Ascents while practicing shooting bags

[lamont]

If you shoot a bag and ascend at edmonds, and then drop back down and do a long u/w swim in, there's really no big deal in terms of deco, particularly on EAN32...

the biggest issue to be aware of is the currents, and you don't want to be floating under a bag and wind up under the ferry... that'd be bad.

other than that, any bubble shower you get on the ascent, you'll recompress when you go back down, and then you'll have a nice decompression from that with multiple passes through the lung filter to get the bubbles out... Particularly with EAN32 your EAD is pretty miniscule, so its probably easier on your system than the OW pool dives were when you got certified...

 

[GulfCoastdiver]

I am diving a shallow (<35 feet) dive site this afternoon with a longish (100 yards) surface swim to get to 15 feet of water. Usually, we surface swim out a ways, drop down, dive the site down to about 30-35 feet, then turn and work our way back up slope, and surface in the shallows to avoid the end of dive surface swim.

Here is the question:

I want to practice shooting my SMB this afternoon, the best place to do so is out in the middle of the dive at about 35 feet. I'd like to work on ascents as well, so I'd want to do a nice, slow ascent with appropriate stops.

Given the dive site, I see a few options, what I'm interested in is whether any one of them would be preferable in terms of dive profiles:

1) Modify the dive plan to shoot the bag out in 35 feet of water at the end of the dive, surface, then do a long surface swim.

2) Shoot the bag at what would be the middle of the dive, then drop back down and finish the dive.

3) Surface swim further out, drop down, do our skills regarding the bag work then finish the dive.

For what it is worth, the total dive time will probably be an hour or so on EAN 32 . . . average depth is, shallow, usually 20-25 feet.
-Doug

I was just wondering why EAN32? Why not 36 or 38? At 35' you can surface then drop back down with out a prob but, I wouldn't do it repetedly.

 

[Cacia]

If this is a Halcyon low pressure inflater style, you might find it difficult to add a tiny bit of air. Mine pretty much takes off before I get the hose detached....
I drag mine from 50ft on drifts like a dive float on many dives once I am seperated for any reason. I wind the cave line on the spool as I ascend. I really avoid bounces even when diving for the bouy (not more than once) because my computer goes nuts and I worry about losing track of my pressure group reality etc.

Plus Lamont has made me paranoid that there is more to it than I fully comprehend! Like venous recompression and shunts that put bubbles on the arterial side and such. I would like to offer a suggestion and that is to shoot your SMB on most dives even when not really needed. This allows you to stay tuned up, model safe practices for other divers, AND avoid boat traffic accidents on safety stops and ascents. I almost shoot mine on every dive even when it seems unneeded. This way, if my marker gets punctured or won't inflate, I am aware that is no longer functional. Boat captains tell me almost every week that they like the SMB's so much and they wish more people used them in the routine procedure of ocean ascents. I am convinced boat propellers are a bigger threat than sharks and many of the usual stuff we fret over.

For me, the "practice" part is actually developing the manual dexterity, bouyancy control, and ability to keep clear as the cave line unfurls rapidly and the spool spins on your "finger" spool. Adding small amounts of air just does not cause the bag to deploy in the same fashion...

 

[Ben_ca]

I was just wondering why EAN32? Why not 36 or 38? At 35' you can surface then drop back down with out a prob but, I wouldn't do it repetedly.

EAN 32 is a DIR standard mix.... makes figuring your EAD in your head a lot easier.

The key to SMB's is to have someone (preferably a DIRF Instructor) show you how it's done and then keep practiceing. Like most DIR guys just dedicate a portion of your dive to skills.... and then it will be no trouble at all.

 

[MXGratefulDiver]

The key to SMB's is to have someone (preferably a DIRF Instructor) show you how it's done and then keep practiceing. Like most DIR guys just dedicate a portion of your dive to skills.... and then it will be no trouble at all.

His AOW instructor already showed him ... then made him do it right ...

... Bob (Grateful Diver)

 

[rjack321]

Plus Lamont has made me paranoid that there is more to it than I fully comprehend! Like venous recompression and shunts that put bubbles on the arterial side and such.

Possible but at this site, with a max depth of 35ft you basically never saturate with N2 (dissolved). And if you do a reasonable ascent (3-4 mins), then N2 in the gas phase will have minimal bubble growth. I agree yo-yoing can be a problem but one or two yo-yos from 30ft (on 32%) then a long (10-12 mins) swim in shouldn't be a problem.

I also agree that Edmonds isn't such a great place for skills practice like this. Shooting a bag goes hand in hand with an ascent and Cove 1,2,3 is a better place for ascents overall. Still, mind the ferry traffic and use an upline if necessary (a 2nd bag tied to the bottom for horizontal control but providing no depth help).

 

[dsteding]

Everyone homed in on my concerns fairly quickly while I wasn't monitoring the thread, thanks for the responses, there is lots of good info here.

Observations/lessons:

1) Don't do this at Edmonds (local divers have pointed out why, and really, it isn't shooting a bag that is an issue, but the combo of wanting to practice at Edmonds, which, as I described in my first post is a rather gentle sloping shore dive with a long surface swim to get to any depth).

2) Do practice shooting bags regularly. As Bob mentioned, he taught me how in his AOW class, and it was one of the coolest things I've done in terms of skills. Call me weird, but I just plain like shooting bags--and can see the utility of the skill, especially up here in crappy viz and on boat dives when doing free ascents.

3) Lamont, your points about the shallow EAD and the effects of doing bounces (i.e., shooting bag and then ascending) are interesting. My original motivation for this post was precisely that issue. One the one hand, I'd have little N loading, and I'd be doing slow ascents, on the other hand, yo-yo profiles just generally get my hackles up. Thinking it through is an interesting exercise, I guess that is why I am a bit of a geek. Thanks for your input.

4) Consider other factors in doing skills. Lamont and rjack, you both mentioned the ferry traffic, when I am diving Edmonds I am always thinking about that (big boats with big props scare me big time). I'm always watching the current, but the ferries still bug me, even when I know where I am. For instance, I was on the south side of the park the other day, on jetty way, and that ferry came in so loud that I thought it was right above me. Even though I knew exactly where I was, I was still a bit freaked. Point being, my situational awareness goes down when shooting a bag, so your scenarios are something to consider . . . I could see losing track of the current while practicing, especially if something like a tangle took all my attention.

5) Catherine, your point about a shooting bag regularly is well taken. I'm integrating this into my dives, but I hadn't considered the practice as a way to not only keep the skills sharp but to check the functionality of your SMB. I'd agree about boats being a bigger threat than sharks, except for the fact that I saw a Great White eat a seal about 200 feet from me while I was in the water surfing. That memory makes it a toss up for me . . .

6) Lynne, we will dive as soon as our schedules allow, its my fault, I've been gone on the weekends, oh, wait, you were in Indo . . . nevermind . . . Scott, I swear, we will get a dive in soon, let me know when you have your doubles sorted out.

 

[TSandM]

You're not weird . . . I love shooting bags. There's just something incredibly FUN about inflating the thing and watching it take off.

It's been a VERY useful skill on some warm water resort-type diving, too . . .

 

[jagfish]

If this is a Halcyon low pressure inflater style, you might find it difficult to add a tiny bit of air. Mine pretty much takes off before I get the hose detached....

Hi Catherine
I believe the type of inflator you are talking about on that H SMB can be filled with either the low pressure hose, or by blowing orally. You can fine tune your air content much better with oral inflation...if the object is to fill minimally and pull back down.

 

[lamont]

3) Lamont, your points about the shallow EAD and the effects of doing bounces (i.e., shooting bag and then ascending) are interesting. My original motivation for this post was precisely that issue. One the one hand, I'd have little N loading, and I'd be doing slow ascents, on the other hand, yo-yo profiles just generally get my hackles up. Thinking it through is an interesting exercise, I guess that is why I am a bit of a geek. Thanks for your input.

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...