How about this for ascent?

[sharpenu]

After reading an article on ascents (I don't remember where), I have changed my ascent profile.

For the last year, I have omitted the safety stop and moved to an ascent rate of 15 fpm. This makes an ascent from 75' last 5 minutes. According to the article, this is better than taking 2 minutes to ascend to 15 feet and the waiting there for 3 minutes.

What do you think?

 

[detroit diver]

sharpenu once bubbled...
After reading an article on ascents (I don't remember where), I have changed my ascent profile.

For the last year, I have omitted the safety stop and moved to an ascent rate of 15 fpm. This makes an ascent from 75' last 5 minutes. According to the article, this is better than taking 2 minutes to ascend to 15 feet and the waiting there for 3 minutes.

What do you think?

I'm not Dr. Deco, but I think you are not spending enough time at the lower ATA level (ie 40 ft and above) to properly offgas. I would get to the 40 foot stop at 30fpm and hold that for a minute, then 30fpm to 30 feet, hold 1 minute, then 30fpm to 20ft and hold 1 minute, and then 30 fpm to 10 ft and hold for 1 minute.

This gives the body circulatory sysytem time to utilize the lower ata's to offgas your nitrogen. You don't get the same offgassing at the lower depths.

I've stayed at a Holiday Inn Express.

 

[Charlie99]

sharpenu once bubbled...
For the last year, I have omitted the safety stop and moved to an ascent rate of 15 fpm. This makes an ascent from 75' last 5 minutes. According to the article, this is better than taking 2 minutes to ascend to 15 feet and the waiting there for 3 minutes.

What do you think?

This is a thread where the ascent rate of 8 feet per minute caused problems: Big Mistake

From the 75' range a better use of 5 minutes, IMHO, would be 30fpm ascent rate to 40 for a short stop of 1/2 minute or so, 25-30' for 1 minute, then 15' for 3 minutes.

I recommend you do some searches on "deep stop".

NAUI has now recommends a brief stop at 1/2 depth: Rule of halves thread

The relative merits of a slow, constant rate (linear) ascent compared to more rapid ascents with multiple stops was tested by Dan Europe. The results of this comparison, sometimes referred to as Hill vs. Haldane is at https://www.daneurope.org/eng/whatascent2.pdf

 

[Falcon99]

Charlie,

That is one of the most insightful documents I have read so far. It provides numbers and explanations to support stops over slow, linear, stop-skipping ascents.

Thanks for the link!!

James

 

[Charlie99]

The two profiles that really caught my attention were:

3m/min w/ 5 min stop at 6m, total ascent time of 13 minutes; vs the 18m/min ascent with 5 minute stops at both 15m and 6 m, which is a LOWER total ascent time of 11.5 minutes.

The 3m/min (10fpm) ascent has bubble score index average of 8.53. The 18m/min (60fpm) ascent had the much better BSI of 3.25. (BSI is simply the sum of two expanded Spencer Scores )

Using imperial terms, the good profiles added a 50' stop after a 82' dive for 25 minutes, 3-1/2hr SI, 82' 20 minute dive. The total ascent time was actually less than the 10fpm ascent with 5 minute 20' stop, since the ascent rate was 60fpm between stops. Contrary to what many would expect, the 60fpm with deep stop had much, much lower doppler bubbling.

I don't know why they chose to have 5 minute stops at both 50' and 20'. From my limited understanding of deco theory and prior testing, it would have made more sense to test somthing more like 2@50', 3@30', 5@15' if one wished to have 10 minutes total stops.

https://www.daneurope.org/eng/whatascent2.pdf

Charlie Allen