Going doubles - questions

[PvilleStang]

Hey, I just saw him talking about his rig in general... And have been watching some theory DVD's about DIR with JJ and George, and just had to let that one out

 

[limeyx]

I thought a single Al80 was heavy when I first started diving but now it feels light. It's all about what you get used to. Double Al80s aren't really that bad.

The problem with AL80s is that if you dive dry in cold water, you have to add a bunch of lead to sink them. You then get to carry that lead on the surface.

 

[limeyx]

Thanks again everyone.

So after some more reading here and on the Deco Stop forums, I've narrowed it down a bit.

What do people think of the Faber LP 85's for a doubles setup. Jim, I see you are recommending that type of setup. They look to be an ideal setup for what we need.

Anyone care to comment on those?

They are 26", neutral empty, -6 full, and weigh 31 pounds empty. Seems like a pretty good match.

From what I have read and calculated, the HP100's I have are going to be too much weight, and the E7-80's I was considering may be tough to trim out.

Thoughts? I know this is getting long, but I want to make sure we get the right setup.

I think the LP85s are great doubles. I have a pair that I need to dive more.

They are long enough so that they are pretty easy to trim out, pretty cheap, and the buoyancy is good.

they hold enough gas for most "tech1" type dives (25-30 mins at 150 ish)

The only issue I have with the fabers is that they are painted, not galvanized so the surface tends to rust a bit.

I think worthington might have some LP85's that are galvanized, but I think they cost more than the fabers

 

[limeyx]

NAUI: Advanced, Drysuit, Deep Diver, Nitrox. I have about 125 Dives in a year and a half. Remeber that the reason for doubles is for redundancy, and reserve gas. 30CF reserve is required here on most charters for dives below 90 feet. That's all we are looking for out of the doubles right now. Nothing beyond the NDL.

Also, throw out all the crap about "30cf" reserve -- if it makes the boat happy, fine, tell them you have a 30cf reserve.

What you need to do is figure out the "right" reserve that you *actually* need for your diving.

Lamont has an online calculator or spreadsheet that will help you maybe, but either way, you need to plan enough gas to get 2 divers safely to the surface assuming one is totally OOA, and assuming a somewhat increased breathing rate. (This is actually same thing for singles too). 30cf is meaningless on its own.

Also, things get a little more complex in doubles as you have more redundancy than in singles, so a valve failure (1st or 2nd stage) does not necessarily mean you lose all your gas.

However, doubles can have some insidious things to trick you -- for instance if you accidentally go diving with the isolator open, your SPG (if you have things rigged up "right") will never drop, so you will eventually get an unexpected OOA experience.

I would highly recommend finding a mentor to help you out adjusting things and getting used to valve shutdowns and checking your valves etc.

 

[SparticleBrane]

The problem with AL80s is that if you dive dry in cold water, you have to add a bunch of lead to sink them. You then get to carry that lead on the surface.

Sometimes...you have to go with what you can afford.
On that note I just doubled up my Al80s. I have the 'brushed aluminum' tanks so there's aluminum and steel against each other...galvanic corrosion Then, there's the salt-water speeding up the process...
I have been recommended to put inner-tubing between the tanks and the bands. Do I just go out to wally-world to get some innertube or what?

 

[SparticleBrane]

if you accidentally go diving with the isolator open, your SPG (if you have things rigged up "right") will never drop, so you will eventually get an unexpected OOA experience.

And by "open" you mean "closed".

 

[Meng_Tze]

Sometimes...you have to go with what you can afford.
On that note I just doubled up my Al80s. I have the 'brushed aluminum' tanks so there's aluminum and steel against each other...galvanic corrosion Then, there's the salt-water speeding up the process...
I have been recommended to put inner-tubing between the tanks and the bands. Do I just go out to wally-world to get some innertube or what?

I have had double al80's without paint/innertube in salt water for years..........no galvanic corrosion. Once you get a skin of AL oxide between the bands and the tank, the corrosion effectively stops. These are the 'white' bands you see on my stages too...

But a metallurgically more astute person may have more science behind this.

 

[Meng_Tze]

And by "open" you mean "closed".

Check, check and tripple check.................others feel that you should never close the isolator............I even got stick from a tank monkey once who told me it was 'forbidden' to close the valve......Told him he should check I did not do forbidden stuff...It is good to have an extra concience

 

[limeyx]

And by "open" you mean "closed".

Ha, oops! Yes, of course.

 

[jduncan]

Okay - So I called the LDS today to inquire about the LP85 setup. He said that he'd be happy to get me a quote on those, and he actually had some there - but claims that they will fail hydro in the first or second inspection. He was talking about the Fabers. He also said that most people like them because they can be overfilled, and that he won't fill them past the 2400 + 10%...so unless I have my own compressor, forget it.

When asked what he recommended, he said he would go worthington HP80 for Lisa and HP100 for me. So...I thought I would bring THAT to the board for digestion!

Thoughts? They are not quite as heavy as the Fabers, and about 1/3 less negative full.

Also, he was nice enough to state he would rig up all three types of doubles for us to try, possibly this weekend.

J