Wednesday, February 2, 2011

Galvanised Rigging Vs Stainless Steel

Galvanised rigging doing its work
I hate stainless steel rigging. There I said it.. Yes it's shiny and looks nice, BUT... I think it is dangerous. Please realise that this is my opinion and many successful voyages have been made with stainless steel rigging, but I feel that galvanised rigging is a cheaper and better alternative that is often overlooked.

Right first some background , Back in the days when I was an obnoxious 16 year old I remember visiting a yacht that was about to head to the US with a very experienced delivery skipper. 

I  commented on the stranded stainless rigging on the mizzen (At least one strand was broken, and taped up with electrical tape).  Said something like "If I was you I'd replace that here in Picton rather than Auckland, the Waiarapa coast can be pretty nasty..." Needless to say he ignored my pimply advice and off he went. He Ignored the BLACK BOX and it was empty (see http://www.johnvigor.com/Black_Box_Theory.html ). Out of luck or bad Kama but anyway the Mast came down and landed on his head. 

I now always do a full rig check before any delivery trip, and normally with stainless steel will find at least one stranded wire, if the rig is over 10 years old or so. Here's some stainless failures I have picked up.

Chubasco- chico 30, Stranded lower after Napier-Auckland run (middle of shroud)
2041- A Challange 68, stranded intermediate, (Inside swage)
Wyuna 11- 42 foot steel ketch, Stranded intermediate (middle of shroud)
An adams 35, Stranded stb cap shroud (inside swage)

Interesting that they seem to fail either at the middle of the wire or inside the swage. Maybe harmonics in the wire cause it to fatigue in the middle? Getting the rig tension right is very important, as is correct alignment and toggling. Often the wire inside the swage that breaks is on the inside closest to the mast, so it may be due to the slack rigging on the lee side loading up the swage unfairly?

Admittedly one strand on 1x 19 wire is only 5% or so lost in  breaking strain, but it creates a stress raiser that can accelerate the breakages of the other strands in the same spot, and also can indicate that the wire is fatigued.  It needs replacing, (orthough we did gingerly sail 2041 across the Tasman after finding the broken strand).

Finding a broken strand can be tricky when its inside the swage, check for an uneven bump on the wire where it exits the swage, (I use feel as much as my eyes). If you find a bumpy strand see if it moves, using fingers, pliers or a screwdriver carefully, any movement is bad, it is broken inside the swage. When you slack of the tension in the wire the strand will often pop back into its spot and look fine, but the break is there, conversly if you crank the crap out of the wire the broken strand may pop out of the swage for all to see.

My folks gaff ketch has galvanised rigging. It's rusty now but it is at least 20 years old. Snow Petrel has mostly galvanised rigging (except under the furler). It is over 7 years old and is mostly still fine, or although the lowers under the ratline seizing's are rusty. (I should have used Linseed oil). The Square rigger I worked on had 30 year old galvanised rigging that was still as good as the day it was put in thanks to worming, parcelling and serving with lots of linseed and stockholm tar protecting it.

This is why I use 10mm 7x7 Galvanised wire, Its cheap, reliable, easily inspected (look for bad rusting, a few small spots are no problem!) and strong (as strong or stronger than most stainless steels). I have a Stainless forestay under my roller reefing head sail as much because it is smoother so the foil rolls better on it, but it is Massively overkill 10mm 1x19 wire with staylocks at both ends rather than swages, and is fully toggled. It is about due for replacement before the next big trip, so I will buy a roll of 7x7 and use Flemish eyes (much stronger than a splice) to terminate it.

The only problems with Galvanised rigging is that it chafes rope and sails more than stainless. And doesn't look quite as "yachty". I use split black poly tubing to stop chafe, and to be frank I don't want my boat to look like a yacht, I prefer a tidy work boat look.

I get 7x7 aircraft grade with a galvanising certificate, as used in Aussie by farm irrigators. Most of the galvanised 1x19 seems to rust to quickly.  Also 8mm is about the smallest practical size to get good galvanising.

However  I am looking into using dyneema for the lowers, backstay and solent stay to lighten the rig..have had a good run with spectra running backstays so...  maybe I will discuss this latter.

Cheers

Ben

5 comments:

  1. I also had had the thought to use galvanized wire and have a spool ready for a emergency. I don't care for the yatchy look either and my new project boat (Meta Dalu 47) definitely has the work boat look and mentality. After the hull was complete Peter Smith fitted it out.

    I will curious to hear your experiences with dyneema. I have been following a very inventive Colligo Marine at colligomarine.com. They have some neat stuff but just concerned how long the dyeema will last in the real world.

    ReplyDelete
    Replies
    1. I am keen to find out more about the Dynex real world lifetime tests as well, guess in a few years the verdict will be out, till then I will stick with my galvanised wire.

      The Dalu 47's look like awesome boats, I love the look and feel of the meta boats, just to save up enough for all that alloy.

      I had a good look over Metapassion when she was in hobart, a fantastic design.

      Cheers

      Delete
  2. Ben.

    Thanks for the great resource here. (I've got the local bookseller bringing your book in BTW - should be here in a couple of days. Heard your dad on Nat Rad recently... great yarn!)

    Have you ever, or has anybody reading this, considered using mild steel rod, galvanised? Obviously it's not very flexible, but should be durable as anything.
    I'm wondering about making discontinuous rigging (for my in-line caps and diagonals) that way, turning up my own end terminals (eyes and clevises), shrinking them on (and running a TIG weld around the end of the rod, in a counterbore in the fitting) then getting them hot dipped.
    I certainly think this could be worth doing at least for the lowest panel, perhaps in a heavier gauge because of the 'idea not previously tested' factor, given that stranded wire so often fails (or at least corrodes) down in the splash zone...

    Andrew Troup

    ReplyDelete
    Replies
    1. Hi Andrew, glad to hear you are getting a copy of the book, I hope you enjoy it.

      The container ships use solid rods to hold the containers on, they seem to last well, and I have never heard of one breaking. Also many bobstays are made from solid rod. Another similar idea is to do what Brent Swain does and use 1x7 galvanised wire and paint it with two pack epoxy, should last a long time and still has some flex and a bit of warning before it fails completely.

      One problem with mild steel rods might be the relative weakness of the stuff, most galvanised wire is pretty high tensile. But then with mild steel if you can keep the loads beneath the fatigue limit it shoudn't fail?

      Let me know how it works out.

      Cheers


      Delete
  3. HI, Guys I am attending a course for yacht Surveyor, I received a question from the course tutor as follow:
    You have been asked to survey the rig and sails of a 100’ gaff-rigged, wooden ketch Were you to find a stainless shroud on the mizzen, what would your recommendation be?

    here a suggestion from Tutor:Regarding question 3:

    The question asks what would you do if you found "a" stainless shroud. I.e. one of a likely 6 stay is of a dissimilar metal, the others being galvanized wire shrouds. Why would this be here, why aren't they all the same? It is an unlikely scenario but has happened. Can you help me? thethys.marine@monaco.mc

    ReplyDelete