Ratio deco

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!

wrybosome

Contributor
Messages
5,125
Reaction score
496
Location
Philadelphia
# of dives
What is it and what does it look like when you use this method? Relying on your brain and being able to recalculate things on the fly sounds valuable

I haven't found any threads that do a good job describing what rd is and how it is done. Could someone give me the $0.25 explainer on this? Or just a link to some good materials. Thanks!
 
More or less, ratio deco is identifying trends in decompression and utilizing those trends to calculate your decompression. Often, it is combined with other things (such as a reshaping of the ascent curve) and utilization of the oxygen window.

You'll often hear of things like "1:1" and "setpoint". These terms refer to the baseline of the ratio. For instance, at 150ft on 21/35 (oxygen/helium percentage), there is a 1:1 ratio between bottom time and decompression time when using 50% oxygen as a deco gas. This ratio breaks down at a certain point, and is not the end all be all of deco. If the dive is deeper or shallower than the setpoint (1:1 at 150), the deco time is modified by simple rules of thumb that mirror what a decompression algorithm would put out. Different depths get different gases and different setpoints.

Oh course, there are assumptions that go along with this, such as standard gases, proper familiarization with the decompression theory, ability to do mathematics underwater, and most importantly, knowing WHY you're doing what you're doing.

Personally, I use ratio deco as a backup to some modified tables I made. Others use it as a primary source of deco information with great success, and others use it without being very successful.
 
You'll often hear of things like "1:1" and "setpoint". These terms refer to the baseline of the ratio. For instance, at 150ft on 21/35 (oxygen/helium percentage), there is a 1:1 ratio between bottom time and decompression time when using 50% oxygen as a deco gas. This ratio breaks down at a certain point, and is not the end all be all of deco. If the dive is deeper or shallower than the setpoint (1:1 at 150), the deco time is modified by simple rules of thumb that mirror what a decompression algorithm would put out. Different depths get different gases and different setpoints.

so you would use different baseline ratios for different depths and gas mixtures, then use rules of thumb to modify deco time? How do you what depths to do the stops at? I hope my questions aren't too stupid, just curious here.
 
https://www.shearwater.com/products/swift/
http://cavediveflorida.com/Rum_House.htm

Back
Top Bottom