Using SMB For Backup Flotation

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On review using the Buoyancy Calculator spreadsheet over in Equipment -> BCs, it is evident that with a steel HP 100 and a wetsuit a complete loss of the wing will result in being about 12# negative even after ditching the weights. This condition occurs at the beginning of the dive, with a full tank, when the wetsuit is compressed at depth.

So, how to provide backup lift?

I'm trying to think through where I'd need this... I jump off the boat into a bottomless void and my BC instantly blows up and I am unable to drop any weight and am not in good enough shape to swim up 12 pounds...
 
Pug has one answer...

(Assuming some set of circumstances where additional lift is necessary....) (...I once watched as a buddy lunged after a lobster hiding beneath a wreck. The sharp edges of the wreck punctured triangular shaped holes in both his drysuit and wing! It was a new drysuit, too....)

Its theoretically possible to attach a SMB and use it as a floatation device, but its unwise. If the thing gets away from you, you could suffer an incontrollable ascent.

Attach the SMB to a reel, inflate it and allow it to ascend. Then swim/reel yourself up the line. If you try both in a controlled environment, you'll see the difference.

(Probably yet a better option is to rely on your buddy... :wink: )

The need may only rarely manifest itself, but its refreshing to see divers such as the OP asking the questions!

Regards,

Doc
 
Attach the SMB to a reel, inflate it and allow it to ascend. Then swim/reel yourself up the line. If you try both in a controlled environment, you'll see the difference.

I think this will be the plan. I'll gather up the equipment and test it at Monterey in the very near future.

(Probably yet a better option is to rely on your buddy... :wink: )

Oddly, I am not of the mindset that my buddy is my backup plan. I haven't done the math but I doubt that a similarly outfitted buddy would have enough flotation to lift me under the circumstances previously described. Perhaps it would work out but better not to count on it.

I am pleased with all the response. When I started diving, I used a jacket BC with 38# of flotation and an Al 80. I didn't know WHY I used that configuration, it was just what the dive shop sold. That, and I was in Singapore where steel tanks were seldom used. Later, I used the same configuration with an added wetsuit and weight belt at Catalina and Monterey. No worries... But now I have 'upgraded' my equipment to a BP/W and an HP 100.

I am still not terribly concerned for myself but my grandson is about to start diving. Suddenly, these boundary conditions of equipment configuration become very important. It is not sufficient to just sit back and see how it all works out. There has to be a plan!

Thanks to all!

Richard
 
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Hmmm, wing failure. Has it happened to anyone on the board?

Not to me personally but I put together a charter to a wreck 50 miles offshore from Fort Myers, FL and a guy onboard brought double 104s and a SS plate while wearing a 3mm wetsuit and split fins. When he jumped in, his inflator elbow came off where it connects to the (OMS) wing and he was unable to establish any buoyancy.

The 25 year old kid nearly gave himself a heart attack trying to swim himself up. He succeeded thankfully.
 
On review using the Buoyancy Calculator spreadsheet over in Equipment -> BCs, it is evident that with a steel HP 100 and a wetsuit a complete loss of the wing will result in being about 12# negative even after ditching the weights. This condition occurs at the beginning of the dive, with a full tank, when the wetsuit is compressed at depth.

So, how to provide backup lift?

I am looking at the OMS SMB which provides about 50# of lift OMS Lift Bags & Surface Marker Buoys http://www.OMSdive.com. This seems like a reasonable approach in that it provides plenty of lift and the desirable SMB function.

Has anyone actually tried to get off the bottom using only an SMB? Is the web strap at the base of the OMS SMB actually capable of staying attached (not just tearing out) while providing the full lift capability?

Are there other methods (not including redundant bladders) that I should consider?

Thanks!
Richard

Richard...... I am assuming you are diving wet with a single tank--? If so a SMB or standard lift bag can become a redundant lift devise----though it is not as simple as those whom have never 'really' practiced the skill will lend you to believe....there are allot of dynamics and tasks involved in executing a safe accent. A far better option would be a dry suit....you are in Calf. and I know much of your diving can be chilly at best.
 
On review using the Buoyancy Calculator spreadsheet over in Equipment -> BCs, it is evident that with a steel HP 100 and a wetsuit a complete loss of the wing will result in being about 12# negative even after ditching the weights. This condition occurs at the beginning of the dive, with a full tank, when the wetsuit is compressed at depth.

The rig will be -12.... not the combination of you & the rig....
Is there a plate, AL or SS involved...?

The key is for the entire rig & you to be balanced to the point where you can swim it up...

If you've already ditched weight (how much), unless your already significantly over weighted (i.e. you didn't need any weight to begin with), you've closed the gap to allow minimal swimming effort...

-Tim
 
Just as a FYI. The dump valves are located on the bottom of SMB's to prevent all of the excess gas from dumping out of the SMB when it hits the surface. If there is significant weight (like a diver with no wing) pulling on and adding pressure to the SMB it could be easily pulled back under the surface if the dump valve was located on top. It is VERY rare that there is a total wing failure. If you are that worried buy a wing with 2 bladders or a drysuit.
 
This is the classic (and perhaps only) situation where a double wing is a good idea.

I'd argue ditching the tank and buying something not so heavy would be the better idea..., and probably cheaper...
 
I'd argue ditching the tank and buying something not so heavy would be the better idea..., and probably cheaper...

Alternatively, bag or sling a pony, so in a situation like this you could ditch all your gear and ascend using only the pony. Won't work if the pony is hard-mounted to your tanks, which is why I say bag or sling it.

Also, I would think that, as long as you had a spool of some sort along with your SMB, you could shoot the bag normally and kind of crawl up the line once it's deployed and floating (like everyone has said, you certainly wouldn't want to attach it to yourself on the way up!).

>*< Fritz
 
https://www.shearwater.com/products/peregrine/

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