50 replies to this topic

[finGrabber]

I’m considering taking the plunge toward more Tech-oriented diving. Among the gear considerations is
diving doubles. So, my first question is how big should a beginners setup be in terms of tank size? And should I look at aluminum or steel?

I know that if I start getting into large steel tanks that I would have to dive dry due to weight issues and wing size but what about diving wet? What's the max size I should look at?

are there other considerations, too?

[PerroneFord]

I’m considering taking the plunge toward more Tech-oriented diving. Among the gear considerations is
diving doubles. So, my first question is how big should a beginners setup be in terms of tank size? And should I look at aluminum or steel?

I know that if I start getting into large steel tanks that I would have to dive dry due to weight issues and wing size but what about diving wet? What's the max size I should look at?

are there other considerations, too?

Wow, now this is a great question.

Honestly, despite their appearance, I don't think that doubles are solely the domain of technical diving. THey serve many useful functions in the water including redundancy, more realistic gas supply, better stability, etc.

Steel tanks, especially in the smaller sizes, are often lighter than their aluminum counterparts. They also require less weight because they tend to be a bit more negative. Personally, I feel that a set of steel 85s for ladies or shorter men, or steel 95s for taller men are a great set of first doubles, depending on the environment. If you are diving with a thin wetsuit and/or don't wear much weight on your belt, a set of Aluminum doubles may be better.

The steel 85 is nice because it is smaller than an Al80, weighs less on land, takes weight off your belt, gives the advantage of nice hose routing, and it holds more gas than an AL80 even without overpumping the tank. You can think of it like carrying two AL80s on your dive, plus a little extra.

I went with Al80 doubles for a few reasons. First, I dive wet. At least for now, and I don't wear a lot of neoprene. I also don't wear weights when I dive. However, I may go back to a small weightbelt with my double set because they do get quite floaty as they empty. About 8 pounds should do the trick, and this is very common with AL80s.

If you go steel, and dive wet, my advice would be to avoid HP steels as they tend to be VERY negative in the water. I'm sure others will chime in.

What are you currently wearing for a BC?

[finGrabber]

Thanks for the info!

I have a Zeagle Ranger that is about to be traded in for a BP/W configuration...I have a DiveRite JR wing that I'm going to add to a stainless steel plate with harness...roughly 40lbs of lift and no extra bulk!

I usually dive a 5mm, no matter where I'm diving because I start getting cold after 4 days of multiple dives a day...and I think I'd add an aluminum back plate for freshwater diving

and steel tanks can be lighter than AL? I would have thought otherwise

[6Gill]

I don't think there is really a starter double set....kinda like asking what size drysuit you need.There are several factors to consider 1)your size/build-you don't want a tank so long it hits the back of your knees or a tank that only comes half way down your back.If we knew your height people could let you know their heights and what tanks they dive along with pro/cons. 2)When looking at buoyancy its also important to also look at the amount of shift from full to empty
Alot of the early divers dove twins because tanks were low pressure(1800psi) and twins was one way to increace capacity.In fact there was a set of triples around for a bit(3x30 on a single outlet manifold) anyone remember those.
All my doubles are steel ( I've never actualy dove twin AL80 so can't comment) ranging in size from 72s to 130s and use the whole range depending on things.

Eric

[captsteve]

thanks to trace and the ginnie springs clinic, i am working on that setup myself.... i really like the low pressure 72 steel tanks. at a 10percent overfill they hold 77 cubic feet. they are much less BULKY and more comfortable than the al80 and hold about the same gas at much less pressure (2250 +10percent). because you use so little air, i cant imagine you needing anything with more capacity. when i asked trace about why the market promotes aluminum tanks, he gave me several answers, but i think the biggest factor is cost. there are also the newer high pressure steel tanks...i have no experience with them and would love some feedback.
my advice would be to go rent a set of al63 and a set of steel 72 and al80s and experiment with al and steel backplates to get your weight right. the steel tanks shouldnt be as much of a problem in saltwater. ultimatly, the biggest problem with steel tanks seem to be, " what can you swim up from depth if your bc fails"
i really dont like aluminum tanks, and after trying on a set of double al80 tanks i definatly would prefer to go with steel. just remember what is right for someone else might not be right for you, and i was really lost on this subject till i started asking trace and norm questions at ginnie springs.

[PerroneFord]

i really dont like aluminum tanks, and after trying on a set of double al80 tanks i definatly would prefer to go with steel. just remember what is right for someone else might not be right for you, and i was really lost on this subject till i started asking trace and norm questions at ginnie springs.

Steve, one thing you have to remember about the Aluminum tanks, and whY I own them. At the end of a dive, if you drain the Al80s down to below 1000psi, they become flotation devices. Even if your BC has failed and you are in a rescue scenario, they WILL FLOAT YOU IN AN EMERGENCY. Empty steel tanks, especially HP steels, will send you to the bottom if you lose your wing, and are not in a drysuit.

The thought of being out in the ocean with several hundred feet of water below me, and having to tread water or drown is not all that appealing. Now in the springs, things might be different. And they are certainly different in the caves, where aluminum tanks can pin you to the ceiling. Make sure you understand the parameters as you select your gear.

That said, twin steel72s are EXCELLENT tanks and I've used them. I'd love to have a set for myself, and may just buy a set.

[captsteve]

i really dont like aluminum tanks, and after trying on a set of double al80 tanks i definatly would prefer to go with steel. just remember what is right for someone else might not be right for you, and i was really lost on this subject till i started asking trace and norm questions at ginnie springs.

Steve, one thing you have to remember about the Aluminum tanks, and whY I own them. At the end of a dive, if you drain the Al80s down to below 1000psi, they become flotation devices. Even if your BC has failed and you are in a rescue scenario, they WILL FLOAT YOU IN AN EMERGENCY. Empty steel tanks, especially HP steels, will send you to the bottom if you lose your wing, and are not in a drysuit.

The thought of being out in the ocean with several hundred feet of water below me, and having to tread water or drown is not all that appealing. Now in the springs, things might be different. And they are certainly different in the caves, where aluminum tanks can pin you to the ceiling. Make sure you understand the parameters as you select your gear.

That said, twin steel72s are EXCELLENT tanks and I've used them. I'd love to have a set for myself, and may just buy a set.

that is somthing that i have considered. the solutions would be to dive "dry",....dive with a 5 mil + wetsuit to provide surface buoyancy or go with an aluminum backplate. to be honest, it is going to take some consideration and thought to get the perfect combinations...... also, i dive almost always in salt water, and it i am amazed by how much less weight i need in fresh water. when i tried your gear perone i was also amazed by how much difference adding a second tank makes in weight and bouyancy.....

[PerroneFord]

You should need MORE weight in fresh water since you don't have all the salts suspending you. I need an extra 4-6 pounds in salt water.

Remember that when full, an AL80 tank is about 3 pounds negative in the ocean. A HP steel tank can be 8-13 pounds negative. When looking at doubles, thats 6 pounds versus 16-26 pounds. A 5mm wetsuit cannot offset the buoyancy of those steels. Low pressure steels generally are 6-9 pounds negatively buoyant. A 5mm suit MIGHT get you neutral at the surface. In neither case will the tanks actually float you. The best you can hope for is to be neutral. If you had to stay on the surface, you'd have to ditch your light, and other gear to stay afloat. The Al80s will let you keep your primary light, backup light, and other gear intact, and still float you.

Diving dry is also a solution. However a suit flood means you'd have come out of it. So assuming your drysuit flooded but your BC was still intact, you'd have to get out of your drysuit before it sent you to the bottom. Now you just have your BC, your undgarments, and your steel tanks. So make sure you get a wing that can actually FLOAT you out of the water.

[finGrabber]

So, even IF you dive dry, you should still have a wing with alot of lift?

[Walter]

You need tanks that are small enough and light enough for your body and strength. You also want tanks that will hold enough air to do the job. Sorry Darlin', but, "" I’m considering taking the plunge toward more Tech-oriented diving," is pretty much a meaningless statement. Exactly what are you hoping to do?

[normblitch]

This vaguely reminds me of the Jock Gusto autograph USD rig that had the (usually soon discarded) plastic shroud over the trips...

nhb

Alot of the early divers dove twins because tanks were low pressure(1800psi) and twins was one way to increace capacity.In fact there was a set of triples around for a bit(3x30 on a single outlet manifold) anyone remember those. Eric

"a lot" is a tad nebulous...maybe say, enough wing to ALONE provide buoyancy in case of total cato of dry suit...too MUCH wing capacity risks adding parasitic drag...

nhb

So, even IF you dive dry, you should still have a wing with alot of lift?

[Walter]

In fact there was a set of triples around for a bit(3x30 on a single outlet manifold) anyone remember those.

No, but I've dived the triple 40s.

[ncdiver43]

I dive double steel 130's HP.. Both in a drysuit and wet suit.. I like not having to wear any weight except for trim.. (salt or fresh water). A dual bladder bc might be worth looking into for redundacy if your not diving dry.. I dont like AL tanks. Reason being they become floats towards the end of a dive.. But its a two sided coin..I guess its really personal preference.

[finGrabber]

You need tanks that are small enough and light enough for your body and strength. You also want tanks that will hold enough air to do the job. Sorry Darlin', but, "" I’m considering taking the plunge toward more Tech-oriented diving," is pretty much a meaningless statement. Exactly what are you hoping to do?

Sorry about for the meaningless statement...I want to dive deeper and stay longer...do I want to exceed recreational limits - yes...do I want to be unsafe while doing so - no

I am 5'7" and have a fair amount of body strength, and I am currently working on a training program that will increase my upper body strength

I do want to see "what's out there" and I know there's lots to see below 130'...I'm interested in cave diving, wrecks, or diving to 180'...the fun thing about diving is we don't know exactly what's out there at any given depth

[Walter]

I'm pretty sure you can handle moderately heavy tanks, do you know your RMT?