Sherwood Oasis/Blizzard and the never ending Piston vs Diaphram
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Greg Barlow
Contributor
I judge a "high performance" reg as one that can meet the US Navy breathing simulator standards with a Class A designation. This is more stringent than that of the CE250 standards (European Community designation). I suggest that you read the past Rodale's articles on their website at www.scubadiving.com, and search the regulator tests on the British magazine Diver at www.divernet.com.
I worked for Rodale's for a little over two years and Sherwood would not submit their regs for testing purposes. Rodale's ended up purchasing some for the tests. Their regs did not meet the Class A standards both in the Rodale's testing and that of Diver Magazine's evaluations. There is a German mag that also runs ANSTI simulator testing. While I have not seen those results myself, I was told by another Rodale's employee that the Sherwoods had also failed their round of meeting the Class A standards.
Class A standards are tough. In fact, a reg must be able to supply enough air at 198' to sustain two divers breathing at an aggressive rate. The Navy calls for a supply pressure of 1,500psi. Rodale's ran their tests at a supply pressure of 750-800psi which obviously is an even tougher test. In short, any reg that can meet this standard is more than enough for nearly any conceivable dive. Any reg which meets the WOB at 1.4j/l or lower qualifies as a Class A. There are regs on the market that can meet this level with a score of around 0.8-1.0j/l, and many at the 1.0-1.3 level.
People's opinions are purely subjective...It has been shown many times that a diver cannot judge the difference in the overall work of breathing on a reg until the difference is more than 0.4j/l. Some regs can be adjusted to appear to have easier breathing, but it is typically the cracking pressure that is bordering on a free flow level. The real work of breathing is much more than the initial effort. The whole breathing cycle must be considered. A breathing simulator is the only objective judge of comparing the overall patterns. Subjective views are important, but they are subjective.
Greg Barlow
I worked for Rodale's for a little over two years and Sherwood would not submit their regs for testing purposes. Rodale's ended up purchasing some for the tests. Their regs did not meet the Class A standards both in the Rodale's testing and that of Diver Magazine's evaluations. There is a German mag that also runs ANSTI simulator testing. While I have not seen those results myself, I was told by another Rodale's employee that the Sherwoods had also failed their round of meeting the Class A standards.
Class A standards are tough. In fact, a reg must be able to supply enough air at 198' to sustain two divers breathing at an aggressive rate. The Navy calls for a supply pressure of 1,500psi. Rodale's ran their tests at a supply pressure of 750-800psi which obviously is an even tougher test. In short, any reg that can meet this standard is more than enough for nearly any conceivable dive. Any reg which meets the WOB at 1.4j/l or lower qualifies as a Class A. There are regs on the market that can meet this level with a score of around 0.8-1.0j/l, and many at the 1.0-1.3 level.
People's opinions are purely subjective...It has been shown many times that a diver cannot judge the difference in the overall work of breathing on a reg until the difference is more than 0.4j/l. Some regs can be adjusted to appear to have easier breathing, but it is typically the cracking pressure that is bordering on a free flow level. The real work of breathing is much more than the initial effort. The whole breathing cycle must be considered. A breathing simulator is the only objective judge of comparing the overall patterns. Subjective views are important, but they are subjective.
Greg Barlow
Capt Jim Wyatt:
With all due respect no regulator is bulletproof and I have seen more than a fair share of Sherwood Brutes grenade.
Mind you we all see a lot of em since they seem to be the reg of choice for dive store rentals so that increases the odds of seeing it but no reg is bulletproof.
Simple? Easy to repair? Mediocre performance? Yes!
Unbreakable? Far from it. 'Nuff said.
Capt Jim Wyatt
Hanging at the 10 Foot Stop
Staff member
ScubaBoard Business Sponsor
Scuba Instructor
d33ps1x:
I did not think anyone would take me so literal. 'nuff said
:bigun2:
hehe
rescuediver009
Contributor
First things first. If you can get an apeks ATX40 for a good price go for it.
Otherwise, don't think twice about the sherwood. Like it has been noted above they are easy and cheap to service, and they are really rugged. Contrary to what mechdiver has said about the humidity being exhaled with the rest of the gas, seeing as the fins are right at your teeth, they do retain some moisture, and they work to an extent. I dove a blizzard for 2 years and I never had any problems with it. The oasis cousin will definetely perform to around 100' without any change in breathing effort.
I would not recommend touching a brut with a ten foot pole. They are recommended as a training reg and do not perform nearly as well. The main difference between that and the rest of the sherwood line-up is the moving orifice in the first stage which is non-existant in the brut.
The only thing i would recommend changing in your set-up is you maximus octo (I think you mean minimus). Although they are really low profile, they are really finicky is the air they supply. When I had my blizzard I used a sherwood standard octo, and it worked great.
Otherwise, don't think twice about the sherwood. Like it has been noted above they are easy and cheap to service, and they are really rugged. Contrary to what mechdiver has said about the humidity being exhaled with the rest of the gas, seeing as the fins are right at your teeth, they do retain some moisture, and they work to an extent. I dove a blizzard for 2 years and I never had any problems with it. The oasis cousin will definetely perform to around 100' without any change in breathing effort.
I would not recommend touching a brut with a ten foot pole. They are recommended as a training reg and do not perform nearly as well. The main difference between that and the rest of the sherwood line-up is the moving orifice in the first stage which is non-existant in the brut.
The only thing i would recommend changing in your set-up is you maximus octo (I think you mean minimus). Although they are really low profile, they are really finicky is the air they supply. When I had my blizzard I used a sherwood standard octo, and it worked great.
shrwdtech
Contributor
Okay... a bit of air cleaing on the "semi-official" side. The moisture retention vanes in the Sherwood regs are not a solution to dry mouth. They are there to help combat it. They do work well for what they are made for. When you inhale, cool air from your cylinder passes the vanes on it's way into you. When you exhale, warmer, moist air from you passes across the cool vanes. The effect is much the same as your glass of Iced Tea (or cold beverage of choice) on a hot day. Condensation forms on the vanes. When enough collects, you will inhale the droplets of moisture into your mouth. Some people aren't bothered much by the dry compressed air, and this isn't a big deal to them. Some people are extremely sensitive to it and really enjoy the clean, not salty, moisture. It's a personal choice, but it does in fact work and make things more comfortable.
Next myth, and this I'm sure will gain all the arguments, and that's fine, but the Sherwood Regs don't breath worse at depth. In fact, anybody who is into the engineering side of things can attest, that it's just the opposite. The Sherwood regs will breath with exactly the same IP at depth as they will on the surface, and will have pretty darn close to the same IP on a near empty cylinder as they will with a full one. I'm not going to teach a service seminar here, but it has to do with the moving orifice in the first stage, and the bellville washers. At any rate, I've personally had an Oasis to deeper than the limits of the Recreational Dive planner, and have enjoyed the performance as much as the regs from other manufacturers. I'm sure many people have all sorts of experiences to the opposite, and that's fine. Narcosis is a good thing.
Lastly, Sherwood regs will be submitted again for testing after our changes this year. They were not submitted in the past for 2 reasons. 1) we hadn't changed them any. Not since 1993. No need or reason to. And 2) when we first introduced our current regs, Rodales LOVED them. They got extremely good reviews. We changed NOTHING, and the next year Rodales hated them. Go figure. *this is a personal view, and not a company view* Rodales testing is nothing to crow about. The inconsistancies in reviews and reporting over the past 10 years leave so much to be desired that it's not worth getting into here. Great articles. Fantastic pictures. But...
Next myth, and this I'm sure will gain all the arguments, and that's fine, but the Sherwood Regs don't breath worse at depth. In fact, anybody who is into the engineering side of things can attest, that it's just the opposite. The Sherwood regs will breath with exactly the same IP at depth as they will on the surface, and will have pretty darn close to the same IP on a near empty cylinder as they will with a full one. I'm not going to teach a service seminar here, but it has to do with the moving orifice in the first stage, and the bellville washers. At any rate, I've personally had an Oasis to deeper than the limits of the Recreational Dive planner, and have enjoyed the performance as much as the regs from other manufacturers. I'm sure many people have all sorts of experiences to the opposite, and that's fine. Narcosis is a good thing.
Lastly, Sherwood regs will be submitted again for testing after our changes this year. They were not submitted in the past for 2 reasons. 1) we hadn't changed them any. Not since 1993. No need or reason to. And 2) when we first introduced our current regs, Rodales LOVED them. They got extremely good reviews. We changed NOTHING, and the next year Rodales hated them. Go figure. *this is a personal view, and not a company view* Rodales testing is nothing to crow about. The inconsistancies in reviews and reporting over the past 10 years leave so much to be desired that it's not worth getting into here. Great articles. Fantastic pictures. But...
rescuediver009
Contributor
First things first. I have no problem with sherwoods.Used a blizard for a number of years and it was great. I agree with you in that they do not breath harder at depth. I believe that what most people are referring to is the cracking resistance as you pass about a hundred feet depending... Now this can be overcome with an adjustable second stage right? What about the maximus. I would be interested in hearing what sherwoodtech has to say about the maximus. and its adjustability. If you set up the maximus and it breathes like crap (i.e. over 2" of water) there is nothing that you can do about it as there are no second stage adjustments internally. Is this true or did I miss something. I am not finding fault. I assume that in your position you would know about it if it exists... or are there design flaws?shrwdtech:
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