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View Full Version : Are AL80 doubles worth it?



vicp
12-12-2009, 11:34
I have a thread in this forum about sizes for LP steel doubles as I am going to put together a set for cave cert.

I also have two AL80 that I do not use very much as I prefer the extra gas and more negative bouyancy charactiestics of my steel LP 108s. Does anyone out there use AL80s for doubles through choice, why and what diving do you do?

It would seem that unfavorable bouyancy characteristics of the AL80s (failrly positive when low/empty) would just be, lets say, doubled.

Thanks

ianr33
12-12-2009, 15:49
Al doubles work great for OW dives down to around 200 feet. Also very nice for climbing ladders back onto boats.I use a modified V weight that sits very low to stop the tails of the tanks getting floaty .

They dont have enough gas for any significant cave dive. At intro level your penetration would be restricted to 1/6 of doubles Thats only around 26 cu feet. Works out to 10 minutes at 100 feet with a SAC of 0.6.

Al doubles hold a little under 160 cu ft at 3000 psi. Well filled steel 104's/108's/130's will hold around 270 cu ft. Thats a big difference.

EDIT: While steel doubles are pretty much standard in Florida caves in Mexico the norm is Al 80's (caves are much shallower there)

fire diver
12-12-2009, 17:25
I use double 80's because I had a lot of single 80s an I wanted to get into doubles diving. I also didn't have the cash to drop on a full set of steels, and the used ones I wanted are very hard to find in my area.

You always have to option of breaking them back down for stage bottles, and using the manifold and bands for a set of steels.

ReefHound
12-12-2009, 18:31
AL80's are a heckuva lot lighter than double steels which may make it easier to transition and get used to the extra weight. They are also an economical way to transition into doubles since you already have the tanks, and as mentioned you can always use them for stages later.

If you go dive the Yucatan you'll mostly find double AL80's for rentals.

comet24
12-13-2009, 22:25
I have a set of Al80's because I had some Al80's laying around. I would go out and buy Al80's to make a set but if you have a few extra's laying around go ahead. Look around a little and you can usual find a set of inexpensive bands and manifold.

skdvr
12-14-2009, 06:27
I have only dove double al80's once and 2 thigns I noticed was

1) How much nicer it was humping them from the parking lot to the water vs my HP1020's.
2) How much extra lead I had to wear.

Now if I owned a set I would do like ianr33 mentioned and have a V-Weight made. I would have had no problem starting off with them and then using the bottles as stages later down the road when I could get the steels that I wanted. BUT, like has also been mentioned they are not the best for deep, drysuit wearing cave dives. Can be a very nice set for OW deeper dives...

Phil

chicken
12-14-2009, 18:53
I just completed my cavern/intro to cave certification with a set of neutrally buoyant AL80 doubles. I used a stainless steel backplate and did not carry one ounce of lead into the water. I bought the set for $200 including manifold and bands hoping it would get me through the training so I could decide if cave diving was for me.

They handled well, my only regret was being able to dive 1/6 of the available air supply...now shopping for bigger tank! If you need weight they make a nice pouch that mounts to the bolts on the tanks.

I also found most fill stations in North Florida are "generous" with the fills so I had a little extra for the dives.

ianr33
12-14-2009, 19:59
They handled well, my only regret was being able to dive 1/6 of the available air supply...now shopping for bigger tank!

Get a single cave filled 104 and you are "allowed" to penetrate almost twice as far as you were with your doubles.

Thats never made any sense to me either!

ReefHound
12-14-2009, 20:41
You don't want to penetrate at all with a single air supply.

You must ensure you do not get further in than you can get out so you must prepare for the case that you must isolate your cylinders and lose half your gas supply and therefore are left with one tank. One third of one tank is one sixth of two tanks.

ianr33
12-15-2009, 11:40
You don't want to penetrate at all with a single air supply.


Huh? May have changed recently but if not Intro divers ARE NOT ALLOWED to dive doubles at Ginnie Springs unless they have a waiver allowing them to do so.

The thinking is that with double tanks new cave divers will rush lemming like to the furthest reaches of a new system.

Personally I consider diving caves on a single (even with an H/Y valve) to be dumb,but it is totally allowed by Intro standards.

ReefHound
12-15-2009, 13:15
I wasn't speaking as to what is "allowed" but giving my opinion on penetrating an overhead environment without redundancy.

If the newly trained cave diver has that mindset then their training didn't take very well, did it?

ianr33
12-15-2009, 18:52
I wasn't speaking as to what is "allowed" but giving my opinion on penetrating an overhead environment without redundancy.

If the newly trained cave diver has that mindset then their training didn't take very well, did it?

I think we can say we agree we disagree with some agencies :smiley20:

<<THE NACD PHILOSOPHY: Quality Training, Safe Techniques, and Respect for the sub aquatic cave environment. ..........

The Introduction to Cave Diving course is taught in a minimum of two days and includes and a minimum of four single tank cave dives. >>

From NACD Training (http://www.safecavediving.com/training.shtml)

chicken
12-15-2009, 19:14
I went to Ginnie with my instructor and there was nothing in the waivers or other paperwork not allowing doubles. We were limited to 1/6 of our air supply with doubles and 1/3 with singles.

I did have the option of diving my AL100 with H valve but chose the doubles because of the redundancy. My certification agency was NSS-CDS for the intro and PSAI for Cavern.

ianr33
12-15-2009, 19:39
I went to Ginnie with my instructor and there was nothing in the waivers or other paperwork not allowing doubles.

As I said,maybe it has changed but a couple of years ago it was an issue
NO DOUBLES IN GINNIE FOR INTRO CAVERS - Cave Diver's Forum - Cave Diving Resource (http://www.cavediver.net/forum/showthread.php?t=3464&highlight=ginnie+doubles)

ssmdive
12-16-2009, 08:44
NACD has an "Intro w/Doubles" to get around the Ginnie rule. I am not NACD, but I just head about it. It expires in one year and you have to go back to single tank is what I have been told.

You can find doubles gear pretty cheap. On another board they have a set of LP 95's in VIP for 500.

faber lp95's - Cave Diver's Forum - Cave Diving Resource (http://www.cavediver.net/forum/showthread.php?t=11614)

Those are pretty good tanks and they will give you A LOT more air than AL80's

AL 80's 5.1 cubic feet per 100 psi. Normal AL 80 fills are 3k = 153
LP 95's 7.2 cubic feet per 100 psi. Cave fills are 3.6k = 259
But even at 3k the LP 95's are 216.

UCFKnightDiver
12-16-2009, 14:55
I went to Ginnie with my instructor and there was nothing in the waivers or other paperwork not allowing doubles. We were limited to 1/6 of our air supply with doubles and 1/3 with singles.

I did have the option of diving my AL100 with H valve but chose the doubles because of the redundancy. My certification agency was NSS-CDS for the intro and PSAI for Cavern.

It says something to the effect of dive within your certification, with the regular Intro card the instructor has the option to teach in doubles but the class was originally meant to be taken in singles, thus Ginnie enforces it. (why the NACD came out with the Intro to Cave with Doubles card) I believe the nsscds card says doubles if I remember correctly (not absolutely sure)

chicken
12-16-2009, 16:33
This is directly from the NSS-CDS website...

Cavern Diver2430 m/100 ft 60 m/200 ft Daylight Zone; No Restrictions

Basic/Intro Cave Diver2430 m/100 ft 1/6rd of Doubles No Decompression

ApprenticeCave Diver2440 m/130 ft 1/3rd of DoublesLimited Deco; No Circuits or Traverses

Cave Diver2440 m/130 ft 1/3rd of Doubles No Staging or Scootering

It didn't cut and paste so good, here is the link NSS-CDS Training Programs | Underwater Speleology (http://www.nsscds.org/test/drupal/trainingprograms)

ianr33
12-16-2009, 19:00
I like the " 1/6 rd " of doubles . Methinks it has been partially (and badly!) changed recently :smiley36:

Just to play Devils Advocate:
1)How many divers doing stage dives have ever done a course for that?
2)What course do you need to do to dive caves deeper than 130 feet?

IMHO at some point experience needs to take over from courses.

navyhmc
12-16-2009, 19:25
I like the " 1/6 rd " of doubles . Methinks it has been partially (and badly!) changed recently :smiley36:

Just to play Devils Advocate:
1)How many divers doing stage dives have ever done a course for that?
2)What course do you need to do to dive caves deeper than 130 feet?

IMHO at some point experience needs to take over from courses.

Not NNS-CDS by any means, but:

1: Not that many. I would guess less than 5,000 worldwide.

2: I would hazard a Deep Tech or Deco equivelent.

chicken
12-18-2009, 06:36
There are a couple of courses beyond full cave. They have technical cave diver and stage diver. Not sure if those are "C" cards. I like the fact they asked me what I used and what I wanted to train in. I dive doubles and training in doubles makes sense.

The best part of the entire weekend was Nitrox fills. I filled my tanks seven times over three days. The shop charged me one price for all of the 32 percent Nitrox I could breathe...$25. They had a trailer with a bank of gas and fills were done on the spot after the dive...sweet.