Double Tank Manifolds, Bad Idea!

[tracydr]

Dr. Tracy

Other options include donning gear in the water and mounting gas supplies on a DPV. Treat your onboard gas as bailout when DPV mounted gas is used.

On a related note, I am a volunteer with the Monterey Bay Veterans' working on their Lift to Freedom Project. The objective was to accommodate the full range of disabilities from ambulatory weight limitations like yours to severe non-ambulatory disabilities like David Riley’s (see link).

The Lift to Freedom is in the final stages of installation and we hope to start sea trials in the fall. We are working on the hydraulics and Nitrox systems now. It is a pretty ambitious project for a small non-profit to undertake but a lot of dedicated people have put it an unbelievable amount of work. It is one of the most gratifying projects I have ever worked on. Hope you can come aboard and dive her soon. Here is an image by Dida Kutz the day she was put back in the water after installing the Lift.

Thanks,very much. I've been wanting to dive Monterey and as a veteran, I'll have to come check out this wonderful project. Please let me know when its ready. I'd love to try it!

 

[Doppler]

Dr. Tracy

Other options include donning gear in the water and mounting gas supplies on a DPV. Treat your onboard gas as bailout when DPV mounted gas is used.

On a related note, I am a volunteer with the Monterey Bay Veterans' working on their Lift to Freedom Project. The objective was to accommodate the full range of disabilities from ambulatory weight limitations like yours to severe non-ambulatory disabilities like David Riley’s (see link).

The Lift to Freedom is in the final stages of installation and we hope to start sea trials in the fall. We are working on the hydraulics and Nitrox systems now. It is a pretty ambitious project for a small non-profit to undertake but a lot of dedicated people have put it an unbelievable amount of work. It is one of the most gratifying projects I have ever worked on. Hope you can come aboard and dive her soon. Here is an image by Dida Kutz the day she was put back in the water after installing the Lift.

The best piece of information to come out of this thread... ONYA, mate. Kudos to everyone involved.

 

[Slamfire]

On a related note, I am a volunteer with the Monterey Bay Veterans' working on their Lift to Freedom Project. The objective was to accommodate the full range of disabilities from ambulatory weight limitations like yours to severe non-ambulatory disabilities like David Riley’s (see link)...

God's Pocket Resort here in BC has had an "elevator" in their dive boat for some time now.

http://youtu.be/Zfd7TPrW9fI

 

[Akimbo]

God's Pocket Resort here in BC has had an "elevator" in their dive boat for some time now…

There have been diver elevators for decades, especially in the UK. I know of at least 20. We haven't found any that accommodates the limitations of the vast majority of disabled divers though. This lift is designed for divers that can't safely (or comfortably) support the weight of dive gear out of the water through paraplegics and quad-amputees. We started by looking at anyone who couldn't safely climb a ladder with all of their gear and tried to accommodate as many more serious limitations as possible.

The inspiration for lift was when the Monterey Bay Veterans helped David Riley, a quad-amputee, dive for the first time since losing his limbs. The poor guy had to be manhandled in and out of the water — not terribly safe, easy, or dignified for anyone involved.

The "Lift to Freedom" has two fixed chairs facing inboard on an oversized swim-step for an ambulatory disabled diver and their buddy. A third chair is provided with wheels for a non-ambulatory diver which locks onto the lift. There are inboard winches to aid dressing divers who need it and assist with wheelchair transfers.

I didn't realize the sensitivity many disabled divers have to being different from other divers until this project. This prompted us to eliminate the ladder entirely so all divers ride the lift while seated. Able-bodied divers have the option to jump off the stern or ride the lift up while standing but we made it a good place to finish gearing up and relax if their buddy isn't quite ready. We only carry six divers so the speed to get in the water isn't much of an issue.

The outboard chairs are great for donning fins with or without crew assistance. Small things like mask defog storage, cold water for overheated drysuit divers, hot water for cold divers, and easy camera handoff are intended to encourage all divers to take advantage of the chairs. The chairs are 24" deep to make room for cylinders and have lap belts for anyone who wants to use them. There is also an option for a crew member to ride the lift down to the -4' stop (or less) and help divers who prefer to gear up in the water.

 

[AfterDark]

Jeff Bozanic agrees with the OP . . . “Ideal” Manifolds… Not So Ideal?

I think it's really difficult to do anything but argue opinions on this topic. The failures that require isolation are so rare to occur DURING a dive (and failures of the isolator or manifold even rarer) that coming up with any statistics is difficult. There is no question that diagnosing a failure is easier in sidemount -- and no easier in backmounted independent doubles, nor are the valves easier to reach that way. The failures that lose you half your gas in sidemount are as rare as those requiring isolation in backmount. The difference is that, to use the gas in the cylinder with a regulator malfunction in sidemount, you have to feather the valve, which can be done (I learned to do it in my sidemount class) but I wouldn't want to have to go very far that way.

There may be some increment in safety in one setup or the other, but it would take a long time of gathering careful data to find it, I think. What I do believe is that independent, backmounted doubles is the worst of all possible worlds, because you can't see the valves, you still have trouble reaching them, and you don't offset that with the manifold's ability to access both tanks if a regulator malfunctions. If you want independent tanks, set them up where you can see and reach them (at least that's my take on it).

The bottom line seems to be that failures are so rare that configuration probably isn't an issue at all. All my years I've had one reg malfunction that wasn't owned by me. None with regs owned by me. OOG once because of entanglement. That's > 2000 dives. A lot of huffing and puffing about nothing really. When was the last time a diver died because of their choice of ID's?

 

[rlynch]

i love the uber lift - awesome..
our regular boat uses a lift here in NC, its smaller than that of course but pure decadence on the "under pressure"
love it.

on the ID's - don't see the point.. increases complexity, solves no problems, might as well dive side mount (other than it makes it easier to carry your tanks to the water than if your side mount, and negates the advantages of side mount for small vertical passages).

My 2 internet cents... (so ignore at your leisure...)

<i dive BM doubles with a manifold, GUE etc...I'm in it for the popcorn at this stage...hella first post...>

 

[tskovan]

Interesting debate, this was my first post on SB, (don&#8217;t think I deserved all the &#8220;Troll&#8221; accusations), I stand by my OP and believe that, for non-cave diving, IDs are a better choice especially when solo diving. To those who said that the valves are in the same place whether using a manifold or IDs, your missing one of the most important points of using IDs. Using the rule of thirds while diving, I always have enough gas in either tank to&#8212;in the event of a failure, ANY TYPE OF TANK OR REGULATOR FAILURE&#8212;simply switch regulators, turn the dive, and go home! It doesn&#8217;t get any easier than that, there is no need to reach for valves, ever. During the added stress of a failure simpler is better IMO, the added task loading of gas management is done easily in a non-stressed manor throughout the dive, and the true TOTAL redundancy IDs give is very comforting when solo diving (which I do almost exclusively).
Also I have my own boat and do a lot of diving at slightly remote lakes in AZ. I bring 6 or 7 tanks with me for a week end, after a dive I slide the empties out of my bands and slide in two full tanks, you can&#8217;t do that with a manifold.
Thanks to everyone who replied intelligently.

 

[DaleC]

I don't dive thirds in OW, I use rock bottom, which is why ID's work for me. I just keep that reserve in each cylinder.
Like the xxx crowd, I also have a system. No matter whether it's BM ID's, SM, or single/pony, my gas management is always the same. This allows me a lot of freedom to move within different rigs without changing basic planning/reactions. Someone used to calculating for manifolded doubles has to make very distinct shift in that regard when moving to ID's no matter where they are mounted.

... increases complexity, solves no problems

What is funny is that I could say the exact same thing about isolation manifolds yet neither of us would be entirely right/wrong.

Nuno Gomes dives ID's I see...

 

[Slamfire]

Could I be redeemed of my manifold sins of complexity and stressfully difficult emergency procedures when I add a stage? My saving grace would be that even though my back has one big tank--since they are manifolded--my stage would grant me true TOTAL redundancy. I often find myself carrying three or more tanks on a dive and never more than two manifolded. I was hoping I could leave some of my shame behind in these occasions.

Seriously now, my point is that proper gas management is still done regardless of the number of tanks that you carry and whether there is a manifold in the mix or not. Manifolds are not an impediment to proper gas planning or execution.

 

[rambaldi]

I don't dive thirds in OW, I use rock bottom, which is why ID's work for me. I just keep that reserve in each cylinder.
Like the xxx crowd, I also have a system. No matter whether it's BM ID's, SM, or single/pony, my gas management is always the same. This allows me a lot of freedom to move within different rigs without changing basic planning/reactions. Someone used to calculating for manifolded doubles has to make very distinct shift in that regard when moving to ID's no matter where they are mounted.



What is funny is that I could say the exact same thing about isolation manifolds yet neither of us would be entirely right/wrong.

Nuno Gomes dives ID's I see...

Last I heard he was diving 3 tanks manifolded together (non-isolation) with a separate tank independent. It makes sense when you are 200 odd metres down though as you loose gas pretty quick at that depth.