Modern research/thoughts on Ascent Rates

[Nick_Radov]

Why can't you just inflate smb by dumping into SMB from your wing / power inflate. I've had a few practice runs and its not as easy as John Chatterton suggests.

Are you suggesting using an open circuit SMB and inflating it by pressing the wing inflation button while simultaneously holding the wing exhaust valve open? Or using a closed circuit SMB and inflating it by temporarily disconnecting the wing low pressure hose? Either approach seems risky for maintaining buoyancy control.

 

[Akimbo]

Are you suggesting using an open circuit SMB and inflating it by pressing the wing inflation button while simultaneously holding the wing exhaust valve open?

I have tried that a few times. Gas doesn't comes out of the courigaged BC hose if you are vertical and you hold the vent below the bubble in the BC's bladder. It is not my preferred method only because the hose is shorter than my regulator hoses.

Try it the next time you are at a safety stop. Orient vertical, push the vent button when it is low, and slowly raise it until you see a few bubble come out.

 

[Manatee Diver]

Are you suggesting using an open circuit SMB and inflating it by pressing the wing inflation button while simultaneously holding the wing exhaust valve open? Or using a closed circuit SMB and inflating it by temporarily disconnecting the wing low pressure hose? Either approach seems risky for maintaining buoyancy control.

Basically you use your hose dump to inflate an open bottom DSMB. Theoretically it shouldn't change your buoyancy until you release it. Sort of like how exhaling into a DSMB doesn't change your buoyancy until you take another breath or release it.

 

[LFMarm]

Basically you use your hose dump to inflate an open bottom DSMB. Theoretically it shouldn't change your buoyancy until you release it. Sort of like how exhaling into a DSMB doesn't change your buoyancy until you take another breath or release it.

This is a great idea because the gas you are using for your BCD is supposed to be the lowest value mix you have with you which is also what you want to use for your DSMB.

 

[Manatee Diver]

This is a great idea because the gas you are using for your BCD is supposed to be the lowest value mix you have with you which is also what you want to use for your DSMB.

I personally just orally inflate. I shoot DSMBs so rarely (not much need in cave diving) that I wouldn't want to try something complicated like that. But I understand the concept as I am doing the same thing when I orally inflate, I release the DSMB as I take a breath so there are no major buoyancy changes.

 

[Nick_Radov]

Basically you use your hose dump to inflate an open bottom DSMB. Theoretically it shouldn't change your buoyancy until you release it. Sort of like how exhaling into a DSMB doesn't change your buoyancy until you take another breath or release it.

That seems super awkward, and likely to result in a loss of buoyancy control as soon as you release the DSMB. Have you actually tried this on a real dive? With my Halcyon wings I have to lift the corrugated hose up pretty high to get it to dump much so it would be a struggle to direct that gas into an open DSMB.

 

[Nick_Radov]

This is a great idea because the gas you are using for your BCD is supposed to be the lowest value mix you have with you which is also what you want to use for your DSMB.

I don't understand what you mean. The wing is inflated from back gas, which is the highest value (highest helium) mix you have. But so what? Even if you use back gas (as most of us do), that's like $1 of gas.

 

[Wibble]

I don't understand what you mean. The wing is inflated from back gas, which is the highest value (highest helium) mix you have. But so what? Even if you use back gas (as most of us do), that's like $1 of gas.

Unless you're on a rebreather. The wing is normally connected to the diluent which is both limited (normally uses 3 litre cylinder) and expensive.

Your drysuit inflator uses air.

None of my SMBs have open bottoms as I want them to remain inflated on the surface when being battered around by the wind and waves. Self-sealing SMBs can slowly fill with water as they bounce up and down.

 

[LFMarm]

I don't understand what you mean. The wing is inflated from back gas, which is the highest value (highest helium) mix you have. But so what? Even if you use back gas (as most of us do), that's like $1 of gas.

Sorry, forgot to mention "when on CCR". Agree with you on OC.

 

[Nick_Radov]

Unless you're on a rebreather. The wing is normally connected to the diluent which is both limited (normally uses 3 litre cylinder) and expensive.

I am out of my depth here not being a rebreather diver, but everyone I've seen uses larger diluent tanks like 7 liter minimum. Little 3 liter tanks don't leave much margin for error if you have a gas leak or something.
But regardless of tank size, why the concern over expense? Are we talking like $1 worth of gas here? Maybe $2? So what.

Your drysuit inflator uses air.

Actually argon, but whatever. I don't see a problem with inflating a small DSMB using the drysuit inflator hose since at the end of the dive you shouldn't need to add any more gas to the drysuit. It works fine with a small DSMB and I do it myself sometimes because my lips get so cold on long dives that I have trouble orally inflating a closed circuit DSMB. With a large DSMB, the little drysuit inflation tank might not have enough gas left in it. Some divers attach an extra inflator hose to their left post and use that for filling DSMBs or lift bags. I'm not sure what the best approach is here?

None of my SMBs have open bottoms as I want them to remain inflated on the surface when being battered around by the wind and waves. Self-sealing SMBs can slowly fill with water as they bounce up and down.

Agreed.