Rod or wire rigging?
Brent
When looking at sailboat rigging that is 2o years old, I get concerned
when I see rust spots on the stainless steel wire at the swag end
fittings. I assume that the time has come to replace the rigging. Is this
true?
I would also like to know what type of life expectancy rod rigging has.
Does it last much longer than wire, or does it suffers from metal fatigue
over an established period of time. Any insight on comparisons of the two
rigging types would be welcome.
Brent
Paul and Cindy Kruse
Just a few thoughts:
I would be concerned about rod rigging for a couple of reasons.
First, it would have to be a very fancy alloy in order to come
anywhere near the strength of wire rope. These sorts of alloys tend
to be subject to stress corrosion cracking and brittle fracture. If
one wire in the rope fractures, then it is not a big deal. If one
wire in a solid rod cracks, then the whole thing is gone.
A little rust does not mean that it is time to replace standing
rigging. I would wait until I saw a combination of these:
1. A significant reduction in the wire rope diameter.
2. More than three broken wires in one lay in one strand.
3. More than seven broken wires in all strands in one lay.
4. Cracks in the swaged fitting.
These are common inspection points published in many wire rope and
rigging manuals and specifications. I pulled these out of NASA's
spec, which they use for GSE for the Space Shuttle. Rope is almost
always replaced before it gets this bad for strictly cosmetic reasons.
BTW, if a swage is done properly, a crack in it does not mean that you
have zero strengh. I have pulled a cracked swage to 200 percent of
its SWL without failure. Of course, an improperlay swaged fitting
could fail at any load.
The problem with CRES fittings, which are used almost exclusively by
the boating industry, is that they are subject to stress corrosion
cracking. In my experience, they last between three and ten years
before developing cracks. This is why they are generally avoided in
the commercial marine world. Galvanized rigging will far outlast CRES
rigging in the marine environment; though it will not look nearly as
pretty.
Also keep in mind that a 5:1 safety factor is common in wire rope
systems, except in mobile cranes which use a 3.5:1. The reason for
these high safety factors is to allow for serious degradation of the
system without failure.
plk...@iu.net (Paul Kruse)
Jonathan Ho
While different people might have different opinion/standards on
riggings, I would replace immediately any strand that has ONE fray wire.
The risk and cost of further damage is just not worth the savings in time
or money.
Secondly, does the NASA standard applicable to sailing? If the equipment
is to be used in space, a monofilament fishing line would be strong
enough to hold up a mast.
Let's take a survey. How soon do you replace a damaged/weakened rigging?
--
Jonathan Ho
The Winning Formula http://www.front.net/post/sailrace.htm
Gary Gentry
Jonathan,
The NASA standard applies to any use where strength, reliability,
and durability are considerations. Wire ropes are not used in
typical space flight vehicles (discounting possible use in space
station applications due to weight constraints and the reasoning
that you expressed). The previous post pointed out that the
standard applied to GSE or "Ground Support Equipment". Since I
did engineering work on the launch pad GSE for the shuttle at Kennedy
Space center for a number of years, I am quite familiar with wire
ropes and with the quoted standard.
An excellent publication on wire rope assemblies in general is put
out by the Committe of Wire Producers of The American Iron and Steel
Institute. One could POSSIBLY obtain a copy by writing to them at
(last known address) 1000 16th Street, Washington, DC 20036.
As for rigging replacement: In industry, the conditions previously
posted out of the NASA standard(s) are quite sufficient. On my boat,
I'm with you. Any single sign or indication of possible impending
failure is grounds for replacement of the affected component(s).
CHEERS!
Nancy/Carl Hunt
>Let's take a survey. How soon do you replace a damaged/weakened rigging?
Immediately -- even if the damage is one strand broken. Paul's post was
informative, but I agree that NASA standards are not necessarily applicable to
a marine environment. How long rigging last may depend upon where you live
or, more aptly, where you keep your boat. In the pacific northwest, you might
get 15 or more years use. In Clearwater, TX you might get 7 to ten years max
life.
One other comment -- rod rigging can be just as servicable as wire rope. The
major difficulty with rod rigging is detecting failure before failure occurs.
With wire rope you usually can see something happening before it happens.
With rod rigging the signs of failure are more subtle and very difficult to
detect.
Carl
Sterling Family
As you point out, a few damaged strands would only weaken the overall
wire slightly. However, I'd worry that whatever had caused the the
first strands to break (corrosion or whatever) might cause the rest to
fail in the future. The question, how far. I'd certainly finish out a
trip, maybe even a season, but it would bother me until fixed. But then
I like Reno once in a while too. Steve
Jonathan Ho
[snip]
> One other comment -- rod rigging can be just as servicable as wire rope. The
> major difficulty with rod rigging is detecting failure before failure occurs.
> With wire rope you usually can see something happening before it happens.
> With rod rigging the signs of failure are more subtle and very difficult to
> detect.
I have seen rod rigging fail, but it was not the rod -- the guy tightened the rod
so much that he pulled the chain plate out of the fibreglass !
Alvaro HIDALGO
Gary Gentry wrote:
>
> Jonathan Ho wrote:
> >
> > Paul and Cindy Kruse wrote:
> > >
> > > Just a few thoughts:
> > >
> > > I would be concerned about rod rigging for a couple of reasons.
> > > First, it would have to be a very fancy alloy in order to come
Hello,
What about the pros & cons of swagged vs unswagged terminal fittings?
Any comments will be appreciated.
Regards
Alvaro HIDALGO
Graham Moss
We run a marine business on Lake Ontario and do most of the wire rigging
in our area.
- For fresh water use, swaged fittings are the most economical choice
and we never see any failure of the swaged fittings.
- Most production boat builders use(d) swaged fittings, likely due to
economy and reasonable performance.
- Our feeling is that for boats that will spend their lives in warm salt
water climates, that the best System would be to use mechanical fitting
such as the Norseman or Stalok on all terminations. Second best would be
to use mechanical fittings for all but the masthead fittings.
- Where swaged fittings are fitted, it is wise to seal fittings with
epoxy or beeswax or nailpolish or ??. However, doing this on old
fittings probably doesn't help, unless the boat has always been in fresh
water. We sometimes apply epoxy to the outer end of the swage during the
swaging process - this does a neat job as the temperature causes the
epoxy to fully penetrate the wire and prevent moisture entering.
For those considering using 316 wire, consider that the fittings ARE
316, and it is usually the fittings that fail in a salt environment -
Also consider that 316 requires at least one size larger wire - If
anyone has any comments or fist hand experience on the use of 316 vs
302/304 S/S we would be interested to hear.
Graham & Gerry Moss
Windjammer Sails, Box 23004 Amherstview PO Kingston Ont.
Canada K0H 1G0. (613) 389-4349 FAX (613) 389-4762
"Everything for sailing - At a good price!"
MAIL WEB SITE
wind...@fox.nstn.ca http://fox.nstn.ca/~windjamm/
dave anderson
Nancy/Carl Hunt (nan...@usa.net) wrote:
: One other comment -- rod rigging can be just as servicable as wire rope. The
: With wire rope you usually can see something happening before it happens.
: With rod rigging the signs of failure are more subtle and very difficult to
: detect.
What about magnafluxing the rod rigging (can you magnaflux stainless
steel? not too magnetic) magnafluxing isn't that expensive.
Matt Pedersen
In article <nancyh.81...@usa.net>, nan...@usa.net (Nancy/Carl Hunt) says:
>
>One other comment -- rod rigging can be just as servicable as wire rope. The
>major difficulty with rod rigging is detecting failure before failure occurs.
>With wire rope you usually can see something happening before it happens.
>With rod rigging the signs of failure are more subtle and very difficult to
>detect.
>
I agree with Carl, rod is pretty good stuff. It's got less
windage and results in less stress on the boat (you don't need
to tension it as much to keep the mast straight).
As far as fatigue failures go, rod rigging can be bought with
indicators that tell you it's time to replace your rigging.
These are small stainless ferrules with a machined in flaw
that are placed at the upper end of the rod. With the deliberate
flaw they fail before the rod itself does. When they fail they
slide down the rod to the turnbuckle, so if you inspect your rigging
occasionally you've got a pretty good indicator right there.
It's hard for the average boat owner to detect stress corrosion
cracking in any stainless alloy, whether it be rod or rope.
As far as alloys go, I think Navtec makes rod rigging with
Nitronic 50. That's A++ good stuff, much better than 316
stainless.
The disadvantage to rod that I can see, is it's hard to get
it replaced in remote areas. It can also fail catastrophically
if you put a big gouge in it, followed by heavy loads.
Matt
Paul and Cindy Kruse
>Hello,
>What about the pros & cons of swagged vs unswagged terminal fittings?
>Any comments will be appreciated.
>Regards
> Alvaro HIDALGO
What do you mean by "unswagged" terminal fittings? You have so many
to choose from. The few that come to mind as being very excellent
options for some rigging applications are:
1. Conventional spelter socket fittings with zinc.
2. Spelter sockets with epoxy.
3. Hand splicing.
Which of these or others are you interested in?
plk...@iu.net (Paul Kruse)
Paul and Cindy Kruse
dav...@newshost.li.net (dave anderson) wrote:
>Nancy/Carl Hunt (nan...@usa.net) wrote:
>: One other comment -- rod rigging can be just as servicable as wire rope. The
>: major difficulty with rod rigging is detecting failure before failure occurs.
>: With wire rope you usually can see something happening before it happens.
>: With rod rigging the signs of failure are more subtle and very difficult to
>: detect.
>What about magnafluxing the rod rigging (can you magnaflux stainless
>steel? not too magnetic) magnafluxing isn't that expensive.
Mag-particle inspection would be suitable for a 400 series CRES alloy,
but not for the alloys commonly found on a boat. An alloy must be
magnetic for this type of inspection. You could use die penetrant,
but that only detects surface cracks. (Mag-particle will detect
sub-surface cracks on magnetic alloys.)
plk...@iu.net (Paul Kruse)
Philip Wright
Alvaro HIDALGO <hi...@vnet.es> wrote:
>Gary Gentry wrote:
>>
>> Jonathan Ho wrote:
>> >
>> > Paul and Cindy Kruse wrote:
>> > >
>> > > Just a few thoughts:
>> > >
>> > > I would be concerned about rod rigging for a couple of reasons.
>> > > First, it would have to be a very fancy alloy in order to come
>> > > anywhere near the strength of wire rope......
>Hello,
>What about the pros & cons of swagged vs unswagged terminal fittings?
>Any comments will be appreciated.
>Regards
> Alvaro HIDALGO
I have never quite understood the American preference to use Rod
rigging on a cruising boat. We all use 1x19 down here and this would
seem to be pretty much the same in the United Kingdom from memory. The
exception is of course on the race track, in that case it is certain
that for stretch, and low wind resistance rod would surely be the item
of choice.
The advantages of 1x19 to the cruising rig are numerous and after 30
years at sea I can say that I have never seen an actual case of
entirely letting gowithin the cable proper. It has always been at the
swage or under the very bottom of the terminal betweeen the pin hole
and the outside radius. It is a pity that all cruisers don't inspect
these terminals with ahigh powered magnifying glass at least eevry 3
months or after every "high stress passage" . I change ALL of my
satanding rigging between 7 years and 10 years. Costly? yes! but of
great bloody comfort down here where the wind blows like blazes for
lots of the year and where there is no real refuge except to stay at
sea. I figure that when I next replace my rigging it will be fitted
with Norseman type terminals which in contrast to rod rigging is about
the best thing to ver happen to terminals
Terry Schell
sa...@werple.mira.net.au (Philip Wright) writes:
<snip>
>The advantages of 1x19 to the cruising rig are numerous and after 30
>years at sea I can say that I have never seen an actual case of
>entirely letting gowithin the cable proper. It has always been at the
>swage or under the very bottom of the terminal betweeen the pin hole
>and the outside radius. It is a pity that all cruisers don't inspect
>these terminals with ahigh powered magnifying glass at least eevry 3
>months or after every "high stress passage" . I change ALL of my
>satanding rigging between 7 years and 10 years. Costly? yes! but of
>great bloody comfort down here where the wind blows like blazes for
>lots of the year and where there is no real refuge except to stay at
>sea. I figure that when I next replace my rigging it will be fitted
>with Norseman type terminals which in contrast to rod rigging is about
>the best thing to ver happen to terminals
While there are some advantages to 1x19 rigging... I am not sure I
agree with the ones you listed. The advantages for wire are:
*cheaper
*easier for amatures to inspect
*avail. almost everywhere
The disadvantages for wire are:
*more static tension (hard on boat and possibly mast)
*typically rod rigging has lower rates of failure
*typically more weight and windage aloft
*possibly more sail chafe (if you are the type of person who allows
the sails to touch the shrouds)
*allows the mast to bend further out of column
Given these trade offs, I would think that rod rigging would be
advisable for anyone who isn't willing to inspect their standing
rigging (from masthead to chainplates) twice a year or so and anyone
who has a wood boat or mast.
Just my opinion,
Terry Schell
ga...@pacintl.com
In article <50lngd$5...@eplet.mira.net.au>,
Philip Wright <sa...@werple.mira.net.au> wrote:
>Alvaro HIDALGO <hi...@vnet.es> wrote:
>
>>Gary Gentry wrote:
>>>
>>> Jonathan Ho wrote:
>>> >
>>> > Paul and Cindy Kruse wrote:
>>> > >
>>> > > Just a few thoughts:
>>> > >
>>> > > I would be concerned about rod rigging for a couple of reasons.
>>> > > First, it would have to be a very fancy alloy in order to come
>>> > > anywhere near the strength of wire rope......
>
>
>>Hello,
>
>>What about the pros & cons of swagged vs unswagged terminal fittings?
>>Any comments will be appreciated.
>>Regards
>> Alvaro HIDALGO
>
>I have never quite understood the American preference to use Rod
>rigging on a cruising boat. We all use 1x19 down here and this would
>seem to be pretty much the same in the United Kingdom from memory. The
>exception is of course on the race track, in that case it is certain
>that for stretch, and low wind resistance rod would surely be the item
>of choice.
>years at sea I can say that I have never seen an actual case of
>entirely letting gowithin the cable proper. It has always been at the
>swage or under the very bottom of the terminal betweeen the pin hole
>and the outside radius. It is a pity that all cruisers don't inspect
>these terminals with ahigh powered magnifying glass at least eevry 3
>months or after every "high stress passage" . I change ALL of my
>satanding rigging between 7 years and 10 years. Costly? yes! but of
>great bloody comfort down here where the wind blows like blazes for
>lots of the year and where there is no real refuge except to stay at
>sea. I figure that when I next replace my rigging it will be fitted
>with Norseman type terminals which in contrast to rod rigging is about
>the best thing to ver happen to terminals
>
Since I don't have to be an expert to toss in my 2 cents valued
comment, :) I can say as someone who charters frequently, that rod
rigging has one nice advantage over wire... when you brush up against
it while forward, it doesn't tear your skin, which has happened to
several people I know.
Perhaps you're right about the wire rigging being superior. All I know
is that the people who charter and who crew on chartered boats, prefer
something that doesn't fray. My experience is that charter companies
don't spend all the time they should maintaining boats (or don't
insist the owner do). This results in things like frayed rigging.
BTW, the only refuge from the wind in the SF bay is in a bar. :)
Jonathan
(http://www.pacintl.com/sailing.html)
Sam Boyle
In an interesting tour of the Valiant Factory, Rich Worstel told me they
won't use anything but Rod. He cited the benefits you just mentioned as
well as the observation that Valiant had no known reports of rod rigging
failures -- he felt it was a superior solution for a boat designed to go
offshore.
Regards,
-- Sam
-----------------------------------------------------------------
sbo...@sailnet.com
http://www.sailnet.com/
-----------------------------------------------------------------
Tim Mueller
(stuff deleted...)
Having been tutored on this by Capt. Giffy Full, here is what I can
remember of his edicts (50 yrs in in the business makes everything he says
an edict):
1. Frayed standing rigging in unsafe. However it got that way, it needs
to be replaced. Of course, this could be a splice which needs to be
reserved or properly booted, but mid-stay fraying is unsafe.
2. Wire is easier to inspect than rod, and usually cheaper to replace,
especially if you're not in a major port. (Try getting rod stock in the S.
Pacific, say, Fiji?)
3. The swag terminals are prone to corrosion from the inside out; inspect
VERY carefully. A simple prophylactic is beeswax, melted into the fitting
after swagging.
Paul and Cindy Kruse
I have been following this discussion of rod vs. wire
rope rigging with great interest, but am now confused
about several apparent inconsistencies. Perhaps someone
can help clear up my confusion.
Quarter inch 6 x 19 IWRC CRES wire rope has a nominal
strength of 6400 pounds. If a quarter inch rod were to
have the same strength, it would have to be made of a
material of at least 130,400 psi yield. I do not know
what alloy rod rigging is typically made of, but two
people have written me that they are using 316 CRES.
According to my Ryerson handbook, rods of this alloy
come with a yield strength of only 35,000 psi. What
this means is that a rod made of this material would
have to be a half inch diameter to have the same
strength as quarter inch wire rope.
Hence, the cause of my confusion: Several postings have
claimed that rod rigging is more aerodynamic than wire
rope. How can this be if the rods have to be twice the
diameter of the wire rope with the equivalent strength?
Ditto concerning claims of weight savings.
According to my ASM handbook, a number of CRES alloys
can be heat treated to an equivalent wire rope strength;
but most of these alloys are not suited for marine
applications.
So my question is: What alloy CRES is giving you guys
rods that are as strong as wire rope or stronger, and
how are you heat treating it? None of the heat treating
facilities that I am familiar with are able to handle a
rod as long as you would need for mast rigging.
Other people have written that rod rigging has an
advantage, in that it does not require as high of a
pre-load as wire rope. Why is this? All the rigging
shops that I do business with will take the
construction stretch out of the wire rope rigging before
they deliver it to me. Are there that many rigging
shops out there that are cutting this corner, that you
must take the construction stretch out after you install
the rigging? If the construction stretch is taken out
of the wire rope, then it should require the same
preload as rod rigging.
Also, if weight and aerodynamics are such important
objectives for you guys with rod rigging, why are you
not using galvanized wire rope? It has an even higher
strength than CRES rope, so that you can use a smaller
diameter rope. It has also been my experience in
commercial and military marine applications that
galvanized wire rope will outlast CRES rope in a marine
environment. Not only that, but it is cheaper.
Thanks in advance for any help in understanding these
things.
plk...@iu.net (Paul Kruse)
Fred Murgetroid
Had a friend of mine experience the failure of a swage fitting on his
Flying Scot while sailing back from Whidbey Island on a planing reach.
He hit a powerboat wake there was a brief slow motion life passing
before the eyes dismasting and there he was in the middle of the
strait. I always replace standing rigging with one broken wire, and
ever since this event pay close attention to the fittings. They usually
leave a little bit of the wire showing so you can tell if it
creaps...Cheap insurance that standing rigging....
David Tallis
>Let's take a survey. How soon do you replace a damaged/weakened rigging?
>--
>Jonathan Ho
>The Winning Formula http://www.front.net/post/sailrace.htm
Personally I would replace my standing rigging at the first sign of
degradation wether that be one broken strand, cracking of the swage or
rusting around the swage. For the higher performance racing yachts I
have replaxced the rigging at two year intervals wether the rigging
looked damaged or not. You just don't know how close you are to a
fatigue failure. Personally I have lost a rig two months after it was
inspected by a rigger and there were no visible signs of damage prior
to it falling. Unless you go to all the expense of X-ray and
ultrasonic testing of the rigging [ which is typically only done for
maxis etc whose rigging is expensive to replace] then an ounce of
prevention is far better than pushing your luck. The cost of replacing
a stay is, for your smaller boat, much cheaper than your insurance
excess and in the long run you just don't want the hassle of having a
rig fall down on top of you. I look at it much like putting cheap
tyres on your car, they are the things responsible for keeping you
attached to earth so why put cheap and nasty ones on, you're just
asking for trouble. When you're out in a big blow on a lee shore you
can beat your life that's when the riggin will let go.
Cheers
David Tallis
Terry Schell
plk...@iu.net (Paul and Cindy Kruse) writes:
>I have been following this discussion of rod vs. wire
>rope rigging with great interest, but am now confused
>about several apparent inconsistencies. Perhaps someone
>can help clear up my confusion.
>Quarter inch 6 x 19 IWRC CRES wire rope has a nominal
>strength of 6400 pounds. If a quarter inch rod were to
>have the same strength, it would have to be made of a
>material of at least 130,400 psi yield. I do not know
>what alloy rod rigging is typically made of, but two
>people have written me that they are using 316 CRES.
>According to my Ryerson handbook, rods of this alloy
>come with a yield strength of only 35,000 psi. What
>this means is that a rod made of this material would
>have to be a half inch diameter to have the same
>strength as quarter inch wire rope.
>Hence, the cause of my confusion: Several postings have
>claimed that rod rigging is more aerodynamic than wire
>rope. How can this be if the rods have to be twice the
>diameter of the wire rope with the equivalent strength?
>Ditto concerning claims of weight savings.
<snip>
There must be some error in your calculations. The breaking strength
of wire and rod are actually equal for a given cross sectional area...
but that is cross section of material, not of the resulting wire. The
rod is 20% stronger for the same resulting diameter because the
"air" in between strands in wire reduces the effective cross sectional
area.
To my knowledge, AISI 316 is the most common alloy for both wire and
rod. I understand that there are some more exotic rod alloys out there
and I cannot speak to their properties.
The big difference is in elongation under load. When a wire is placed
under load it can stretch more (because it can "squeeze" out the air
between strands). There is no way around this with wire... the best
you can do is pre-tension the rig so that the wire is permanantly
"squeezed" and so the mast will not fall off to leeward as much when
the sail forces increase the tension.
I hope this helps...
Terry
Matt Pedersen
In article <514i4v$g...@cc.iu.net>, plk...@iu.net (Paul and Cindy Kruse) says:
>
>I have been following this discussion of rod vs. wire
>rope rigging with great interest, but am now confused
>about several apparent inconsistencies. Perhaps someone
>can help clear up my confusion.
>
>Quarter inch 6 x 19 IWRC CRES wire rope has a nominal
>strength of 6400 pounds. If a quarter inch rod were to
>have the same strength, it would have to be made of a
>material of at least 130,400 psi yield. I do not know
>what alloy rod rigging is typically made of, but two
>people have written me that they are using 316 CRES.
The typical alloy used by Navtec is Nitronic 50. They
list the breaking strength of their -6 (.198 Dia) rod
as 6300 pounds. Sorry I don't have the material
properties of Nitronic 50 alloy handy.
>Hence, the cause of my confusion: Several postings have
>claimed that rod rigging is more aerodynamic than wire
>rope. How can this be if the rods have to be twice the
>diameter of the wire rope with the equivalent strength?
>Ditto concerning claims of weight savings.
Comparing a rod to 302 wire rope, shows almost no weight
savings. However, the rod has better corrosion resistance,
and of course a smaller diameter. The more corrosion
resistant 316 alloy is weaker than 302, so therefore needs
to be heavier (greater cross section).
>So my question is: What alloy CRES is giving you guys
>rods that are as strong as wire rope or stronger, and
>how are you heat treating it? None of the heat treating
>facilities that I am familiar with are able to handle a
>rod as long as you would need for mast rigging.
I can't vouch for whether the Nitronic 50 is heat treated,
but if it is it could be coiled, or even induction heat treated.
>Other people have written that rod rigging has an
>advantage, in that it does not require as high of a
>pre-load as wire rope. Why is this?
The wire stretches more under load; the coiled strands have
a tendency to want to unravel under load, which is something
rod doesn't do. Rod has about 30% less stretch than 1x19
wire. By the way, typical rigging is either 7x7 or 1x19
(7x7 if you want flexibility, like halyards or running
backs; 1x19 where you want less stretch, like headstays
and shrouds).
The idea is to keep the mast from sagging off under load,
so with a given loading condition the mast with rod will
sag off least. Or to look at it another way, you have either
1) less load on the rod for the same sag, or
2) less sag on the rod for the same load.
>Also, if weight and aerodynamics are such important
>objectives for you guys with rod rigging, why are you
>not using galvanized wire rope? It has an even higher
>strength than CRES rope, so that you can use a smaller
>diameter rope. It has also been my experience in
>commercial and military marine applications that
>galvanized wire rope will outlast CRES rope in a marine
>environment. Not only that, but it is cheaper.
If you don't mind having rust on your decks and fittings
and doing a lot more mast climbing for visual inspection,
then galvanized may be acceptable. It is easier to tell
when it's getting toward the end of its useful life. Be
careful to get hot dip galvanized rope, the electrogalvanized
stuff just doesn't get a thick enough layer of zinc put down to
provide good protection.
>Thanks in advance for any help in understanding these
>things.
>
>plk...@iu.net (Paul Kruse)
Hope this helps.
Matt
Paul and Cindy Kruse
tsc...@s.psych.uiuc.edu (Terry Schell) wrote:
>There must be some error in your calculations.
Yes, there must be some error in my calculations. Otherwise, what you
say simply cannot be true. I was hoping that someone could show me
the error.
>The breaking strength
>of wire and rod are actually equal for a given cross sectional area...
That depends upon the strength of the metal being used. The
difference in strength between one sample of metal and another can be
as much as a factor of 30 or more. Even within the same alloy, it can
be a factor as high as eight or ten, depending upon heat treatment and
work hardening. So a simple area comparison is not going to work.
>but that is cross section of material, not of the resulting wire. The
>rod is 20% stronger for the same resulting diameter because the
>"air" in between strands in wire reduces the effective cross sectional
>area.
>To my knowledge, AISI 316 is the most common alloy for both wire and
>rod.
This is true, but 316 can be either work hardened or heat treated for
additional strength. It is quite possible in theory to have a 316 rod
that has the same strength as a 316 wire rope; but not without some
very expensive manipulation of the rod's metalurgical properties.
Part of my question is how is this done? Has someone come up with a
method that actually works and is within the budget of a recreational
sailor?
The wires in a wire rope are cold worked to a very high strength. To
my knowledge, it is not practical to heat treat a rod to the same
strength. I'm hoping that someone can add to my knowledge in this.
>I understand that there are some more exotic rod alloys out there
>and I cannot speak to their properties.
I'm hoping that someone can...
>The big difference is in elongation under load. When a wire is placed
>under load it can stretch more (because it can "squeeze" out the air
>between strands). There is no way around this with wire... [snip]
Actually, there is. Proof loading the wire before installing it will
take out the construction stretch. After that, all the wires are
pretty well settled. Buying pre-formed wire rope helps greatly. You
can also use high density wire rope, in which the wires are not round.
A high density wire rope will have the same cross sectional area of
metal as a solid rod, to within about five percent or less. In the
last couple of years, high density ropes have become cheap enough that
we have started using them on our mobile cranes in my regular job.
plk...@iu.net (Paul Kruse)
Paul and Cindy Kruse
pede...@halcyon.com (Matt Pedersen) wrote:
>The typical alloy used by Navtec is Nitronic 50. They
>list the breaking strength of their -6 (.198 Dia) rod
>as 6300 pounds. Sorry I don't have the material
>properties of Nitronic 50 alloy handy.
I appreciate this a great deal. That is a very impressive strength
for a rod of that size. Perhaps someone could post what the alloy is
and how it is hardened?
Could you post their address so that I can get a copy of their manual?
>Comparing a rod to 302 wire rope, shows almost no weight
>savings. However, the rod has better corrosion resistance,
>and of course a smaller diameter. The more corrosion
>resistant 316 alloy is weaker than 302, so therefore needs
>to be heavier (greater cross section).
As my previous calculations showed, you are correct. 316 is certainly
weaker than the rod you are talking about.
>I can't vouch for whether the Nitronic 50 is heat treated,
>but if it is it could be coiled, or even induction heat treated.
I suspect that it is cold work hardened by drawing it, similar to how
wire is made. Perhaps someone can post something on this?
>>Other people have written that rod rigging has an
>>advantage, in that it does not require as high of a
>>pre-load as wire rope. Why is this?
>The wire stretches more under load; the coiled strands have
>a tendency to want to unravel under load, which is something
>rod doesn't do. Rod has about 30% less stretch than 1x19
>wire. By the way, typical rigging is either 7x7 or 1x19
>(7x7 if you want flexibility, like halyards or running
>backs; 1x19 where you want less stretch, like headstays
>and shrouds).
Yes, the fewer wires the better for most standing rigging. It would
last better, but also tends to have a slightly lower strength.
>The idea is to keep the mast from sagging off under load,
>so with a given loading condition the mast with rod will
>sag off least. Or to look at it another way, you have either
>1) less load on the rod for the same sag, or
>2) less sag on the rod for the same load.
Are you making this comparison with wire rope that has had the
construction stretch removed?
Also, do you have any marine experience with high density wire rope?
>If you don't mind having rust on your decks and fittings
>and doing a lot more mast climbing for visual inspection,
>then galvanized may be acceptable. It is easier to tell
>when it's getting toward the end of its useful life. Be
>careful to get hot dip galvanized rope, the electrogalvanized
>stuff just doesn't get a thick enough layer of zinc put down to
>provide good protection.
Are you speaking about galvanized rope by experience? If so, I would
like to talk with you more off line about this. Your experience
appears to be different than mine.
>Hope this helps.
It does. Thanks for posting it.
plk...@iu.net (Paul Kruse)
Paul Kamen
plk...@iu.net (Paul and Cindy Kruse) writes:
>.....do you have any marine experience with high density wire rope?
I'm using "dyform" wire rope on my Merit 25, with good results.
--
fish...@netcom.com
http://www.well.com/~pk/fishmeal.html
-"Call me Fishmeal"-
Frank Ross
Paul and Cindy Kruse wrote:
>
> rope rigging with great interest, but am now confused
> about several apparent inconsistencies. Perhaps someone
> can help clear up my confusion.
>
>
> So my question is: What alloy CRES is giving you guys
> rods that are as strong as wire rope or stronger, and
> how are you heat treating it? None of the heat treating
> facilities that I am familiar with are able to handle a
The alloy is called Nitronic 50 and when it is cold worked 60% it has a
yield strength of about 199,000 psi. It does not need heat treating. If
you want to do it right get an alloy called MP35N which has a yield
strength of 290,000 psi when properly cold worked and aged. I suspect
that the people who told you that they had 316 rod rigging actually have
Nitronic 50. You can't tell the difference by looking at it.
> Other people have written that rod rigging has an
> advantage, in that it does not require as high of a
> pre-load as wire rope. Why is this? All the rigging.
There is a presumption that the effective modulus of solid rod is
slightly higher than that of multi-strand wire rope. I am not sure that
I believe this and I have never tested it directly.
Frank Ross
Double Eagle USA 97357
vande...@alpha.unisg.ch
plk...@iu.net (Paul and Cindy Kruse) writes:
>I have been following this discussion of rod vs. wire
>rope rigging with great interest, but am now confused
>about several apparent inconsistencies. Perhaps someone
>can help clear up my confusion.
>Quarter inch 6 x 19 IWRC CRES wire rope has a nominal
>strength of 6400 pounds. If a quarter inch rod were to
>have the same strength, it would have to be made of a
>material of at least 130,400 psi yield. I do not know
>what alloy rod rigging is typically made of, but two
>people have written me that they are using 316 CRES.
>According to my Ryerson handbook, rods of this alloy
>come with a yield strength of only 35,000 psi. What
>this means is that a rod made of this material would
>have to be a half inch diameter to have the same
>strength as quarter inch wire rope.
>Hence, the cause of my confusion: Several postings have
>claimed that rod rigging is more aerodynamic than wire
>rope. How can this be if the rods have to be twice the
>diameter of the wire rope with the equivalent strength?
>Ditto concerning claims of weight savings.
Your calculations may be right, your assumptions are not.
Rods are not made of 316 but usually of Nitronic 50,
UNS No. S21910, a high strength austenitic stainless steel
alloy made by Armco. It is composed as follows:
%
C 0.06
Mn 4.0-6.0
Si 1.00
Cr 20.5-23.5
Ni(max) 11.5-13.5
P 0.04
S 0.03
Mo 1.5-3.0
N 0.2-0.4
Cb 0.1-0.3
Alternatively, but much more seldom and more expensive,
Cobalt MP25N is used for rods. Occasionally, for certain
applications where strength is less important than weight
one can also see Titanium rods. A compromise, finally, is
Dyform (British Ropes trademark?) 1x19 wire, which consists
of specially formed wires to put more metal into the same
diameter.
A regular 1x19 wire with a diameter of 6.35mm (1/4") has
a breaking strength of 3220kg. An equal diameter Dyform
1x19 wire has a breaking strength of 4020kg, Nitronic 50
of 6.5mm diameter (6.35 not available) 4500kg and Cobalt
MP35N of 6.35mm 5355kg.
For equal diameter wires/rods of dia 9.5mm the values are:
1x19 6580kg
Dyform 8760kg
Niitronic 50 9750kg
Cobalt MP35N 12049kg
Here is some additonal comparative data calculated for the
same given load from Rggarna, taken from Matthew Sheehan's
1990 "Sailing Rigs and Spars" (good book):
Diameter Breaking Stretch Weight
strength
mm kg mm/m kg/m
Standard 1x19 stainless wire 11.00 9450 2.1 0.451
Dyform 1x19 stainless wire 10.00 9770 2.1 0.466
Nitronic 50 Rod 9.50 9750 1.74 0.560
Cobalt MP35N Rod 8.71 10045 1.73 0.500
(stretch calculated at 25% breaking strength)
Hope this helps.
Cheers from Claas (who has a Nitronic rig)
Paul and Cindy Kruse
Thanks for the post. It must have taken you some time to put
together. This is just the sort of data that I was looking for.
plk...@iu.net (Paul Kruse)
Paul and Cindy Kruse
fish...@netcom.com (Paul Kamen) wrote:
> plk...@iu.net (Paul and Cindy Kruse) writes:
> >.....do you have any marine experience with high density wire rope?
>I'm using "dyform" wire rope on my Merit 25, with good results.
I'm glad to hear that. I have been using dyform 6 x 36 IWRC XIPS on
several mobile cranes with very good results. I did not know if
anyone was using it in a marine application. What alloy are you
using?
plk...@iu.net (Paul Kruse)
Scott Truesdell
David....@uts.edu.au (David Tallis) wrote:
> >Let's take a survey. How soon do you replace a damaged/weakened rigging?
>
> >--
> >Jonathan Ho
>
>
> ...The cost of replacing
> a stay is, for your smaller boat, much cheaper than your insurance
> excess and in the long run you just don't want the hassle of having a
> rig fall down on top of you.
And if you're seriously on a budget, you can get away with replacing only
three stays -- the two uppers and the forestay -- say, every four years
and all standing rigging every eight years.
Sealing swages against corrosive intrusion is an easy do-it-yourself job.
--scott
Paul and Cindy Kruse
Frank Ross <frank...@qmail2.aero.org> wrote:
>The alloy is called Nitronic 50 and when it is cold worked 60% it has a
>yield strength of about 199,000 psi. It does not need heat treating. If
>you want to do it right get an alloy called MP35N which has a yield
>strength of 290,000 psi when properly cold worked and aged. I suspect
>that the people who told you that they had 316 rod rigging actually have
>Nitronic 50. You can't tell the difference by looking at it.
Thanks for the information. This would certainly beat out the wire
rope for strength.
>> Other people have written that rod rigging has an
>> advantage, in that it does not require as high of a
>> pre-load as wire rope. Why is this? All the rigging.
>There is a presumption that the effective modulus of solid rod is
>slightly higher than that of multi-strand wire rope. I am not sure that
>I believe this and I have never tested it directly.
Actually, it is very difficult to model the Young's modulus for wire
rope. It is not linear, and varies in a somewhat random step function
as load is increased. It also has a terrible hysterisis in it for new
rope. This is what I had previously refered to as "construction
stretch," by which it is commonly known in the wire rope industry. If
you proof load it to 40 percent of breaking before installing it, you
will have taken out the construction stretch. After that, it will
behave fairly close to the solid rod for a while, before it sort of
goes wild for about the last 50 percent of its strength before
breaking.
All this applies only to standard rope with round wires. High density
ropes tend to act more like rods.
Again, thanks for the post. I sort of figured that I would connect
with at least a few people who knew what I wanted to know when I
posted that RFI.
plk...@iu.net (Paul Kruse)
Graham Moss
Regarding rod vs Wire, a short story - A friend of mine has a son who
owns an X-102 which has rod rigging. The son is in the process of
sailing the X-102 around the world. So far it has been sailed from
Kingston to Newfoundland, down the Coast, through the Panama, to Hawaii,
to Victoria, back to Hawaii and soon to Singapore (Mostly single handed)
My friend, who happens to be a materials engineer, joined his son on the
trip from Hawaii to Victoria - During this trip, one of the rod upper
stays parted - They were lucky to not lose the spar and to have spare
wire stays on board. My friend brought back the broken pieces and did an
analysis on the cause of the failure - It was simply a fatigue failure.
This boat had seen more than most, but what worried me was that when rod
fails, it fails completely and suddenly - With wire, usually one or two
strands go and this can be seen and repaired before the mast is lost.
Something to think about?
Regards,
Graham Moss
Graham Moss
Paul Kamen wrote:
>
> plk...@iu.net (Paul and Cindy Kruse) writes:
>
> >.....do you have any marine experience with high density wire rope?
>
> I'm using "dyform" wire rope on my Merit 25, with good results.
On J-24,s Dyform is sometimes used, but only for lowers as this wire
apparently is hard on Mylar headsails when tacking. I have no first hand
experience and wonder if you have experienced any problems with your
sails chafing?
Regards,
Graham Moss
J-24 # 4260 "Kwela"
Matt Pedersen
In article <5160ka$o...@cc.iu.net>, plk...@iu.net (Paul and Cindy Kruse) says:
>
>pede...@halcyon.com (Matt Pedersen) wrote:
>
>>The typical alloy used by Navtec is Nitronic 50. They
>>list the breaking strength of their -6 (.198 Dia) rod
>>as 6300 pounds.
>I appreciate this a great deal. That is a very impressive strength
>for a rod of that size. Perhaps someone could post what the alloy is
>and how it is hardened?
Navtec says the alloy typically has a yeild strength of 190 kpsi.
It cannot be heat treated, but it does gain strength from cold
working. I have some data from Carpenter Stainless on their
equivalent of Nitronic 50 (Nitronic 50 is a trade name).
Diameter % Cold Work 0.2% Offset Yield Ultimate % Elongation
1.00 0 65 kpsi 120 kpsi 45
0.25 0 65 120 40
0.230 15 140 165 20
0.208 30 170 190 15
0.185 45 190 215 10
0.158 60 215 230 8
If you want to see the details of composition, it is available
at http://www.abbottball.com. Basically it's 22% Chromium,
13% Nickel, 5% Manganese, 0.06% Carbon.
>Could you post their address so that I can get a copy of their manual?
Navtec
New Whitfield Street
P.O. Box 388
Guilford, CT 06437
(203) 458-3163
>>The idea is to keep the mast from sagging off under load,
>>so with a given loading condition the mast with rod will
>>sag off least. Or to look at it another way, you have either
>>1) less load on the rod for the same sag, or
>>2) less sag on the rod for the same load.
>
>Are you making this comparison with wire rope that has had the
>construction stretch removed?
1x19 wire is usually wound with a pretty high load to begin
with, so it is usually not post processed to remove
construction stretch. 7x7 usually doesn't come with the
construction stretch removed.
Matt
Paul Kamen
>What alloy are you using?
Have no idea - it's the wire that was supplied by Ballenger Spar Systems
when they built my replacement mast last year. Very modest cost increment
over conventional wire.
Frank Ross
Paul and Cindy Kruse wrote:
>
>
> for a rod of that size. Perhaps someone could post what the alloy is
> and how it is hardened?
From "Metals Handbook 9th Edition" Nitronic 50 ...C 0.06 max, Cr 21.0,
Ni 12.0, Mo 2.0, N 0.30, Nb 0.20, Mn 5.0. I have no first hand knowledge
of how Navtec orders its rod but Nitronic 50 has been around the
fastener industry for years and it is usually cold worked about 60% to
develop the 212ksi ultimate tensile strength. This is a nice compromise
between strength and ductility and it allows for a small amount of
additional cold work such as the cold heading operation that the rigger
needs to do so that the rod can be terminated. IMHO the real "magic" of
rod rigging is not in the properties of the rod itself but the clever
way in which Navtec has solved the problem of "how the heck do you put a
fitting on the end of this stuff" particularly given the fatigue
environment.
Another alloy used for rod rigging is MP35N which is Co 35.0, Ni 35, Cr
20, Mo 10. This material is a bit more expensive than Nitronic 50 but it
too has been in high strength corrosion resistant fasteners for years.
By a process of cold work and ageing it can be brought up to 300 ksi
ultimate tensile strength. Also, MP35N has a modulus of elasticity of
33.6E6 where as the modulus of Nitronic 50, 304, 316, et al. is about
28E6. This means that you can carry heavier loads at less deflection
with the MP35N.
> >sag off least. Or to look at it another way, you have either
> >1) less load on the rod for the same sag, or
> >2) less sag on the rod for the same load.
>
> Are you making this comparison with wire rope that has had the
> construction stretch removed?
> .
I too have heard this argument but would like to do some testing. Once
the construction stretch is removed it is hard for me to see how the
stress-strain behavior of the wire rope is significantly different from
that of rod. Does anyone have some rod that they could donate for some
destructive testing?
> Also, do you have any marine experience with high density wire rope?
> .
Yes, I have gone to all dyform wire but I can not say, objectively,
whether it has helped or not. All I can say is I don't have to retighten
the shrouds as much as I had to when I had 304 McWhite wire.
Frank Ross
Paul Kamen wrote:
>
>
> I'm using "dyform" wire rope on my Merit 25, with good results.
> .
Just wondering, were you using the dyform when you lost the two masts in
a row?
Martin Schoon
Graham Moss wrote:
>
> Paul Kamen wrote:
> >
> > plk...@iu.net (Paul and Cindy Kruse) writes:
> >
> > >.....do you have any marine experience with high density wire rope?
> >
> > I'm using "dyform" wire rope on my Merit 25, with good results.
>
> apparently is hard on Mylar headsails when tacking. I have no first hand
> experience and wonder if you have experienced any problems with your
> sails chafing?
>
as far as I am concerned. They do have a somewhat abrasive finish (sp?).
No problem for me as I only have a blade-jib.
--
========================================================================
Martin Schoon <Martin...@era-a.ericsson.se>
"Problems worthy of attack
prove their worth by hitting back"
Piet Hein
========================================================================
Fiori Product Development
In article <517r6r$5...@nwnews.wa.com>, pede...@halcyon.com says...
>Navtec says the alloy typically has a yeild strength of 190 kpsi.
^^^^^^
Sorry, that should read "ultimate"
Matt (posting from work)
Paul Kamen
Frank Ross <frank...@qmail2.aero.org> writes:
>Just wondering, were you using the dyform when you lost the two
>masts in a row?
No dyform on the first failure. Mast was old, wind was strong, backstay
was tight, mast just broke off at the hounds (where forestay attaches).
Dyform might have contributed in some way to the second failure. The new
rig was set up with the same backstay adjuster, and the same displacement
of the backstay blocks might have produced more load in the rig because
of the reduced forestay stretch. The new mast failed when the lower panel
buckled to one side, right at the spinnaker halyard exit port. The dyform
wire was all inspected by Ballenager and declared re-useable.
Now I use less backstay displacement.