Standing rigging

stevebirch2002 · Dec 24, 2006

Hi Colin

5mm standing rigging. If you think it needs changing then it does,
rather like when to reef!

Insurance companies here in the UK like standing rigging to be changed
every ten years. That includes the botlescrews which are the usual bits
to fail!!

Have a look at the New Vega Forum on HYPERLINK
"Pro Movies 60"www.albinvega.proboards60.com

Cheers

Steve Birch (Technical)

vegatern · Apr 20, 2009

What was the diameter of the standing rigging on the Vega as originally equipped? Has this proven adequate or have there been changes over the years? I am particularly interested in the forestay. thanks.
Craig V1519

pjacobs55 · Apr 20, 2009

Craig:
My understanding is that the original rigging was 5mm 316 stainless wire.
This is slightly larger than 3/16", and slightly smaller than 7/32".
302/304 stainless wire is stronger, but has less corrosion resistance than 316 wire, which is slightly weaker.

My research shows the breaking strengths as follows:
3/16" 1x19 304 stainless 4700lbs
3/16" 1x19 316 stainless 4000lbs
(I could not find a listing for 5mm 304 stainless wire).
5mm 1x19 316 stainless 4410lbs (original wire)
5mm 1x19 Navtek Dyform 316 stainless 5368lbs

My personal choice for a new forestay would be for the Dyform wire. It's the original size, but 30% stronger, according to product literature. The only unfavorable comment I can find on it is that it tends to "unwind" when being tensioned by a hydraulic backstay tensioner (not a common Vega accessory!)

I've looked into this because I believe my boat has the original standing rigging, almost 40 years old. There's not a speck of rust on it, and all the swaged fittings are crack-free. I'm very hesitant to change this wire, probably good Swedish steel, for some dubious offshore stuff of unknown quality. My main concern is my forestay, as it's taken years of 'furler abuse' and may be needing replacement.
BTW, have you strengthened your forestay attachment?

Sorry to have rambled on so long ... hope this helps!

Peter
#1331 'Sin Tacha'

pjacobs55 · Apr 20, 2009

Craig,
One more note on Dyform wire at

navtec.net

vegatern · Apr 21, 2009

Thanks Peter and Tom. I had thought the wire on the boat, 7/32nds, was same as original and after a little thought, perhaps too little, decided to jump up one size for the forestay. I then discovered that the toggle at the masthead is a 5/8" pin to the mast, and a 5/16" pin to the wire. As near as I can tell from the catalogs, even 7/32nds wire wants at least a 3/8" pin so the original wire must not have been 7/32. I ordered bushings today so at least my solution seems to be the same as yours Tom.
Yes, I made a new stem plate this winter from 1/4" plate and had it welded in solid, no tack welds, so that's done.
Craig Tern#1519

TJBurkett · Apr 22, 2009

Brian Toss in his book the Riggers apprentice uses a formula based on the boats righting moment at 30 degrees of heel to calculate shroud load. The formula is (RM x 1.5)/ 1/2 beam. Based on a graph in his book the RM for the vega is about 10,000 ft lbs. doing the calculation gives 3,750 lbs for the shroud load. 1/4 1x19 has a breaking strength of between 6-7,000 lbs so that provides a pretty generous safety margin. So 1/4 is probably overkill but it makes me feel a bit better on a dark and stormy night.

adamtait2002 · Apr 23, 2009

It's also very important that, if you do go for 'overkill' in your
choice of standing rigging strength, that you build in a weak link
somewhere: it is FAR better to break a shroud than to pull out a big
lump of fibreglass from the deck and hull.

Cheers,
Adam V1030

pjacobs55 · Apr 23, 2009

I just received an email from Navtec, to my enquiry about Dyform wire availability, with this reply:

"Dyform wire currently has a world wide shortage due to problems with the wire mill that manufactured it. The mill suddenly decided that if they were to continue to make Dyform they would need the cost to rise by between 150-200%. We felt that large a price increase would obsolete the wire as no one would buy it. Since then we have been working with another mill to produce the wire. To date they have not been able to produce the wire to the same specifications. We are still working with them but it has become a very slow process. At this point I would not expect to se any available wire until late 2009 at the earliest."

So ... my second choice would be 7/32" 316 stainless 1x19 wire, with a breaking strength of 5400lbs. I'm not comfortable using 3/16" 316 wire as it less strength than the original 5mm wire, and (to me, anyway) 1/4" wire is overkill, except maybe on a forestay with a roller furler.

One thing I've found measuring my rig (I'm pretty sure it's all original):
- The eyes on the ends of the wires all have 3/8" holes on both ends.
- The pins at the top of the shrouds are 3/8", but the turnbuckles all have 5/16" holes and pins, making the turnbuckle pins the 'weak' link.
- The chainplate material is also 5/16" diameter.

More research required before decisions are made ......
But I have to remind myself: this setup has stood the test of time!

All the above is just my opinion.

Peter
#1331
'Sin Tacha'

Vega1447 · Apr 23, 2009

Hi Adam -that's an intriguing comment.

I can see the logic - like using light line for a gybe preventer.

But deliberately engineering weakness into the standing rigging would feel
like driving a car into a wall! Physically possible but psychologically
impossible!

Surely most people just make all the components as strong as
possible/reasonable?

And leave it to Mother Nature to find the weak spot?

John

V1447 Breakaway

John A. Kinsella Ph: +353-61-202148 (Direct)
+353-61-333644 x 2148 (Switch)
Mathematics Dept. e-mail: John.Kinsella@...
University of Limerick FAX: +353-61-334927
IRELAND Web: John Kinsella's Website

rogerefairest · Apr 24, 2009

I have to agree with Adam you need a weak link which is the one that can be replaced the easiest and cheapest and I am quite convinced that this was the idea of the people who build the Vega.
If you look at the backing plate on the chain plate of the back stay you will notice that they are made of aluminium, why did they not made it of super duper stainless steel? My guess is that is because is far easier (and cheaper by a factor of 1 to 4000) to change the backing plate than to change the mast (ie the weaklink) after corrosion starts working its black magic where the backstay and the mast meet.My question is, why fix it if it ain broken? I would keep the standard kit, you start messing about and suddenly your deck becomes the weak link, there is not much you can do to jury rig whatever (if anything is left) is left of the chain plates.

adamtait2002 · Apr 24, 2009

Hi John

By no means am I advocating 'deliberately engineering weakness' into the standing rigging, just a point that is weaker than the deck. It is simply another factor to consider when designing your rig. You should balance the 'psychology' of knowing that if your rig breaks it will snap a cable and you may lose the mast, against the 'psychology' of knowing that if your rig breaks it will do so by pulling a dirty great big chunk of fibreglass from your deck/hull and you may lose your mast. In this instance you would be holed too; admittedly above the waterline, but you'd be dealing with a bigger problem all the same.

All engineers in all areas build in weak links - you know where they are and you keep an eye on them.

Kind Regards,
Adam

adamtait2002 · Apr 24, 2009

Hi John

By no means am I advocating 'deliberately engineering weakness' into
the standing rigging, just a point that is weaker than the deck. It is
simply another factor to consider when designing your rig. You should
balance the 'psychology' of knowing that if your rig breaks it will
snap a cable and you may lose the mast, against the 'psychology' of
knowing that if your rig breaks it will do so by pulling a dirty great
big chunk of fibreglass from your deck/hull and you may lose your
mast. In this instance you would be holed too; admittedly above the
waterline, but you'd be dealing with a bigger problem all the same.

All engineers in all areas build in weak links - you know where they
are and you keep an eye on them.

Kind Regards,
Adam

Vega1447 · Apr 24, 2009

Hi Adam,
a fascinating insight into design principles. Very interesting.

Thanks

John

V1447 Breakaway

Adam Tait wrote:

albinvega1493 · Apr 24, 2009

I think there was a long thread about standing rigging somwhere back some time ago. It was my understanding that the original 5mm rigging was already "oversize" and that 3/16 is the closest wire size to original.

In refiting the decks of "Kemanalea" I found that the aluminium channel under the deck where the chain plates bolt in was badly corroded, and we replaced them with stainless channel. In refitting the standing rigging, we went with 7/32 forestay and backstays, and 3/16 for the rest. Anything more I think is overkill and risks making the deck, already a weak spot, an even weaker link.

I guess if I was headed for Drakes passage, I might consider going heavier, but only if I strengthened all the supporting structures around the chain plates. Even then, you are dealing with more weight aloft, which adds to side to side motion, which makes rollover more likely.

That being said, seems like 1/4 standing rigging is a risky proposition to me.

albinvega1493 · Apr 25, 2009

Another side note,

The pin diameter of all fittings at the top of my mast, and at the top of all shrouds, is 5/16. The hole diameter in the swaged fittings is 3/8, so either Vegas were shipped with a mismatch pin/hole size, (which according to my rigger is a "no-no") or the boat was re-rigged with a mismatch at some point. If you have 3/8 pins at the top, then the fittings at the top have likely been drilled out to take a larger pin, which makes that then the weak point. There is not an excessive amount of stainless in the tangs at the top to allow for drilling out without significantly weakening the fitting.

So . . . if you are going with 1/4 wire, you can't get a 1/4 terminal that takes a 5/16 pin. You have to go to a 3/8 pin, if you drill the tang out to take the 3/8, that defeats the purpose of going to 1/4 wire. You then have to change out the tangs at the top.

So . . . 1/4 wire is pointless without beefing up the tangs at the top, and the chainplates at the bottom. If you go 1/4 without doing that, all you have done is introduced weak links both at the top and the bottom of the rig.

Me thinks Albin knew what they were doing in the beginning.

adamtait2002 · Apr 25, 2009

Indeed, Selden Spars ran some tests in the 90s (I think) to find out
how important the question of point loading is (which occurs when you
have a mismatch in pin/hole size). They discovered that with static
loads you can expect a 5% decrease in strength for every 7% increase
in hole size above the ideal.

So, to take Larry's example of 3/8" holes with 5/16" pins, the 20%
difference in size would weaken the rig by almost 15%. In real terms
this is comparable to cutting 2 to 3 yarns out of a shroud; a scenario
that would have each of us replacing the wire in a hurry.

If you drill out the fittings at the masthead to take a bigger pin,
and avoid point-loading, then you need to check that you have at least
the diameter of the pin in spare metal all the way around the hole so
as not to weaken the fitting. As Larry points out, there isn't enough
stainless to allow for drilling, and so you need to change out the
tangs.

Albin really did know what they were doing; it is important to
understand that the rig is a 'system' and, although not complicated,
it really isn't as simple as just upgrading the thickness of the wire.

Don't even get me started on those that add a babystay without adding
running backstays

Fairwinds and pleasant sailing,
Adam

vegatern · Apr 25, 2009

A very interesting thread. At the mast head I replaced the 5/8-5/16 toggle with a 5/8" - 5/8 toggle and inserted a bushing to take it to the 1/2 eye on the wire. I agree the 1/4" headstay was a mistake, but I'll have to live with it for a while.

In Daniel Spur's book, or Donald Street's perhaps, I read that any two wires should support the displacement of the boat. A loaded boat for cruising may justify the larger wire, but then again, I wasn't thinking of the deck.
Craig

pjacobs55 · Apr 26, 2009

Craig:
You inserted a bushing: did you make one or are they available in stores? Also, is it stainless steel?
Thanks!
Peter
#1331 'Sin Tacha'

vegatern · Apr 27, 2009

Peter,
The toggle is not a comfortable fit at the masthead. It was almost $75. The bushing was $20 from the boatyard and the Norseman fitting at the stem, for the larger wire, adds some cost as well. Before I take the mast back to the boat, and since I can return some of these bits and pieces, I think I'll scrap the 1/4 inch headstay and have one made of 7/32" SS with a 5/16" swaged aircraft eye at the mast. Live and learn.
Your comment about the "nubs" on the chain plates was timely. I had ordered new ones from Steve B. and they arrived last week. The new chainplates have larger, beefed up nubs. I'll try to get a picture posted before installation. At least those I'm very pleased with.
Craig Tern #1519