Question Dive planning exercise, please check my work

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!

Presumably they were worried about slow tissues on-gassing during ascent? E.g. 40 msw at 5m/min would take a whooping 8 minutes, so for compartments slower than 12.5 minutes it's probably safe to ignore.
 
Presumably they were worried about slow tissues on-gassing during ascent? ...
I never read the detailed primary source materials, myself. I was taught during my open water course (YMCA/NAUI, in 1986) that the U.S. Navy brought up their divers (salvage/repair divers wearing heavy gear) from air dives at an ascent rate of 60 fpm per the U.S. Navy Tables. This predated the use of these tables for SCUBA.

rx7diver
 
I never read the detailed primary source materials, myself. I was taught during my open water course (YMCA/NAUI, in 1986) that the U.S. Navy brought up their divers (salvage/repair divers wearing heavy gear) from air dives at an ascent rate of 60 fpm per the U.S. Navy Tables. This predated the use of these tables for SCUBA.

rx7diver
Well, either they were wrong or you misremember. The hard-hat divers were brought up at 25 ft/min, and the "new" scuba divers wanted to go 100 ft/min. The Navy only wanted one set of tables so they compromised on 60 ft/min for everybody. That is now 30 ft/min for everybody.
 
Nobody puts mooring blocks in at valuable dive sites?
No that is completely prohibited. 1) you'd need a permit from DNR (they own all submerged lands) and they aren't going to give you one, and 2) you'd kill all the waterskiers blasting around when they run into your buoy.

In the past they've been protected by anonymity, not publishing the numbers, the fact that most are nearly impossible to find from shore even with a scooter, and lastly depth. GUE Seattle has the NOAA data online now and Scott Boyd's book and website has a bunch of their numbers, but there's nobody to mentor newer divers in how to actually dive them. And most of the AN/DP instructors are fairly well clueless themselves. And the rare GUE T1 course isnt really teaching anyone the boat practical side of things. And no charters as role models either, they all went out of business since scooters became common.
 
Well, either they were wrong or you misremember. The hard-hat divers were brought up at 25 ft/min, and the "new" scuba divers wanted to go 100 ft/min. The Navy only wanted one set of tables so they compromised on 60 ft/min for everybody. That is now 30 ft/min for everybody.
Interesting. Do you have a source for this? I'll google when I have time.

rx7diver
 
The current Navy tables (Rev 7A) say nothing about ascent rates for NDL dives. The only statement is:
9-6.3
Ascent Rate. The ascent rate from the bottom to the first decompression stop,​
between decompression stops, and from the last decompression stop to the surface​
is 30 fsw/min (20 seconds per 10 fsw). Minor variations in the rate of ascent​
between 20 and 40 fsw/min are acceptable.​

Older versions of the Navy tables:
Rev 4 (1999): 30 ft/min
Rev 1 (1981): 60 ft/min

EDITED: 1981 was Rev 1, not Rev 2. See U.S. Navy Diving Manual - Wikipedia.
According the to attached reference, the US Navy ascent rate changed from 60 to 30 ft/min in 1993.
In 1993, the rate of ascent to the first decompression stop was changed in the US Navy Diving Manual from 60 fsw/min (18 msw/min) to 30 fsw/min (9 msw/min).​
 

Attachments

  • OH ch 17.pdf
    1.3 MB · Views: 79
Interesting. Do you have a source for this? I'll google when I have time.

rx7diver
See also this quote:
Because of the development of scuba apparatus in WWU, the tables were now made to include​
more appropriate depth increments, and the rate of ascent had been changed from the earlier 25 fsw/min to 60 fsw/min, where it has remained. The ascent rate was a compromise; Navy scuba divers wanted a rate of 100 fsw /min, but it was difficult to winch a tethered diver up at this rate, and the same rate had to be used by all Navy divers (Lanphier, 1990). The choice was a figure somewhat in between,​
the easy-to-calculate 60 fsw/min or I fsw/sec. Decompression "theory" did not enter into this choice.​
which is from page 15 of the 1994 DSAT report on the development of the RDP; that report is too big to attach here. It used to be available on Rubicon. I'd be happy to provide it to you on Dropbox if you want a copy.
 
I'd be happy to provide it to you on Dropbox if you want a copy.

Would you mind to also share it with me?

Thanks
 
page 15 of the 1994 DSAT report on the development of the RDP; that report is too big to attach here. It used to be available on Rubicon. I'd be happy to provide it to you on Dropbox if you want a copy.

Would you mind to also share it with me?
The DSAT Report on the RDP is now available in the ScubaBoard Download Library.
 
See also this quote:
Because of the development of scuba apparatus in WWU, the tables were now made to include​
more appropriate depth increments, and the rate of ascent had been changed from the earlier 25 fsw/min to 60 fsw/min, where it has remained. The ascent rate was a compromise; Navy scuba divers wanted a rate of 100 fsw /min, but it was difficult to winch a tethered diver up at this rate, and the same rate had to be used by all Navy divers (Lanphier, 1990). The choice was a figure somewhat in between,​
the easy-to-calculate 60 fsw/min or I fsw/sec. Decompression "theory" did not enter into this choice.​
which is from page 15 of the 1994 DSAT report on the development of the RDP; that report is too big to attach here. It used to be available on Rubicon. I'd be happy to provide it to you on Dropbox if you want a copy.
Additional info on Why 60 ft/min.
 

Attachments

  • Ascent Rates - Lanphier_OCR.pdf
    78.1 KB · Views: 75
https://www.shearwater.com/products/swift/

Back
Top Bottom