How to Sever the Liferaft Painter?

[offline]

two words..


Explosive Bolts

[Weyalan]

FWIW, the Hammar H20 HRU incorporates both
a) A hydrostatic release unit
b) A weak link

The attachment of the painter to the ship is via a loop of 8mm (5/16") double-braid rope (typical breaking strength 1820kg / 4000 lbs, manufacturers quoted minimum breaking load 1630kg / 3580 lbs)

In the the event that your boat sinks and the HRU is activated (by hydrostatic pressure, typically at around 2.5m - 4m depth (8' - 13'), then the double braid rope is cut, but the weak link remains, so the liferaft painter is still attached to your boat, and will not simply drift off into the distance.

The Hammar weak link typically has a break strength of 2.2kN (225kg / 490 lbs), so that when the HRU has cut the 8mm (5/16") rope, you still have to exert well over 200kg to break the liferaft free from the boat... again, preventing the liferaft from simply drifting away.

The theory is that your liferaft has way more than 220kg of positive buoyancy, so that your boat sinking will not drag the liferaft under, but will break the weak link.

That's the theory, anyway.

For me, if you want to save yourself $150, attach your painter to the liferaft with a loop of 3mm (1/8") double braid, which will have a breaking strength of around 170kg (375 lbs) and you'll get change from $1... it will serve the same purpose.

[IslandHopper]

Originally Posted by nigel1

BTW how was the tow

If i mentioned the word "delay", and said we all flew home after 4 weeks without even starting the mains.......

Would that sound unusual to you......?

[hellosailor]

Explosive bolts are noisy.

"I don't understand the reluctance to have a raft deployment system that is 100% hands-off" As evans said there are issues with life rafts not being secured. There have been numerous comments over the years as to "our life raft was swept off the deck, cannister and all" and proper installation/location of a raft on deck seems to be a question that none of the players really wants to get into, perhaps because it might get so many people upset.

Some boats have space to put a cannister under the helm seat, where breaking waves are unlikely to tear it free as it is secure in the cockpit. A rare few have storage in the bridgedeck, just outside the companionway, which seems like another very good place to keep it--but that's got to happen during boat design time.

All the fancy releases are just points of extra expense, complication, possible failure, compared to a simple "lash it down and use your knife". The idea that the boat can go down so fast it takes the raft with it seems like a very thin percent of sinkings. If you're going to use a hydrostatic release to prevent that, how do you actually TEST that to see if a cockpit-mounted (don't want it to wash off the deck) cannister is going to release AND manage to get clear of anything else (mast, rigging, sails) to make its way up to the suface? No testing? Liability issues, makers will be reluctant to go there.

Catch-22, "marine grade".

[ParidiseParrot]

Keep the water out of the boat. IF money is short that is about the last place to put it safetywise. 2/3's don't inflate. You will let the servicing go out of date because of hassle and cost. Crash pumps , Yachtsavers and a million other things add more to safety. Rafts are only useful if serviced and your boat is a raging inferno.

[xymotic]

Originally Posted by ParidiseParrot

Rafts are only useful if serviced and your boat is a raging inferno.

Sorry, but that's just not true. You ever actually tried to find a leak in a boat when the bilge is 1/2 full of water? I have and it is not as simple as plugging a hole. You have to find the hole first.

And 2/3's of rafts never deploy? Where does that random stat come from?