How much C02 in lifejacket canister?

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sam_uk

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Hi I assume there is more CO2 in a lifejacket canister than there needs to be, and that the excess comes out of a dump valve. Does anyone know what the safety margin is? Twice as much as needed? 1.5x as much?

Also how many litres of C02 are there in a 150N lifejacket?

Can anyone think of a way of putting a delay on a auto inflating lifejacket so it would fill after 60 seconds immersion?

Points if anyone can guess why I want to do this!

Thanks

Sam
 
sam_uk said:
Hi I assume there is more CO2 in a lifejacket canister than there needs to be, and that the excess comes out of a dump valve. Does anyone know what the safety margin is? Twice as much as needed? 1.5x as much?

Also how many litres of C02 are there in a 150N lifejacket?

Can anyone think of a way of putting a delay on a auto inflating lifejacket so it would fill after 60 seconds immersion?

Points if anyone can guess why I want to do this!

Thanks

Sam
Click to expand...

Whoaaa stop.

There is not more co2 in a canister than you need, there is no dump valve, e.g if you were to put a c02 bottle from a 275n jacket onto a 150n jacket it would burst the bladder not "dump" the excess.

The only reason I can think you would want a 60s delay is to perhaps experience secondary drowning...?
 
Xskipper said:
There is not more co2 in a canister than you need, there is no dump valve, e.g if you were to put a c02 bottle from a 275n jacket onto a 150n jacket it would burst the bladder not "dump" the excess.
Click to expand...

We fired off a friend's old lifejacket last autumn to see what would happen. One side inflated but the other, thanks to a twist where it was packed round the neck did not. A significant puff of gas came out from the cylinder attachment and afterwards the inflated side was still nice and firm - ie no leaking hole.

Conclusion: that lifejacket, at least, had a dump valve.
 
Ubergeekian said:
We fired off a friend's old lifejacket last autumn to see what would happen. One side inflated but the other, thanks to a twist where it was packed round the neck did not. A significant puff of gas came out from the cylinder attachment and afterwards the inflated side was still nice and firm - ie no leaking hole.

Conclusion: that lifejacket, at least, had a dump valve.
Click to expand...

Are you sure the gas did not come from the threads of a loose CO2 bottle, I have never come across a jacket with a dump valve but have seen many burst or split the seam from having the wrong bottle.

Can you remember what make of jacket/activation device it was?
 
I stand to be corrected, but I'm pretty sure most lifejackets don't have a relief valve ( whereas I believe most liferafts do ).

Divers ABLJ Adjustable Buoyancy Life Jackets do have relief valves, for obvious reasons.

I was taught that blowing a few breaths into the oral inflation tube to give a little buoyancy was a Bad Idea, because the auto / manual CO2 cylinder when fired might possibly burst the jacket with painful and / or low performance results.

My 175 Newton KRU jobs have 38g cylinders.
 
Xskipper said:
Whoaaa stop.

There is not more co2 in a canister than you need, there is no dump valve, e.g if you were to put a c02 bottle from a 275n jacket onto a 150n jacket it would burst the bladder not "dump" the excess.

The only reason I can think you would want a 60s delay is to perhaps experience secondary drowning...?
Click to expand...

OK thanks, seems like my dump valve guess was off..
 
Xskipper said:
Are you sure the gas did not come from the threads of a loose CO2 bottle, I have never come across a jacket with a dump valve but have seen many burst or split the seam from having the wrong bottle.

Can you remember what make of jacket/activation device it was?
Click to expand...

I'm afraid I can't remember the make, but I'll ask him when next I see him. Everything seemed secure, both before and after the test.
 
Seajet said:
I stand to be corrected, but I'm pretty sure most lifejackets don't have a relief valve ( whereas I believe most liferafts do ).

Divers ABLJ Adjustable Buoyancy Life Jackets do have relief valves, for obvious reasons.

I was taught that blowing a few breaths into the oral inflation tube to give a little buoyancy was a Bad Idea, because the auto / manual CO2 cylinder when fired might possibly burst the jacket with painful and / or low performance results.

My 175 Newton KRU jobs have 38g cylinders.
Click to expand...

This is correct, all liferafts will have dump valve because the differences in temp may affect the volume of gas being put in from the bottle and you want your liferaft to fully inflate even in (especially in) sub zero temperatures.

The same cannot be said for lifejackets- the volume of gas put in is so small temp variations make little difference and it is possible to top up orally after inflation.

150N= 33gm cylinders, 175/190N=38gm cylinders and 275N=60gm cylinders.
 
Emergency mast head float

I was considering their use as a very heavy weather mast head float.

After consultation with my unstayed mast manufacturer they seemed to think the forces would be acceptable.

So when things get _really_ hairy and you already have your drogue of choice out, you could run the un-inflated jacket up a halyard (well lashed on to minimise flapping and windage)

In the event that you go turtle, beyond your angle of vanishing stability, the jacket would inflate and help to bring you upright.

However a delay would be nice so it only activated when you were well and truly turtle, and not still subject to the considerable rotational forces that got you there in the first place.
 
My AVS is only about 116 degrees - before the mast hits the water!

Hoisting a lifejacket to the top of the mast in those conditions, it'll probably be raining like hell anyway which would dissolve a salt tablet so you'd need a hydrostatic deployment anyway. In that case just get a pressure sensor that deploys at the depth of water that the mast head is going to be once the boat is inverted! :)

Don't see what this gives you though unless your vessel is stable once inverted. Even then once it is all the way over a couple of kg push vertically up the mast isn't going to help a lot.

150n jacket = 15 kg = 15 litres displacement ( at the surface )
 
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I'm pretty sure some life jackets do have a dump valve because I seem to remember reading it. I will go and look after this.

Also, I have a twin life jacket and I believe (but I am still unsure of this and stand to be corrected) that ONE cylinder is enough to inflate the whole jacket (I manually inflated it once, so the tubes were linked) and that the other cylinder was a backup - but BOTH would activate if both were working correctly meaning over twice the volume of gas would enter the Life jacket, so a dump valve would certainly be necessary.

Now, that back up system has never sat quite right with me, so I will check and maybe someone else will jump in here...

Back to volume of gas - don't know at moment, but if you had two identical cylinders, one empty and one full and knew the weight of each, therefore you would know the weight of CO2 and doing 'O' level chemistry and working out atomic mass and so forth, and probably chucking in some moles and Pressure and temperature equations, you get your volume - yup, I forgot all my chemistry too.

Anyway, I'm off to find that link about dump valve - I think it was a crewsaver twin Elite jacket, or Cosalt (same manufacturer I think) - back in a mo'
 
Pinnacle said:
Any chance you could run that one by me again.......?:confused:
Click to expand...

Angle of Vanishing Stability. More here:
http://www.sailingusa.info/cal__avs.htm

Boats which have a stability angle of less than 140 degrees may be left floating upside down once capsized.

I hope never to find out whether my boat is stable inverted! I do however think that 15kg of buoyancy at a 6meter distance will give you a considerable turning moment..
 
Question for Chrissie ?

A significant snag may be that in a B2 inverted knockdown, the rig may well be broken & floating alongside ( possibly trying to punch a hole in the boat ).

The problems with activating a masthead system even if the rig could take the unusual loads, means there would be a BIG question mark over electrics, salt tablets, etc, and if you're not really sure it will work what good is it ?!

Donald Crowhurst had an idea along these lines on his trimaran Teignmouth Electron, but as far as I remember didn't even get the system armed, let alone try it.

A couple of Hirrondelle catamarans at my club have masthead floats, but have more or less given up the idea these would keep the boat upright, so have filled them with radar reflectors.

The loads on pulling a cruiser up by the masthead are toe-curling to imagine, I used to have a coke bottle I could hoist to the masthead of my Contender dinghy when I realised I'd blown it, but success with anything bigger would be questionable at best.

Good Luck, but don't rely on it !
 
sam_uk said:
Angle of Vanishing Stability. More here:
http://www.sailingusa.info/cal__avs.htm

Boats which have a stability angle of less than 140 degrees may be left floating upside down once capsized.

I hope never to find out whether my boat is stable inverted! I do however think that 15kg of buoyancy at a 6meter distance will give you a considerable turning moment..
Click to expand...

Yes I know.....

But the OP said that at 116deg, his mast wouldn't be in the water. :confused::confused:
 
Seajet said:
A significant snag may be that in a B2 inverted knockdown, the rig may well be broken & floating alongside ( possibly trying to punch a hole in the boat ).

The problems with activating a masthead system even if the rig could take the unusual loads, means there would be a BIG question mark over electrics, salt tablets, etc, and if you're not really sure it will work what good is it ?!

Good Luck, but don't rely on it !
Click to expand...

My understanding is hydrostatic lifejackets are reasonably reliable. Sure it _may_ not work, but if I am standing on my cabin roof in the dark, I would rather have something which _may_ tilt things in my favour rather than just hoping another wave will tip me back upright..
 
This video is interesting at 3.5 mins in.

An Interlock jacket this time.

http://www.ispl.co.uk/video/challenger-worksafe-275-lifejacket

Twin cylinders.

One cylinder fully inflates jacket. The gent could then pull the other handle.

Of course if he got dunked and the mechanisms both worked, then BOTH 60g bottles would inflate the jacket.

There must be a dump valve on this jacket too, surely?

Great idea by the way. I toyed with the idea of getting a damaged lifejacket some years ago and doing similar for a very tippy dinghy I had.

Good luck
 
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