Deploying DSMB

[David Martin]

Originally Posted by Digger

...add some more air depending on depth. If you're miles down, just put in a bit to get it on its way. If you're at 6m, you're going to need to fire in a fair bit to get it full at the surface.

A totally full DSMB is slightly, but not that much more visible than a part-inflated one. I used to try to fully inflate the DSMB each time, until Andy Kerslake asked me "why?" on Fundamentals.

If using a "fill by demand valve" DSMB, I'd add the air slowly, and stop before it gets more than you can keep down by swimming down/breathing out. This let's you check everything is squared away just prior to release, rather than filling the DSMB quite full, and needing to hope that nothing's caught. This would be unlikely to leave it full at the surface, but makes for a safer deployment.

I now use the small closed circuit Halcyon DSMB. This is approx 3L? volume. It's so easy to fill by exhaling into the valve, that I don't bother to use the direct feed. A good breath as shallow as 3m will have the DSMB fully inflated at the surface. They are about 1/2 the width of a standard DSMB, and about 3ft long. I know a couple of others with these DSMBs, and we've never had problems with surface cover spotting/tracking them.

David

[Dominic]

I used to try to fully inflate the DSMB each time, until Andy Kerslake asked me "why?" on Fundamentals.

Because most dSMBs rely on internal pressure to seal the end..?

I now use the small closed circuit Halcyon DSMB. This is approx 3L? volume

Ah! Great! I was really, really tempted by one of these at the last dive show I went to, but the sods sold out by the time I went back

So - you've answered my "lack of visibility" concern already.. but does the small size make for any awkwardness with reeling back in or anything? ie it's not so small you might wind up sinking it on ascent?

[MattS]

Thanks for the link to the video, it has convinced me I really don't want one of those spool thingies. Looks a right faff.

This is what I do;
1. Attach DSMB to line
2. Face down tide
3. Pull 6" to 1ft of line off the reel
4. Hold the DSMB with two hands and drop the reel
5. Place right ear on right shoulder
6. Hold DSMB open a few inches above reg exhaust
7. Breathe out once. You should hear the gas traveling up the DSMB, give the bag a a quick shake. Breathe out a second time
8. Move one hand down the line to the reel
9. Hold the reel at arms length keeping the line taught, check line is clear
10. Let go of the bag and open the ratchet.

I never inflate a DSMB to the point which it can pull me up. At 20m two breaths in a Buddy DSMB is about enough to fill it on the surface. For shallow dives I use a much smaller DSMB, which also serves as my backup. I usually deploy off the bottom; either drifting or ascending to my first deep stop.

[MattS]

Because most dSMBs rely on internal pressure to seal the end..?

If the bag is not full water pressure will seal the end.

but does the small size make for any awkwardness with reeling back in or anything? ie it's not so small you might wind up sinking it on ascent?

I think that is known as using the DSMB as a crutch. Rather than winching up the line, you could try ascending and recovering the line which is less effort. If you stay neutral during the ascent even a very small closed end DSMB will stay on the surface.

[Jules]

I think the essense of all these posts is to always have your own DSMB and reel, regardless of your buddy and his, and practice deploying it (the best way for you) till it comes as second nature. I really feel that my DSMB is my get out of jail free card. One time when i wasn't very experienced and lost my buddy at 40 m in shit viz (the wreck was supposed to be on the sea floor at 30m) I realised this. I will not dive in the uk without one.

[David Martin]

I used to try to fully inflate the DSMB each time, until Andy Kerslake asked me "why?" on Fundamentals

Originally Posted by Dominic

Because most dSMBs rely on internal pressure to seal the end..?

I'd fully inflated them for "visibility"/"beacuse I always had".
I hadn't noticed any that how full it was affected how it deflated. Those that deflated tended to deflate at least part-way, no matter how full they were (presumably until the open end hung underwater a bit), the others seemed OK with partial inflation.

Originally Posted by Dominic

Ah! Great! I was really, really tempted by one of these at the last dive show I went to, but the sods sold out by the time I went back

So - you've answered my "lack of visibility" concern already.. but does the small size make for any awkwardness with reeling back in or anything? ie it's not so small you might wind up sinking it on ascent?

You shouldn't be able to wind it back up if its inflated - you'll need to be 3 Kg -ve and winding in fairly hard. Although clearly, if any DSMB is deployed with neglible volume it would be possible to wind it back in.

I can't really think of any real disadvantage of the small size for normal diving. It's a smaller area to display if you're truly lost and trying to signal a searching boat/helicopter, but IMO the ease of use more than outweighs this. A fully inlflated 3ft Halcyon DSMB is certainly more visible than a 1/3 inflated Buddy DSMB. It's harder to thread the line from your spool/reel through the 30mm D-ring, than it is through a large tape loop on the buddy DSMB, but after a few practices it's easy enough.

I wish they'd put SOLAS tape on them, like they did on the 6ft version - I may add some myself. I originally bought one as a backup red - but liked it so much that I used it as my main DSMB, and then bought another as backup....

David

[tiewrapdiver]

I think i've pretty much tried every DSMB (except for the posh halycon ones), reel or spool and most techniques.

All i have to say is that whatever method you decide on, keep practising that method till you can do it alone, with your mask off. I love using my spool but i need more practise after i had a right game trying to do it with my mask flooded (as a drill). So as Berty BSAC says PRACTICE PRACTICE PRACTICE!!!

[Clive W]

Originally Posted by tiewrapdiver

I love using my spool

Would that be a new spool or the one the fish are playing with at the bottom of the Minch.

[Mdemon]

Self inflate type.
.... Some people say that if you leave it open water can get in and damage the bottle. Not seen any evidence of this....

Me neither, and I think it's bollocks. I was offered similar pearls of wisdom by my LDS, well-intentioned and very helpful. Not convinced, I opened it up and found the same one-way valve band around the inflation post as there is in the spare air attachment. In short, I don't believe it makes any odds and I leave it fully open. I'll check the bottle after a few more dives and post if I find anything...

[beanie]

Originally Posted by Mdemon

Me neither, and I think it's bollocks. I was offered similar pearls of wisdom by my LDS, well-intentioned and very helpful. Not convinced, I opened it up and found the same one-way valve band around the inflation post as there is in the spare air attachment. In short, I don't believe it makes any odds and I leave it fully open. I'll check the bottle after a few more dives and post if I find anything...

I've just opened mine up and there was one big load of gunk in there DougParker only knows what it was - a mixture of salt and ali oxcide me thinks not sure how salt water could of got in there!!