SF2 is an expedition rebreather. No CO2 monitoring. Pity they had to go to Shearwater and did not design their own elecs... that's a big commercial risk.
Fair point. CO2 monitoring would be good to have, unfortunately still not market ready, at least in this segment. Re building your own elecs: I think they partly do. If the primary shearwater fails there’s always a secondary unit and manual ops that can bring you back to the surface before you need to bail out.
I seriously doubt that gas costs are a factor if you're not an instructor or other kind of professional diver. How many dives to 50m+ do you do each year? If you do your own fills it's about 25-35€ per simple dive depending on how much you pay for helium. An SF2, including training, it's about 10k€, and you still need some gas, scrubber, batteries and o2-sensors. I'm an active technical diver and could dive a couple of decades on OC for the price of going CCR with an SF2 unit. Most people buy rebreathers because of the cool-factor, some people actually need them for complex dives... gas costs is mostly irrelevant.
Hi, thanks for your comment! Gas costs are only one factor for me. Still, not a completely irrelevant one. My personal operating minimums imply that I will use at least 21/35 for every dive between 30 and 45m and 18/45 between 45 and 60m. I do about 40-50 dives a year, and most are below 30m, i.e. I am on some sort of trimix on most of my dives. Call me a gas hog, but I am currently only using 1/13th of the amount of gas compared to what I used while diving OC. A pro doing 150 of those dives a year might get the consumption down even more. As mentioned in the video, a lot of these gas savings are offset by the cost for scrubber, cell replacement and unit maintenance. You are right that the cost savings alone do not justify rebreather diving. And yes, the coolness-factor can be quite a strong motivator. I do not remember denying that... ;)
Alex, this was very helpful. I am currently considering the SF2 and found a unit that I can use for both bm and sm. However, I own 2 KISS GEMS (am an instructor,) one for bm, one for sm or teaching (easy switch.) I paid less for these units than a rebreather diver will pay for two computers, though new, they are around $4,500 (I got both used VERY cheap from an instructor I trained with.) I only need one 02 sensor to monitor P02 as GEM is PSCR and everything is manual, though the ADV automatically adds Nitrox ever 3rd breath or so depending on your breathing. The GEM uses cartridges, and depending on your RMV, you will get up to between 4-6 hours on one cartridge, though it is highly recommended to stick with changing them out after 4 hours. I can use my setup with trimix and I hotplug all my gases into the unit. It is set for 3:1, but there are ways to get it far beyond that. The only drawback to the GEM is the chest mounted CLs, which are OK bm, but tricky sm. I like the idea of the SF2 with nothing on my chest. Yet, I am wondering if it is 1) worth moving to a full eCCR when I am mostly teaching sm rec. and beg. tech. up to 40 meters as the GEM is incredibly simple and therefore, safer and 2) is it worth the cost of not having chest CLs, but having to maintain and "feed" the beast more than I do with my GEM? One advantage of eCCRs is that PSCRs do allow gas to leave the loop, so it is not bubble free, and the GEM releases bubbles from the DSV, so I do see about 1/3 the bubbles I would in OC. But your presentation is making me think more about it - cost of unit/training/maintenance and setup. I do like the quickness and ease of OC, and I mostly dive sm, so don't have tanks on my back. Thanks for this explanation of your training!
Thank you for your comment, rabukan 58! It seems that you have figured (and configured) your GEM quite nicely. That usually makes for safe and fun operations. I did for a few years consider moving from OC to an RB80 clone, to keep my DIR configuration. And then noticed that some hard-core PSCR RB80 divers started moving to ECCR. That made me reconsider it. I believe that the PSCR concept is very robust, and, with proper training, quite safe. Particularly if complemented by a PO2 monitor like in your GEM. Lucky us that George Irvine III is not active in these discussions anymore.. ;) My key consideration when moving on to an SF2 from a GEM would be to compare them against your most common personal dive profiles regarding risk profile, the workload for normal/abnormal procedures, and gas logistics/cost. Which, I am sure you are doing already. Maybe a bit philosophical: the discussion about the cost of various rebreather types and models appears to be less one about overall cost and more one about how the cost streams vary over time. Some require more initial capital outlay, others less. But after a few years, the differences seem to disappear. We whine about how we always need to replace something and about how expensive the sensors and the scrubber etc. are. And still, hardly anyone has ever gone back to OC.. ;)
An update Alex. I just purchased a KISS Sidekick. For the reasons you explained, a CCR saves quite a lot of money on gases, especially helium, etc. in both OW and caves, but I chose the Sidekick because I prefer mCCR over eCCR. My preference, but I think it is safer, though if you don't monitor, all rebreathers can be more risky over OC. I am also almost always diving sidemount in OC, so I chose what I felt is a simple sidemount CCR. I looked into the SF2 sidemount, but the SK is smaller, though they are similar. It was a tough choice, but the SK, up front, is quite a bit less expensive to purchase. But, I think the SF2 is a great rebreather. Thanks again.
That is certainly a good choice of rebreather and of operating philosophy. MCCR requires more presence of mind, which hopefully translates into a higher safety margin. Enjoy your system, and many safe dives!
Hi Alexander - thanks for the high quality review. You should do some more vids!
For a guy that’s not an instructor you sure have plenty of good knowledge to share. 👍
Thanks for your video. Very informative. You are very well spoken and knowledgeable on a fairly new product. 👍
Thanks to share your experience. 👌
SF2 is an expedition rebreather. No CO2 monitoring. Pity they had to go to Shearwater and did not design their own elecs... that's a big commercial risk.
Fair point. CO2 monitoring would be good to have, unfortunately still not market ready, at least in this segment.
Re building your own elecs: I think they partly do. If the primary shearwater fails there’s always a secondary unit and manual ops that can bring you back to the surface before you need to bail out.
I seriously doubt that gas costs are a factor if you're not an instructor or other kind of professional diver. How many dives to 50m+ do you do each year? If you do your own fills it's about 25-35€ per simple dive depending on how much you pay for helium. An SF2, including training, it's about 10k€, and you still need some gas, scrubber, batteries and o2-sensors. I'm an active technical diver and could dive a couple of decades on OC for the price of going CCR with an SF2 unit. Most people buy rebreathers because of the cool-factor, some people actually need them for complex dives... gas costs is mostly irrelevant.
Hi, thanks for your comment! Gas costs are only one factor for me. Still, not a completely irrelevant one.
My personal operating minimums imply that I will use at least 21/35 for every dive between 30 and 45m and 18/45 between 45 and 60m. I do about 40-50 dives a year, and most are below 30m, i.e. I am on some sort of trimix on most of my dives.
Call me a gas hog, but I am currently only using 1/13th of the amount of gas compared to what I used while diving OC. A pro doing 150 of those dives a year might get the consumption down even more. As mentioned in the video, a lot of these gas savings are offset by the cost for scrubber, cell replacement and unit maintenance.
You are right that the cost savings alone do not justify rebreather diving. And yes, the coolness-factor can be quite a strong motivator. I do not remember denying that... ;)
Alex, this was very helpful. I am currently considering the SF2 and found a unit that I can use for both bm and sm. However, I own 2 KISS GEMS (am an instructor,) one for bm, one for sm or teaching (easy switch.) I paid less for these units than a rebreather diver will pay for two computers, though new, they are around $4,500 (I got both used VERY cheap from an instructor I trained with.) I only need one 02 sensor to monitor P02 as GEM is PSCR and everything is manual, though the ADV automatically adds Nitrox ever 3rd breath or so depending on your breathing. The GEM uses cartridges, and depending on your RMV, you will get up to between 4-6 hours on one cartridge, though it is highly recommended to stick with changing them out after 4 hours. I can use my setup with trimix and I hotplug all my gases into the unit. It is set for 3:1, but there are ways to get it far beyond that. The only drawback to the GEM is the chest mounted CLs, which are OK bm, but tricky sm. I like the idea of the SF2 with nothing on my chest. Yet, I am wondering if it is 1) worth moving to a full eCCR when I am mostly teaching sm rec. and beg. tech. up to 40 meters as the GEM is incredibly simple and therefore, safer and 2) is it worth the cost of not having chest CLs, but having to maintain and "feed" the beast more than I do with my GEM? One advantage of eCCRs is that PSCRs do allow gas to leave the loop, so it is not bubble free, and the GEM releases bubbles from the DSV, so I do see about 1/3 the bubbles I would in OC. But your presentation is making me think more about it - cost of unit/training/maintenance and setup. I do like the quickness and ease of OC, and I mostly dive sm, so don't have tanks on my back. Thanks for this explanation of your training!
Thank you for your comment, rabukan 58! It seems that you have figured (and configured) your GEM quite nicely. That usually makes for safe and fun operations.
I did for a few years consider moving from OC to an RB80 clone, to keep my DIR configuration. And then noticed that some hard-core PSCR RB80 divers started moving to ECCR. That made me reconsider it. I believe that the PSCR concept is very robust, and, with proper training, quite safe. Particularly if complemented by a PO2 monitor like in your GEM. Lucky us that George Irvine III is not active in these discussions anymore.. ;)
My key consideration when moving on to an SF2 from a GEM would be to compare them against your most common personal dive profiles regarding risk profile, the workload for normal/abnormal procedures, and gas logistics/cost. Which, I am sure you are doing already.
Maybe a bit philosophical: the discussion about the cost of various rebreather types and models appears to be less one about overall cost and more one about how the cost streams vary over time. Some require more initial capital outlay, others less. But after a few years, the differences seem to disappear. We whine about how we always need to replace something and about how expensive the sensors and the scrubber etc. are. And still, hardly anyone has ever gone back to OC.. ;)
An update Alex. I just purchased a KISS Sidekick. For the reasons you explained, a CCR saves quite a lot of money on gases, especially helium, etc. in both OW and caves, but I chose the Sidekick because I prefer mCCR over eCCR. My preference, but I think it is safer, though if you don't monitor, all rebreathers can be more risky over OC. I am also almost always diving sidemount in OC, so I chose what I felt is a simple sidemount CCR. I looked into the SF2 sidemount, but the SK is smaller, though they are similar. It was a tough choice, but the SK, up front, is quite a bit less expensive to purchase. But, I think the SF2 is a great rebreather. Thanks again.
That is certainly a good choice of rebreather and of operating philosophy. MCCR requires more presence of mind, which hopefully translates into a higher safety margin. Enjoy your system, and many safe dives!