Lift for LP 120s

[apadua]

Hi Guys,

I have a DiveRite BC with a Travel Wing - 27lbs of lift. I usually dive with 12-14lbs of lead when using S80s.

I'm going to travel to Cozumel where they offer LP120s as part of the "package". Do i have to be concerned with Lift? By removing some of the lead can I compensate for the extra weight of the tank, all else being equal?

What else woudl I have to take into consideration in order to do this math?

I'm contemplating whether it's worthwhile to take my BC on the trip or just rent one there.


THanks,

Andre

 

[deepstops]

Drop 4 lbs. of lead and you should be fine with the wing.

 

[Jim Baldwin]

Andre,

If you are headed to Cozumel diving LP 120's then you are diving with Living Underwater. They are only op that uses LP steel tanks. I have been diving with Jeremy for the past eight years. Excellent operation.

You will not have any problem with your your travel wing. The BP/W combos I dive with in Cozumel have from 25 to 35 pounds of lift. The 120 LP steels are going to be about 10 lbs heavier (45 to 48 lbs full) than the AL 80's you are use to diving with. At the end of the dive they will be about 2-3 pounds negative.

Dropping half the weight you are diving with might be a good starting point. If by chance you find yourself a little light at the end of the dive your divemaster will be carrying extra weight so he can easily add a couple of pounds.

If you are comfortable diving in your rig then take. One less thing to have to get use to under the water. If you have questions about the op drop me a PM.

 

[scubafanatic]

Have you ever dove LP 120's before ? They're BIG AZZ tanks ! My very 1st personal tanks were a pair of Faber LP 120's, lot's of air (although I've heard many reports of tanks in Coz being short-fills so don't get your hopes too high)...and not only are they heavy, they're wide @ 8 inches versus 7.25 inches diameter, and they're LONG....and if you're on a 6-pack and doing back roll entries, perching on the narrow/slipper boat 'lip' while awaiting the signal to 'go' might be 'interesting' trying to keep your balance on the edge without falling in to early...so be careful !

Sometimes with a really big/heavy tank, the extra gas you carry is wasted fighting bouyancy control/balance/trim issues, and propelling a heavier mass object through the water (more drag/inertia).

One one liveaboard trip, I actually switched back to AL80's (after spending most of the trip using a Faber HP100) because the HP Fabers were short filled.....everyone was getting 3000 psi, so the gas capacity between a 'full' AL 80 versus an underfilled HP 100 was really pretty close, and the Fabers had what felt to me to be poor bouyancy characteristics...excessively negative...and I was fighting the tank and using more gas up anyway, so back to an AL 80 I went!

By the way, I have MUCH experience diving bigger tanks (own 2 twinsets, (4) HP 120's....(1) HP 130...(2) HP 100's...(1) LP 108...along with an AL80, a LP 85) ...and have dove (but don't own all of the following tanks: LP 95, twin LP95's, twin AL80's, AL 100, Faber HP 100) so I speak from experience.

 

[halocline]

One one liveaboard trip, I actually switched back to AL80's (after spending most of the trip using a Faber HP100) because the HP Fabers were short filled.....everyone was getting 3000 psi, so the gas capacity between a 'full' AL 80 versus an underfilled HP 100 was really pretty close, and the Fabers had what felt to me to be poor bouyancy characteristics...excessively negative...and I was fighting the tank and using more gas up anyway, so back to an AL 80 I went!

That wouldn't have been the fling, would it? I got a couple of short fills there as well, but eventually they started topping them off. Regarding the buoyancy, maybe you had the older faber 3180 + 10% tanks, not the FX 100? The FX is less than a pound negative empty.

 

[apadua]

No, never tried anything but S80s.

These suckers must be heavy - 1lb negative when EMPTY?

I'lll post details when I'm back, but that's mid-July.

Cheers!

 

[deepstops]

Andre,

If you are headed to Cozumel diving LP 120's then you are diving with Living Underwater. They are only op that uses LP steel tanks.

No they aren't.

The 120 LP steels are going to be about 10 lbs heavier (45 to 48 lbs full) than the AL 80's you are use to diving with. At the end of the dive they will be about 2-3 pounds negative.

PST LP 120 = .8 lbs. negative when empty
Faber LP 120 = Neutral when empty
Worthington LP 120 = 1 lb. positive when empty
Luxfer AL80 = 4.4 positive when empty

I stand by my original statement to remove 4 lbs. and the wing has sufficient lift. It works regardless of the tank brand and he won't find himself light and depending on the DM to give him weight at the end of the first dive.

Dropping half the weight you are diving with might be a good starting point. If by chance you find yourself a little light at the end of the dive your divemaster will be carrying extra weight so he can easily add a couple of pounds.

Then again, it might not.... Why would he drop 6-7 lbs when there's 4 lbs. difference (see above).

 

[scubafanatic]

That wouldn't have been the fling, would it? I got a couple of short fills there as well, but eventually they started topping them off. Regarding the buoyancy, maybe you had the older faber 3180 + 10% tanks, not the FX 100? The FX is less than a pound negative empty.

...nope, it was Nautilus Explorer/Socorro Islands, I believe it was the older HP Fabers. Usually I'm the 'big' tank fan, but on that trip I think the AL80 was a better choice, at least for the tropical conditions we faced. However, Nautilus Explorer spends half it's dive season servicing the dry-suit crowd way up north (Pacific Northwest/Alaska) if memory serves, so it might be the case that that HP 100 Faber are more suitable for dry-suit diving, where the extra weight is beneficial.

Can you tell me more about the 'short fills' on Fling ? What tank were you using ? What prompted them to straighten out and start doing 'full fills' ? Define FLING's definition of a 'full fill' ? 3500 psi on a HP tank ? Or just letting your tank cool down and then just top off again to 3000 psi ?