LP95 or even LP108 for Sidemount Diving?

[northernone]

I agree, however you're tall, I'm tall, I don't consider 5'10" tall enough for 121's, no offense @Caissy

 

[Caissy]

@northernone Thanks A LOT for your offer!!! Please PM me when you plan to be in Ottawa. If we can't go dive, we can certainly go for a beer...

Also, just to help the discussion, here are Faber's Low pressure cylinders characteristics from this web site: https://www.techdivinglimited.com/category-s/227.htm

In Sea Water with Valve: Faber LP-85
Service Pressure: 2400+10% (2640) PSI
Buoyancy *Full: -3.80 lbs
Buoyancy *Empty: +2.32 lbs
Buoyancy difference: 6.12 lbs
Weight Empty: 31.2 lbs
Outside Diameter: 7.0"
Length: 25.98"

In Sea Water with Valve: Faber LP-95
Service Pressure: 2400+10% (2640) PSI
Buoyancy *Full: -5.37 lbs
Buoyancy *Empty: +1.69 lbs
Buoyancy difference: 7.06 lbs
Weight Empty: 37.2 lbs
Outside Diameter: 8.0"
Length: 23.8"

In Sea Water with Valve: Faber LP-108
Service Pressure: 2400+10% (2640) PSI
Buoyancy *Full: -5.02 lbs
Buoyancy *Empty: +2.98 lbs
Buoyancy difference: 8.00 lbs
Weight Empty: 41 lbs
Outside Diameter: 8.0"
Length: 26.8"

In Sea Water with Valve: Faber LP-120
Service Pressure: 2400+10% (2640) PSI
Buoyancy *Full: -4.87 lbs
Buoyancy *Empty: +4.07 lbs
Buoyancy difference: 8.94 lbs
Weight Empty: 44.9 lbs
Outside Diameter: 8.0"
Length: 29.33"

In Sea Water with Valve: Worthington LP-108
Service Pressure: 2400+10% (2640) PSI
Buoyancy *Full: -10.70 lbs
Buoyancy *Empty: -2.60 lbs
Buoyancy difference: 8.10 lbs
Weight Empty: 45.95 lbs
Outside Diameter: 8.0"
Length: 26.5"


*** I have updated the buoyancy characteristics of each cylinder as I made a mistake with the -/+ signs... Thanks for pointing it out...! ***

 

[Caissy]

I agree, however you're tall, I'm tall, I don't consider 5'10" tall enough for 121's, no offense @Caissy

No problem @tbone1004

@bamafan How tall are you?

 

[northernone]

@northernone Thanks A LOT for your offer!!! Please PM me when you plan to be in Ottawa. If we can't go dive, we can certainly go for a beer...

Also, just to help the discussion, here are Faber's Low pressure cylinders characteristics from this web site: https://www.techdivinglimited.com/category-s/227.htm

In Sea Water with Valve: LP-85
Service Pressure: 2400+10% (2640) PSI
Buoyancy *Full: 3.80 lbs
Buoyancy * Empty: 2.32 lbs
Weight Empty: 31.2 lbs
Outside Diameter: 7.0"
Length: 25.98"

In Sea Water with Valve: LP-95
Service Pressure: 2400+10% (2640) PSI
Buoyancy *Full: 5.37 lbs
Buoyancy * Empty: 1.69 lbs
Weight Empty: 37.2 lbs
Outside Diameter: 8.0"
Length: 23.8"

In Sea Water with Valve: LP-108
Service Pressure: 2400+10% (2640) PSI
Buoyancy *Full: 5.02 lbs
Buoyancy * Empty: 2.98 lbs
Weight Empty: 41 lbs
Outside Diameter: 8.0"
Length: 26.8"

In Sea Water with Valve: LP-120
Service Pressure: 2400+10% (2640) PSI
Buoyancy *Full: 4.87 lbs
Buoyancy * Empty: 4.07 lbs
Weight Empty: 44.9 lbs
Outside Diameter: 8.0"
Length: 29.33"

From these numbers, we can see:
- The in sea water weight difference between the lightest LP85 and the heaviest LP95 full tank is only about 1.5 lbs
- The difference in buoyancy between full and empty is 3.5 lbs for the LP95 and only 0.8 lbs for the LP120
- Only the LP85 is 7" in diameter, the other 3 are all 8" tanks
- Length difference between the shortest (LP95) and the longest (LP120) is 5.5".

But for me, if I compare them all with the LP85 that I'm used to dive with, I can see (round numbers):
- LP95 is shorter by 2", wider by 1" and 1.5 lbs heavier in sw
- LP108 is longer by 1", wider by 1" and 1.5 lbs heavier in sw
- LP120 is longer by 3", wider by 1" and 1 lbs heavier in sw

The buoyance characteristics also play a role, and the LP120 is pretty hard to beat with only 0.8 lbs difference in sw!

None of them seem to be a big difference from what I'm used too, the LP108 being the closest. Hmm...

Sounds good to me!

Note about those buoyancy characteristics. From full (air) to empty. (Without reg/bands etc.) Its -4 to +4. Something like 8lbs of air inside.

 

[Caissy]

Sounds good to me!

Note about those buoyancy characteristics. From full (air) to empty. (Without reg/bands etc.) Its -4 to +4. Something like 8lbs of air inside.

I agree that there's 6lbs to 8lbs of air inside, but that's on a scale at the surface. In water, these numbers are different based on the cylinder's characteristics, in addition to the sea vs fresh water difference. But maybe I'm wrong? (please correct me if I am!!)

 

[tbone1004]

@Caissy the mass of the air does not change from salt to fresh. The buoyancy characteristics are based on displacement and we assume the cylinders volume is fixed *it does change ever so slightly with pressure*.

 

[J-Vo]

Although the numbers between the LP85s and the LP108s are similar, the 85s are pretty much a set it and forget it tank while the 108s have to be trimmed during the dive much like AL80s or worse. I would guess the larger the LP tank the more exaggerated this gets, but Ive only used 85s and 108s. This is for Faber. I have used Worthington 85s and they are quite a bit heavier.

 

[victorzamora]

Although the numbers between the LP85s and the LP108s are similar, the 85s are pretty much a set it and forget it tank while the 108s have to be trimmed during the dive much like AL80s or worse. I would guess the larger the LP tank the more exaggerated this gets, but Ive only used 85s and 108s.

It's not that bigger=worse, it's that different tanks have different characteristics. For example, LP45s, LP85s, and LP121s all behave the same when empty. The difference comes in how much gas they hold, and, therefore, how much heavier those tanks are when full. LP121s hold almost 12lbs of EANx/Air with a cave fill. That means they're 12# negative when full, which is more than twice as negative as the LP45s. However, it's the empty-characteristics that matter for float and for buoyancy needs.

This is for Faber. I have used Worthington 85s and they are quite a bit heavier.

Yeah, the HDG Worthington tanks are notably more negative than the Fabers. I prefer them for applications when I need lead.

 

[kelemvor]

Hi everyone!

I've been diving LP85 in sidemount for a while now and I love them! However, I'm starting to do deeper technical dives (no cave) and I wouldn't mind having more gas...

So anyone having experience diving LP95 or even bigger tanks, say even LP108? How to they trim compared to the LP85? What are their buoyancy characteristics from full to near empty?

A few notes about my diving:
- I have my own compressor, so cave fills are easy for me...
- I dive in cold water in Canada with a drysuit and a thick undergarment that I use most of the year, so I need quite a few pounds of lead to compensate for my undergarment, so the extra weight of the cylinder simply means less lead for me, as oppose to warm water divers being over weighted with heavier cylinders...
- I dive with the xDeep Stealth 2.0 Tec harness with 42 lbs (19 kg) of lift
- I very often dive with a deco cylinder (40 cf of 100% O2) and often a stage, so I'm used to dive with 3-4 tanks. I'm hoping to go deeper/stay longer with this set up...

Let me know what you guys think!

I dive worthington LP108's in sidemount. They trim out nicely, they remain negative even when empty. When I sidemount them, I need no lead at all in freshwater - even with my "bag" drysuit. They are heavy as heck on land, and very negative when full. You aren't going to be dismounting them to squeeze through restrictions unless you're a roidmonster. Donning the tanks can be a chore, I've never attempted to don one in the water as it would sink like a rock if I lost control of it. That means I've got to don on land and get in with close to 200lbs of gear on. However.. in the water.. it's a dream come true. Gas gas gas, all day long. They trim out so easily, I never have to worry about my trim. If you dive them, DEFINITELY have redundant buoyancy. Drysuit+bcd or maybe dual bladder bcd. If you lost buoyancy compensation with these things in deep water you'd probably have a very bad day. For some reason, the buoyancy loss drill in cave class was actually super fun even with these. I couldn't help but laugh the whole time I was doing the drill, it just seemed hilarious. Actually that was probably the only part of cave class that was easy and fun.

I've borrowed/dived lp95's and they are significantly lighter. I didn't have any problem trimming them out, but I needed lead to dive them with my drysuit. Luckily, I had enough spare webbing, a buckle, and some lead so I was able to whip up a weight belt that day.

I highly recommend overfilled big LP108s if you have not bought steels yet. I fill mine to 3600psi most of the time, and combined that gives me 295cuft of gas. Compare that with a pair of al80's where you have a combined total of around 160cuft if they're slightly overfilled. If you do the same with your lp95's you'll have 260cuft. I'm not sure I'd replace 95's with 108's.. that's a lot of cash for 45cuft of gas, and the 108's as I said are a bear to manage on land. 95's might even be light enough to squeeze through a no-mount restriction with. That's way beyond my level of diving, so I've never even tried it. It might be easier to stick with 95's and add an al80 stage bottle. Although the need for an additional regulator probably makes the cost about the same.

If I was diving outside of a cave in sidemount, I might consider the negative buoyancy just too much risk. In the caves I've dove, you can always "bounce out" if you must. Much more risky to have all that weight in open water.

It's too bad you're in Canada. I've got 4 worthington LP108's and I've occasionally wanted to trade a pair for some lp95's. I've never really pursued it, though.

 

[northernone]

I agree that there's 6lbs to 8lbs of air inside, but that's on a scale at the surface. In water, these numbers are different based on the cylinder's characteristics, in addition to the sea vs fresh water difference. But maybe I'm wrong? (please correct me if I am!!)

I think of the compressed air inside is detachable ballast. 8lbs of air in any tank, is 8lbs of ballast.

(Side note: I don't dive with people who breathe their tanks down empty on deco dives... in a true emergency the last thing I'm concerned about is if my tank trim is off with 300psi left in my tanks.)