April 14, 2013

Never trust your lifelines

LIFELINES COVERED IN WHITE PLASTIC look pretty shippy on a boat, but don’t let them fool you. Few have sufficient strength to prevent a heavy crewmember crashing through and falling overboard.

The trouble is that lifelines are strung from thin vertical poles, called stanchions, that don’t have much stability. Stanchions have small bases where they’re attached to the deck, and the leverage applied by a falling body is tremendous.

In some cases, lifelines are too low to be effective, and serve only to catch you behind the knee and flip you overboard. If you fall from a high cabintop while the boat’s heeled, you could miss the lifelines altogether.

Offshore racing authorities usually require two rows of lifelines each side with a maximum height of at least 24 inches. But 30 inches, which catches most people high on the thigh, is better if the stanchions are well anchored. They must be through-bolted, never screwed, and fitted with large and heavy backing plates underneath to spread the stress load.

Lifelines should be regarded purely as back-up protection. Primary protection comes from strong harnesses attached to substantial fittings, or jackstays, by tethers short enough to keep you on board.       

Finally, be aware that white plastic coating can hide corrosion, so bare 1 x 19 stainless-steel wire is actually safer.

Today’s Thought

Who can hope to be safe? who sufficiently cautious?

Guard himself as he may, every moment’s an ambush.

— Horace, Odes

Tailpiece

Paddy O’Reilly and a friend were lying on the beach at Fort Lauderdale.

“Begorra, there goes a beautiful lass,” said his friend.

“Yes,” said Paddy appreciatively. “Nice legs, too.”

(Drop by every Monday, Wednesday, Friday for a new Mainly about Boats column.)

6 comments:

Edward said...

IIRC Jay Fitzgerald recommends something like getting a 300lb friend drunk and betting him he can't rip off the stanchion as a test of their worth:)

I've seen boats with braided line used instead of wire. What are your thoughts on this practice?

Shoreline Sailboats said...

I was racing last summer on my father’s Cal-27. Heading downwind wing on wing because the chute would be overwhelming. I was on the low side idly stopping the jib sheet from running in and out slamming the rig. We went into a low trough and as we came out the righting momentum of the wave threw me into the upper lifeline. It broke and the lower one flipped me over so hard that my head slammed into the hull hard as I hit the water. Everything went white and I swam to the surface as the boat streamed away. My dad went hard over with the helm and they picked me up. I have a great respect for the power of waves – now.

Anonymous said...

Hi John,
The admiral and I replaced the upper lifelines on our 30 foot boat last year. The pvc coating on the old ones was discoloured, shrunken and cracked. I cut away the covering at a crack and was surprised to find the wire looked pretty good. I understand the crack provides an entry point for water and the corrosion occurs deep inside where you wouldn't expect it. We were replacing our standing rigging and saved a few bucks by turning our 1x19, 1/4 in. shrouds into lifelines. We are trying out 3/16 in. dyneema for the lower lifelines.
Cheers,
Don P

John Vigor said...

Shoreline: I'm glad to hear it all turned out okay. You were lucky not to have been knocked out, and luckier still to have a father who knew what to do and the skill to do it.

--John V.

John Vigor said...

Edward:

Modern synthetic lines are the equal of stainless steel wire in strength. Even the Coast Guard has started using them for lifelines. I personally would be worried about chafe in the stanchions and the weakening effect of sunlight, which might mean they would need to be replaced more often than stainless steel lines. Of course, that's not so much a concern if you're using taxpayer money. For now, I'd stick to plain (uncovered) stainless steel until the synthetic lines have proved themselves over a longer time.

--John V.

Edward said...

Hi John,
That's about where I'm at with synthetic rope. But when I weighed the rope vs wire for standing rigging and lifelines on a 26ft catamaran I had, I was seriously tempted to switch:)
What about tension of life lines? When I do the math of a 150lb man hitting a line after accelerating for a few feet and hitting a line, there is a huge loading when you put pressure perpendicular to the line. I wonder could cheaper line be used that was somewhat slack?
Thanks Edward