What size doubles?

[cool_hardware52]

I gave the drysuit answer, yes. And with a drysuit, he would be able to keep his suit neutral at all depths, of course.

With double steel tanks he should not be diving in a wetsuit. That is probably a different thread. Or else someone can take up that gauntlet here.

Thanks, Tobin. Good point.

Are you suggesting that the initial buoyancy of the diver's drysuit will not impact the required wing size?


Tobin

 

[Mr. Bubble]

I think I have opened up Pandora's box......:11doh: This is much more complicated than my DPV scooter specialty coarse Maybe they need a coarse just for doubles.

Please continue......



Mr.B

 

[cool_hardware52]

I think I have opened up Pandora's box......:11doh: This is much more complicated than my DPV scooter specialty coarse Maybe they need a coarse just for doubles.

Please continue......



Mr.B

I'll run an example for you of how I would size a wing for doubles.

First a few assumptions:

1. Your Drysuit cannot loose more buoyancy than it starts with. Put on your undies and suit and stand up in neck deep water. Vent all the gas you can from your suit, Now add lead until you sink when you pick up your feet. The amount of lead represents the buoyancy of your suit when with minimum gas in it. For this example lets say it takes 25 lbs of lead to get neutral in your suit at the surface. While it is very unlikely, it is possible that a total failure of your suit, i.e. ripped neck seal, torn suit etc. a suit that cannot trap gas can loose all of it's initial buoyancy, but no more.

2. You may need to use all of your back gas. This means you could be lighter at the end of the dive by 100% of your gas.

3. If you have an extended stay at a shallow stop you will want to inflate your suit a bit, for warmth. That makes your suit a bit more buoyant than what was determined in #1, say 3 lbs of extra inflation gas.

Lets say you are using 130's

Your gas will weigh ~21 lbs, that means you need to be negative at the start of the by 21 (gas) + 3 (extra inflation for suit) or 24 lbs. To stay at the surface you need to use 24 lbs of your wings capacity.

Now what happens if your suit fails? You could need another 25 lbs of wing capacity.

24 + 25 = 49 lbs.

What might your rig require to float it at the surface?

Plate and harness 6 lbs. Regs 5 lbs., Manifold and bands 5 lbs. Can light 2. Full 130's -22 lbs. Total - 40 lbs with full tanks, around -20 with empty tanks. You will also need about 4 lbs of ballast i.e. in a belt.

Remember this is just an example. What if your suit is only +18 lbs and you are using LP85's?

Tobin

 

[DeepSeaExplorer]

You can't go wrong with AL 80s as your first set of doubles. They're cheap and well suited for all types of diving, especially in the beginning. Later, if you want to get into big dives or cave diving, you'll want to get a big set of steels. Either way, you'll eventually want several sets anyway. But, what you don't want, is to have to use big set of steel tanks for a smallish dives because that's all you have.

 

[fweber]

You can't go wrong with AL 80s as your first set of doubles. They're cheap and well suited for all types of diving, especially in the beginning. Later, if you want to get into big dives or cave diving, you'll want to get a big set of steels. Either way, you'll eventually want several sets anyway. But, what you don't want, is to have to use big set of steel tanks for a smallish dives because that's all you have.

Why would you say that al80's would make a better first set, than say steel lp85's?Pressuming that if you are diving doubles you are considering going into deco and wouldn't want to be dumping weight and finding yourself to be a cork. The 85's will lead to a lighter overall rig, with equal or better gas volume.

 

[DeepSeaExplorer]

Most tech divers in my area wear Al80s, they work for probably 80% of non-cave tech dives. There's absolutely nothing wrong with the buoyancy of 80s. It's just different and easily compensated for. I have four sets of doubles: 2 are AL 80s, and 2 are steels. I have a lot more dives on the 80s than any of the others. Why spend 3 times as much for steels if you don't have to. Then, there's also the issue of steels in the ocean without a drysuit. But, I won't go there...

 

[cool_hardware52]

Why would you say that al80's would make a better first set, than say steel lp85's?Pressuming that if you are diving doubles you are considering going into deco and wouldn't want to be dumping weight and finding yourself to be a cork. The 85's will lead to a lighter overall rig, with equal or better gas volume.

I prefer to dive my LP 85's vs AL80's. A pair of 80's + the required ballast makes for a heavier rig out of the water.

OTOH, a pair of AL80's can often be had fairly inexpensively, and if you get Luxfers you have stage bottles in waiting if you progress to that point.

Tobin

 

[fweber]

I prefer to dive my LP 85's vs AL80's. A pair of 80's + the required ballast makes for a heavier rig out of the water.

OTOH, a pair of AL80's can often be had fairly inexpensively, and if you get Luxfers you have stage bottles in waiting if you progress to that point.

Tobin

Tobin, I agree. While I don't have any lp85's I do have several sets of old 72's which have fairly similar characteristics. I was questioning DeepSeaX's whole hearted endorsement of the al80's as a first set. I've had a couple sets of just those, and the only two positives that I think they really have is the low cost and their adaptability to stages.

With the cost of everything else that is involved in a transition to doubles and presumably deco or tech diving, the lower initial cost of the al80's may or may not represent a meaningful savings in the long run.

 

[nereas]

I'll run an example for you of how I would size a wing for doubles.

First a few assumptions:

1. Your Drysuit cannot loose more buoyancy than it starts with. Put on your undies and suit and stand up in neck deep water. Vent all the gas you can from your suit, Now add lead until you sink when you pick up your feet. The amount of lead represents the buoyancy of your suit when with minimum gas in it. For this example lets say it takes 25 lbs of lead to get neutral in your suit at the surface. While it is very unlikely, it is possible that a total failure of your suit, i.e. ripped neck seal, torn suit etc. a suit that cannot trap gas can loose all of it's initial buoyancy, but no more.

2. You may need to use all of your back gas. This means you could be lighter at the end of the dive by 100% of your gas.

3. If you have an extended stay at a shallow stop you will want to inflate your suit a bit, for warmth. That makes your suit a bit more buoyant than what was determined in #1, say 3 lbs of extra inflation gas.

Lets say you are using 130's

Your gas will weigh ~21 lbs, that means you need to be negative at the start of the by 21 (gas) + 3 (extra inflation for suit) or 24 lbs. To stay at the surface you need to use 24 lbs of your wings capacity.

Now what happens if your suit fails? You could need another 25 lbs of wing capacity.

24 + 25 = 49 lbs.

What might your rig require to float it at the surface?

Plate and harness 6 lbs. Regs 5 lbs., Manifold and bands 5 lbs. Can light 2. Full 130's -22 lbs. Total - 40 lbs with full tanks, around -20 with empty tanks. You will also need about 4 lbs of ballast i.e. in a belt.

Remember this is just an example. What if your suit is only +18 lbs and you are using LP85's?

Tobin

When I do the math for my twin 130s, I get 40 lbs also. So I have opted for a 50 lbs Oxycheq doubles wing. These run about $350 each. A good price.

If you get a 50 lbs doubles wing, it will serve you for any sized doubles, not just for your smaller initial steel 85s or alum 80s.

Tobin himself offers the best backplates, if you don't already have one. He can even rig it for you Hogarthian, with 4 D rings and a metal buckle. His backplates are variable sized (small, med, and large) and variable weighted, however for twin tanks you would likely only need the traditional 6 lb backplate. You can adjust the straps yourself to be tight or loose, when you get it.

 

[Mr. Bubble]

"Then, there's also the issue of steels in the ocean without a drysuit. But, I won't go there.."

Please expand. I am using single steel 120's with a wet suit now.

Heres the deal. I want to get full cave certified, but I don't want to go down there and take my certification using doubles for the first time. I also want to get advanced nitrox and advanced wreck training. I would like to have a dry suit, but I would also rather go on a few dive trips this year too, so a wet suit 5/7 is all I can muster for exposure suits for the forseeable near future. I wish I could buy all the gear AND go an all the trips, but I have to do half and half for a while.

Thanks for all the great info...lots of good points....lots of things to think about....and yes, my dive instructor recommended the multiple route as well.....so there goes another dive trip I could have taken.

I am real surprised to learn that there is not a magic set, or something that works for the majority. Like, I am x ft tall and wear a wet suit and want to do this...so get that,

or I am x feet tall and wear a dry suit and want to do this, so get that...it just seems odd that I have to try out everyone in the store to get what I need. Then theres the Wing it's self. Would'nt different twins perform differently using different wings? IMO, yes they would. So, now I have to try out 4-5 sets of doubles with 4-5 sets of wings...oh yeah, and don't forget your exposure suit, wet and dry.......Ughh....

Well, maybe this time next year I will have it figured out.