How long is the painter on a liferaft?

[Burnham Bob]

My life raft is going off for service and they asked me to poke the painter inside the canister so it doesn't go off in the courier's van. It's actually just a heavy duty tape loop. I had tied that loop with some stout cord to the pushpit. (I could just imagine launching the life raft and the crew telling me 'you didn't say hold on to the loop'). How much comes out of the canister when you pull the loop? And presumably just pushing it over the side with the loop secured would be enough to inflate it? I've had it three years and these things have just occurred to me. Does the canister sink activating the trigger mechanism when the rope becomes taught and then the life raft surfaces?

 

[duncan99210]

The painter is quite long - about 10 - 15 metres, you have to pull it out before it will activate the raft. The raft is buoyant - I did the calculation on mine and found that it's volume would displace more than it weighted, hence it'll float. I was trying to sort in my mind how the Hamar release system works and that's how it does it, by cutting the raft free from the sinking boat and then allowing the floating raft to initiate itself by floating up from the sinking vessel.

 

[sarabande]

Duncan, can you remember how much the canister weighed and the volume please ?

I am sure the makers have all got it well worked out, but I'd like to see the buoyancy in Newtons being greater than the Newtons needed to trigger the COs canister.

 

[prv]

I am sure the makers have all got it well worked out, but I'd like to see the buoyancy in Newtons being greater than the Newtons needed to trigger the COs canister.

The former is easy to work out, but how are you going to discover the latter without trying it?

Pete

 

[prv]

I was trying to sort in my mind how the Hamar release system works and that's how it does it, by cutting the raft free from the sinking boat and then allowing the floating raft to initiate itself by floating up from the sinking vessel.

...with one extra wrinkle, the plastic weak link that comes with the hydro unit. Once the raft has been inflated as you describe, the link breaks so that the raft isn't dragged down by the sinking boat.

However, if the raft was released manually instead of by the hydro, the painter remains threaded onto the little loop of rope and the weak link is neutralised so you don't lose the raft before boarding.

This all assumes that you've put the right bits through the right holes when installing it - I believe an MCA study a few years back found lots which had been rigged incorrectly and would either drag the raft down after hydro release, or let it float away after a manual one. Hammar modified the way the kit comes in the packet, and colour-coded the plastic, to make it a bit more idiot-proof.

Pete

 

[fisherman]

I think it the case that if a canister went deep enough without deploying the air spaces inside would be compressed enough to render it not buoyant.

 

[KenMcCulloch]

...with one extra wrinkle, the plastic weak link that comes with the hydro unit. Once the raft has been inflated as you describe, the link breaks so that the raft isn't dragged down by the sinking boat.

However, if the raft was released manually instead of by the hydro, the painter remains threaded onto the little loop of rope and the weak link is neutralised so you don't lose the raft before boarding.

This all assumes that you've put the right bits through the right holes when installing it - I believe an MCA study a few years back found lots which had been rigged incorrectly and would either drag the raft down after hydro release, or let it float away after a manual one. Hammar modified the way the kit comes in the packet, and colour-coded the plastic, to make it a bit more idiot-proof.

Pete

I understood that the painter attachment at the raft end incorporates a weak link?

 

[onesea]

I understood that the painter attachment at the raft end incorporates a weak link?

I think your both right, hyrdostatic link should break first??? Ripping of from life raft fairly difficult preferable to ripping a whole in it....

 

[prv]

I understood that the painter attachment at the raft end incorporates a weak link?

Maybe - I don't know. Certainly it wants to be a pretty strong "weak" link, otherwise in heavy weather the raft is going to blow away before you can board it! The instructions always talk about cutting the painter.

Obviously if you put enough force onto the painter it will separate from the raft - nothing is unbreakable. Maybe Onesea is right and it's just that the attachment is designed so that when (not if) the painter rips free, it doesn't take a chunk of the tube with it.

I know if I was in a raft tied to a boat that had sunk, I'd be cutting the painter rather than waiting for some weak link to operate!

Pete

 

[awol]

I understood that the painter attachment at the raft end incorporates a weak link?

The length of painter is quoted on the test certification, at least mine is. Having experienced my raft inflating I can report there is no obvious "weak link" but the volume of the aft is >1m3 and the painter ain't that strong.

 

[cryan]

If you have it connected properly what will happen is that the Hamaar will cut through the (usually white) chord loop at the top of the Hydrostatic Release Unit. You should have the liferaft securing straps attached to the white chord. The painter should be connected to the weak link (now usually red and plastic) below the main body of the HRU. When the vessel sinks the HRU will fire a knife blade through the white chord. The liferaft will then float free from the cradle( they are buoyant) and as it floats to the surface and the vessel sinks the painter will payout from the cannister (usually at some rate as the acsent of the cannister will be rapid) when it reaches the bitter end it will be suddenly braked by the other end which is still secured to the weak link of the HRU which is still very securely attached to the vessel. This braking causes a sudding jerking force which both sets off the liferaft inflation and breaks the weak link allowing the painter to come free and float away with the raft.
Not only is it highly unlikely that the considerable length of painter will be pulled fully out during transportation but even if fully out it still needs a solid jerking pull to fire off the inflation. However all transport companies seem to fear this. At sea we used to gaffer tape the painter end up to the cannister before sending them ashore so as it couldn't be pulled out.

 

[Burnham Bob]

Never occurred to me that the whole boat might be sinking or sunk. I rather assumed that we would launch the life raft whilst still floating and that we would then board the life raft from the boat or from the water with the boat not yet under. As for floating, having just lifted it off the boat I'd be surprised if it does, but thinking about it maybe the specific gravity is less than water. As for floating free from the cradle, mine is on the pushpit and secured by a strap with a quick release buckle so unless that's freed the raft would go down with the ship!

 

[john_morris_uk]

Maybe - I don't know. Certainly it wants to be a pretty strong "weak" link, otherwise in heavy weather the raft is going to blow away before you can board it! The instructions always talk about cutting the painter.

Obviously if you put enough force onto the painter it will separate from the raft - nothing is unbreakable. Maybe Onesea is right and it's just that the attachment is designed so that when (not if) the painter rips free, it doesn't take a chunk of the tube with it.

I know if I was in a raft tied to a boat that had sunk, I'd be cutting the painter rather than waiting for some weak link to operate!

Pete

Unless your boat sinks in ten metres of water? I remember a discussion about whether it might be sensible to stay attached to the boat that is sitting on the bottom underneath you.

Its a fairly silly discussion as its unlikely to occur in real life. Mostly the boat disappears in to water that's a a bit deeper than the length of the painter of the life-raft!

 

[prv]

Never occurred to me that the whole boat might be sinking or sunk. I rather assumed that we would launch the life raft whilst still floating

Well, obviously that's the ideal as you want to get into the raft dry, but in a sudden collision or similar you might not get the chance. Auto-launching rafts have saved lives on fishing boats in particular.

As for floating, having just lifted it off the boat I'd be surprised if it does

So you were expecting to chuck it overboard and have it sink? :ambivalence:

They do float.

As for floating free from the cradle, mine is on the pushpit and secured by a strap with a quick release buckle so unless that's freed the raft would go down with the ship!

Indeed, that's why one end of the strap perhaps ought to be fitted with a hydrostatic release.

(I can't really talk here as ours is actually stowed next to the companionway below deck...)

Pete

 

[fisherman]

You could be in the situation where the boat sinks in less than 10m of water, the raft floats up but does not auto inflate because the end of the painter has not been reached.

 

[Pitterpatter]

You could be in the situation where the boat sinks in less than 10m of water, the raft floats up but does not auto inflate because the end of the painter has not been reached.

Funny, I was just about to say that many of the replies here are from people who, like me, are based around the Forth. Our raft has an 11m painter and there are large parts of the area we sail in that are not that deep. It has crossed my mind many times that if the boat sank the raft would not deploy correctly. Many of the respondents here must be in the same situation. However, if the boat did sink in these places I guess we could all cling on to the mast!

To be fair, we do spend a lot of time in deeper water (the Forth does get to about 20m deep in places!) and we bought the raft for a longer trip a while back. But it does still make sense having the raft on board. It gives swmbo a degree of security and (an important fact that is often overlooked in discussions about liferafts on this board) it makes you look like you are a 'serious sailor that regularly heads of into the blue yonder', even though we are rarely more than half a mile from shore.

 

[john_morris_uk]

Funny, I was just about to say that many of the replies here are from people who, like me, are based around the Forth. Our raft has an 11m painter and there are large parts of the area we sail in that are not that deep. It has crossed my mind many times that if the boat sank the raft would not deploy correctly. Many of the respondents here must be in the same situation. However, if the boat did sink in these places I guess we could all cling on to the mast!

To be fair, we do spend a lot of time in deeper water (the Forth does get to about 20m deep in places!) and we bought the raft for a longer trip a while back. But it does still make sense having the raft on board. It gives swmbo a degree of security and (an important fact that is often overlooked in discussions about liferafts on this board) it makes you look like you are a 'serious sailor that regularly heads of into the blue yonder', even though we are rarely more than half a mile from shore.

Apart from facile remarks that you can easily drown or die from exposure half a mile from the shore, the easy answer is that if the life-raft fails to inflate just give a tug on the painter and it will soon trigger the firing mechanism. They don't need too much of a violent pull to set them off.

 

[cryan]

To be fair, we do spend a lot of time in deeper water (the Forth does get to about 20m deep in places!)

Better check your lead line mate .There is about 75m of water between the bridges and about 45m at the Oxcars. Most tankers at Houndpoint will have draughts over 20m.