Checking out mast tangs and stays

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stooibrown

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Looking for advice about inspecting the standing rigging on my wee Skipper 17. A couple of years ago the mast fell down after the rivets on the forestay mast tang sheared. If it'd hit me on the head I think I'd be with Davey Jones now. Afterwards I drilled out all the tang rivets on the mast and replaced 'em (with Inconel). Any suggestions for inspecting the condition of these rivets - is there anything which might reveal impending failure? I could drill 'em all out again and re-rivet but I don't want to do this too often as the holes in the mast will get enlarged and could start to crack. Also, what should I look for in the cables and fittings? Thanks.
 
The stainless fittings need a paste between the stainless and the alloy, also only use Monel rivets to secure. Sailspar who use stainless fittings used to use a foam (sticky one side, can't remember the name!) between the fittings and the mast, this worked really well. If you do have to drill out the fittings, only drill of the head of the rivet and tap the other part back in the mast, this will stop the hole becoming to big.
On the cables look for rust stains around the swages, could be a sign of problems in the swage. If you live near a rigger most riggers will do a free rig check if you ask!
 
What is far more reliable is through bolt through tang on one side then through the mast and through the tang on the other side. My mast on 21fter has 5/16 ww bolts 8mm.
I would not rely on pop rivetts. The forestay can use the same bolt with a plate from each side joining together at the front.
regarding SS wire. I have been convinced by 4 exaples of friends who have lost masts due to wire failure that calender period replacement is the only safe way. About 12 to 15 years is OK but 25 years is almost guaranteed to fail. Failure can not be predicted by inspection. Wire is not so expensive. good luck olewill
 
There in lies the problem of running an older boat with a budget.

With the riveted fittings I am sure there are many boats with older rivets than the OP's. Unlucky? Badly designed? misused at some point in its life could all be causes I would guess. Through bolting depending on how much of a purist you are the weight aloft is not a help, if you have internal halyard it could easily cause issues. Plus you have more issues with S/S for our old friend electrolysis to consider when putting the bolts through.

It is easy to say and true that older wire is more likely to fail, then again it depends on the usage and if its over sized as well. It would be interesting to see the stats on age of rigging and failure. Wire is not that expensive your right but the end fittings are near enough 2/3 of the coast of the rigging the costs soon mount up.

The funny thing with rigging failure, when ever a mast comes down there is always the thought about where it landed. Apart from in dinghy parks I cannot think of a mast hitting someone. I think primarily its because normally you are upwind and it falls down wind, its still not a nice thought...
 
Thanks for all your responses. There's a certain satisfaction to keeping an old tub afloat, especially if you're Scottish and disinclined to part with cash ;-) I'll look into the through-bolt idea - that sound like a good un for my situation. I have already made a forestay tang that reaches round the side of the mast, so through bolting it is a possibility. I also plan to swap out stays on a calendar basis, as suggested.
About where the mast lands: it failed in a flat calm in Oban harbour (but held through a very rough crossing of the Lady's Rock overfalls in F5 half an hour previously!!). Since it was the forestay, it came down in the cockpit and literally missed me and crew by inches. I regard it as a serious risk, especially as on my boat (and many others) there was no redundancy to prevent catastrophe. BTW, she now has two parallel forestays!
 
Yeah, I was thinking exactly the same thing. An alternative might be to bolt a tang to the mast and add a short, strong strop to each of the stays' so that if a tang does fail then the bolted tang/strop will take the loads until the sail can be dropped. I'll think about it and post a piccy when I've made my mods.
 
The one thing the OP can be sure of is that Inconel rivets will outlast the boat! The same cannot be said for the aluminium that surrounds them, or possibly the stainless tangs. Was Duralac paste used when the rivets were replaced, or some other means of excluding water?

My YM article (thanks for the compliment) talks about fatigue in tangs and in cables. To minimise the problem ensure that the fittings can articulate correctly by using toggles, and keep the rig tight. Slack rigging is by far the biggest source of fatigue failure.
 
stooibrown said:
Thanks for all your responses. There's a certain satisfaction to keeping an old tub afloat, especially if you're Scottish and disinclined to part with cash ;-) I'll look into the through-bolt idea - that sound like a good un for my situation. I have already made a forestay tang that reaches round the side of the mast, so through bolting it is a possibility. I also plan to swap out stays on a calendar basis, as suggested.
About where the mast lands: it failed in a flat calm in Oban harbour (but held through a very rough crossing of the Lady's Rock overfalls in F5 half an hour previously!!). Since it was the forestay, it came down in the cockpit and literally missed me and crew by inches. I regard it as a serious risk, especially as on my boat (and many others) there was no redundancy to prevent catastrophe. BTW, she now has two parallel forestays!
Click to expand...

re forestay failure. if you have a jib tack connection to the boat. Hank on jibs then if yoiu have a jib up you have a reduntant forestay in the luff and halyard. I had a clevis pin at the foot of the forestay fall out while racing a few years ago. The rig went slack but stayed up. Anyway a bit scary but actually no harm done. I went forward and fitted a screw driver in the place of the clevis pin held in with gaffer tape. Fortunately I have a high field lever so could quickly lengthen the forestay then tension up quickly.
So after that i consider forestay of least concern re failure compared to side stays. I certainly would not fit parallel forestays. So difficult to equalise tension especially with a jib on one.
I have had as a matter of intereest 2 gear failures in the last week. One a tang on the deck taking a vang and turning block for outhaul just tore the ss through the hole. Granted it was a bit light for the job. (last Sunday) The last night Fri night race had a single pulley on the main sheet traveller just part one leg. No dramas and easily fixed but there is so oftyen maintenance to be done. Yes one of our clubs monthly night races 2 hrs starting at 6.30 PM only took 2 hrs finishing just after dark. Just gorgeous steady 12 knots wind. Plenty of moon light. I wish I could share it with my forum friends. (in dark of winter)
good luck olewill
 
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