Mailing List Archive Mailing List Archive
Okay, here it goes. Measurements done with a Stren 50lb digital fish scale ($40 at Turner's). All measurements are with valve and (dare I admit?) boot. Taken in fresh water chlorinated swimming pool. Catalina S80 - 38lb 7oz full (3100psi). 32lb 12oz empty (400psi). Buoyancy full -1lb 13oz. PST HP120 - 45lb 11oz full (3500psi). Buoyancy full -9lb 10oz. I'll weigh an empty one when I have one. This appears to match the PST published numbers, however, this doesn't mean that the published numbers for the 104 are correct. Someone needs to check a single (anybody have their doubles broken down for viz?) to verify. I measured the Catalinas for a comparison, and it exactly matches the published figure of -1.8lb (.8lb being 12.5oz)... the below web site reports that it should be -2.1 full. My dry-land weight is a bit heavier than published. So, if the 120 does indeed hold 120cf at 3500, then it's empty buoyancy should be 10oz. The published number of 0.4lb would be 6.4oz, so mine would be a little over 3oz heavy... probably the valve and boot. Looks like maybe PST's published numbers are based on the tank only, while Catalina includes the valve and boot for a "diving configuration" number. This little Stren scale is nice, but with a 50lb limit, you aren't going to be checking your doubles on land. It was creaking and groaning under my single 120 :) On 7/29/2002, Bill Barnes wrote: >Rich, >This issue has come up before, and since you admit to owning a HP 120, 8-) >which is great for single tank diving. >Would you be willing to take a hanging scale and drop the full (3500 psi) >tank in a drum of fresh water and determin its buoyancy? >Could you also do the same when the tank has 500 psi in it? >We would really like to have some accurate numbers to set the record >straight with. > >I am trying to do the same with my double LP 95's and 104's. I have heard >the double LP's are 15 to 22 # negative full. >Some people also check the buoyancy with AL backplate, wings, and regs in >place. >Checking stages this way really shows the difference in tanks >Bill. > >> -----Original Message----- >> From: Rich Lockyer [SMTP:rlockyer@li*.co*] >> Sent: Saturday, July 27, 2002 7:05 PM >> To: Art Greenberg; quest@gu*.co* >> Subject: Re: [No Subject] >> >> The "college boy" math at subaqua agrees very closely with the published >> data below for the HP120, unless the baseline 36lb dry tank weight is >> wrong. >> It's a little over 2 pounds off on the 104, assuming a fill of 2640. If >> we >> assume a fill of 2400, then it's closer. >> >> http://www.subaqua.co.uk/cgi-bin/cylinder-buoyancy.cgi?units=imperial >> >> The published data on the 5thD chart is obviously incorrect, unless they >> tested with a gas other than air, as they are showing a buoyancy swing of >> only 3 pounds for 100cf of gas on the 95 and 104... a little more for the >> 120, but nowhere close to the reality of 9 pounds. >> >> I own the PST HP120 (not the Genesis) and it is quite nearly neutral when >> empty in salt water, and it's empty weight is quite close to the full >> weight of my AL80s. There's no way it's as negative as some charts I've >> read report it to be. >> >> I'm not going to proclaim that the HP120 is the ideal cylinder for >> everyone, but for a taller diver such as myself, it does trim very well >> and >> is a great single-tank solution. >> >> >> >> On Sat 7/27/2002, Art Greenberg wrote: >> >The "published" buoyancy data are wrong. >> > >> >On Sat, 27 Jul 2002, Christos Koutentis wrote: >> > >> >> Dear List: >> >> >> >> I would like to ask a queation regarding low pressure and high pressure >> steel >> >> cylinders. >> >> I understand that HP 120's are considered not exactly kosher DIR due to >> >> buoyancy issues, and that LP 104 steels are more appropriate. >> >> The published weight and bouyancy figures per cylinder don't seem to >> support >> >> this, with units in pounds as follows: >> >> Weight Buoyancy Full Buoyancy empty >> >> LP 104 45 -8.2 -0.7 >> >> HP 120 36 -9.4 -0.4 >> >> >> >> Of course this is with air, which we never use but I would appreciate >> any >> >> feedback whatsoever. --Rich http://richlockyer.tripod.com -- 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]