Conference unifix::sailing

As I recall, 316 stainless steel wire is more corrosion resistant (and 
more expensive) and less strong than 304. Whether you need to increase 
the wire diameter to compensate for the reduced strength would depend on 
the details of your mast rigging and the displacement of your boat and 
how much safety margin you want and what kind of sailing you do. 
Increasing the wire diameter might require new turnbuckles, etc, and 
might be very expensive. 

The Rigging Company does not list 3/16 inch 1x19 wire in 316 alloy -- 
smallest size listed is 1/4 inch.

3/16 inch 304 1x19: 4700 pounds breaking strength, $0.96 per foot
1/4 inch 304 1x19:  8200 pounds breaking strength, $1.40 per foot
1/4 inch 316 1x19:  6900 pounds breaking strength, $1.69 per foot

So 316 is about 16% less strong and 21% more expensive than 304, at 
least in the 1/4 inch size. 

    I have recently been reading an article on rigging in which it was
    suggested that turnbuckles and standing rigging should be replaced
    at intervals of 6 to 8 seasons. (In my mind quite an expensive routine
    maintenance operation unless the wire is fraying or there is obvious
    wear or distortion to the terminals or turnbuckles).
    However, one particular point which caught my attention was that the
    writer warned particularly against increasing wire diameter as a means
    to achieving more strength to the rig. He considered that this in
    itself could achieve the opposite effect in that to get the same
    tension in the rig could present greater load to the chainplates etc.
    which could overstress the hull fittings and bring about rig failure as
    a result.
    Regards,
    Tom
    

re .3:

>>    However, one particular point which caught my attention was that the
>>    writer warned particularly against increasing wire diameter as a means
>>    to achieving more strength to the rig. He considered that this in
>>    itself could achieve the opposite effect in that to get the same
>>    tension in the rig could present greater load to the chainplates etc.
>>    which could overstress the hull fittings and bring about rig failure as
>>    a result.

Huh? This doesn't make sense to me. The tension in a shroud (or stay) is 
simply the load on the shroud. The tension is the same regardless of the
wire diameter. Some tension in the shrouds from tightening the
turnbuckles is necessary to keep the mast straight under sail loads.
This is because shrouds stretch under additional load. Keeping the mast
straight under sail loads requires that the sail load be relatively
small compared to the load from tightening the turnbuckles. The less
elastic the shroud is, the less load from the turnbuckles should be
necessary to keep the mast straight (a perfectly inelastic shroud would
require no load from the turnbuckles). A large diameter shroud will
stretch less for a specific total load than will a small diameter
shroud. Seems to me that a larger wire diameter will reduce the overall
chance of rig failure, not increase it. 

I'm certainly no expert on sail rigging and I agree with Allen's "Huh?" and
explaination.....except for the conclusion.

It would seem that the larger diameter wire would achieve the required tension
with less stretch. It is also true that tension is tension regardless of the 
diameter.

The "rub" comes when you consider dynamic load! If the wire is less elastic,
then more of the peak dynamic loads (puffs?) will be transmitted to the
terminal hardware. Rip out a deck plate?

I'm aware of this only through the considerations we  (C.G. Aux) give to this 
issue when towing other vessels. It is the dynamic load which threatens our
towing bridle, cleats, etc.

Perhaps the orginal concern for changing wire diameter comes from this.

Regards,
Jerry   

re .5:

Possibly, but .... winds speeds increase fairly slowly (a few seconds)
and as there is no initial slack in the rigging the increased load is
applied relatively quite slowly compared to the shock load of a tow line
suddenly becoming taut. Moreover, 1x19 wire has so little elasticity
that stretching isn't enough to reduce shock loads even in smaller 
diameters (1/4 inch wire stretches on the order of .001 inch per inch of
length for a load of 1000 pounds, 3/16 inch wire stretches roughly twice
as much). 

RE: .2,

>>>  3/16 inch 304 1x19: 4700 pounds breaking strength, $0.96 per foot
>>>  1/4 inch 316 1x19:  6900 pounds breaking strength, $1.69 per foot

Buy the 3/16" 304 stuff about twice as frequently as you might replace the
316, and you'll end up spending about the same, while feeling more sure 
and knowing the whole rig is still to spec.

RE: .5,.6,

The change in windspeeds probably doesn't provide very much dynamic load, 
but pitching into a seaway and really throw a rig around and make it stop 
short from time to time.  I've seen a rigging failure induced this way on 
a sailboat delivered up the ICW with sails never bent on -- they just 
rocked and rolled enough to break a shroud and pitch the mast over just 
past Cape Fear while attempting to make Wilmington, NC.  (Yes, of course 
it wasn't well maintained; it was one of those semi-abandoned Florida 
dreams-gone-stale that some penny-pinching hippie up north bought for 
a song.)

J.

    Nordsman (?spelling) in Flordia has a 316 wire called "DYFORM" which is
    made in England.  The wire 1X19 has a larger interior wire as well as 8
    of the other wires also being larger but the overall diameter is the
    same. This will give the same strength as 304.  I, and two other boats,
    just rerigged all of our standing rigging (we ordered 2000 feet of
    wire) using "DYFORM" and the Nordsman fittings.  These fittings are
    more expensive than the normanal type, but can be reused over and over.
    The surprising thing of this was how easy it was to put on the Nordsman
    fitting - less than 10 minutes per end.
    
    I would suggest for your area to consider the 316 - but that would
    really depend on what type sailing you're going to be doing.  You could
    use the Nordsman fitting with 304 and just replace the wire as needed.
    
    I am under the impression that 304 will last 10-15 years, but that's
    dependent upon location and type of sailing.  Normally the fittings
    will give first, i.e. hairline cracks. 

re -.1:

You mean Norseman fittings. They (and the similar Sta-Lok fittings) are 
available from various discount mail order companies (Defender 
Industries, for one). With the appropriate inner compression cone the 
fittings can be used with 1x19, 7x7, and 7x19 wire. Nice, but the 
initial expense is significant (eg, about $29 for an eye fitting for 
1/4 inch wire).

    Just a bit more background to the source of my comments in .3
    I must say that until reading the article I would have agreed with Alan
    in .4
    During 1989 Yachting Monthly gathered a team of professionals to
    assemble and publish a detailed appraisal of the modern offshore yacht.
    This was published as a magazine series and is now in book format
    entitled the Complete Offshore Yacht. The book is excellent.
    Amongst those responsible was David Thomas, a successful naval
    architect who has designed such yachts as the Elizabethan 31, Hunter
    Sonata, Sigma 33 and Horizon 32. He was assistant editor to Yachting
    World for many years and completed the infamous 1979 Fastnet race in a
    Sigma 33.
    I believe the comments in a Chapter entitled The Seaworthy Rig were
    his. I quote from this passage - " The thickness of standing rigging
    inevitably has a bearing on its lifespan. An oversized wire is under
    less stress than one working close to its limit. Having said that,
    beware of rushing out and fitting oversized wigging because it needs
    considerably greater tension to impose tight which can set up
    intolerable strains in the hull (for example making a forestay tight),
    always assuming the mast does'nt crumple at sea through undesigned
    compression loadings".
    
    The book incidentally is well worth the 9 pounds sterling price.It can
    be obtained mail order, if anyone wants an address for ordering please
    let me know.
    Regards,
    Tom
    

    Even if the wire is 314, what's the composition of the steel in the
    swage fittings?  Are stainless steels with higher chromium contents any
    more resistant to cold working induced brittleness.  I've never seen a
    1x19 were fray but I've seen a lot of cracked swages.
    
    When a swage cracks, it's necessary to replace the whole shroud - two
    swages and the wire in between.  The Norsemen fittings may be
    worthwhile if they allow moudular replacement of only the failed
    component - either one of the end fittings or the wire.  Plus if
    they're more resistant to cracking, they may not need replacement as
    frequently as swaged fittings.
    
    I have seen an instance of rigging being too strong.  In a heavy air
    race a seven thousand pound IOD rammed a 3400 lb Etchells right at the
    upper shroud.  The shroud and fittings all held.  But the chainplate
    itself was torn right out of the Etchells hull.  A quick release of the
    sheets saved the mast but what a mess on the Etchells' deck.  The
    swages and turnbuckles were bent beyond redemption and a good deal of
    glasswork needed on the hull.  If the shroud had just snapped, only the
    shroud and fittings would had to have been replaced.  Ironically, the
    Etchells belonged to Dave Curtis and the IOD belonged to his business
    partner Norm Cressy.
    
    - gene

    Sam,
      Why re-rig?  Just get a new boat!  ;^)
    

re .10:

I'd very much like a mail order address for the book.

re rigging tension:

Huh? .... again. Consider the headstay. Initially it is under some load
as a result of tightening the turnbuckle. The force of the wind on the
headsail results in a sideways load on the headstay. The result of this
load deflects the headstay into a curve to leeward. The amount of
curvature, for a given sideways load, depends on the tightness of the
headstay and the elasticity of the headstay. Since a larger diameter
wire is less elastic (for a given load) than a smaller diameter wire, it
would seem to me that, for an equal initial (turnbuckle) load on the
headstay, a larger wire is preferable. Now then, the general advice is
to tighten the headstay to reduce sag to leeward (and various companies
make nice profits selling hydraulics to make this easy -- er, sorry,
that's the other note). So, if one has installed a larger diameter
headstay, one is inclined to overdo things a bit and tighten too much,
which could well result in hull, chainplate, etc, damage. But, this is
user error (with a bit of creativity, the typical user can break
anything, and often will). It still seems to me that a larger wire
diameter is safer PROVIDED that you do not tighten the rig any more than
you would with a smaller diameter wire. Many books recommend (strongly)
increasing rigging wire diameter one size before going offshore to
minimize the chances of rig failure. Seems to be a difference of
viewpoint here. 

    Pete Gough initially drew my attention to the book in note 1425.
    
    Write or phone: Barnacle Marine Ltd.,
                    Blomfield Place,
                    25, St. Botolphs Street,
                    Colchester,
                    Essex, CO2 7EA
                    England.            Telephone:0206-760555
    
    The Complete Offshore Yacht      Mastercharge or Visa accepted.
                                     Price: 9.95 pounds plus postage.
    
    Regards,
    Tom
    

RE:.13 by MSCSSE::BERENS "Alan Berens"

> Many books recommend (strongly) increasing rigging wire diameter one size 
> before going offshore to minimize the chances of rig failure. Seems to be 
> a difference of viewpoint here.

Alan,  before I would increase rigging wire diameter on any boat,  I would
try to make sure that the rig would still fail before the hull.  Think about
it for a second.  Think about it for a second:  there you are in a killer 
storm,  and get knocked down by a massive wave.  As the boat rolls 360
degrees,  which would you rather happen:  The rigging wire parts or the
chainplates come through the deck?


Phil

re .15:

I'd vastly prefer that nothing fail, no matter what. Certainly, the 
chainplates might fail instead of the wire, so might the turnbuckles or 
mast tangs. Many boats have undersized rigging, and all components 
should be increased in strength before hazarding one's life on the briny 
deep. Highly stressed components will fail from fatigue sooner than less 
stressed parts, which is another reason for increasing wire diameter 
(and chainplate strength, etc). One reason I'm fond of Valiants is that
they have rolled 360 degrees without losing the rig. 

    I think .15 has a very good point. All mechanical systems will fail
    under some load. The "fail safe" design theory says to design the
    system to fail with minimal or no damage. Some bridges have light 
    non-structural beams built into the truss, they fail first and alert
    inspectors -> a mechanical fuse. 
    
    In this case it seems you'd want the shroud to fail just below the
    yield strength of the chainplate and hull.