Ascents while practicing shooting bags

[TSandM]

Yes, Edmonds is a great place to challenge yourself with skills if you stick to the shallows . . . of course, by some standards, it's ALL shallow.

 

[dsteding]

Well, you can still do this safely. The way to do it though is not to yo-yo. Go do a dive around the park, then shoot a bag and surface with a slow ascent. Then drop and ascend up the contour where you'll probably do 15+ minutes of deco going from ~20-35 up to 5-10... That's more than enough time for any possible free-phase badness caused by surfacing would be compressed and filtered through the lungs and then the pressure would come off gradually...

What wouldn't be as good would be to go on a dive and then come back and start yo-yoing up and down with multiple attempts to shoot the bag and do ascent drills... Still at EUP with EAN32, this wouldn't be guaranteed to get you hurt (OW SI often do this with CESA drills with their students and only very occasionally do they get bent) but its something to avoid...

And I've done skills dives at EUP where we only went down to around 10-15 fsw and filmed ourselves doing backkicks and bag shooting and stuff (and on this contour if you get blown south you'll wind up hitting the dock, which may get you a ticket, but you won't get tangled up with ferry props). I think we did this first, and then for the second dive went on a fun dive. The good thing about doing the skills dive at EUP was that we had tons of ambient to film ourselves, and the 10 foot depth mades all the buoyancy skills actually harder.

Actually I should have some short film clips of me from that session at EUP that I could put up on my website again...

I see what you are saying, basically shoot the bag at 30 feet, do a slow ascent, the descend and do the usual upslope ascent. I agree, yo-yo'ing is what I was trying to avoid, even those instructors practicing CESAs sorta freak me out.

I also agree on the shallow skills practice, always good stuff. Can you post your website link? I imagine that is an interesting site to check out.

 

[SparticleBrane]

even those instructors practicing CESAs sorta freak me out

Just curious--why? I'm of the understanding that you can be that deep for an essentially infinite amount of time, immediately surface, and be fine. Thus if someone were on scuba for ~10 minutes and then did a CESA from 15ft, it's highly unlikely (however, possible) that they'd get DCS...even if they did it multiple times.
edit: I'm not advocating this, of course...just going about it hypothetically.

 

[dsteding]

Just curious--why? I'm of the understanding that you can be that deep for an essentially infinite amount of time, immediately surface, and be fine. Thus if someone were on scuba for ~10 minutes and then did a CESA from 15ft, it's highly unlikely (however, possible) that they'd get DCS...even if they did it multiple times.
edit: I'm not advocating this, of course...just going about it hypothetically.

Perhaps I need to clarify my point: My comment about CESAs was more along the line of multiple CESAs in one day, particularly multiple ascents from say 20 feet at a relatively fast rate (I consider 60 fpm--or the "no faster than your bubbles" a fast rate).

Personally, if a DM chooses to do such things, then that is what they choose. I know what you mean in terms of nitrogen loading at that depth, and the low probability for DCS.

For my personal dive planning, I am going to avoid yo-yo profiles like what we are discussing. I know that faster ascent rates (some experience from my early dives) lead to generally not feeling as well after a dive. I am somewhat extrapolating from that personal experience to not want to do yo-yo profiles--i.e., multiple ascents on one dive, even with slower ascents. The repeated change in pressures, even with low nitrogen loading, is something I think I'll avoid.

Full blown DCS? Agreed that is probably not likely under such conditions. Feeling like crap and raising the posibility of DCS for no good reason? Maybe. This is why I wanted to bounce my ideas off of this particular forum instead of simply going out and blindly practicing say, five bag shots and ascents from 30 feet.

 

[SparticleBrane]

I completely understand...

 

[lamont]

Just curious--why? I'm of the understanding that you can be that deep for an essentially infinite amount of time, immediately surface, and be fine. Thus if someone were on scuba for ~10 minutes and then did a CESA from 15ft, it's highly unlikely (however, possible) that they'd get DCS...even if they did it multiple times.
edit: I'm not advocating this, of course...just going about it hypothetically.

I don't know that we've really got valid physiological models of what happens we we yo-yo really badly like an OWSI doing CESAs all day with a huge class...

I just get mental images of a soda bottle being shook up...

 

[TSandM]

You know, at bottom it comes down to a risk-benefit ratio. Is there a lot of risk from doing an ascent and subsequent descent at Edmonds? No. Is it avoidable? Yes. I think it would be considered DIR to avoid avoidable risk.

You can do the same exercise by shooting the bag at the end of a Cove 2 dive and doing your ascent up the line, without the yo-yo effect. Or, you could keep the entire dive so shallow that yo-yo-ing is probably harmless (which I have done, both at Edmonds and Cove 2, as ascent drills remain a challenge). Both are legitimate options.

 

[dsteding]

You know, at bottom it comes down to a risk-benefit ratio. Is there a lot of risk from doing an ascent and subsequent descent at Edmonds? No. Is it avoidable? Yes. I think it would be considered DIR to avoid avoidable risk.

Yup, agreed.

Lamont-nice mental image regarding the soda bottle.

 

[lamont]

Yup, agreed.

Lamont-nice mental image regarding the soda bottle.

Yeah, to clarify, tough, I think there are some things which are reasonbly safe. Doing a normal ascent at edmonds and then dropping back down and swimming upslope for 10-20 minutes is going to be fine. You are going to enough deco there for something like a 40 min dive at 100 fsw after you go back down. Any bubbles will get crushed and filtered and be fine.

Also, swimming out to the can buoy in cove 2 and doing 1 min stops to 40 and then back up should be okay because you're not giving yourself any time for gas loading to occur and you're taking off the pressure at a 10 fpm rate. You can then do a dive afterwards down to the I-beams and you'll just crush all the bubbles and filter them out and clean up nicely if you spend 15 mins coming up from the honey bear.

Doing the ascent/descent drills *after* a dive where you've gotten gas loading (even EAN32 at 35 fsw) I don't think is wise because of the soda bottle.

Also, doing something like toxing or unconscious diver drills is best done with no prior gas loading at ~10-20 fsw because you'll likely be doing some rapid ascents (and I'd take some EAN along for added insurance)...

 

[MXGratefulDiver]

I don't know that we've really got valid physiological models of what happens we we yo-yo really badly like an OWSI doing CESAs all day with a huge class...

I just get mental images of a soda bottle being shook up...

There's a reason why we do the CESAs at the beginning of the day's first dive ... the soda's still flat ...

... Bob (Grateful Diver)