2 Side Mount AL40's and a Back Mount S100?

[coldcanbefun]

According to this, two AL40 weighs 30 pounds, basically the same as a single HP100. So it’s a wash: your config and double HP100 weigh the same.

But seeing as you’ve said you don’t need the extra gas, use double LP50 or LP72 and save as much as 20 pounds…

And wearing a set of LP50 doubles is even sleeker than a single 100. To me, that is the right solution here. Two redundant regs, no swapping for ‘balance’, options for gas capacity for different dives, and the skills 100% grow with you.

But hey, here’s no scuba police….

Thanks @tmassey all good points.

The two 40's on the side feel more comfortable to me than two 100's on my back, its just to much (for me).

A smaller set of doubles is definitely of interest to me, and will probably explore that at some point, but not this year, probably part of a tech course.

I really do appreciate your input.

 

[coldcanbefun]

This is pretty nutty for a NDL dive in my opinion, as is the idea of keeping three 2nd stages around your neck. And again, the whole idea of taking 180 cft on a NDL dive is really questionable as well, except in certain situations where you are trained in overhead and diving thirds (or more conservative). The set up does not fit the type of diving you are describing, and TBH it’s less safe than simply carrying and breathing your back gas from one tank, and having a bailout bottle. Why? Because your plan is needlessly complex, it WILL be confusing to have three 2nd stages around your neck, and neither of the small tanks are very useful as bottom gas. Small tanks are used for two things; deco and bailout.

You also haven’t talked about what kind of gas you’re using, but if it’s air, a 2 hour dive to 50 ft is going to exceed NDLs. Long dives tend to load up the slower compartments and they take longer to clear. There’s a very good reason that recreational divers typically use one tank; it’s almost foolproof and it helps to keep them out of unexpected deco trouble. Your 40 is a viable (excessive, but that’s ok) bailout bottle and the best practice IMO would be to keep the hose stowed like a stage hose unless you need it.

I dive with three tanks most of the time; SM AL80s and a AL80 stage, in caves, using 32%, and it took me multiple courses to learn how to safely mitigate the risks involved. Like you, I didn’t know what I didn’t know and was very surprised at how much new task loading there was carrying extra cylinders. With a third tank, you are either breathing it or the 2nd stage is stowed (you can find plenty of photos to see how) and the valve is closed. I suggest you re-think this whole idea to conform to what technical divers have been doing for decades.

Thanks, I appreciate your suggestions.

I am *not* wearing all three 2nd stages around my neck.

I plan on staying down as long as I can while still within NDL. Wouldn't it be funny if after all this discussion about NDL/RMV/SAC the limiting factor turns out to be the temperature :O

I plan to get an extra 30 minutes (15 minutes each) from the 2 40's, leaving 1000psi in both as bailout gas. I'll let you know if this is not the case in practice.

I agree with you that stowing one of them and using the other is more sound, the only reason to use both is to practice managing two side mount tanks, which I think is OK as well for that reason. I may do either, or leave one in the truck depending on the day/dive. Learning to manage the two side mount tanks is a big part of this. You are correct that this configuration does not match the dive from a purely planning point of view. But then you really don't need any tanks at all in a pool, you are wearing them in the pool to learn how to manage them, not because the dive requires them.

 

[J-Vo]

@coldcanbefun

The fact you like to tinker and are considering this config makes me think you will be moving into more advanced diving in the future. It can not be understated how much safety familiarity and seamless protocols brings to advanced diving. From this standpoint, talk of using completely different configurations for different dives is a red flag for me. As others have said, a time tested standardized side mount or doubles config will be safer and it can grow into your future diving.

 

[coldcanbefun]

@coldcanbefun

The fact you like to tinker and are considering this config makes me think you will be moving into more advanced diving in the future. It can not be understated how much safety familiarity and seamless protocols brings to advanced diving. From this standpoint, talk of using completely different configurations for different dives is a red flag for me. As others have said, a time tested standardized side mount or doubles config will be safer and it can grow into your future diving.

Thanks @J-Vo and yes I do have an interest in doing more training down the tech path. Unfortunately it will probably be a year before I will be able to do so. I didn't mean to step all over established protocols with this thread, just wanted give myself an interesting project to pursue, teach myself a few things, and enjoy some new challenges this winter. All in fairly simple, shallow, shore dives, i.e. read good environment to try new things.

 

[halocline]

Learning to manage the two side mount tanks is a big part of this.

Ok, but these are not sidemount tanks as you have described them. They are more like small stages or bailout bottles.

If you want to learn how to manage sidemount, take a sidemount class and learn to dive SM. It really is that simple. There's a LOT to learn to do it really well. Self taught SM divers are frequently....lets say, less than perfect, lol.

I am *not* wearing all three 2nd stages around my neck.

Then I guess I misunderstood your description of having both small tanks routed behind your neck and the big tank on a necklace, which is still a 2nd stage around your neck. If you want to clarify that, good. The alternative is to have 2nd stages stowed on the smaller tanks, by that I mean held in place against the tank, with the valve closed. That is how you carry stages and deco bottles unless you are breathing off them.

 

[coldcanbefun]

Ok, but these are not sidemount tanks as you have described them. They are more like small stages or bailout bottles.

If you want to learn how to manage sidemount, take a sidemount class and learn to dive SM. It really is that simple. There's a LOT to learn to do it really well. Self taught SM divers are frequently....lets say, less than perfect, lol.



Then I guess I misunderstood your description of having both small tanks routed behind your neck and the big tank on a necklace, which is still a 2nd stage around your neck. If you want to clarify that, good. The alternative is to have 2nd stages stowed on the smaller tanks, by that I mean held in place against the tank, with the valve closed. That is how you carry stages and deco bottles unless you are breathing off them.

The two AL40's go up the back around the neck and are bolt snapped to the shoulder snaps, left tank to right shoulder strap and right tank to left shoulder strap. The 100 is on a necklace.

Look, I get it, a 40 isn't an 80, so its not a proper side mount setup. To me what seemed like like a bit of practice to maybe take that next step toward some more formal training is aggreges to the majority of the people here, who no doubt have more training than I do. To be completely honest this conversation has left me questioning my decision making. Although I personally still do not see the gravity perceived by the rest, I can't ignore the reaction even if I'd like to.

At this point I'm not sure if I'm going to continue forth with just the one (stowed) as redundant air or my original plan, but either way I still have to get a lot of diving in this winter one way or the other. Here are a few certain facts that resulted from this conversation:
1) I may not do the side mount self experimentation as I thought I would, or maybe I will, I need to process this conversation a bit more.
2) If I do go ahead and give it a try, I will unavoidably be self conscious of anyone else seeing me doing it. Thankfully its winter so the chances of an empty beach are high.
3) I would never bring this setup on a dive boat or anywhere else where I knew there would be other divers. This is a direct result of this conversation, I did not feel that way before. Which I guess deserves a thank you to all who replied, otherwise I would have been on a dive boat next summer with people shaking their heads in disgust and me oblivious to why. That would have not been fun, you helped me avoid that.

 

[Celt]

The two AL40's go up the back around the neck and are bolt snapped to the shoulder snaps, left tank to right shoulder strap and right tank to left shoulder strap. The 100 is on a necklace.

Look, I get it, a 40 isn't an 80, so its not a proper side mount setup. To me what seemed like like a bit of practice to maybe take that next step toward some more formal training is aggreges to the majority of the people here, who no doubt have more training than I do. To be completely honest this conversation has left me questioning my decision making. Although I personally still do not see the gravity perceived by the rest, I can't ignore the reaction even if I'd like to.

At this point I'm not sure if I'm going to continue forth with just the one (stowed) as redundant air or my original plan, but either way I still have to get a lot of diving in this winter one way or the other. Here are a few certain facts that resulted from this conversation:
1) I may not do the side mount self experimentation as I thought I would, or maybe I will, I need to process this conversation a bit more.
2) If I do go ahead and give it a try, I will unavoidably be self conscious of anyone else seeing me doing it. Thankfully its winter so the chances of an empty beach are high.
3) I would never bring this setup on a dive boat or anywhere else where I knew there would be other divers. This is a direct result of this conversation, I did not feel that way before. Which I guess deserves a thank you to all who replied, otherwise I would have been on a dive boat next summer with people shaking their heads in disgust and me oblivious to why. That would have not been fun, you helped me avoid that.

You’ve only made one mistake, telling the internet experts your plans instead of showing the results. Over the last 50 years I’ve tried more ways of carrying tanks than I care to remember but don’t regret trying any of them. The first question you need to ask is , what do I need to make this dive? You only need to get to where you want to go and back.

 

[halocline]

The two AL40's go up the back around the neck and are bolt snapped to the shoulder snaps, left tank to right shoulder strap and right tank to left shoulder strap. The 100 is on a necklace.

Look, I get it, a 40 isn't an 80, so its not a proper side mount setup.

Do you understand that what you are describing is three 2nd stages around your neck, with three hoses presumably coming from the right? When the 2nd stage on the left D ring is clipped, is the hose running on top of the necklace or underneath? If on top, it impedes access to the necklace 2nd stage. If underneath, the 2nd stage necklace impedes access to the 2nd stage on the left D ring.

Which hose do you don/doff first, because without establishing this and adhering to it, your hoses are very likely to get tangled with each other as you attempt to switch between them. Have you established a protocol for switching from the BM tank to one of the small tanks; i.e a routine as to whether you will always switch between the BM andd left tank or right tank? Because that also matters with regards to managing the hose routing. What if there’s an emergency and you need to switch quickly; do you unclip the other small tank from a D-ring or do you go directly to the necklace? If you go to the necklace, have you figured out how to keep the hose from the reg on the left chest D ring out of the way? What about air sharing, how will you manage that? (I realize you are intending this as a solo set up, but even so, it’s irresponsible to not have a plan fro assisting another diver) How about valve drills? Have you figured that one out, and how you would deal with a sudden leak? It will get very confusing, very fast. And these are just a few of the details.

There are good reasons why people take classes in technical diving for complex, multi tank set ups. Years of thought and course development have gone into training divers to successfully manage all the things that can go wrong. Think about it.

BTW, the size of the tanks has nothing to do with why your 40s are not sidemount tanks. They are not SM tanks because you are not using them as such. You don’t seem to understand this, which makes sense because as I said in an earlier post, we don’t know what we don’t know. Diving is not so much about the gear choice as it is about the techniques and protocols, tailored to specific environments and demands. Then the gear selection, and training to manage the inevitable task loading, follows to support what you need to do on the dive.

 

[NothingClever]

I looked around to see if there was anyone else diving this configuration and was a little surprised that i really didn't see anyone doing it for long recreational dives.

I have 15 dive sites I have to map this winter...

@coldcanbefun

I think your mission is to entertain yourself with an equipment experiment more than it is to accomplish a serious surveying and mapping effort. I don't mean that phrase "entertain yourself" in a condescending way but simply in a frank way.

It’s evident you're dead set on doing something that a whole lot of other people (with more experience) are rejecting in favor of simpler, vetted methods. It seems you're set on learning the hard way rather than the easy way.

If you were introduced into a serious surveying effort with experienced divers and going through pre-dive planning, I think chances are much higher that you'd conclude you're just playing with dive equipment rather than really prototyping a more effective equipment configuration for extended BTs. The other survey divers would be getting on with things UW and topsides with data review while you're still focused on trying to define and refine your procedures.

If it were me, I'd be on a twinset to free up my hands for uninterrupted, organized and thorough data collection.

Whatever your mission really is, good luck with surveying your 15 sites this winter.

Let us know how things go.

 

[Still Kicking]

the majority of the time spent at an average depth of 40'-50'. There are a few that drop to 85' but those are the exception. Excepting the few deeper dives, I plan on staying down for a few hours NDL permitting

What tables permit a few hours at 40-50'?

As for mapping, you might want to look into a Navionics subscription. It provides access to extensive bottom mapping of the US coast. No need to dive a site to map it -- cherry pick the good sites and ground-truth the bathymetry.