Mailing List Archive Mailing List Archive
All -- Many thanks to everyone who responded to my message on why PST 104s are the preferred tank for cave and tech diving. I got some terrific responses and appreciate the time they took. For the list and anyone who's interested, they're summarized below. Basically, the consensus is that the PSTs have a reputation for being more durable *and* for caving they start more negative and stay more negative so you stay off the roof. Here's the summary. A few of the authors would like me to point out that their responses are based on personal opinion so your mileage may vary. Best - Bill ------ Original Message: > I'm in the market for a set of doubles and checked the archives for > recommendations. It looks clear that almost everyone is using PST 104s > but I can't figure out why. What about OMS 98s or 112s? > > Here are the specs I have -- am I missing something or are these > notoriously innaccurate buoyancy and weight specs just plain wrong: > > cu. ft Fill Wt. Bouyancy Full/E liters > OMS J-098G S 98 2640 38 -7.73 / 0 15.45 > OMS J-112G S 112 2640 41 -8.00 / -1 17.66 > > As far as I understand it, the PST 104s (can't find reliable specs) have > about the same weight and buoyancy characteristics as the OMS112s for > less capacity and are larger and heavier than the 98s for not much gain > in air. Before I regret buying a pair of 98s, I'd appreciate any help > you can offer. Responses -- Jon Breazile, breazile@ne*.co* wrote: >The 104s are great because they are heavy. The OMS 112s are almost >the same. The more you can take off your weight belt, the better. >The 104s also have a history of being very tough. Some people have >had sets for 20 years with a lot of overfilling (3500 PSI) and they >still pass hydro. J. Scott Landon, landonjs@a1*.sw*.um*.du*.co* wrote: >the pressed steel tanks are several pounds more negative and have thicker, >better steel. if you empty your oms tanks, you will be too buoyant. i >have an original set of 104s from 1971/1972 that are still perfect. buy >pressed steel tanks unless you are using them for sidemount cave diving or >deco bottles. trust me, you want the 104s. the galvanized finish is much >better than painting as well. and one more thing: >ever notice how oms magically had there 95s become 98s when the physical >dimension of the tank did not chnage. they are 95s, not 98s. don't let a >little savvy marketing fool you. buy the pressed steel 104s. Jeff Bentley, jbentley@cr*.co* wrote: (This gets the zen message award) >Are you sure there is only 104 in the tank when at working pressure? Bill Bowden, BBOWDEN@co*.vo*.fl*.us* wrote: >IMHO- I've got a set of 104's and a set of 112's. I use the 112's the most. >Lighter out of the water, better bouancy characteristics, slightly more air, >paint over galvanized for the ocean, internal coating for the ocean. 104's >are more traditional and almost indestructable. Laurence J. Roth, roth@me*.ne* wrote: >I've been diving OMS 98's off shore and I don't notice any difference form >PST 95's. (I wouldn't be surprised if the actual capacity was the same) >The tanks are manufactured in Italy and are the same tanks Scubapro and >some other dealers sell. I have a couple of steel 80's made by the same >company, that I use for stage bottles and they are excellent. (short, >neutrally buoyant, and higher capacity than the usual 72's) > >I wouldn't recommend the OMS manifolds since they have brass to brass >connections. The Scubapro / Diver's Supply, etc. manifolds (they are >made by the same Swiss company) are much better and have long, dual o-ring >connections. They will survive being "bumped" much better Ron Price, RPRICE@wp*.it*.lu*.ed* wrote: >I've noticed the preference for PST-104s among the >cavers. I dive mostly deep wrecks (140'-250') in the >Great Lakes and here I see A LOT of OMS tanks. I >dive OMS-120's and wouldn't recommend them >unless you are large/tall person. At 6'3" I can get a >way with it. 120s with two slings are alot to handle. > >I think the OMS tanks have great characteristics (e.g., >weight, buoyancy, etc) and I see them routinely get >pumped to 3,300-3,500PSI -- even though its not >recommended and I avoid it. The 120's provide >enough gas for ANY dive that I'll ever do, and probably >too much gas for most of the diving (<300') that I do. If >had to do it again, I would go with 112s (they become >127s at 3,000PSI). I think that 98s might be a little >close (diving something like 3rds) for some deeper >dives. It all comes down to what type of diving you're >doing. > >It may come down to price. I haven't bought any 104s, >so I don't know how they compare... but, OMS tanks >aren't cheap. Be prepare to drop $380-450 per >tank---- Michael Picou, picou.michael@MA*.DC*.ST*.FL*.US* came through with specs (go Michael!) though my gut reaction is that this is the innacurate U.S. Divers info since the bouyancy change full to empty isn't enough to account for the gas volume. >I have some info on the PST 104's that I found in Vol 15 No. 4 of >Discover Diving Mag, I will assume its accurate: > >capacity 104 @2400 psi >O.D. 8 in >length 26.19 >weight 46lb >buoyancy -5.3full/ -2.5 empty > > The buoyancy is interesting in that for a set of 104 doubles the >gain is > 5.6 lbs. (full to empty), while the OMS would be around 15 lbs. >You may also want to check the length of the OMS as this can be a >problem for (me included) short folks. Good luck!! And....last but not least, Peter Gottlieb, TMBG@ix*.ne*.co* provided the gossip and a guarantee <g> -- >I don't have any scientific data, just gossip, speculation and a lilttle >logic. Take it for what it's worth. > >1) A few months ago, I read a letter from the president of OMS stating >something to the effect of, "OMS tanks are just as good as other tanks, >and they are actually quality tanks. Really. There's nothing wrong with >OMS tanks. In fact, let me tell you how we make them, and how they are >really good tanks. Really." Sounded almost too good to be true. The only >time I have ever read spin control like that was when it was needed. > >2) A friend of mine dove a set of double 121's and found them >excessively buoyant once they were about 1/2 capacity, with full cave >gear (this would include a neoprene driest, though). > >3) Another friend was interested in purchasing a set of OMS tanks, and >asked a dealer rep if they would guarantee that new tanks would, under >normal diving conditions, pass the first hydro in 5 years. He wouldn't. >Even Genesis has replaced failed high pressure tanks that are older than >that. There are 104's made 40 years ago that are still being restamped. > >4) How is it that tanks that are the same physical size (displacement >and internal volume), and material are different weights? Wall >thickness. I have heard that the way the OMS tanks, in general, are made >lighter than comparable steel tanks by decreasing the wall thickness, >and using an internal coating. Due to this coating, the tanks cannot be >whipped, or tumbled. If you never drain your tanks, that might not be so >bad, but the slightest bit of debris that gets in could damage the >coating. Not to mention if some yahoo shop worker isn't paying attention >and whips/tumbles them anyway - bye bye coating, bye bye tanks, hello >corrosion. > >Again, while these are just gossip and speculation, I am sticking with >the tried and true pst's, which have a history, and great reputation. I >did try an OMS46 for a deco bottle, that was just about perfect, until I >got to the price. For that money, I can get 3 AL80's. I will put up with >the size difference. ...[snip].... If you're not happy with >the pst's, I will buy them off you. > >Let me know if they work out for you. Maybe they are the singing fat >lady for whom we are all looking. Best Regards -- Bill -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
Navigate by Author:
[Previous]
[Next]
[Author Search Index]
Navigate by Subject:
[Previous]
[Next]
[Subject Search Index]
[Send Reply] [Send Message with New Topic]
[Search Selection] [Mailing List Home] [Home]