Lp 120?

[Juris Diver]

Would you buy an LP 120?

I'm a recreational diver, wear a wet suit, do both beach and boat dives, and most of my current dive buddies rent their tanks (AL 80s).

I've decided to go with Pst LPs and I think 104s are the way to go, but is there any reason to get a 120?

Doing the math, it looks like going with a 120 would just mean that I'd be ending my dive with a lot more air than my dive buddies.

Assuming we surface with 500 psi left in our tanks, here's the calculations:

current pressure/max pressure X capacity = CU feet of air left

For dive buddies using AL 80:

500/3000 X 80 = 13 CU of air left

LP 104:

500/2640 X 104 = approx 20 CU of air left

LP 120:

500/2640 X 120 = approx 23 CU of air left

Given the type of diving I do and the kind of tanks my current buddies use, is there any reason to go with the 120? The way I see it, LP 104 looks like the better option: 5 lbs lighter; if I want to someday do tech diving, I can switch to DIN, get a dry suit, double up, and not be excessively weighted (as I would probably be if I had 2 120s on my back); and for the time being still have plenty of air for the typical one tank dive.

Am I missing something? Would anyone recommend an LP 120 over an LP 104?

Thanks! :whack:

 

[Uncle Pug]

Really now... are you going to be getting into tech diving and spending all that moolah???? Hmmmm... honestly????

Am I missing something?

Yes... you are a recreational diver with a wetsuit who may one day get into tech diving but currently you dive with guys who are renting Aluminum 80s. (BTW - its best not to dive steel wet anyway.)

Why not just get a couple of AL80s and save your shekels for a backplate/wing setup and then save some more for a drysuit and then save some money to buy a couple of LP104s while trying to find a buddy who will commit to the steep learning/dollar curve of tech diving... then train together in buddy skills while you both continue to save up lotsa money for the next step.

Oh... and if you ever do get into tech diving - those AL80s will become stage bottles.

 

[Juris Diver]

Excellent advice. Exactly what I NEEDED to hear.

 

[sumguy]

Uncle Pug, why is it that everyone says you shouldn't dive steel tanks with a wetsuit? The only argument I can come up with, is the amount of ditchable weight. If you're diving aluminum, you've got approx. 4# more ditchable than with steel. Is this the reason, or is it something else?

And, even if Juris diver gets aluminum tanks, do you think he should go DIN?

Juris diver, I'm not disagreeing with UP. Sounds like good advice, especially since he's mentioned a future use for the al 80s. I'm just wondering what the big no-no is about wet steel.

 

[Uncle Pug]

Originally posted by sumguy
Uncle Pug, why is it that everyone says you shouldn't dive steel tanks with a wetsuit?

Yes, ditchable weight is the issue but with a single tank it is not such a big issue because you are going to have enough to ditch.

 

[JamesK]

From what I understand, LP120 are actually less negative in the water than LP104s. That is because of the excessive amount of water they displace, makes up for their extra weight.

(Note, I do not dive LP120's, this is simply info that I have received from some other sources that do dive double 120's)

 

[scubafanatic]

I've got 2 Faber LP 120 steels and love 'em!!!

I bought 2 so I could loan 1 to any potential dive buddy and we could both 'go the distance' without having one of us 'shortchanging' the dive by having their AL 80 run dry.

Even if you only want to shell out for 1 tank for yourself, it's nice having all that extra margin.......so on a group dive it won' t be you who sucks their tank dry first and ends the dive 'early'.....let someone else have that 'honor'!

Also, you've got a substantial safety margin for any OOA situation......or if you meet the unexpected problem (hit by a downdraft/current that forces you to drastically increase your air consumption....encounter a thermocline where cold water increases your air comsumption....etc).

Do the math........an AL 80 (which is really an AL 77) will give you 77 cu. ft @ 3000 psi. A LP 120 steel will give you 120 cu. ft @ 2640 psi......and since most shops are set up to fill the common 3000 psi AL 80, they will generally go ahead and give you 3000 psi too......so a LP 120 filled to 3000 psi = 136 cu. ft.

Yes, the 120 LP steel is 40 % heavier, but in exchange you get 77 % more air than an AL 80.....almost as much air as double AL 80's !!!

In addition, if you wear a wetsuit, you will need a LOT of lead to achieve neutral bouyancy.....and a steel tank will greatly reduce the amount of extra lead on your weightbelt.

(in a full 7 mm suit I still need 18 lbs of lead, even with the 'heavy' steel tank......I would probably need another 10 lbs of lead to submerge if I dove an AL 80...so what's the point of 'saving' weight by diving an AL 80, only to turn around and negate those weight 'savings' by loading up on so much weight you end up lugging as much or more weight than if you went with LP 120 steels in the first place......at least with the LP 120 you get a LOT of extra air with the weight)

Some people say it's riskier to dive 'steel's as they're
negatively bouyant, so if your BC fails it's hard to swim up to the surface, but that's an overgeneralization of the real facts, some 'steels' are actually positively-bouyant at the end of the dive......it greatly depends on the size tank and the brand/manufacturer......my Faber LP 120's are actually 4 lbs 'positive' at dive's end.

Heck, even at the start of a dive, when my tank is full and 5 lbs 'negative' I still need 18 lbs of ditchable (weightbelt) weight........so even if a BC fails and I can only shed 18 lbs I'll still be heading to the surface...fast!

Hope this helps,

Karl

 

[Rick Murchison]

Originally posted by sumguy
Uncle Pug, why is it that everyone says you shouldn't dive steel tanks with a wetsuit? The only argument I can come up with, is the amount of ditchable weight. If you're diving aluminum, you've got approx. 4# more ditchable than with steel. Is this the reason, or is it something else?

Let me use a specific example -
My steel 95 at the beginning of a dive, with my Micra, is the same as 17 pounds of lead (that's 12 pounds more than an AL80 by the way). In a 3 mil suit, that's about six pounds negative for me (which is zero at the end of the dive - perfect!) - so I don't need to carry any weight at all. Furthermore, I'll lose another eight pounds of buoyancy due to suit compression at depths of 100 ft or so, so at the beginning of a dive, even with no ditchable weight, I'll need about 14 pounds of lift in my BC just to be neutral, with no ditchable weight at all. If I were to have a total BC failure at this point I'd have to overcome that 14 pounds to swim back up to the surface - and even more important, to stay on the surface once I got there I'd have to keep swimming, because I'd still be five or six pounds negative.
Does this mean I can't dive my 95 in a wetsuit? No... I can... but I always carry a lift bag with me. If I have a BC failure I'll still have a rough time on the surface, but at least I'll be able to conserve my energy getting there.
Rick

 

[ebbtide]

hp 120's by PST is what ive just bought .
havent tried to dual them up UET but then agin i havent tried to get narced , ya the alum 80s i got i use for hanging a bottle for my decojust in case . and so i dont have to worry about a lenghtly hang and low air .

 

[Uncle Pug]

Originally posted by ebbtide
ya the alum 80s i got i use for hanging a bottle for my decojust in case

Ebbtide... yoos worries me...