A few questions about SF

[Chun Zhou]

I am a beginner of SF2. I read a few RB books, SF2 website, and user manual but still have some questions about it.

1. I can check ext voltage from SW but what is the threshold to change it? Not like power indicator as a percentage.
2. How long does its absorbent duration? Any offical test report? I was told by my instructor that it is 3 hours.
3. Someone told me the world deep record is Mag and recommend that. However SF2 only allow to 100M on user manual, I also check JJ is 100M as well. I will definitely not go VERY deep. Just curious what if to 120 - 150m using SF2. Any issue and risk from a product(hardware) perspective?
4. It is very hard to detach the head and upper section(carbon fiber). Any tips?
5. Any stand or foundation available on the market for SF2? JJ, VMS, revo they all have a strong stand which SF2 don't. When diving outdoors, it is hard to keep it stand on the uneven ground. The 1st stages on two sides often kick the rock ... ...
6. My instructor told me ALWAYS COMPLETELY open OPV. Why not the design it just ON / OFF rather than a dry suit valve?

 

[michael-fisch]

1. Its a 9V battery when it drops below 8,5V it's shot.
2. Absorbant duration has a lot of variables;

 

[michael-fisch]

I am a beginner of SF2. I read a few RB books, SF2 website, and user manual but still have some questions about it.

1. I can check ext voltage from SW but what is the threshold to change it? Not like power indicator as a percentage.
2. How long does its absorbent duration? Any offical test report? I was told by my instructor that it is 3 hours.
3. Someone told me the world deep record is Mag and recommend that. However SF2 only allow to 100M on user manual, I also check JJ is 100M as well. I will definitely not go VERY deep. Just curious what if to 120 - 150m using SF2. Any issue and risk from a product(hardware) perspective?
4. It is very hard to detach the head and upper section(carbon fiber). Any tips?
5. Any stand or foundation available on the market for SF2? JJ, VMS, revo they all have a strong stand which SF2 don't. When diving outdoors, it is hard to keep it stand on the uneven ground. The 1st stages on two sides often kick the rock ... ...
6. My instructor told me ALWAYS COMPLETELY open OPV. Why not the design it just ON / OFF rather than a dry suit valve?

2nd try:

1. Its a 9V battery - when it drops below 8,5V it's shot.
2. Absorbant duration has a lot of variables; rate of CO2 absorbtion, rate of breathing, type of sorb, how high you fill the sorb cannester, sorb temperature, etc.
When I did tests on my cheap sorb I found I was getting around 6 hrs under the following conditions:
Water temp 7°C, Sorb cannester full of CD Grade sorb (the coarse stuff), depth 50M then I noticed my breathing rate had gone up noticeably - bailed out to OC bottom mix, ascended to 30M and went back on the CC which now at 30M worked fine for the rest of the dive as long as I didn't descend more than a few meters. Unless you have completely lost the ability to feel what your body is telling you and you don't suddenly have an extreme stress situation, a CO2 Hit starts slowly and if noticed early is easily managable. Flame is now on for all those who think they know better!
3. SF2 RBs are currently certified to 100M, probable due to the limits of the testing organisation. Mine has been deeper than 120M and I know several people who have regularly taken them deeper than 150M - they work.
4. I filed 2 wide but shallow screwdriver slots front and back into the top of my upper tube, about 20mm wide and 2,5mm deep. In order to loosen the head stick a very wide blade screwdriver into the slots and twist gently - head is now loose.
5. Get an extra long backplate, have a metalworking friend bend a piece of 15-18mm thickwalled stainless steel tubing 316SS or 1.4571 V4A with Titanium) to approx the width of your backplate at the backplate and the rounded width of the SF2. Spotweld it (just 2 tiny points) to the bottom of the backplate and now tilt it up slightly so that the backplate is tilted back about 25mm off the vertical. Now weld the tubing to the backplate properly. You now also have a place to put the argon bottle (I hope you are using a suit gas, because I have only done one dive using air in my SF2, learned my lesson and all other dives have had He in the mix).
6. I did that 2 or 3 times, used incredable amounts of diluent and never did it again, now the OPV is as closed as possible (still usable as a pisspoor waterdump since due to the design of the OPV it's impossibe to get the last cm of water out. I'd look at what the Shearwater controller lists for number of dives and hours on your instructors SF2 and draw my own conclusions - looks to me like another case of zero to hero.

7. After almost dieing due to inhaling a caustic cocktail at depth, operation, intensive care and over 3 months of rehab while being seen by a slew of medical specialists, I finally got their OKs to continue diving. Found I was now very susceptible to sorb dust and now use the filter sheets from JJ Scim kits in the top and bottom of my sorb cannester which has helped a lot. Do not dive with insufficient bailout gas!
8. 20" Cooper hoses and a Golem Gear DSV are a great improvement over the SF2 hoses and DSV.
9. Get a few extra QC4 plugs for your stage bottles, they have a habit of dieing.

Michael

 

[kensuf]

I am a beginner of SF2. I read a few RB books, SF2 website, and user manual but still have some questions about it.

1. I can check ext voltage from SW but what is the threshold to change it? Not like power indicator as a percentage.
2. How long does its absorbent duration? Any offical test report? I was told by my instructor that it is 3 hours.
3. Someone told me the world deep record is Mag and recommend that. However SF2 only allow to 100M on user manual, I also check JJ is 100M as well. I will definitely not go VERY deep. Just curious what if to 120 - 150m using SF2. Any issue and risk from a product(hardware) perspective?
4. It is very hard to detach the head and upper section(carbon fiber). Any tips?
5. Any stand or foundation available on the market for SF2? JJ, VMS, revo they all have a strong stand which SF2 don't. When diving outdoors, it is hard to keep it stand on the uneven ground. The 1st stages on two sides often kick the rock ... ...
6. My instructor told me ALWAYS COMPLETELY open OPV. Why not the design it just ON / OFF rather than a dry suit valve?

1. I replace the 9v battery whenever it's below 7.2v. The solenoid will keep firing to 6.8v (maybe lower), but I pre-emptively replace it at 7.2v. Some 9v batteries start out at 8.6 or 8.7, so swapping at 8.5 is unnecssarily wasteful.

2. 3 hours is the CE rated duration of the scrubber. Only you can decide if you want to push beyond that, if you decide you need to push beyond 3 hours on the scrubber you should consider your workload (working hard = more CO2 produced), water temperature (cold warmer reduces scrubber efficiency) and depth. Personally, I've pushed the scrubber well beyond that under "perfect" conditions (lots of resting while on deco in relatively warm water) but I would never consider pushing the scrubber beyond 6 hours, period. I would also always start a new scrubber whenever you're going deep (below 45m) or have already hit the CE limit on the scrubber. At the end of the day, a few $$ saved by stretching out absorbent beyond it's useful life is not worth the risks associated with hypercapnia.

3. I've had the SF2 to 110m and know some people that have been to 120-130m. I don't know anyone that's had one deeper. There is a lot of risks diving deep, period.

4. There's a lever that comes with newer SF2's that helps with detaching a head. ScubaForce USA has also been sourcing a different o-ring for the head over the past few months.

5. Huh? I don't think I understand. I've never had a problem like this.

6. I can't comment on the design specifics and why they chose a drysuit OPV, but hey, it works great.

 

[broncobowsher]

Most every real rebreather on the market has a 100M rating. Most will go deeper. Go deeper, you are on your own. Shy of imploding a battery or a computer there isn't really anything that puts a limit on them. Scrubber limits and how much gas you carry are about it. I think that it is a bit of a gentleman's agreement not to chase deep ratings. Add in a liability factor of someone taking a rebreather past its rated depth, you are on your own. "We never sol [that person who did it] a machine rated for that". The deepest CE rating is 100M. I am not expecting them to add anything to that.

 

[Chun Zhou]

1. I replace the 9v battery whenever it's below 7.2v. The solenoid will keep firing to 6.8v (maybe lower), but I pre-emptively replace it at 7.2v. Some 9v batteries start out at 8.6 or 8.7, so swapping at 8.5 is unnecssarily wasteful.

2. 3 hours is the CE rated duration of the scrubber. Only you can decide if you want to push beyond that, if you decide you need to push beyond 3 hours on the scrubber you should consider your workload (working hard = more CO2 produced), water temperature (cold warmer reduces scrubber efficiency) and depth. Personally, I've pushed the scrubber well beyond that under "perfect" conditions (lots of resting while on deco in relatively warm water) but I would never consider pushing the scrubber beyond 6 hours, period. I would also always start a new scrubber whenever you're going deep (below 45m) or have already hit the CE limit on the scrubber. At the end of the day, a few $$ saved by stretching out absorbent beyond it's useful life is not worth the risks associated with hypercapnia.

3. I've had the SF2 to 110m and know some people that have been to 120-130m. I don't know anyone that's had one deeper. There is a lot of risks diving deep, period.

4. There's a lever that comes with newer SF2's that helps with detaching a head. ScubaForce USA has also been sourcing a different o-ring for the head over the past few months.

5. Huh? I don't think I understand. I've never had a problem like this.

6. I can't comment on the design specifics and why they chose a drysuit OPV, but hey, it works great.

#1. Clear
#2. So 3 hours for CE test. The condition is 4 degree, 100M or 40M, 797 and moderate CO2 rate, right?I I know the duration is based on variables, just wonder the “boundary”. For example: I always use 797, always dive in the water warmer than 4 degree, always not deeper than the test condition, that means 3 hours is a guarantee.
#3. Clear
#4. Very interested in.
#6. Since it is a drysuit OPV. Will you like to fully open or close it?

 

[Chun Zhou]

2nd try:

1. Its a 9V battery - when it drops below 8,5V it's shot.
2. Absorbant duration has a lot of variables; rate of CO2 absorbtion, rate of breathing, type of sorb, how high you fill the sorb cannester, sorb temperature, etc.
When I did tests on my cheap sorb I found I was getting around 6 hrs under the following conditions:
Water temp 7°C, Sorb cannester full of CD Grade sorb (the coarse stuff), depth 50M then I noticed my breathing rate had gone up noticeably - bailed out to OC bottom mix, ascended to 30M and went back on the CC which now at 30M worked fine for the rest of the dive as long as I didn't descend more than a few meters. Unless you have completely lost the ability to feel what your body is telling you and you don't suddenly have an extreme stress situation, a CO2 Hit starts slowly and if noticed early is easily managable. Flame is now on for all those who think they know better!
3. SF2 RBs are currently certified to 100M, probable due to the limits of the testing organisation. Mine has been deeper than 120M and I know several people who have regularly taken them deeper than 150M - they work.
4. I filed 2 wide but shallow screwdriver slots front and back into the top of my upper tube, about 20mm wide and 2,5mm deep. In order to loosen the head stick a very wide blade screwdriver into the slots and twist gently - head is now loose.
5. Get an extra long backplate, have a metalworking friend bend a piece of 15-18mm thickwalled stainless steel tubing 316SS or 1.4571 V4A with Titanium) to approx the width of your backplate at the backplate and the rounded width of the SF2. Spotweld it (just 2 tiny points) to the bottom of the backplate and now tilt it up slightly so that the backplate is tilted back about 25mm off the vertical. Now weld the tubing to the backplate properly. You now also have a place to put the argon bottle (I hope you are using a suit gas, because I have only done one dive using air in my SF2, learned my lesson and all other dives have had He in the mix).
6. I did that 2 or 3 times, used incredable amounts of diluent and never did it again, now the OPV is as closed as possible (still usable as a pisspoor waterdump since due to the design of the OPV it's impossibe to get the last cm of water out. I'd look at what the Shearwater controller lists for number of dives and hours on your instructors SF2 and draw my own conclusions - looks to me like another case of zero to hero.

7. After almost dieing due to inhaling a caustic cocktail at depth, operation, intensive care and over 3 months of rehab while being seen by a slew of medical specialists, I finally got their OKs to continue diving. Found I was now very susceptible to sorb dust and now use the filter sheets from JJ Scim kits in the top and bottom of my sorb cannester which has helped a lot. Do not dive with insufficient bailout gas!
8. 20" Cooper hoses and a Golem Gear DSV are a great improvement over the SF2 hoses and DSV.
9. Get a few extra QC4 plugs for your stage bottles, they have a habit of dieing.

Michael

Thank you Mike, very detail comments.
#1. You think the threshold is 8.5 of 9 but seem other think it could be much lower to 7.2v
#2. The water temp where I often dive is down to 7 degree(higher than CE), I always use 797, always use new sorb for a deeper(>40m) dive, ... ... anyway, try to keep anything within the test condition to ensure 3 hours is safe.
#3. Clear
#4. I will try
#5. Wow, customized a stand. I need a craftsman friend. I hope someone can do and sale on market.
#6. I know the full open idea is for easier dewater but some friends told me my DPV often vent gas - they joke I have a bubble CCR. That why I doubt is it possible to close a bit but you surprised me that you like close as possible.
#7&8. Thanks for the reminder.
#9. What is extra QC4 plugs?

 

[rjack321]

#2. So 3 hours for CE test. The condition is 4 degree, 100M or 40M, 797 and moderate CO2 rate, right?I I know the duration is based on variables, just wonder the “boundary”. For example: I always use 797, always dive in the water warmer than 4 degree, always not deeper than the test condition, that means 3 hours is a guarantee.

There are multiple CE tests including 40m and 100m
40m is air dil, 4C, 1.6 liter per min co2. That is working quite hard, like navy swimmer hard. Nobody swims that hard for 3 hours. And there is no ascent, no resting. Typical semi leisure swimming pace for most of us is about 0.5 to 0.9 L per min O2 or (roughly) 35 to 65% of the workload of a CE test depending on conditions.

100m is 10/90 trimix, 4C, 1.6 L per min Co2, no ascent, no deco, just hard work at depth until breakthrough.

 

[kensuf]

#1. Clear
#2. So 3 hours for CE test. The condition is 4 degree, 100M or 40M, 797 and moderate CO2 rate, right?I I know the duration is based on variables, just wonder the “boundary”. For example: I always use 797, always dive in the water warmer than 4 degree, always not deeper than the test condition, that means 3 hours is a guarantee.
#3. Clear
#4. Very interested in.
#6. Since it is a drysuit OPV. Will you like to fully open or close it?

On #2, there's only two guarantees in life -- death and taxes. If you improperly pack your scrubber, if the sorb is a bad batch, you miss an o-ring, prolapse a mushroom valve, or any of a number of things, you could put yourself at risk of a CO2 hit.

#6 - close it all the way when I do my pos/neg tests and leave it closed until the dive is done.

 

[Pavao]

#4- I hold the MAV port on the counter lung and fingers inside loop hose port on the head, pull apart, the center section along with the head will come apart from lower section, then just hug the center section with 1 arm and break it apart from head

#6- I always dive it all the way closed.
Your later comments about bubbles always coming out from there is because too much gas on the loop, I was trained to dive minimal loop volume, and with that there is quite a ways to go before it’s full enough for a need to vent, I’m not experienced enough yet that it never happens, but it’s only a few times during a dive, when it does it’s a reminder I have too much gas in the loop