Recreational Ascent Rate in the last 15 feet

[rsingler]

Yeah, that's true of a lot of multi-day trips, so I figure "a dive's a dive" up to the safety stop, however you use your gas. No point in clear vis in not enjoying the sights at 20-30 feet when you can see your boat and all the folks hanging at their stop.
But I was truly impressed to see the "bloom" in GF from the safety stop up. Well, actually it started when I looked at my Perdix tissue map while hanging out at the stop, and then went, "WTH?!" when I happened to glance at it again just after surfacing.
Since then, and after pondering the issue, I'm starting to become a POV warrior for really slow ascents during the transition from 2 to 1 atm. Especially for multi day trips, no matter how shallow the dive was on day #4.

3 to 10 fpm is what I'm teaching my students now, for final ascent from 15 feet. We'll see if the agencies eventually climb on board. In any case, whether the students really understand it or not (and the ol' Coke can always helps), the drill has a side benefit of really developing their buoyancy control, given the volume change in their bcd's from 15-0 ft. That makes it a twofer, in my book.

If you ask me now, the correct answer for any rec dive after #1 is 10 fpm or less. The range line is now hot, ladies and gentlemen. Fire away...

(BTW, for the lurkers reading along with this thread, what is being advocated applies only to 0-15, or 0-30 feet. Ascending this slowly when deeper in the water will add to your gas loading in "slower" tissues, and is not helpful.)

 

[vam]

I figured I like to do 15fpm, but if I'm being real I often rush it at the end, so I voted 30fpm. Then I actually checked my logs, and it turns out I'm almost always much slower than 15fpm. I guess time flies when you're having fun.

 

[njdiverjoe]

Yeah, that's true of a lot of multi-day trips, so I figure "a dive's a dive" up to the safety stop, however you use your gas. No point in clear vis in not enjoying the sights at 20-30 feet when you can see your boat and all the folks hanging at their stop.
But I was truly impressed to see the "bloom" in GF from the safety stop up. Well, actually it started when I looked at my Perdix tissue map while hanging out at the stop, and then went, "WTH?!" when I happened to glance at it again just after surfacing.
Since then, and after pondering the issue, I'm starting to become a POV warrior for really slow ascents during the transition from 2 to 1 atm. Especially for multi day trips, no matter how shallow the dive was on day #4.

3 to 10 fpm is what I'm teaching my students now, for final ascent from 15 feet. We'll see if the agencies eventually climb on board. In any case, whether the students really understand it or not (and the ol' Coke can always helps), the drill has a side benefit of really developing their buoyancy control, given the volume change in their bcd's from 15-0 ft. That makes it a twofer, in my book.

If you ask me now, the correct answer for any rec dive after #1 is 10 fpm or less. The range line is now hot, ladies and gentlemen. Fire away...

I'm a big fan of slow ascents from 15 to the surface and on dives with decent amounts of deco I'll add a stop somewhere between 5-10 feet if conditions allow. The time at the stop allows some time for the blood to make a full circulation.

 

[johndiver999]

As a practical matter, a super slow ascent rate from shallow is not always beneficial.

For example, if it is rough, on an anchor line ascent, trying to hang on from a depth of 8 ft is just going to get you beat to hell and thrashed around. Also for a drift dive, with a live boat, I don't like being submerged at a very shallow depth where I am vulnerable to being hit by a boat. So from a depth of 5-8 feet maybe, I am not often going to be hanging out unless the conditions are very benign.
.

 

[MaxBottomtime]

For the majority of my dives, I spend a long time between fifteen feet and the surface going through the photos I took during the dive. This ascent took twelve minutes from fifteen feet. I'm never in a hurry to surface unless I'm really cold. If I am cold, I usually make a five minute safety stop, then slowly shiver my way to the surface.

 

[dmaziuk]

But I was truly impressed to see the "bloom" in GF from the safety stop up. Well, actually it started when I looked at my Perdix tissue map while hanging out at the stop, and then went, "WTH?!" when I happened to glance at it again just after surfacing.

The way I see it, you can lose only half of the gas loading in the 5-minute compartment on the way from 70-ish feet to SS. Other TCs - even less than that. So all remaining off-gassing will happen at or above SS, that's how the model works for no-stop diving.

I'm not arguing ascent rates, I'm all for shallower = slower. I'm just not convinced that when the model designed for yes-stop diving shows a "bump" near a boundary condition on a no-stop dive, that bump is as meaningful as it looks.

 

[njdiverjoe]

As a practical matter, a super slow ascent rate from shallow is not always beneficial.

For example, if it is rough, on an anchor line ascent, trying to hang on from a depth of 8 ft is just going to get you beat to hell and thrashed around. Also for a drift dive, with a live boat, I don't like being submerged at a very shallow depth where I am vulnerable to being hit by a boat. So from a depth of 5-8 feet maybe, I am not often going to be hanging out unless the conditions are very benign.
.

Agreed on the points about getting hit by a boat. For not getting beat up you can always let go of the anchor line.

 

[rsingler]

I'm just not convinced that when the model designed for yes-stop diving shows a "bump" near a boundary condition on a no-stop dive, that bump is as meaningful as it looks.

No argument there. But when things shift from "predominantly" ongassing to offgassing, ya gotta pick somewhere to start. For me, a 20 ft deco stop or 15 ft safety stop is as good a place on the spectrum as any. Concur that there's no physiological "place" where things change, given the multiple theoretical compartments involved.

Seeing the rise in GF Lo's in the tec community over the last while, it's apparent that we can get up there a ways (at a reasonable ascent rate) before things begin to change (unless you're a deep stop guy, but let's not go there, in this thread).

 

[dmaziuk]

No argument there. But when things shift from "predominantly" ongassing to offgassing, ya gotta pick somewhere to start. For me, a 20 ft deco stop or 15 ft safety stop is as good a place on the spectrum as any.

I'm partial to no-limit depth myself, perhaps rounded down to Haldane's original 10 m, even. I.e. where I can't by definition on-gas to the point of hitting M0 upon surfacing.

 

[mi000ke]

I do mostly boat diving, and to "bake in" the slow ascent from safety stop so I don't have to pay too much attention I do my safety stop at 15' about 20 yards off the end or to the side of the boat, then slowly make my way to the ladder and hang out at about 5 feet letting others go up or just waiting a few minutes, then surfacing. It probably averages to less than 15 fpm. Plus it gives me a chance to breath down my tank safely while still looking around at the marine life.