Where should I start to approach the rebreather world

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

Joining is quick and easy. Log in or Register now!

tbone1004

Technical Instructor
ScubaBoard Supporter
Scuba instructor
Messages
19,043
Reaction score
11,659
Location
Greenville, South Carolina, United States
# of dives
I'm a Fish!
Don’t act like you got my joke the first time. I know the truth!
the scary part of it is I'm actually about to buy a Tres Presidente so have been doing a bunch of in depth digging on the RB-80/RBK. Can't justify spending 2.5x for the RBK over the 3P, but it's a sexy little unit
 

rsingler

Scuba Instructor, Tinkerer in Brass
Staff member
ScubaBoard Sponsor
Messages
6,188
Reaction score
8,243
Location
Napa, California
# of dives
500 - 999
Reasoning: according to the scrubber monitor I always get well over 3h30 out of the top scrubber.
And to me, this is the crux of the problem in this silly debate. This is a very dangerous thought to propagate. What it implies, but doesn't state, is that two of these half-sized sorb canisters could therefore give you 7 hours of diving. Of course, that is very unlikely in anything but the warmest of shallow water dives (low gas density/max efficiency) of low physical effort.
To state the obvious, the downstream canister is not virgin sorb after this dive, and I would dispute a claim that rotating this canister to the top for the next dive would give you another 3h30m, simply because while the rMS may be indicating a depletion front, it is certainly not indicating a transition point to absolutely fresh sorb. How do we know this? The Revo itself shows that the difference between RST and RCT is not two to one, but only an extra fraction of an identical can of sorb. Part of that absence of a doubled RST is conservatism on Revo's part. But part of it is a recognition that there is probably a small amount of CO2 extraction that is going on in the downstream canister. Otherwise you'd only need one.
A single 5" high axial scrubber? Uh, no thank you.
 

Degenerate

Contributor
Messages
565
Reaction score
450
Location
EU
Why 50mins?

I've a couple of 40 min BT 60+m dives on sequential days where only one of the two scrubbers was replaced. Runtime 2h for one and 2h15 for the other.

Obviously increasing the dive by another 10 mins results in 20+ mins of additional deco (playing that through MultiDeco shows it to be another 40 mins runtime.

So, reality was one of two scrubbers replaced for each dive (total lime is 1.3kg x2)

Theoretical 3h dive you're talking about is... one of two scrubbers replaced for each dive. Reasoning: according to the scrubber monitor I always get well over 3h30 out of the top scrubber.

May I posit that you would replace all your scrubber after the first dive and all your scrubber after the second? Or is yours going to last a total of 6 hours?
I would not replace my scrubber after the first dive, I would absolutely use the same sorb for dive #2.
You are not saving anything on sorb in this scenario.

When did bragging how many dives you can do on a scrubber become the new chest thumping? Who gives a sh-t? Sorb is cheap, dump the sh-t after a dive or save it if it's got life. No need to argue and fuss over it and use it as a measure of the length of your d-ck. Feels like when you're on an OW boat and a dude in an al80 and a dude in a steel 130 compare how much gas they came back with, but are too stupid to realize they're diving two different volumes to start.
Using RMS to be able to strecth your sorb is not a selling point for the Revo. It's superceded by the fact that sadly you're diving a Revo.
It's not about banging your chest, and it's not about saving money either.
It's about someone making claims that are laughable and straight up wrong.
Yes, sorb is cheap as chips but posting straight up lies to feel better about diving a specific unit is not really okay.
It is pretty funny though, and I hope Wibble will continue to rave about his magically powered unit.
 

Valyngar

Contributor
Messages
218
Reaction score
98
Location
Finland
# of dives
200 - 499
the scary part of it is I'm actually about to buy a Tres Presidente so have been doing a bunch of in depth digging on the RB-80/RBK. Can't justify spending 2.5x for the RBK over the 3P, but it's a sexy little unit
Having seen it live, it's horrible mammoth. Unit was with double 12l. Probably weighted like 60 kg. JJ ccr like small compared to it.
 

broncobowsher

Contributor
Messages
2,297
Reaction score
1,779
Location
Arizona
Revo twin scrubber benefit/cost savings.

Go dive and burn up 60% of your scrubber. Don't care how you do it, just do it.
No do that same dive again.

Normal single scrubber rebreather you have to dump and repack. Toss 40% of good material.
rEvo you toss the one scrubber filled (50% of total) and refill, second scrubber only have 10% used up, is still usable. You have 90% of your available scrubber capacity.

That is how you can avoid tossing so much sorb with a rEvo. Does it always work that way? NO! It doesn't. But it works close enough to that. If you are just doing a bunch of screwing around diving, couple hours in a day/weekend, you just toss a scrubber and cycle the other in. Next time out you are at 100%. None of this counting up the stack time, it's rated for 3½ and I have 1½ hours on it, what will my next dive be next weekend? Will it just be another 1½ quick weekend or will I find a seat on a boat at the last minute for that cool 2½ dive I have been trying to get on for weeks? Crap, now I have to dump the scrubber and start fresh. rEvo, you just have usable scrubber for the next weekend.

If you can't understand that, please don't dive with me. It is a very simple concept. It works well. That is all before you get into (ab)using the results of a temp stick/RMS to get even more life out of a scrubber.
 

Rol diy

Contributor
Messages
390
Reaction score
229
Location
Ont
Never dove a revo... but always liked the double scrubber design... don't like the dewatering issues...
What seems to be 2 scrubbers is really 1 scrubber that splits in half
Some one said its 5inchs tall.. its really 10inchs tall 2 PC scrubber.
All that's really happening is you are using up the sorb that you can't use in a normal scrubber because it might be breaking though,
the reaction front it not flat, it pointy..
( I hope everyone knows this) ...
so now you get to use up the sorb that on the sides which you wouldn't do on a normal scrubber, because there is another good half scrubber after it...

I am a bit surprised that no one has modified an axial scrubber that can get loaded form both ends with a dividing plate in the middle... dump incoming side, reload, put it in backwards....

When I get to my ultimate homebuilt rebreather it will have double scrubber stackable, but with a twist,
 
https://www.shearwater.com/products/perdix-ai/

Top Bottom