A weighty question...

[scubakat]

So I've decided to take the plunge & purchase my own LP Steel tanks. I wanted to buy the PST LP80's, but according to my LDS, they have been discontinued.

Now I am entertaining the idea of the LP95's, but I am wondering how that will affect my weighting. My goals are to get weight off of my belt & minimize the total weight I carry on land.

Currently with a PST LP80 I wear 28 pounds of lead. The 80 weighs 34 pounds and is in the water is -7# when full, -1# empty. 62# dry.

The PST LP95 weighs 44 pounds and in the water is -10.4# full & -3.3# empty. Take off 3# for a 25# belt. 69# dry.

From my (admitedly sketchy) calculations I think I could take 3# off of the belt for an overall gain of 7# on dry land.

Do I have this correct? I seem to defeat my purpose here. Any other ideas? (No aluminum please .

-kate

 

[BetterLateThannever]

I will be buying my first tank soon and plan to by a TK-80 aluminum. Why do you say "no aluminum please"

Jimbo

 

[greg somers]

I would have thought the weight factor of having to carry it would be a real issue.The out of water weight would be a killer getting into and out of the water...especially in the cold stuff you dive in.I don't know where people get a bad thought about AL.In my neck of the woods 1 in 10000 tanks would be a steel and only because it's old or a very large one.That's my thought...
Cheers
Gasman

 

[Warhammer]

Thomas could better answer your question because he works for Pressed Steel. But he recently, as in 2 weeks ago, sent me an updated copy of the specs for all Pressed Steel tanks and the LP80 is on that list. So I think it's still available.

If reducing your weight belt and overall weight is your main concern, then why not get HP tanks instead of LPs? You'll loose a good bit more weight that way and could even gain air as a bonus. For example, using the amount of weight you said you use now with a PST LP80 to go on.

PST LP80

• E Weight============34.4Lbs
• F Weight============40.8Lbs
• E Bouyancy==========-1.0Lbs
• F Bouyancy==========-7.0Lbs
• Belt Wt=============28Lbs
• Total Kit Full===68.8
• Total Kit Empt===62.4

What you're using now. BTW, that's alot of weight on your belt. Are you sure that isn't for an Aluminum 80 vs LP80?

PST LP95

• E Weight============43.8Lbs
• F Weight============51.5Lbs
• E Bouyancy==========-3.3Lbs
• F Bouyancy==========-10.4Lbs
• Belt Wt=============26Lbs
• Total Kit Full===77.5
• Total Kit Empt===69.8

That's 8 1/2Lbs heavier overall when full, but you'd loose 2Lbs off your belt and gain 16cft of air since the LP95 holds 96.6cft @ 2640 vs the LP80's 80.6cft. You'd also have the potential of further air gain if you overfilled the tank.

PST HP80

• E Weight============28.6Lbs
• F Weight============35.2Lbs
• E Bouyancy==========-3.3Lbs
• F Bouyancy==========-9.3Lbs
• Belt Wt=============26Lbs
• Total Kit Full===61.2
• Total Kit Empt===54.6

You'd loose 7.6 off weight overall and 2Lbs off your belt. But if you couldn't get a complete fill, you'd only have roughly 70cft of air @ 3000PSI. This would be my first choice if I was mainly concerned with loosing weight.

PST HP100

• E Weight============34.1Lbs
• F Weight============42.3Lbs
• E Bouyancy==========-1.3Lbs
• F Bouyancy==========-8.8Lbs
• Belt Wt=============28Lbs
• Total Kit Full===70.3
• Total Kit Empt===62.1

You'd gain 1.5Lbs of weight and your belt would be the same. But you'd gain 21cft of air with a full fill. And even if you could only fill the tank to 3000PSI, you'd still have roughly 87cft of air. So with this tank you'd have virtually the same weight but more air.

 

[BetterLateThannever]

Let me rephrase that......Huh?

Jimbo :bonk:

 

[Mverick]

Aluminum 3000psi
80 cf Catalina 32 lbs +4lb bouyant when MT
80 cf Luxfer 32 lbs +4lb bouyant when MT
36lbs total weight. Have to add the 4lb bouyant in lead to your belt to keep you down.

HP steel 3500psi
PST 80cf 28lbs -3lb bouyant when MT
25lbs total weight. Get to take 3 lbs off your belt.

LP steel 2640psi
PST 80cf 34.4lbs -1 when MT
33.4lbs total weight.

Steels tend to last forever if you take care of them. I don't know about the aluminums.
HP steel at 25lbs over Aluminums at 36lbs ought to give you the hint at why you go to steels. If you do buy Aluminum get Luxfers. They are weighted better throughout the tank. Problem with HP tanks is getting a fill to 3500psi can sometimes be a pain. Although I've never had a problem with mine. I own all 3 HP, LP, and Aluminum.
If you dive a drysuit use steels if you dive a wet suit use aluminums. Drysuit give's you redundancy on lift. You can deal with the problem of steels not going positively bouyant at the end of the dive with redundant aircells. ie drysuit and BC, one pops you've still got the other. There is nothing wrong with aluminums. Steels are better in some instances.

 

[greg somers]

Made in Australia and they are definately lighter than any steel tank.I guess the standards are different in your guys neck of the woods.
Cheers ears,
The Gasman

 

[Mverick]

Who makes them?
Luxfer HP AL are 3300psi,228Bar, here and weigh 35lbs,16Kg, MT. Neutraly bouyant also. HP steel 80cf is only 25lbs with the bouyancy included. Or 28 pounds negating bouyancy. Which makes the HP steel a lot lighter than the HP Aluminum.

Aluminum is a more bouyant material than Steel.
Another is made by the Parkway Group T80HPY/DV 80cf 3500psi 36lbs and 2 lbs bouyant. Making it 38lbs. Still not close to a HP steel.

What kind of pressure are you putting in your HP tank?

3500HP Steel 80 is 19.75in tall and 7.25in Diam. 25lbs
3300HP Aluminum 80 is 25.85 tall and 7.25in Diam. 35lbs
3500HP Aluminum 80 is 21in tall and 8in Diam. 38lbs
weights are with Bouyancy included.

Have you ever weighed a Steel and your HP Aluminum. I bet you'd be suprised at the outcome.

My LP 112 are 41lbs each and 26in long 8in Diam. Hold 2640. At 3300psi which I usually fill them to they hold around 140cf. Don't Over pressurize HP Steels, dangerous. And Never overpressurize an Aluminum but the LP steels take it day in day out and still pass Hydro.
Until I see some numbers and manufacturers I'm not believing a Aluminum is lighter than a steel at the same cf.

 

[scubakat]

Originally posted by Warhammer
Thomas could better answer your question because he works for Pressed Steel. But he recently, as in 2 weeks ago, sent me an updated copy of the specs for all Pressed Steel tanks and the LP80 is on that list. So I think it's still available.

Yes, I received the same data from him & was puzzled when the LDS told me they were discontinued.

Originally posted by Warhammer

If reducing your weight belt and overall weight is your main concern, then why not get HP tanks instead of LPs? You'll loose a good bit more weight that way and could even gain air as a bonus.

My other concern is for consistently getting a fill to standard operating pressure. Local boats and sometimes shops have trouble getting even AL80's up to 3000 psi, let alone the 3500 for an HP.

Originally posted by Warhammer

What you're using now. BTW, that's alot of weight on your belt. Are you sure that isn't for an Aluminum 80 vs LP80?

Man... Ok, so I went back to my log book, & the last dive that I did with the LP80 & a 7mm 2pc wetsuit I wore a whopping 36 pounds. I'm wearing at least 40 with the Catalina AL80 that I've been using for the last few weeks.

So Greg... if the AL80, empty, weighs 32# + 40# belt then the dry weight of the rig is 72#. That's why I said no aluminum please .

-kate

 

[Mverick]

I hate to ask but here goes. Are you sure your not overweighted on your weight belt?
With my drysuit and an Aluminum 80 I wear 30lbs. With a HP 100 steel. I wear 24lbs. And I'm overweighted on both. I like a little extra though. 40lbs on a weight belt is alot.

At the end of your dive when your on the surface you should be neutral. Not sink. With nothing in your BC. A little air in the BC to help keep your head above water if fine but that's after this test. But with nothing in the BC you should still float a little. With the tank at 500psi or so.

You're probably right just kinda suprised. That's alot of weight.