Sidemount Rebreather

[Jlukescuba]

Looking at getting into CCR later this year. So far I have narrowed it down to three rebreathers: Kiss Sidewinder, Divesoft Liberty Sidemount, and Kiss Sidekick. I am getting into technical diving / cave diving and am looking for a very versatile rebreather. I am also diving deep into underwater photography and videography as well as scientific diving since I am a Marine Biologist. I am looking for a rebreather that can be used in shallow and deep technical depths as well as in a variety of caves. I am stationed out of Florida right now but am due to move to the Caribbean and several other countries around the world so it needs to be travel friendly. Looking for input more specifically on kiss sidewinder vs liberty, thanks!

 

[grantctobin]

Looking at getting into CCR later this year. So far I have narrowed it down to three rebreathers: Kiss Sidewinder, Divesoft Liberty Sidemount, and Kiss Sidekick. I am getting into technical diving / cave diving and am looking for a very versatile rebreather. I am also diving deep into underwater photography and videography as well as scientific diving since I am a Marine Biologist. I am looking for a rebreather that can be used in shallow and deep technical depths as well as in a variety of caves. I am stationed out of Florida right now but am due to move to the Caribbean and several other countries around the world so it needs to be travel friendly. Looking for input more specifically on kiss sidewinder vs liberty, thanks!

Kind of a can of worms. I’d toss the Gemini on the list just to add to the difficulty of the decision.

All are cave functional and effective at the ranges you’re indicating. The Liberty and the Sidekick are more fussy about trim vs the sidewinder, and you lose an “onboard” bailout vs the Sidewinder or Gemini or Choptima etc. I think bringing a rebreather into a cave with your entire diluent and bailout constrained by a single first stage (or a single valve o-ring, though that one is a little more debatable) is silly. That is the “stock” config of the Sidekick or Flex without adding a sphere or additional onboard dil or a stage. Few hundred feet at a continuous depth with no bailout or dil? Doable but ****** and if you’re asking these questions you’re not yet in a position to evaluate that narrow issue. I’m of the belief you need two bottles. The Liberty at least allows a 2L onboard dil.

The difficulty with all of them is that they are inferior for deep boat diving vs their backmount equivalents. When you say “deep technical depths,” what do you mean? Are you expecting 200’? 300’? 400’? How much ability will you have to ship unit back to manufacture if it needs to go back for service or for repair? Do you expect to need to do so in the field? What is your current level of experience in overhead diving? Are you CCR trained? How important is it to you that others around you are using the same unit?

There’s a lot to unpack, but answers to these will help guide the argument.

Bias: some time on a sidekick, a lot of hours on a sidewinder, only surface experience with the Liberty, bought a Gemini

 

[tbone1004]

Responding here since your duplicate post in technical will likely get deleted by the Mods since they try to minimize duplicate postings.

First, if you are doing true Scientific Diving that is sanctioned you will likely be put on an AP Diving Inspiration so keep that in mind. Most of the university and gov't programs use them so just keep that in mind. It's not a bad rebreather but admittedly I only use one when I'm doing that type of diving with the university.

My primary rebreather is essentially a KISS Sidekick and you mentioned that so I'll talk about that first. This type of unit is incredibly versatile because it can be clipped off like a stage bottle with a single tank backmount rig, doubles, or sidemount. For some reason this started on the right side of the diver but for a myriad of reasons I have mine on the left and is what I typically recommend. Downsides are it does not have dil/O2 "onboard" like the Liberty though with a sphere/holder on the bottom it gets pretty close. It's a super simple rebreather concept and it works well for what it is. Parts are the frame/counterlung, canister, head, 2x loop hoses, DSV/BOV. Not a whole lot going on which is great. For normoxic boat diving you hop in with a set of doubles for bailout, this unit, and a 50% AL80 and you're good to go, deeper just adds extra deco bottles.
This unit is really sensitive to trim changes both in roll and pitch so if you're doing a lot of heads down stuff for survey work it's not ideal.

Next in line is the Liberty which is an infinitely more robust unit and is fully self contained. Again, it was technically designed to be used on the right but I much prefer it on the left and it also makes it usable with backmounted bailout. It does not use Shearwater electronics which is a putoff to some people and it is very complex in terms of not only the head but also the number of parts that have to go together to get it to work. Frame, canister, scrubber, lid, 2x elbows to counterlung, counterlung, loop hoses, dsv/bov. It's a lot, takes a lot longer to assemble, but you have the sled with the tanks on it which makes it fully self contained except for bailout. The biggest downside to this unit is it is BIG! I'm 6'3" and I would not want to be any smaller to dive this unit, it's a behemoth and can be a bit unwieldy if you are on the smaller size, cough @grantctobin cough!
Biggest advantage is the head is fully modular and fully redundant so if one module fails you can buy a replacement module and install it yourself vs. shipping the head back. The others don't have any electronics other than the isolation boards but if somethin goes wrong or you need a cable replaced you have to send it back to get it serviced which can prove irritating if you are out of the country.
The other potential advantage for the Liberty is that the canister and loop can be quickly and easily adapted to the backmount frame. Spend an $3k or so and you'll get the full backmount kit with the iBov, lungs, loop hoses, etc. so it can quickly go between the sidemount frame and the backmount frame. The "Liberty Heavy" is a boat diving machine for deep technical dives and is how my Meg is configured which is the unit I use when I'm on a boat.
Same concept as the Sidekick where you can treat it like the left side sidemount bottle or a stage and attach it to any backplate/wing setup for backmount or as the actual left side bottle in sidemount. If you aren't doing long cave penetrations you don't need to connect the bailout to the unit so it is truly self contained but if you are doing long cave dives you'll want them connected because 2l just isn't enough gas.
This unit has the lungs higher up on your body so it is less sensitive to pitch but is still very sensitive to roll.

Downside to either of the above rigs in their sidemount configuration is the loop hoses are under your arm and for working dives it can definitely feel like it is in the way compared to a rig with backmounted counterlungs.

Sidewinder/Gemini are the current cool kids on the block. Technically they can be used under a backplate/wing but the backplate really does need to be customized to handle it which limits its versatility a bit. Advantage though is that it isn't really a sidemount rebreather, it's a backmount rebreather that is really wide. This lets you have traditional loop routing and is the only one of the three that is really practical to use with a BOV. The others can have them adapted but it's really awkward. This is probably first on my list of the lot for cave diving but definitely last on the list for boat diving.
Locating the O2 for this unit is irritating. If you stay with sidemount configuration for bailout you can't really sit because the O2 bottle is underneath your butt and if you are diving it with doubles you have to stash the O2 bottle somewhere, typically where you would put a drysuit inflator bottle but then it's on the wrong side which isn't ideal.
This unit is not particularly sensitive to trim whether in pitch or roll because of the lung location, though all rebreathers are fairly pitch sensitive compared to OC.

 

[Jlukescuba]

Thank you so much for this extremely informative response! I‘ve had a hard time trying to get legitimate information on the listed systems and really appreciate you taking the time to respond and answer my questions. I will definitely keep your points in mind when it comes time to order my ccr. Another question I have for you is your thought process behind moving the sidekick and liberty to your left instead of the right?

 

[Jlukescuba]

Responding here since your duplicate post in technical will likely get deleted by the Mods since they try to minimize duplicate postings.

First, if you are doing true Scientific Diving that is sanctioned you will likely be put on an AP Diving Inspiration so keep that in mind. Most of the university and gov't programs use them so just keep that in mind. It's not a bad rebreather but admittedly I only use one when I'm doing that type of diving with the university.

My primary rebreather is essentially a KISS Sidekick and you mentioned that so I'll talk about that first. This type of unit is incredibly versatile because it can be clipped off like a stage bottle with a single tank backmount rig, doubles, or sidemount. For some reason this started on the right side of the diver but for a myriad of reasons I have mine on the left and is what I typically recommend. Downsides are it does not have dil/O2 "onboard" like the Liberty though with a sphere/holder on the bottom it gets pretty close. It's a super simple rebreather concept and it works well for what it is. Parts are the frame/counterlung, canister, head, 2x loop hoses, DSV/BOV. Not a whole lot going on which is great. For normoxic boat diving you hop in with a set of doubles for bailout, this unit, and a 50% AL80 and you're good to go, deeper just adds extra deco bottles.
This unit is really sensitive to trim changes both in roll and pitch so if you're doing a lot of heads down stuff for survey work it's not ideal.

Next in line is the Liberty which is an infinitely more robust unit and is fully self contained. Again, it was technically designed to be used on the right but I much prefer it on the left and it also makes it usable with backmounted bailout. It does not use Shearwater electronics which is a putoff to some people and it is very complex in terms of not only the head but also the number of parts that have to go together to get it to work. Frame, canister, scrubber, lid, 2x elbows to counterlung, counterlung, loop hoses, dsv/bov. It's a lot, takes a lot longer to assemble, but you have the sled with the tanks on it which makes it fully self contained except for bailout. The biggest downside to this unit is it is BIG! I'm 6'3" and I would not want to be any smaller to dive this unit, it's a behemoth and can be a bit unwieldy if you are on the smaller size, cough @grantctobin cough!
Biggest advantage is the head is fully modular and fully redundant so if one module fails you can buy a replacement module and install it yourself vs. shipping the head back. The others don't have any electronics other than the isolation boards but if somethin goes wrong or you need a cable replaced you have to send it back to get it serviced which can prove irritating if you are out of the country.
The other potential advantage for the Liberty is that the canister and loop can be quickly and easily adapted to the backmount frame. Spend an $3k or so and you'll get the full backmount kit with the iBov, lungs, loop hoses, etc. so it can quickly go between the sidemount frame and the backmount frame. The "Liberty Heavy" is a boat diving machine for deep technical dives and is how my Meg is configured which is the unit I use when I'm on a boat.
Same concept as the Sidekick where you can treat it like the left side sidemount bottle or a stage and attach it to any backplate/wing setup for backmount or as the actual left side bottle in sidemount. If you aren't doing long cave penetrations you don't need to connect the bailout to the unit so it is truly self contained but if you are doing long cave dives you'll want them connected because 2l just isn't enough gas.
This unit has the lungs higher up on your body so it is less sensitive to pitch but is still very sensitive to roll.

Downside to either of the above rigs in their sidemount configuration is the loop hoses are under your arm and for working dives it can definitely feel like it is in the way compared to a rig with backmounted counterlungs.

Sidewinder/Gemini are the current cool kids on the block. Technically they can be used under a backplate/wing but the backplate really does need to be customized to handle it which limits its versatility a bit. Advantage though is that it isn't really a sidemount rebreather, it's a backmount rebreather that is really wide. This lets you have traditional loop routing and is the only one of the three that is really practical to use with a BOV. The others can have them adapted but it's really awkward. This is probably first on my list of the lot for cave diving but definitely last on the list for boat diving.
Locating the O2 for this unit is irritating. If you stay with sidemount configuration for bailout you can't really sit because the O2 bottle is underneath your butt and if you are diving it with doubles you have to stash the O2 bottle somewhere, typically where you would put a drysuit inflator bottle but then it's on the wrong side which isn't ideal.
This unit is not particularly sensitive to trim whether in pitch or roll because of the lung location, though all rebreathers are fairly pitch sensitive compared to OC.

Another follow up question is your thoughts on the Liberty Computers. I am not necessarily turned off by the idea of them but I would like to hear your input on them especially when compared to the Shearwater computers.

 

[tbone1004]

Thank you so much for this extremely informative response! I‘ve had a hard time trying to get legitimate information on the listed systems and really appreciate you taking the time to respond and answer my questions. I will definitely keep your points in mind when it comes time to order my ccr. Another question I have for you is your thought process behind moving the sidekick and liberty to your left instead of the right?

For me the biggest thing is if it's on the right it makes it essentially incompatible with backmount bailout for the same reason stage/deco bottles are all on the left. Long hose gets trapped and that's not OK. It also can get in the prop wash and the loop hoses under your right armpit are somewhat limiting for right arm dexterity.
In sidemount configuration, at least with what is the most common hose configurations the right bottle is "yours" in an emergency and has the long hose where the left bottle is "mine" and is not considered donatable. If you have the unit on the right then donating a long hose has to come off of the left side and that's a big problem because crossing hoses is really not great for the guy receiving gas because it creates some wicked torque on the mouthpiece and shortens the effective length of the hose. You should never have to share gas with your buddy, but you never know when you're going to have to share with a rando and keeping it on the left minimizes the changes in gas donation techniques for both backmount and sidemount configurations.

I use a Divesoft Freedom on my Kisskat as well as my primary deco computer. Biggest thing is they don't have bluetooth to download dive logs. They also have a proprietary cable for charging/data transfer which is irritating and you can only transfer logs to a computer vs check on your phone like with a Shearwater. They're also not quite as user friendly from a UI perspective but functionally they're perfectly fine. The two of mine have done some serious dives.

 

[Jlukescuba]

Kind of a can of worms. I’d toss the Gemini on the list just to add to the difficulty of the decision.

All are cave functional and effective at the ranges you’re indicating. The Liberty and the Sidekick are more fussy about trim vs the sidewinder, and you lose an “onboard” bailout vs the Sidewinder or Gemini or Choptima etc. I think bringing a rebreather into a cave with your entire diluent and bailout constrained by a single first stage (or a single valve o-ring, though that one is a little more debatable) is silly. That is the “stock” config of the Sidekick or Flex without adding a sphere or additional onboard dil or a stage. Few hundred feet at a continuous depth with no bailout or dil? Doable but ****** and if you’re asking these questions you’re not yet in a position to evaluate that narrow issue. I’m of the belief you need two bottles. The Liberty at least allows a 2L onboard dil.

The difficulty with all of them is that they are inferior for deep boat diving vs their backmount equivalents. When you say “deep technical depths,” what do you mean? Are you expecting 200’? 300’? 400’? How much ability will you have to ship unit back to manufacture if it needs to go back for service or for repair? Do you expect to need to do so in the field? What is your current level of experience in overhead diving? Are you CCR trained? How important is it to you that others around you are using the same unit?

There’s a lot to unpack, but answers to these will help guide the argument.

Bias: some time on a sidekick, a lot of hours on a sidewinder, only surface experience with the Liberty, bought a Gemini

Thank you for your response and your “concerns“ lol. I did see that you can use the Liberty sidemount in an “off board“ configuration for those deep and longer cave penetrations. When regarding the deep technical dives, I plan on diving with a relative max of 300ft. I am looking at conducting deep coral research on reefs deeper than 140ft. Since I will be moving to and working in more remote areas, a unit that I can both work on it and send it out if I need to would be preferred. I plan on getting full cave certified this year after graduation as well as getting ccr certified. It is also not important to me if others around me are using different units. I know it may seem like I am rushing through but I am being very methodical about my approach and am open to input and suggestions. I am choosing this route instead of going to grad school so I am fully committed to this journey. Thank you again for your input!

 

[Jlukescuba]

For me the biggest thing is if it's on the right it makes it essentially incompatible with backmount bailout for the same reason stage/deco bottles are all on the left. Long hose gets trapped and that's not OK. It also can get in the prop wash and the loop hoses under your right armpit are somewhat limiting for right arm dexterity.
In sidemount configuration, at least with what is the most common hose configurations the right bottle is "yours" in an emergency and has the long hose where the left bottle is "mine" and is not considered donatable. If you have the unit on the right then donating a long hose has to come off of the left side and that's a big problem because crossing hoses is really not great for the guy receiving gas because it creates some wicked torque on the mouthpiece and shortens the effective length of the hose. You should never have to share gas with your buddy, but you never know when you're going to have to share with a rando and keeping it on the left minimizes the changes in gas donation techniques for both backmount and sidemount configurations.

I use a Divesoft Freedom on my Kisskat as well as my primary deco computer. Biggest thing is they don't have bluetooth to download dive logs. They also have a proprietary cable for charging/data transfer which is irritating and you can only transfer logs to a computer vs check on your phone like with a Shearwater. They're also not quite as user friendly from a UI perspective but functionally they're perfectly fine. The two of mine have done some serious dives.

Thank you again for taking the time to respond to my questions. I really appreciate your input on the matter.

 

[mr_v]

@tbone1004, somewhat related question about Liberty... Would you consider using it as a bailout rebreather in the standard sidemount config?

 

[tbone1004]

Thank you for your response and your “concerns“ lol. I did see that you can use the Liberty sidemount in an “off board“ configuration for those deep and longer cave penetrations. When regarding the deep technical dives, I plan on diving with a relative max of 300ft. I am looking at conducting deep coral research on reefs deeper than 140ft. Since I will be moving to and working in more remote areas, a unit that I can both work on it and send it out if I need to would be preferred. I plan on getting full cave certified this year after graduation as well as getting ccr certified. It is also not important to me if others around me are using different units. I know it may seem like I am rushing through but I am being very methodical about my approach and am open to input and suggestions. I am choosing this route instead of going to grad school so I am fully committed to this journey. Thank you again for your input!

You may want to check with whatever organization is funding/sanctioning this research because they often will dictate specific rebreathers that may or may not be used. I am not allowed to use anything but an AP Inspiration for all of the university funded work and many others are in the same boat so you may want to check on the requirements of the funding for the research.
Not sure what you mean by "off board" configuration but all of the units in question will easily accept off-board diluent addition, granted so will pretty much every CCR so there is that.

@tbone1004, somewhat related question about Liberty... Would you consider using it as a bailout rebreather in the standard sidemount config?

As a B/O breather I have no problem with the onboard Dil bottle but for a primary breather absolutely not. Also of note, you are a f*cking moron if you use the onboard bottles with a BOV. There is no more gentle word for it, using a BOV with an onboard 3l or heaven forbid 2l is just asking for a Darwin Award.