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Safe life AND fail safe

andlauer

New member
Joined
15 Mar 2007
Messages
310
Location
Paris France
Bonjour
The aircraft ingeneering have defined two maintenance concepts:

- Safe life when the parts are systematically changed after there tested safe life period, independantly of there state.

- Fail safe maintenance is a litle more tricky. The aircraft is build up with redondant strength and any failure will not endanger the flight. Recurent checks must be done to detect any failure in order to change the failing part. The check period is defined in order to avoid double failures.

For the Jester Challenge I think we are in a dual logic of safe life and fail safe. Some structural parts as rigging may be changed in order to cross with sufficient safe life ahead. But recurent check should be done periodically during the crossing to detect any failure and fix it. Some Jester Challengers had broken shrouds...

As a consequence you should expect to first prepare the boat to leave in the best possible status and then spend the crossing checking and fixing all failing bits and parts.

A crossing is something like "The Secret Life of Walter Mitty".

The less equipment you have the less will fail but the more critical failures will be. An optimum, highly dependant of the skipper spirit, should be found.
Eric


/forums/images/graemlins/smirk.gif
 

eebygum

Member
Joined
6 Nov 2002
Messages
304
Location
Manchester
I like the concept.....

I completely replaced and upgraded all the standing rigging last winter because it was past it's safe life period (10 years), but I did'nt want to leave the replacement until the final year/pre-departure because I wanted to bed the rigging in; find any faults or weak spots in advance so it's safe maintenance up to the point of departure and beyond.

My other principle was to slightly "oversize and build in redundantcy".... upgrade the rigging diameter; dual backstay's; inner storm forestay as emergency forestay etc. I told the rigger was I was planning to do and with that in mind he took on the english habit of sucking hard through his teeth and saying..."It's only as strong as the weakest link"... better beef up that masthead fitting; replace with a larger through hull deck fitting etc.

It's proved to sail very well this summer (apart from loosing the inner forestay Highfield lever over the side; I might have been able to stop it if I was'nt so busy listening to the Red Hot Chilli Peppers on my ipod);

The upgrade has given me more confidence in the boat; it's the sanity of the skipper I'm worried about.
 

damo

New member
Joined
22 Feb 2005
Messages
3,430
Location
k keeper,Portishead
"it's the sanity of the skipper I'm worried about. "

But you can beef up mental strength as well.... /forums/images/graemlins/smile.gif
 

barnaclephill

New member
Joined
6 Nov 2006
Messages
252
[ QUOTE ]
Some structural parts as rigging may be changed... Some Jester Challengers had broken shrouds...


[/ QUOTE ]
One option is to have a spare halyard, so that its free end can be moved to attach to where a broken shroud is. The other option is to carry Spectra rope for this purpose - it was invented to be standing rigging, and for example, the 5 and 6mm lines have breaking strengths of 1100 and 1570kg respectively.

For rigging, I have the shrouds well inside of their lifespan, and a little oversize. They turnbuckles I haven't changed as they have so much more metal it's hard to see them fail.

Having said that above about the turnbuckles, last weekend the bolt in the genoa block (on the travelling car) broke through the bolt. 8mm of metal fatigue. It has got me thinking seriously about checking every complex fitting to see how it can be jury-rigged or jury-repaired with shackles and wire before-hand, or I must bolt/weld on attachment points nearby to make a jury repair.
 

Gargleblaster

Well-known member
Joined
16 Dec 2003
Messages
1,143
Location
Medway, Gillingham Reach
I've twice had one year old rigging fail on me in mid ocean. in 2006 it was my stbd inner shroud in 2007 it was my port inner shroud. The problem with the inner shrouds is that I don't have a halyard at that height. Even the Uphaul is about 2 metres above the inner shroud attachment points.
I carry a complete set of spare rigging. However in a big seaway I have never been courageous enough to climb the mast with an inner shroud disconnected. I have done it in calm water and worry about the way the mast bows under my weight.
Inner shrouds are the most likely to fail on you according to the experts and that has been proven in my case. I believe what causes the failure is wear hardening from the stretching caused by waves hitting the mast, as I notice that after a succession of waves washing over the deck, some halfway up the mast, often the inner shrouds have a slackness in them that then requires retightening.
While I will continue to carry a complete set of spare rigging I tend to think it is unecessay weight as I can't think now of a situation where I can fit them in a seaway. However in 2006 I could have replaced my inner shrouds in Larjes Harbour on Flores where I had been forced to turn around by an unfavourable wind when my stbd inner shroud failed. Interestingly enough I took the risk that a NW that was blowing would take me back all the way to the UK on port tack which in fact it did after 17 days of sailing.
 
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