Alternative to doubles

[rongoodman]

Since you're going to be diving off boats, instead of in caves, I'd go for a standard set of manifolded doubles, unless you have some physical problem limiting your access to the valves or being unable to carry them. They're stable in the water, provide access to all your gas and redundancy, and pretty much everybody understands them. They don't have to be huge--you can add a stage for deeper dives if you need to. Valve drills aren't rocket science either.

 

[Dive Bug Bit Me]

There have been a number of good comments here that I would take on board. As is outlined, the more common approach for ocean tech diving is manifolded doubles. These also work well for ship penetration if you ever choose to go that route. In retrospect if I were to do it again I would have learnt in side mount because I ended up falling in love with caves.

If you are only doing AN/DP you may be able to do this in a single with H or Y valve. (with a pony for deco gas) I would consider my air consumption rate and needs. Speak to your instructor and see what he thinks. You can always move to doubles / side mount , etc when you need that extra gas.

The most task loaded I have been on a course was AN/ DP where all the skills were new (and I was signalling remaining deco each minute) The instructor also entertained himself by throwing random scenarios at me. The added challenge of managing a second pony and trying to breath it down evenly with my back gas would have been too much.

 

[Pullmyfinger]

It's going to depend on your instructor, you should go over your options with him. When I took AN/DP the options were to use either manifolded doubles or a larger single tank with an H-valve.

My instructor mentioned that TDI allows some latitude in equipment selection for their instructors. So your instructor may have different preferences than mine did.

AN/DP covers one deco gas....a 40cu. ft. tank is typical, and is what we bought.

My instructor did our course with 2 deco tanks ( two 40 cu. ft. tanks).

I have no idea if this course is taught with independent back mounted doubles or not.....again, it would depend on your instructor.

For the purposes of this training, I don't see any advantages to doing it with a single tank and an H-valve. If your buddies are diving manifold doubles (or side mount), then you should consider doing it in doubles as well.....just my opinion. I've heard it mentioned before that some divers go with the big single/H-valve setup due to cost.....if that's driving your decision (not saying it is).....then just keep saving up and budgeting for a set of doubles.

I got with my instructor a little over a year before I took the class.
I spent that time getting all the gear together for my wife and I........I KNOW it's expensive, but you'll be glad you took the time getting everything together.

Your buddies are diving doubles, correct?

If you are looking to do your training and diving in a single tank/H-valve for back gas, with a Stage bottle AND a deco tank......It doesn't matter what any of us say....the equipment configuration options (manifold doubles, independent doubles, or sidemount) are certainly up to your instructor also.

Discuss your options and the pros and cons of each with your instructor, and go from there. Consider what your dive team is doing.

**With your dive team in mind...it seems your two choices are manifold doubles vs. sidemount.

Have fun in the class.

-Mitch

 

[waterpirate]

I think this a universal point of discovery. The question being "how can I get there with what I have?". All this gear is expensive and going the traditional route in the beginning is the way to go IMHO. Changing gear for the mission or by choice after a bunch of an/dp dives is also a choice not a dodge.

I have found copious amounts of good used gear for sale all over the country. I bought 2 sets of manifolded hp 100's for 500 each. Buying new gear is not reqired, buying the correct gear is reccomended.
Eric

 

[Queequeg]

LOTS of good thought here! Thank you. I can now express more clearly what I meant to say having read the replies.

First...I dont see myself going beyond 150' range or seeking training beyond AN/DP. Mostly, we are just trying to get the certifications to do some of the wrecks we want to see that lie in the 100-150' range.

So therein lies my weighing of cost, function, and frequency. As stated here by others, a single tank with deco bottles is sufficient to 150', I agree. I think 150' is right on the edge, and is why I was thinking of slinging two 40's also. As far as cost, I already have this equipment. I don't have doubles. And of course the question arises when going this route, "Do I need two sets of doubles?" If we were eventually going to seek training and dives beyond 150' , I certainly then would be setting myself up with doubles.

The subject of my dilemma really is we are talking 100-150' and not beyond that. It just seems I can use a 120, or larger, and sling a 40 for deco and 40 for reserve. But the gas management and OOA situations people here have raised are a valid concern.

Lots of good discussion here. I truly appreciate it everyones input.

 

[DevonDiver]

First...I dont see myself going beyond 150' range or seeking training beyond AN/DP. Mostly, we are just trying to get the certifications to do some of the wrecks we want to see that lie in the 100-150' range.

Which raises other issues, that may affect your optimal configuration... Will you intend to penetrate these wrecks?

Single, large, cylinder with two bulky stages (on a jacket BCD?) is far from a perfect set-up for over-head/confined environments.

I still think you should investigate sidemount - still have two slung tanks, but get rid of the bulky back-mounted single. It's not expensive either, especially if you already dive a BP&W.

Also, you are creating some issues with regards Rule of 1/3rds. Will you use your main tank for in/out and maintain a stage of the contingency 1/3rd? What if there's an issue with the contingency? Will you add 2 regs to it, so you can share air? Same applies for your deco tank... will you factor that for 1/3rds also? If you lost it.. would you have enough back-gas to deal with a worst case (extended deco and air-share on your contingency tank for ascent)? If penetrating a wreck, you'll be tempted to stage your tanks at the entrance? What happens then to your reserve?

Diving doubles (whether backmount or sidemount) addresses those issues. Compromising based upon the existing contents of your dive crate doesn't...

You'll learn more about the technical diving attitude to kit compromise when you do your course (hopefully... if your instructor is worth his salt).

 

[VooDooGasMan]

Banjo, your set up will be fine, Is your 120 a LP or HP, option here is either tank pump to higher pressure for more psi, and pump more in al 40's. I put in over on all my tanks, Only twice have I gone under 1000 psi to get that last bit of video in the shallows.

The only thing that you need more gas for is more bottom time at the 150' range, so that is the ? do you want to go that far on a boat to get a few minutes, or a 40 min bottom time. so dive the set up you have then go to dubs, side mount, rebreather.

 

[DevonDiver]

so dive the set up you have then go to dubs, side mount, rebreather.

The issue is that he's about to pay for what is probably the most optimum and cost-effective series of courses to learn doubles/sidemount.

Why dive a hotch-potch compromise on those courses, gaining less benefit from the training, and then have to pay again for training, or struggle to self-educate on new kit... at a later date?

...and if he subsequently wanted to undertake the Extended Range or Advanced Wreck courses... what then? Most instructors would insist on doubles bm/sm for those, I think. With zero experience in those rigs, it's a non-starter.

It'd be better to rent some doubles for the course/s and get the best value from it. Then he'd be in a superior position to make a judgement call about whether he'd be satisfied to carry on his deco wreck diving in a giant mungo cylinder and danglies.

 

[danvolker]

Hey friends,

I'm taking the intro to tech course, advanced Nitrox and deco procedures. When considering gear configurations, my buddies are going doubles. One is doing back mounted HP 100's, the other is doing sidemount 119's. We are planning on OW dives, Northeast, Midatlantic, 100-150' range. No penetration, no caves.

I dive a Dive Rite Transplate with the venture wing and an hp120. I trim out nicely with this setup. I sling a 40 on occasion on deeper dives.

I'm thinking , rather than doubles, I can dive my hp120, and sling a 40 on each side? One forty for reserve, the other as a deco gas. That gives me 200 cu ft of air, just as much as my buddy diving double 100's, without the hassle.

Is this unconventional? Its not my idea, the owner of my LDS, who I dive with quite a bit, did this, until he went side mount. It seems to me such an easier and cost efficient way to go than back mounting doubles or buying a side mount rig. Especially when we are talking about dives in the 100-150' range...seems sufficient to me.

Please weigh in. Whats the disadvantage of this?

Thanks
:cool2:

I used to dive a LP 120, which could be hot filled to the point of really being a 160. I would dive it with big monster freedive fins, and had the ability to go very fast with this set up. When I penetrated into shipwrecks, to video jewfish or something, I would be able to be motionless as long as I needed for the shot.....I thought this was perfectly balanced and trimmed.
When I went through Fundies, and the pool work was simulating the motionless necessities you may have in the exploration of a shipwreck, getting in to smaller passageways, having to twist and turn and maintain perfect bouyancy at all times without effort, a few things became clear about the 120's.... they were stable at crusing speed--in that I would not be getting rolled to one side or the other, with my body acting like a wing for stability. At a dead stop, the 120 is a big tank---it sticks up very high vertically, and this is like a big lever constantly trying to roll you to the left or right. Your feet can counteract this for a while, but it become more and more work, and the precision of what you are doing becomes more important.
By switching to double 80 aluminums, I got the center of gravity much lower--the tanks are much closer to your back, and the tanks are much lower vertical profile, and close to neutral, meaning the don't try to pull you down one side or the other. Also, the wing is so far out on each side, it is like having pontoons on either side of you, which cradle the tank...these pontoons cause tremendous natural stability.

So my advice on this, will have to do with where you want to go in the next few years.....If you never want to explore into an area where you may need to just move very very slowly, in order to negotiate the penetration, maybe you can get away with the big single tank. You say you don't want to penetrate, but it is hard to imagine how you will not get the urge to do "some" exploring at some point. If true, and you also NEVER need to be almost dead stopped, then yes, you might save money diving the single setup you described.
I would say though that the diver you could be, 2 years from now, if you went to doubles, would be a diver that could safely enjoy many more challenging conditions than the one in the big single tank.

 

[VooDooGasMan]

Devon in op's first post, he wants to do it and now dan has said he has and switched, you can dive any configuration you wish, only you can make the switch. It may have been he tried lifting dubs, that alone changes minds on some. the first thing that needs to be taught(not many no how easy it is when you know the tricks)is how to lift and set dubs down. Then there is side mount, for me I have my second one hanging from boat, and I do like having both hanging and rolling over then hook them.

If he wants to dive it, why not, I have taken two al 40's down 20 years ago, sidemount is nothing new, just perfected for divers that can not self teach like DUMP and others have, or is he self teaching and wanting to take a class all in one. Is the class so the charter boat will accept him to dive these wrecks?