This isn't about MacGregors... but you're my friends,

[robbarnes1965]

I knew beer solves everything!

[mastreb]

there are numerous drawbacks to increasing the wire diameters having to do with the elasitic modulus of the steel and the force.

Judy, my presumption is that heavier duty wire would have less spring at a given load, thereby increasing the shock loading of the mast and transferring more force onto the fittings than a smaller, more elastic wire would transmit?

So what you really would want is the most elasticity within your allowed range of motion that can stand up to the maximum expected strain force, correct? This would argue for the thinnest wire that meets the maximum load + safety margin specification.

Matt

[DaveB]

Lets face it, fatuige will weaken swage or any other connection in due time. Setting a original Stay is only a giving strength it was installed, over time structual failures begin to happen.
Wonder how many people ck their standing rigging connections before they go out Trailer Sailing.
I see absolutly no reason why not go with a 5/32 headstay on a boat that has no Bulkheads suporting a standing riged boat.
The Boat flexes and takes any shock the standing rigging does.
I have done one size larger on my Alberg 35 and went thru 40 ft. seas for 3 days. I had no problems on the 12 day crossing .
Mac.X is a very flexable hull and just getting rail down 20 degrees you can feel the slack of the leeward stay. Not so on a bulkhead mounted stay.
Why I like a 5/32 headstay and will take acidential jib, 4 ft hammer bow wave, quarter powerboat wave 5 ft. and take those shock waves with stride.

Dave

[Dimitri-2000X-Tampa]

Wow, only 1.75 lbs more huh...guess I didn't do the math..

It still seems a bit strange that the headstay is thinner than the side stays, afterall, it is a triangle of sorts. So far I have only replaced the side shrouds but not the forestay, but I do keep an eye on it to make sure that no strands have ever broken free, etc. As for metal fatigue, that is not really high up on my list of concerns here. Obviously, broken strands and corrosion could lead to disaster but if it looks good, does it really have a limited shelf life due to fatigue?

[Sumner]

Wow, only 1.75 lbs more huh...guess I didn't do the math..

It still seems a bit strange that the headstay is thinner than the side stays, afterall, it is a triangle of sorts. So far I have only replaced the side shrouds but not the forestay, but I do keep an eye on it to make sure that no strands have ever broken free, etc. As for metal fatigue, that is not really high up on my list of concerns here. Obviously, broken strands and corrosion could lead to disaster but if it looks good, does it really have a limited shelf life due to fatigue?

A new forestay is less than $50.00 I'd just put one on if there is any doubt.

Sum

===================================
Our MacGregor 26-S
Our Endeavour 37
Our Trips to Utah, Idaho, Canada, Florida
Mac-Venture Links

[Judy B]

Wow, only 1.75 lbs more huh...guess I didn't do the math..

It still seems a bit strange that the headstay is thinner than the side stays, afterall, it is a triangle of sorts. So far I have only replaced the side shrouds but not the forestay, but I do keep an eye on it to make sure that no strands have ever broken free, etc. As for metal fatigue, that is not really high up on my list of concerns here. Obviously, broken strands and corrosion could lead to disaster but if it looks good, does it really have a limited shelf life due to fatigue?

I dont' think shelf life is the right term. That's how long something lasts if you aren't using it. You use the wires on your boat.

Work hardening is what happens when you bend most metals. Your shrouds get bent.
Metal fatigue is what happens at places where point loads converge. if your rigging isn't aligned in a very specific way, point loading occurs.

Over simplyfying, we can say individual wires in shrouds break due to work hardening and metal fatigue. They don't break because the wire rope isn't strong enough to handle the tension we put on it.

Trailerable boats are notorious for bending wires in weird ways during mast raising and lowering.
Forestays with furlers can contribute to point loading unless the installation is done with great attention to detail

1. They typically break because we subject them to sideways forces that break a few strands at a time.
2. They fail because of corrosion inside the Nico press ferrule.

It seems to me: Nico press swages seem to be more prone to corrosion than rotary swages. I would guess that there are ways to prevent corrosion, but I'm no expert on nico swages. I would guess that you could put some special kind of sealant on the wire before swaging the ferrule onto it. Professional riggers put a sealant on the wire when they use a rotary swage machine, but again, I'm no expert on rotary swaging either.

[mastreb]

Wrapping the swages with butyl tape and pressing it on will certainly slow down corrosion due to exposure, and can't hurt anything. The tape should last quite a while.

[Judy B]

Wrapping the swages with butyl tape and pressing it on will certainly slow down corrosion due to exposure, and can't hurt anything. The tape should last quite a while.

Riggers put sealant inside the swage, not around the outside. The idea of putting it inside is to completely preclude water from contacting the stainless steel which is inside the swage fitting. Water can't occupy the same space as the sealant.

I think there's a good argument to be made that putting sealant around the outsaide of the swage is more likely to encourage corrosion than using no sealant at all.

The logic goes something like this: Water inside a swaged fitting becomes stagnant. Stagnant water doesn't contain enough oxygen for the chromium in the stainless steel to form a corrosion resistant coating. SS needs oxygen to oxidize and build up a molecular layer of Chromium Oxide, which gives stainless its protective barrier to oxidation. If you let water in, and the water gets stagnant (I guess low oxygen saturation levels?), the stainless steel corrodes quickly. Sealant on the outside might trap water, while simultaneously preventing oxygen from reaching it.

Stagnant water on stainless steel causes "crevice corrosion". It's the #1 cause of failure of stainless parts on sailboats.

[mastreb]

Crevice and pit corrosion is caused primarily by the chlorine ions in sea water. When people talk about "stagnant water" they're talking about sea water without dissolved oxygen and with dissolved Cl- ions. Fresh water won't do this. Without sufficient oxygen to react with Chromium, the chlorine ions will react with the iron wherever an CrO barrier has not formed as you point out. So if your swage was wet with sea water when you sealed it, yes, you'd have trouble brewing. But if you wash it out with fresh water and let it dry for a few days without getting rewetted, this wouldn't be an issue. Humidity alone isn't going to deliver enough chlorine ions to be a problem.

Irrespective, filling a swage with sealant would still do a better job by keeping all reactive chemicals away. Judy, what are those guys using?

[DaveB]

I deal with this on a day by day isual on a major Water park., corrosion is constant maintanance,
12% clorine in our systems corrode pipes , and will discolor gelcoats in 1 mo..
Most public clorine is 4% or less.
We go thru 1500 gals in one week of clorine when park is open.
Dave

Crevice and pit corrosion is caused primarily by the chlorine ions in sea water. When people talk about "stagnant water" they're talking about sea water without dissolved oxygen and with dissolved Cl- ions. Fresh water won't do this. Without sufficient oxygen to react with Chromium, the chlorine ions will react with the iron wherever an CrO barrier has not formed as you point out. So if your swage was wet with sea water when you sealed it, yes, you'd have trouble brewing. But if you wash it out with fresh water and let it dry for a few days without getting rewetted, this wouldn't be an issue. Humidity alone isn't going to deliver enough chlorine ions to be a problem.

Irrespective, filling a swage with sealant would still do a better job by keeping all reactive chemicals away. Judy, what are those guys using?

[Judy B]

...<snipped>...Irrespective, filling a swage with sealant would still do a better job by keeping all reactive chemicals away. Judy, what are those guys using?

I'm not sure what the professional riggers use. A good guess would be Sikaflex 291 or 291 LOT, or anything else you'd typically use to bed stainless steel. I use 29- LOT for bedding chainplate. It's moisture cured. The 291-LOT is a slow cure, light adhesive, the 291 is a faster cure, medium adhesive.

I'd have to ask the guys at my rigshop or Jerry Montgomery to see what they use. I never asked because I don't use nico press swages. I pay riggers to do rotatary swaging for me.

[seahouse]

Judy wrote...

I think there's a good argument to be made that putting sealant around the outsaide of the swage is more likely to encourage corrosion than using no sealant at all.

The logic goes something like this: Water inside a swaged fitting becomes stagnant. Stagnant water doesn't contain enough oxygen for the chromium in the stainless steel to form a corrosion resistant coating. SS needs oxygen to oxidize and build up a molecular layer of Chromium Oxide, which gives stainless its protective barrier to oxidation. If you let water in, and the water gets stagnant (I guess low oxygen saturation levels?), the stainless steel corrodes quickly. Sealant on the outside might trap water, while simultaneously preventing oxygen from reaching it.

Stagnant water on stainless steel causes "crevice corrosion". It's the #1 cause of failure of stainless parts on sailboats.

Judy is 100% correct IMHO.

Crevice corrosion is a problem on stainless steel in fresh ("stagnant") water, too, regardless of whether or not chloride is present, although the process is accelerated in salt water conditions. While it might not be immediately “intuitive”, be aware that pure distilled water is considered to be highly corrosive as well.

It is the exclusion of oxygen that is the initiator of a small pit in the surface of stainless. Putting a protective coating or cover of any kind on stainless steel carries the risk of making corrosion worse because, in addition to excluding oxygen, pinholes or nicks in the coating will concentrate the process of pit formation.

BTW- as I’ve mentioned before, related to this; a high polish on stainless will increase its corrosion resistance by minimizing the presence of corrosion- initiating microscopic pits.

Putting tape around the shroud would not be waterproof- it is not possible, because of the contour/ texture of the metal strands, to prevent water from flowing into the joint from higher above the shroud. It would also contain the water and prevent drying, accelerate oxygen starvation, and hence corrosion, in the area. Therefore it’s not a procedure I would recommend.

The pit corrosion process in stainless steel appears to be contradictory on the surface, because it would lead you to ask “how can the exclusion of oxygen from a small area cause oxidation in that area?” The short answer is that, even though the pit area is small, there are still several different chemical reactions happening simultaneously in different regions of that pit that contribute to the erosion of the metal in that area. In none of those is the presence of chloride ion obligatory.

I would also guess that any substance used during the swaging process would be very thin, low viscosity, that would flow freely around the joint, and would have minimal lubricity, otherwise it would weaken the gripping friction of the swage.

- Brian.

[Dimitri-2000X-Tampa]

So are you guys saying that cable covers like this will cause corrosion?

http://www.westmarine.com/webapp/wcs/st ... sNum=50094



I have always used these on the outer shrouds to reduce the chafing on my sheets (and the clew end of the Genny on a close reach for that matter).

[Sumner]

So are you guys saying that cable covers like this will cause corrosion?

http://www.westmarine.com/webapp/wcs/st ... sNum=50094



I have always used these on the outer shrouds to reduce the chafing on my sheets (and the clew end of the Genny on a close reach for that matter).

I think they are talking about....



....rigging tape.....

http://www.defender.com/product.jsp?pat ... &id=323039

...although the shroud covers (like you showed above--1st picture above) might also contribute to corrosion over time but you need it in my estimation. I'd think you could replace all of the rigging on our boats for $300 or less (I don't think we paid that much to do ours) so if you replaced every 10 years that would come out to about $30 a year or about 10 gallons or less of gas for your car.

To replace the rigging on our Endeavour it is in the $3000-$3500 range so somewhat more. One selling point was that our rigging had been changed out by the PO, but still it probably should be changed in 4-5 years again,

Sum

===================================
Our MacGregor 26-S
Our Endeavour 37
Our Trips to Utah, Idaho, Canada, Florida
Mac-Venture Links

[mastreb]

I'm not sure what chemistry could explain corrosion in anoxic distilled water. Iron (not even stainless) boats that sink in anoxic waters decay exceptionally slowly. Rusting stainless steel requires at a minimum oxygen and water. The vast majority of waters have dissolved oxygen. If a water intrusion is truly stagnant, the oxygen will be rapidly depleted by oxidation of the Chromium in the stainless, and the reaction will stop. It's the same reaction that occurs with stainless in the air. The reason chlorine ions change this is their preferential reaction with chromium which is not barrier forming, leaving the oxygen to react with the iron and causing pit and crevice corrosion.

You can see pit and crevice corrosion at work on the mast bracket of the M at the fittings. That mast bracket is 304 stainless, and so it rusts a lot faster than most of the fittings on the boat. Wherever it connects to a fitting, you'll see crevice corrosion if you keep your boat in salt water and don't wash that bracket down. I'd be surprised to hear reports of the same kind of corrosion occurring in Ms that have lived their lives on freshwater lakes.

In any case, I think Judy is correct about not wrapping fittings with tape, because you can't guarantee a seal, and without a seal capillary action on a stay under tension could keep sea water moving through the fitting but protected from ever drying out. That's a worst case scenario for corrosion.