I need your help. DSMBs, what are people's questions/concerns/etc.?

[Rob9876]

P.S.: And just to clarify, I have not tried this multiple times. Once I started falling and slipping on the slippery platform I decided that it was probably better to practice these drills another time with a buddy present, rather than (as I was) solo and the last diver left at the quarry for the day (I know, brilliant).

 

[mattfish]

I'm sorry, but I am not understanding this question. I edited your comment here as I think you missed a couple letters. Please correct me if I was wrong to do so.

Yes I missed the DS of DSMB there. Thanks. That first question was about how you would hook the end of the cord to the double-ender that you then clip to the spool through a hole, then clip the other end to a D-ring. And when the buoy is deployed and at the surface, how would you clip the line and the spool again so that you could let go and the spool wouldn't drop to the depths and unwind on the way down.

It would be great to see details of how to manage that.

We all agree that a DSMB should be full at the surface. I stole the idea of marking a DSMB for various depths that correspond to atmospheric pressure: so 1/2 from the top would be 10 m/33 ft, 2/3 from the top would be 20 m/66 ft, 1/4 from the top 30 m/100 feet

That is pure genius!!!!! I am going to go measure and mark my DSMB right now.

 

[wetb4igetinthewater]

Yes I missed the DS of DSMB there. Thanks. That first question was about how you would hook the end of the cord to the double-ender that you then clip to the spool through a hole, then clip the other end to a D-ring. And when the buoy is deployed and at the surface, how would you clip the line and the spool again so that you could let go and the spool wouldn't drop to the depths and unwind on the way down.

It would be great to see details of how to manage that.

Okay, I think I understand, and I'll reach out to you to you with that section to ensure that I have addressed it properly.

 

[admikar]

While marking is no harm, I try to fill it as much as possible regardless of depth. It has OPV, so can't burst and I don't want to hold it any longer than neccessary.

 

[SlugLife]

(I haven't read beyond the first post yet) What I'd look for from a DSMB document, is an adequate step-by-step guide, from start-to-finish, that would allow an average AOW diver to reliably deploy a DSMB without too much fuss, and without paying for a class. It doesn't have to cover everything, but rather just enough to become competent and reliable.

• Choosing a DSMB (size, features, etc)
• Choosing a spool/reel. Pros and cons.
• Setting up a spool/reel for easier deployment.
• Options for stowing a spool/reel on your BCD/pockets/etc.
• Ordered step-by-step for deploying from unclipping/retrieving spool and DSMB, until you're sitting there at the safety stop.
• Ascending, and re-spooling your reel.
• A trouble-shooting and FAQ section (i.e. "My finger-reel gets tangled!" or "How full should it be before I release?")
• Bonus tips section, including things like (a) Using the DSMB as redundant bouyancy under water and (b) Using the DSMB on the surface like a pool-noodle for stability and redundant surface-flotation (c) marking a DSMB at half, 2/3rds, etc.

 

[SlugLife]

I believe the idea is that a controlled ascent with a DSMB as BC would be difficult. you would have to vent air on the way up, and if you ever overshot on venting, add air. If the DSMB is full on the surface, you have complete control of your ascent rate while reeling yourself up.

It's not that bad, I've done it but only once. Just take your time. First establish relatively neutral buoyancy, then slowly ascend and dump air. I haven't experimented with whether it's better to tuck under your arms, or go length-wise, but I'd suggest front-to-back. You should only add air at the beginning, and for minor-to-moderate bouyancy changes, use finning, not constant fussing with adding or removing air. If you're negative, swim up until your neutral, then positive, then dump a tiny bit of air at a time. If you're positive, fin downwards direction a little, and dump a little air, until you're slightly negative.

I'd generally say you're better off being a little negative when doing this technique while ascending.

I think laying parallel on top of one’s DSMB with inflator valve in one hand for positive control and the other hand free to burp the OPV toggle is a better technique for using a DSMB as redundant buoyancy.

A longer DSMB has the advantage of being long enough for the upper end of the DSMB to pass under the groin and extend up a little bit. Make sure to squeeze some air into that end. This helps keep the DSMB properly positioned.

Laying across it like a pool noodle seems like a bad idea.

I haven't experimented much with it, but this seems correct for ascending. Having the DSMB front-to-back will give you easier access to the dump. Side-to-side would cause air-trapping and trim issues.

On the surface though, using it like a pool-noodle is great, and I've done that dozens of times.

 

[SlugLife]

I'm definitely familiar with the balanced rig concept. I'm also often overweighted -- especially in cold water. Here's are a few reasons why: (1) my body weight tends to go up and down, changing the amount of weight I need (wish it didn't, but that's reality); (2) my dives tend to alternate willy nilly between warm saltwater to cold (for me) thermoclines in freshwater quarries, so I'm often not in the same conditions, same kit, etc. consistently to fully dial in my weighting; (3) sometimes diving with newer divers I like to have a little extra weight in case I need to help them hold a safety stop also. Ultimately, I don't think I'm usually too far off from optimal weighting, but I do err on this side of overweighting for reasons stated to avoid popping up.

I don't know how much you over-weight, but hanging out in the Accidents-and-Incidents section, there are numerous fatal accidents where the diver being over-weighted is a noticeable contributing factor to the accident itself, or preventing a successful rescue. For changes like salt/fresh water, I'd suggest putting the extra weights on a weight-belt or easily-accessed ditchable pocket.

 

[Rob9876]

I don't know how much you over-weight

Not much, probably 0 to 4 lbs. Less than what I have in 1 of my 2 ditchable weight pockets.

 

[BRT]

Yes I missed the DS of DSMB there. Thanks. That first question was about how you would hook the end of the cord to the double-ender that you then clip to the spool through a hole, then clip the other end to a D-ring. And when the buoy is deployed and at the surface, how would you clip the line and the spool again so that you could let go and the spool wouldn't drop to the depths and unwind on the way down.

It would be great to see details of how to manage that.

That is pure genius!!!!! I am going to go measure and mark my DSMB right now.

Yes I missed the DS of DSMB there. Thanks. That first question was about how you would hook the end of the cord to the double-ender that you then clip to the spool through a hole, then clip the other end to a D-ring. And when the buoy is deployed and at the surface, how would you clip the line and the spool again so that you could let go and the spool wouldn't drop to the depths and unwind on the way down.

It would be great to see details of how to manage that.

That is pure genius!!!!! I am going to go measure and mark my DSMB right now.

How will you hold it down at 30' while it approaches half full?

 

[wetb4igetinthewater]

I think laying parallel on top of one’s DSMB with inflator valve in one hand for positive control and the other hand free to burp the OPV toggle is a better technique for using a DSMB as redundant buoyancy.

A longer DSMB has the advantage of being long enough for the upper end of the DSMB to pass under the groin and extend up a little bit. Make sure to squeeze some air into that end. This helps keep the DSMB properly positioned.

Laying across it like a pool noodle seems like a bad idea.

My response here is a bit late, but I'm having some trouble with this. If I understand correctly, a longer DSMB is straddled, correct? So for a not full DSMB, this is going to result in the lowest point (crotch) to have no gas, and some gas at both ends, only one of which has an OPV. As you dump gas from the front (I'm assuming you have this part of the DSMB in front of you), how are you to manage the expanding gas in the part of the DSMB that is behind your back?

Does my question make sense?