SF2 or REvo rebreathers
- Thread starter JonnyQuest
- Start date
Please register or login
Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
- Ability to post and comment on topics and discussions.
- A Free photo gallery to share your dive photos with the world.
- You can make this box go away
Unfortunately i’m headed to Miami today or I’d walk across the street to CCDS and ask myself. If it’s only a needle valve, that would be great. Personally i’m not a fan of blocked-IP first stages for a variety of reason. There really isn’t any real task loading with a needle valve, and you’re gonna have an O2 MAV anyway, might as well just do it.
Yeah, you’ll definitely be able to get parts for it pretty much forever.
Yeah, you’ll definitely be able to get parts for it pretty much forever.
victorzamora
Contributor
Many KISS (and Kiss-style-orifice) divers are replacing springs to increase IP, along with a smaller orifice, to get deeper max-depth settings. I think that's what rddvet was referring to.
Honestly, blocked first-stages are an incredibly easy fix if that's not your flavor. However, there's still a benefit to needle over orifice...even if they've both got capped first-stages...namely setting your flowrate on a dive as opposed to on a bench, as well as still being adjustable for kick vs deco vs scooter, etc.
Besides, other than depth limit, is there a downside to the capped first stages? Seems to me like 400ft would be more than enough for the vast majority of CCR divers, and uncapping is easy enough for those that want the depth.
Edit: 400ft per Kensuf, below. I originally posted "~300ft"
Last edited:
The first stages on the Fathom are Apeks DS4's. The O2 1st stage replaces the stock spring with a stronger one and it also comes with a block to lock the IP at a fixed rate, which should be good enough to get you to 400' without any modification. Divers that need to go beyond 400' can adjust the IP through the use of a hex key on the 1st stage, or they can remove the block plate and then have to fiddle with the needle valve on descent and ascent.
I'm not sure how many people are going deeper than 400' on a regular enough basis that it's a real concern.
Thanks for that, I use a rEvo so I am familiar with the setup. Any change in IP is caused by adjusting the spring tension using a hex or allen key. It was just when the OP mentioned that they could adjust the IP without going near the spring I thought maybe I am missing something that's all.
For me, it's not the depth limit that I dislike, I only mentioned it because it is one aspect of diving a CMF/blocked 1st stage. I'm definitely not diving to those depths, and probably not anytime soon either.
The major thing for me is that a needle valve requires no modification to the first stage. You can put a needle valve on any first stage since it's just an LP port, and depending on manufacturer, a LPI hose.. If my high pressure seat blows on my O2 reg, I can swap it to another reg in 30 seconds with an adjustable wrench without having to disassemble two regs to make the swap. I'm not doing the ridiculous dives that those guys are doing, so more often than not I'm not bringing a whole bunch of extra spare gear with me. Certainly not a whole reg disassembly kit. Carrying one spare 1st stage of any normal type makes it about a 2 minute delay. Conversely with a blocked first, if my O2 reg is a DS4, and I don't have a spare DS4, but some other spare reg, there's no guarantee that the first stage spring and blocking plug will function correctly in the event I needed to swap. Sure you can make it a moot point by only buying one specific brand and model of reg, but not everyone does that.
Obviously if you're doing a 400+ foot dive 37k feet into a cave, you're gonna have a bunch of spares of everything in the truck, backed by a personally owned dive shop. Most people aren't diving like that. So for probably the majority of divers, the utility of being able to put a needle valve on any (yes, I know there are exceptions) standard reg is pretty useful. Playing with the needle valve is damn near autonomous once you've got even a little bit of time on one, so I'd say the task loading trade-off is on par with a CMF where you can't tune flow to minimize manual intervention. Twist the valve and hit the MAV every 30 minutes, or no adjustment and have to hit the MAV every 5 minutes. Pick your poison, I could argue either way, however my preference is for less manual intervention.
I get the arguments for either, and could justify both, but I like the needle valve over a CMF for several reasons. Others equally like a CMF/blocked 1st. I don't understand the post by Charlie on another forum saying it has both. I just don't see a need. Either way, whatever it is that they're doing, it works for them. They're doing some big ass dives on the units.
Personally, if I were looking for a "1st world Pelagian," I'd just pick up a cheap af COPIS Meg, gut the head and put in two Shearwaters, some BMCL's, and a needle valve instead of the CMF and call it a day. Cheaper than a Fathom, and 99% of the way there. I'm assuming they need a 9v to run some sort of isolation board for the cells. If you're willing to run without that, nothing needed in the head at all.
The major thing for me is that a needle valve requires no modification to the first stage. You can put a needle valve on any first stage since it's just an LP port, and depending on manufacturer, a LPI hose.. If my high pressure seat blows on my O2 reg, I can swap it to another reg in 30 seconds with an adjustable wrench without having to disassemble two regs to make the swap. I'm not doing the ridiculous dives that those guys are doing, so more often than not I'm not bringing a whole bunch of extra spare gear with me. Certainly not a whole reg disassembly kit. Carrying one spare 1st stage of any normal type makes it about a 2 minute delay. Conversely with a blocked first, if my O2 reg is a DS4, and I don't have a spare DS4, but some other spare reg, there's no guarantee that the first stage spring and blocking plug will function correctly in the event I needed to swap. Sure you can make it a moot point by only buying one specific brand and model of reg, but not everyone does that.
Obviously if you're doing a 400+ foot dive 37k feet into a cave, you're gonna have a bunch of spares of everything in the truck, backed by a personally owned dive shop. Most people aren't diving like that. So for probably the majority of divers, the utility of being able to put a needle valve on any (yes, I know there are exceptions) standard reg is pretty useful. Playing with the needle valve is damn near autonomous once you've got even a little bit of time on one, so I'd say the task loading trade-off is on par with a CMF where you can't tune flow to minimize manual intervention. Twist the valve and hit the MAV every 30 minutes, or no adjustment and have to hit the MAV every 5 minutes. Pick your poison, I could argue either way, however my preference is for less manual intervention.
I get the arguments for either, and could justify both, but I like the needle valve over a CMF for several reasons. Others equally like a CMF/blocked 1st. I don't understand the post by Charlie on another forum saying it has both. I just don't see a need. Either way, whatever it is that they're doing, it works for them. They're doing some big ass dives on the units.
Personally, if I were looking for a "1st world Pelagian," I'd just pick up a cheap af COPIS Meg, gut the head and put in two Shearwaters, some BMCL's, and a needle valve instead of the CMF and call it a day. Cheaper than a Fathom, and 99% of the way there. I'm assuming they need a 9v to run some sort of isolation board for the cells. If you're willing to run without that, nothing needed in the head at all.
_Slacker_
Contributor
Yea, you are missing a bit. The needle valve is just an adjustable orifice. It can be run with a blocked or unblocked 1st stage. There are pros and cons to each method but diving it blocked removes the variability of O2 flow vs depth. With an unblocked 1st: diving a square profile it makes little difference. Diving say a cave with lots of ups and downs, it requires a bit of adjustment for every significant depth change. Diving it blocked you only need to make changes if your metabolic rate changes (scooter vs swimming, working vs deco, etc). It's not a difficult adjustment to do, but when you are fully loaded one less thing to do is nice. Every significant depth change you already have to mix your breathing gas, clear your ears, and add/dump gas from the wing and drysuit. Now fill your hands with a scooter, a light, and a reel.
As for your justifications above: You can still swap any reg before the dive without issue, you just may have more adjustments during the dive if you changed from a blocked to unblocked first stage.
As for your justifications above: You can still swap any reg before the dive without issue, you just may have more adjustments during the dive if you changed from a blocked to unblocked first stage.
Good discussion. Johnny I think you have a valid point. I never thought about an issue with the reg and swapping out. Though my understanding is what slacker described. You can switch regs to an unplugged but would just have more fiddling to do.
It would be interesting to hear Charlie's exact reason for the choice.
It would be interesting to hear Charlie's exact reason for the choice.
Similar threads
