Contemplating doubles...AL vs. Steel

[HilaryRN71]

Hello SB'ers...

I'm thinking about a switch to doubles and am having a hard time deciding what I want.

I mostly dive CA (drysuit) and once I switched to steel and enjoyed the bouyancy improvement, I didn't think I'd go back to AL. However, I do notice back fatigue (ok sometimes PAIN) with my current tank (faber e-series 100cf). I'm very concerned about handling the additional weight. (I would double up 8o's) I think....hope...some of the back pain will be improved when I switch from my BC to the backplate/wing, but am not sure...

I've researched the AL80's that are neutrally bouyant, and have thought this seems like it might have potential.(I'm 5'8'' so height doesnt' bother me too much) Yes, I realize I'll have to add a little weight around my belt, but with the DUI weight harness, I don't mind a bit extra weight so much. V-weights would be an option also. Soooo....any thoughts? Would love any possible feedback. Thanks.

 

[DA Aquamaster]

E7-100's are virtually the same weight as AL 80's with the added benefit of needing a few less pounds of lead due to improved bouyancy.

I think you would be moving in the wrong direction and making things worse in terms of total weight you would need to move up and down the ladder if you went with AL 80 doubles as opposed to E7-100 doubles. They are a tough tank to beat.

I checked the numbers and an E7-100 weighs 32 lbs, is 8.8 lbs negatively bouyant when full and -1.3 lbs negatively bouyant when empty.

In comparision a S80N weighs 35.2 lbs, is -5.8 lbs when full and is neutral when empty. And an S80 weighs 31.7 lbs, is -1.9 lbs negative when full and 4 lbs positive when empty.

So... the using neutral 80 doubles rather than E7-100 doubles would require you to carry 6.4 more pounds of tank weight plus 2.6 pounds more lead on your belt for a total increase in dry weight of 9.0 lbs.

Switching to a regular 80 would save .6 lbs in tank weight but would require 10.6 lbs more lead on your weight belt for a total gain of 10 lbs in weight compared to E7-100's.

The only option I can think of that would reduce your total weight would be going with Faber steel 72's. They weigh 29 lbs each, are 11.3 lbs negative when full and are 5.9 lbs negative when full. They would save you 6 lbs in tank weight, and would require 9.2 lbs less lead for a total weight savings of 15.2 lbs compared to double E7-100's. But you would be giving up 57 cu ft of gas capacity compared to E7-100's.

You would gain 42 cu ft of gas capacity compared to a single E7-100 and would be carrying about 15.5 more pounds more total weight than a single E7-100 to acheive it.

So it's an issue of whether you want to enjoy only a 15 lb weight increase from a single E7-100 to double Faber 72's or whether it's worth enduring a 30 pound increase for the extra gas offerred by double E7-100's.

My wife went the Faber 72 route and it works for her, especially with the weight requirements for a dry suit. But it does put some tighter limits on her gas planning even with a low SAC rate. So whether it works for you depends on whether the available gas is going to be adequate.

 

[Don Burke]

Hello SB'ers...

I'm thinking about a switch to doubles and am having a hard time deciding what I want.

I mostly dive CA (drysuit) and once I switched to steel and enjoyed the bouyancy improvement, I didn't think I'd go back to AL. However, I do notice back fatigue (ok sometimes PAIN) with my current tank (faber e-series 100cf). I'm very concerned about handling the additional weight. (I would double up 8o's) I think....hope...some of the back pain will be improved when I switch from my BC to the backplate/wing, but am not sure...

I've researched the AL80's that are neutrally bouyant, and have thought this seems like it might have potential.(I'm 5'8'' so height doesnt' bother me too much) Yes, I realize I'll have to add a little weight around my belt, but with the DUI weight harness, I don't mind a bit extra weight so much. V-weights would be an option also. Soooo....any thoughts? Would love any possible feedback. Thanks.

It sounds like you are a good candidate for double 72s. Mine require 12 pounds less lead than my AL80s, plus they are lighter in air. That makes me about 20 pounds lighter on the boat.

The neutral AL80s are neutral because they are heavier. That is not the direction you are looking to go. The standard AL80s would be easier on your back and knees. 72s would be better still.

 

[DA Aquamaster]

Steel 71.2's (the old "standard" 2250/2475psi steel 72) are about 2 pounds lighter than the Faber 72's but and are about 4 pounds more negatively bouyant than an AL80. So on a set of doubles you save 3-4 lbs of tank weight and can dive with about 8 pounds less lead for a total savings of 10 pounds dry weight compared to double AL 80's and the loss in gas is not all that great compared to the 77 cu ft in an AL 80. When I travel, I rent AL 80's (paired as independent doubles) and have to add 8 pounds of lead - I notice the 10 pound increase in total weight, but it's not excessive.

However, they do not compare nearly as well to an E7-100. A steel 72 is about 5 pounds lighter than an E7-100, but you need to carry about 1.5 pounds more weight, so for a set of doubles, the weight savings is only about 7 pounds. Also, steel 72's only hold 71.2 cu ft when they are filled to 2475 psi - a 10% overfill. At their normal 2250 psi service rating, they only hold 65 cu ft. So a set of double 72's at 2250 psi is only 130 cu ft of gas. The extra 70 cu ft of gas offerred by double E7-100's is worth the extra 7 pounds of weight empty (although the difference is closer to 11 pounds with the tanks full).

One problem with "standard" steel 71.2's is that they are not all that standard. They can vary a couple pounds in weight and bouyancy traits depending on who made them and they also very up to an inch in lenght. Their neck and shoulder profiles are often different as well. The height differences can cause problems when pairing them with a manifold and the shoulder differences can create some limitations in band placement.

Personally, I dive double steel 72's, but that's mostly because I already own 20 of them and since I dive independent doubles, the height differences are not an issue. And with 20 of them, I could probably pair most of them off successfully, but expecting to buy 2 to 4 steel 72's and pair them all off successfully may not be realistic unless you are buying tanks made by the same manufacturer, so the codes on the shoulder become important.

 

[HilaryRN71]

Well this is exactly the input I was looking for..so I appreciate it. Why do they FEEL so much heavier??? lol I'm just a wuss girl. But it makes sense...if the doubled steel 100's are only 11 lb. heavier than the 72's, it makes sense. Will the weight feel better (in y'alls opinion) when I get a backplate and it's secured properly and distributed well?

 

[KOMPRESSOR]

Will the weight feel better (in y'alls opinion) when I get a backplate and it's secured properly and distributed well?

I'd vote for YES here. I've recently switched from a very heavy single 12L liter HP (4400psi) tank to "LP" (3450psi) steel doubles (12 liter x 2). So far I feel "lighter" in the water, but it is of course heavier on shore. However, it's not "that bad" because my web/BP keeps it very stable. More important, if you're changing from a regular BCD to BP, you're going to have a revolution when it comes to stability. But since you're also switching to doubles it's going to take some time to adjust. I wish you good luck with it!

PS! If you're just looking for the most comfortable rig for recreational diving, listen to the advice on small doubles. I dove for a week with a small set of doubles rigged on my old Eclipse 40. Darn, I'm still having wet dreams about it! What a feeling!!!

 

[strazz]

Have you considered using E7-80s? I haven't used doubles, but I do have one of them and I like it much more than my AL80. One nice thing about them is that they're about $200 each, compared to ~$350 each for E7-100s.

 

[spectrum]

Have you considered using E7-80s? I haven't used doubles, but I do have one of them and I like it much more than my AL80. One nice thing about them is that they're about $200 each, compared to ~$350 each for E7-100s.

I have E7-80s we dive as singles and I've seen this come up before. Some of those that have tried it found the rig to be very dense and hard to trim out since the cylinders are only 20 inches long. For the right diver though it is an appealing rig,

Pete

 

[Hoosier]

Have you considered using E7-80s? I haven't used doubles, but I do have one of them and I like it much more than my AL80. One nice thing about them is that they're about $200 each, compared to ~$350 each for E7-100s.

It sounds like she/he doesn't care about the financial part... I bet most divers who are using AL80s is because of the budget, not others.

I'd vote for YES here. I've recently switched from a very heavy single 12L liter HP (4400psi) tank to "LP" (3450psi) steel doubles (12 liter x 2).

So, in your world, 3450pst is LP, not HP LOL~~~

 

[HilaryRN71]

Thanks again...I HAVE considered the E 80's, and when I firsted started thinking about doubles, that was what my initial thought was. That seems to be the double's configuration that alot of girls use with success. They are alot easier to find than the 100's, at least they were when I was shopping around for my 100cf last year. It seemed like every shop that I called had the 80's but took many calls til I found the 100. It's not so much about cost...I'm in this sport for the long haul.. Gave up worrying about price awhile back. I just want what I'm going to be the happiest with. And without a set to "try out" I'm just trying to think thru every aspect...