AL80s for a first set of doubles. They actually trim out a little better (for me) and the bands/manifold provide enough ballast so that you typically don’t need more weight than you would with a single AL80 and a BP/W.

A 60 lb wing sounds pretty excessive to me. When I was diving BM doubles in a wetsuit, I used a 45 lb dive rite rec wing and I thought that was too big. It’s all about the wing profile, I’m sure you understand that. In general, more compact wings are more pleasant to dive with, but of course like anything else there are exceptions. I think the AL backplate, even with AL80 doubles, is good. That’s what I always used, but again I was using manifolded doubles. If you insist on independent doubles, then I would go right for side mount and spend the money on a decent harness and some training with a really good, qualified SM instructor.

 

[SouthernSharktoothDiver]

@steinbil I'll consider it. It'd mean also getting new valves, as I don't currently have any left handed valves, unfortunately. I'm planning to take the rig on a test dive in safe conditions (still, clear, shallow water with a buddy) before taking it into real dive conditions, so if switch regs periodically to balance the air consumption is a pain then, I'll look at making the switch

 

[SouthernSharktoothDiver]

@halocline Good feedback. I do already have the Lp 72's, but I'm not married to the idea of using them for this. Could always use some of my AL 80's (admittedly kinda sucks since I already have Lp 72 bands, but the $70 I spent for two sets of those isn't gonna kill me if I don't use them).

Hadn't thought through the wing profile issue. I do fossil diving, in a river, so generally I dive pretty negative, and sometimes am bring up an additional ten or so pounds of whatever I found down there (which obviously, in an emergency, is ditchable. Sharks teeth and glass bottles aren't worth dying over), so I thought I'd want the extra lift. However, you have a point, the current might make diving the big 60 wing a pain in the tuchas. I'll probably give it a try and if it sucks, see if anybody on here wants to do a 1-1 swap or something.

SM is out due to entanglement risks/me not wanting to faff around with a tank on each side of me. I'll definitely consider the manifold issue. Do you mind sharing why independent doubles would less safe? I understand issues can occur during the switch/you could lose track of which tank had what gas (pressure, both tanks will hold the same gas mix), but presuming I drill the switch a lot (which I intend to) it feels like the safety issue falls out, unless I'm missing something. I'm not super opposed to a manifold; independent doubles just seemed simpler when I was making this plan, but I could definitely pencil a manifold into the scheme.

 

[rongoodman]

I would think that that big of a wing would wrap right around those small tanks, making air trapping a real issue.

 

[SouthernSharktoothDiver]

@rongoodman Possibly. This is the sort of issue I had not considered, and why I made this post. Thanks for making that point.

 

[tmassey]

I echo the general thoughts of the people writing above.

What you’re descr is a pretty unique configuration. Unless you truly have substantial and very unique requirements, I would suggest that you create a configuration that is a little closer to the tried and tested configuration that technical divers have been using for a generation now. And nothing you wrote points to me as needing that unique configuration.

You are doing a great deal of thinking, asking questions and getting additional information. All of those things are excellent! However, you seem to be falling into the trap that I find that many people – myself included! – fall into when they first start going into a new field. Starting from a point of an experience, you start extrapolating certain ideas or perceptions or feelings and end up creating a unique configuration.

Ask yourself: are the thousands of people that have moved in this direction before you unable to see the objections that you’re putting out? If they aren’t, that means they saw them too and yet ended up with a very different configuration. One that they have been very happy with for a long period of time and are doing very advanced things with.

Ask yourself: are your needs so completely different that they would force you to end up in a very different configuration? If not, you might want to ask yourself why all of these other people have made the choice that they made when you ended up with such a different choice. Maybe the things that you are weighing heavily as important aren’t as important? Or maybe you’re missing items that are important that push them in a different direction?

This is all a very long winded way for me to say: I would strongly suggest you start with the well tested and proven configuration. That means if you want to go back mounted doubles, I strongly suggest that you go with bands and an isolated manifold. I also suggest that there’s absolutely no reason to have a 65 pound lift wing. I dive 130s with a 45 pound wing. That’s pretty much the absolute limit, but it’s doable.

Now, if you do have things like strength or mobility problems, or the possibility of a manifold is for some unstated reason impossible, then independent doubles is certainly a choice. However, I would recommend that you consider mounting them in the way that everybody else has chosen to mount independent doubles: sidemount. Sidemount is not my preferred configuration for a number of reasons, but I don’t have strength or mobility problems. If you do, it would be something to be considered.

And this is coming from someone who actually has created his own independent back mount doubles configuration! I have absolutely dove it a handful of times successfully. But because I have actually done it successfully, I know the annoyances and rough edges. To me, the only time backmount independent doubles is useful is if you absolutely cannot get a set of true doubles. But I find the need for that is much less today: it’s a lot easier to rent such tanks now that it was 10 years ago. And now that we are deeply into the world of sidemount, it is usually better to go in that direction if you truly can’t get backmount doubles and need the extra gas capacity.

Anyway, that’s my suggestion. Keep thinking, keep questioning, keep asking. But also be humble: acknowledge that you’re not the first person to blaze this trail, and if you’re going in a direction substantially different than the choices everyone else has made, it’s probably because of something you’re missing. It’s better to start with a known and accepted configuration to get some initial experience and only then should you consider making changes.

As for your choice of LP 72 tanks: I’m a huge fan of them as doubles. You can search for LP 72 and my scuba board name and you’ll find all kinds of posts where I have gone through tremendous amount of work to be able to build LP 72 doubles! But: that’s also because I own my own compressor and can fill them to a point where they’re useful. If you can only fill them to the rated pressure, they’re not worth using IMHO. HP 100 or AL80 would make more sense.

 

[inquis]

Independent doubles strikes me as the worst of the backmount & sidemount worlds. Why not stick to a mainstream approach when starting out and benefit from the experience of others?

 

[SouthernSharktoothDiver]

@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