Chainplates???

[TritonSailor]

Hi everyone,

I was looking at the chainplates on my Triton and noticed the starboard shroud chainplates looked a little funky. Is this caused by a leak or just degradation over time? Do they need to be replaced? I searched on this site before I asked and found a thread with onlinemetals.com, what width and thickness would I get for the rigors of offshore sailing?



Thanks Everyone...

Jeff

[triton #227]

The green colour is because the chainplates are bronze they may be leaking a little but even if they are not they will still bleed through the paint from the salt air.

[Tim]

Verdigris
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Verdigris in Prague Underground

Verdigris is the common name for the green coating or patina formed when copper, brass or bronze is weathered and exposed to air or seawater over a period of time. It is usually a basic copper carbonate, but near the sea will be a basic copper chloride.[1] If acetic acid is present at the time of weathering, it may consist of copper(II) acetate. Its name comes from the Middle English vertegrez, from the Old French verte grez, an alteration of vert-de-Grèce ("green of Greece"). The modern French spelling of this word is vert-de-gris.



The vivid green color of copper(II) acetate makes this form of verdigris a very common pigment. Until the 19th century, verdigris was the most vibrant green pigment available and frequently used in painting. Verdigris is lightfast in oil paint, as numerous examples of 15th century paintings show. However, its lightfastness and air resistance is very low in other media. Copper resinate, made from verdigris, isn't lightfast, even in oil paint. In the presence of light and air, green copper resinate becomes stable brown copper oxide. This degradation is to blame for the brown or bronze color of grass or foliage in many old paintings, although not typically those of the "Flemish primitive" painters such as Jan van Eyck, who often used normal verdigris. In addition, verdigris is a fickle pigment requiring special preparation of paint, careful layered application and immediate sealing with varnish to avoid rapid discoloration (but not in the case of oil paint). Verdigris has the curious property in oil painting that it is initially bluish-green, but turns a rich foliage green over the course of about a month. This green is stable. Verdigris fell out of use by artists as more stable green pigments became available.

Verdigris has also been used in medicine and as a fungicide.

Copper(II) acetate is soluble in alcohol and water and slightly soluble in ether and glycerol. It melts at 115 °C and decomposes at 240 °C. It can be prepared by reacting copper(II) oxide, CuO, or copper(II) carbonate, CuCO3, with acetic acid, CH3COOH . It is used industrially as a fungicide, a catalyst for organic reactions, and in dyeing (The Merck Index , Ninth Ed., 1976).

[edit] External links

* National Pollutant Inventory - Copper and compounds fact sheet

[edit] References

1. ^ Sharp, D. W. A: "Penguin Dictionary of Chemistry", page 419. Penguin Books, 1990 (2nd edition)

[TritonSailor]

So, based on the in depth illustration of what Verdigris is, I have nothing to worry about. Does that about some it up? I guess I wouldn't have questioned it if I'd known that they used something other than stainless steel for the chain plates. The forces they undergo must not be as much as I thought. I guess I need to go out and educate myself before coming back and asking questions. I probably should've known this. Hopefully in a few years I'll have some common sense knowledge under my belt, so I'll be able to contribute to the resources instead of draining them. Thanks to those who helped. We'll see you around

[Tim]

The verdigris isn't bad--in fact it's a protective layer.

Bronze is a strong metal. It may be "softer" than stainless steel, but that doesn't mean it isn't strong and worthy, and it doesn't corrode, form crevice corrosion, or have a host of other problems associated with metal in a saltwater environment. This is why it was (and is) commonly used.

The original Triton chainplates are surprisingly puny, yet they undeniably work. I'm not aware of any documented Triton chainplate failures. This is not to suggest you shouldn't carefully inspect yours and consider replacement as needed. Chainplates aren't a place for guesswork.

[TritonSailor]

Thank You Tim. I was just a little worried because I didn't see the exposed part of the chainplate on deck in the same condition. Now that I know what the issue is, a little scrubbing down below should uncover anything I trully should be worried about, i.e, cracks, bends, and wear.

Thanks Again,

Jeff

[David]

While the bronze chainplate may be fine, if you are seeing green fuzzies on the plates below deck, it might be an indicator of sea water getting below. Just as important as the integrity of the bronze plate is the condition of the mounting bolts and nuts; and if there is any water saturation to the area of the knees or bulkheads the chainplates are mounted to. It might be an opportune time to remove the chainplates and inspect everything.

[Tim]

Hopefully yours won't look like this, but this is what's possible, since the tops of the original knees are open (i.e. not glassed over), and if a leak has been occurring long enough, well...

[Rachel]

Well that'll convince even the most skeptical to check things out. Yikes!

I'll concur that bronze is good stuff. I'm completely biased in favor of it. First of all, as has been mentioned, no sneaky crevice corrosion to hide in the metal just waiting to ruin your day. Second, no endless cycle of rusting/streaking/polishing necessary. Just let it develop its natural protective patina and go on your merry way.

I have not looked this up myself yet, but when I asked a knowledgeable person about replacing my stainless chainplates with bronze, and how that would affect the sizing, he quoted the specs from Skene's Elements of Yacht Design and said that the size was the same for bronze or stainless in my case (1/4" wire). I would double check this figure before using it, of course, and I also imagine that at some point on the size scale the bronze ones would need to be larger, but apparently not at our boats' size scale.

Rachel

[Tim]

Here is a chainplate sizing chart from a venerable copy of Skene's. The penned notations refer to another, unrelated project, so ignore.

[David]

Other than Schaefer stainless steel chainplates, I don't know of any other sources--I think Spartan marine may have bronze chainplates. My concern for bronze is not knowing what kind it is and therefore how resistant to corrosion it is. If I were going to make my own chainplates I would spring for Monel. My grandfather invented the processes to smelt it and I've always been partial to it. I think though, the more important aspect is the fiberglassed wood knees turning to punk as in Tim's photos. You never know if you don't inspect.

[Rachel]

Although, since bronze is easy to work, couldn't you just buy bar stock? And if you bought U.S.-made silcon bronze, wouldn't you know what type it is? Or are there different grades within silicon that I'm not aware of (very possible, as I have not fully researched this yet).

I'm thinking of something like this, from Atlas Metals:

http://www.atlasmetal.com/silicon-bronze-flat-bar.php

I understand that Alaskan Copper is a good source as well, although I don't see silicon bronze listed as coming in bar form. Might be worth a call though.

http://www.alaskancopper.com/bb_rbs.php

I'm assuming others know more about it than me, and if so, I'd love to hear it.

Rachel

[David]

I'm sure, with the stock you found, Skene's and a drill press you could make a great set of chainplates.

[TritonSailor]

I hope I'm luckier than the owners of that knee! In the case I'm not, would it be more prudent to get SS316 as a replacement instead of bronze? I think it was Zach on another thread that mentioned www.onlinemetals.com. They have SS316 flat bar .25"X1"X12" for $7.00 each http://www.onlinemetals.com/merchant.cf ... &top_cat=0 I don't know if it's the right kind, but they also have C954 flat bronze .25"X1"X52" for $36.17 http://www.onlinemetals.com/merchant.cf ... op_cat=850. This is the only flat bronze the site had. If I did purchase either one of these, like David said I would have to find a nice sturdy drill press.

Thanks for the responses everyone.
p.s sorry for the long links Tim, I tried using BBCode to shorten them, but it wouldn't work for me :)

Jeff

[David]

Where's my brain: Garhauer now makes both chainplates and turnbuckles.

[Rachel]

Jeff,

As I'm sure you're sick of reading by now, I definitely have a preference for bronze. It's easier to work, and it's not susceptible to crevice corrosion, as stainless steel is.

That said, if I were to use stainless, I would use 316 alloy. It's not quite as strong as 304 overall, but it is less susceptible to corrosion, and slightly stronger is not that useful if it breaks. Given that Skene's gives the same specs for bronze and stainless (and perhaps wrongly assuming that they have used 304 as the standard alloy), I would think that you could use 316 of the same dimension as 304, but again, why change from bronze? (And if you do, please check on this before going with 316.)

Another consideration with stainless is that you want to be sure to polish it very carefully before installing it, because any less-polished spot is a place where crevice corrosion can start, if I understand it correctly.

By the way, crevice corrosion usually comes about where stainless steel is not allowed to get the oxygen it needs to form its protective oxidation layer. So, for example, where chainplates go through the deck (and are often damp and not oxygenated) is often where you see evidence of corrosion and/or have breakage when they get older.

Rachel
bronze-biased

[David]

Lack of O2 and stainless. It is not simply a lack of oxygen that causes crevice corrosion, but a lack of oxygen and the presence of sodium clorine (sea water) or a similar acid. The clorine reacts with the passivation coating that stainless steel has, causing an acidic reaction, removing the coating and allowing the metal to deteriorate in that area. The effect is most prone in crevices where seawater cannot circulate--thus the name--the O2 depletes and the corrsion cycle begins. 316 stainless is much less prone to crevice corrosion and other forms of corrosion because of the increased level of chromium and the addition of molybdenum. Duplex stainless steel is completely invulnerable to crevice corrosion.

The chainplates Schaefer sells are 304 stainless BTW.

For Jeff, the stainless stock you can buy at onlinemetals or metalsdepot or other sites is not polished, which you would have to do yourself. Frankly by the time you buy a drill press beefy enough to drill the chainplates and a buffing machine strong and large enough to polish them, you would probably be better off buying them from a mfg, or sticking with the bronze chainplates that are on your boat now.

[Zach]

David,

You bring up an interesting point... corrosion on stainless seems to happen on the side that is trapped.

I guess if one were worried, a small spacer behind the chain plate at each of the bolts to keep it from laying directly against the bulkhead. Its not like the bolts aren't already in sheer, which has always bugged me a bit...

Zach - Master of over thinking things.

[Rachel]

It absolutely happens where it's "trapped" - if there is going to be a problem that's where it will be.

I think an even worse spot is where the chainplate passes through the deck, since there is often saltwater there, and you're *trying* to keep caulk, etc. up against the metal and eliminate air flow (which would end up being water flow into the boat). I've seen many more stainless chainplates with small cracks or even failures there than at the bulkhead.

Stainless likes to be dry and have good air flow around it. Or otherwise to be completely sealed off, but that's hard to accomplish.

Its not like the bolts aren't already in sheer, which has always bugged me a bit...

I'm not sure I get that. Wouldn't you want the chainplate bolts to be in sheer?

Rachel

[David]

It's ok for stainless steel to be thoroughly wet as long as there is some circulation of oxygen. I mount the Marelon scoop over the raw water intake thru-hull with #10 stainless self tapping screws that screw into the hull but not thru it. They were new when I installed the thru hull in 1990, and looked just as bright when I removed them this last time for a bottom job in 2007. In the case of those screws, the threads were embedded in the hull and the heads were exposed to sea water--and the screws were fine.

Personally I think the more pressing issue with chainplates if moisture is present is the distinct possibility of rot in the bulkhead or knee where the chainplate attaches. When I get around to finishing the deck so I can install the chainplates I plan to overbore all the mounting holes and then redrill into solid epoxy to prevent that possibility in the future. Sealing the chainplates thru the deck will be easy and permanent.

[Rachel]

Sealing the chainplates thru the deck will be easy and permanent.

I'll be interested to see your method when you do that, since I'll no doubt be re-bedding chainplates at some point here (on some boat ;) I understand the overdrill/fill part to protect wood/core, but I've not seen a good method for permanently sealing through-deck chain plates. Seems like they always tend to "work" a bit.

I was thinking I would either move them to the outside of the hull, or, if I keep them through-deck, perhaps fabricate some small fiberglass "hills" on the deck right where the chainplates go through (to discourage water), and then also use coverplates for more caulking area.

Rachel

[David]

<<perhaps fabricate some small fiberglass "hills" on the deck right where the chainplates go through (to discourage water), and then also use coverplates for more caulking area. >>

You are reading my mind.

David

[David]

Here’s my take on chainplates ‘working”. Assuming they are caulked correctly, they work for a couple of reasons:
1) They are loosely attached to the boat (i.e. the fasteners have failed to some extent from corrosion, or the substrate they are attached thru has failed from water intrusion and rot)
2) The slot though the deck is too large, filled with some sort of caulking and allowing the chainplate to move laterally in the slot. Invariably this sort of movement leads to a failure in the caulking bond allowing water to seep past, and rot the attachment knee and/or the deck core at the slot opening (which only makes the "slot" wider),.
3) The chainplate is too thin and torques above the deck,
4) The chainplate is too thin and extends too high above the level of the deck slot, providing too much torque on the chainplate, and forcing it to move laterally in the deck slot, failing the caulking bond,.
5) The chainplate is not aligned to the shroud,
6) The shoud is not toggled correctly—at both the bottom and top of the shroud--and forces the chainplate out of alignment

So, To stop them from working and disrupting the caulking bond, I plan to
1) Size them not to breaking strength but to “bending” strength. For me the added weight and expense pale in comparison to the damage from water intrusion and the potential of loosing my rig.
2) Refine the deck slot to be as narrow as possible. On my Bristol, the slots are outboard of the deck coring, but if there were coring it would be sealed as well,
3) Build a base shoulder above the deck from fiberglass stock, epoxied to the deck with a slot that is a press fit around the chainplate. The shoulder is large enough that the chainplate cover can be mounted to it. The shoulder strengthens the slot and keeps rainwater from running over the chainplate cover.
4) Mount the chainplate so it extends above the shoulder as little as possible, only high enough to accommodate the lower end of the turnbuckle toggle.
5) Mount the chainplate cover over the chainplate in a thick bond of 5200.

I think these steps will prevent any movement from the chainplates.

[Chris Campbell]

All of those sound like sound ideas to minimize movement of the chainplate relative to its hole in the deck, but I personally would still expect some movement there, and plan for it. The rig exerts a very large pull on the hull at that point, enough so that it can deform the shape of the hull/deck/bulkhead that the chainplate attaches to. The bulkhead is pulled tight to the deck, the hull is pulled in, the deck is lifted by the hull pulling in, etc. Also the difference in expansion and contraction of dissimilar materials (stainless or bronze chainplates, fiberglass deck and hull, wooden bulkhead or knees). Small movements, to be sure, but movements nonetheless, which is why chainplates are bedded through the deck, not locked in place with epoxy.

Of course on steel or carbon fiber boats they make the chainplate integral with the deck, hull, and supporting bulkhead or knee, which eliminates the deck hole (very slick!), but we don't have that luxury in our plastic boats.

[David]

If your hull is deforming from your rigging; if your bulkheads are moving from tightening your rig, I would comment to you that perhaps you have your rig too tight. Different boats are built to different standards and structural strengths; different uses and different tuning standards.

I am not suggesting these things for anyone. I can only tell you about what I am doing for MY boat. It doesn't deform or move; the bulkheads don't move and the chainplates don't move. I did not say above that I was epoxying the chainplates in place, I simply said that I was reducing the slot as much as possible and reducing the chainplates ability to torque as much as possible. As to the contraction or expansion of stainless steel and that in itself causing chainplate movement, I disagree with you entirely.

[Zach]

Rachel,

Shear meaning, the bolts are being side loaded. When a bolt is in shear, it has a considerably reduced yield strength. Yeild, meaning the loading it takes before the bolt is permanently deformed. In shear, the bolt deforms around 60% of its yeild strength... whereas in tension its closer to 90%.

Bolts do best, when put under tension. Stretching themselves out along their axis clamping things together.

I like tension, because the top bolt, or bolt with the tightest fitting hole doesn't take the brunt of the load until it deforms and other start carrying... instead they are all being stretched fairly equally.

When a builder takes a large metal plate and threads it, embedding it in the deck... the bolts going down from the fitting on deck, are put under tension.

(This is where I shut up, and say... it takes a bigger bolt. Grin.)

I was pointing out, that since the bolts are already in shear... a small spacer holding the chain plate off of the bulkhead a wee bit, would allow for air circulation. Touch longer lever arm for the bolt to bend, but perhaps corrosion would be less of a topic.

Zach

[TritonSailor]

Thank You for your responses everyone!
I'm going to be inspecting all four of the shroud chainplates, if they are in good shape with no doubt, I'll keep them and just replace the bolts. That way money will be saved and I'll know that the bolts are safe.

Thanks Again.

Jeff

[bcooke]

I can only tell you about what I am doing for MY boat. It doesn't deform or move;

Umm... all hulls flex. Its part of what makes them strong. Creating an immobile, perfectly static boat hull is theoretically and practically impossible. A stiff hull also imposes much higher stresses on the entire structure and will have a much shorter lifespan. Its much easier to allow for the movement.

Bolts are designed to hold in shear. Its what bolts do. Naturally the shearing action makes them less strong in shear than tension but that doesn't make them bad. Just size them appropriately. Trying to make a chainplate attach using bolt tension sounds like a lot of unnecessary work to me. I have never heard of well designed chainplate bolts failing. Certainly not Triton chainplates. Stock Triton chainplates might look wimpy but they have never been known (to my knowledge) to fail. Stock Triton chainplates have sailed many thousands of ocean miles without mishaps.

Stainless chainplate stock is a PITA to drill.

Its not uncommon for the wood inside of the Triton chainplate knees to be rotted out. Mine were and I replaced them. Its a relatively easy job. On the other hand, the chainplate knees derive most, if not all, of their strength from the fiberglass surrounding them. The wood is more to give it shape and to support the tabbing from the compression loads from the chainplate bolts (installed in shear).

[David]

<<
Umm... all hulls flex. Its part of what makes them strong..>>

Maybe yours does but mine sure doesn't deform at the chainplates.

We all have different ideas of what is strong. Personally I don't think oil canning, or flexing of the hull, or as previously explained the bulkheads or chainplate knees moving to be strong.

[Rachel]

David,

I don't think oil-canning or major hull flexing is what Britton is getting at. I believe the situation arises because the chainplates are attached to a bulkhead, or knee, belowdecks, but then they pass throughthe deck. Even on the very wide "beam style" chainplates on something like a C & C 40 (which have a built in flange at deck level), there are challenges in bedding them where they pass through the deck.

Conversely, if you attach the chainplates directly to the hull, you don't have this problem. Not because a hull cannot move slightly, but because they are attached there, and don't pass through another part of the boat along the way. Of course that type of attachment does not result in optimal sheeting angles, and also has a certain stylistic look.

Maybe it is possible to "lock in" the deck and the chainplate knees to not move independently; that's why I was interested in your "easy and permanent" approach and hope that you post it here as you implement it. I haven't seen one of those yet, on this style of chainplate attachment, but of course who doesn't want easy and permanent if it's practical!

Rachel

[David]

I don't know what Britton was getting at frankly. Well engineered fiberglass boats do not flex. Flexing fiberglass will eventually lead it to failure in the flex areas, hulls that flex are not a desireable charactistic of offshore boats. It's a nice myth and if your boat flexes I suppose it's well intentioned. Some boats do flex: chainplates do pull the hull out of form, bulkheads move to the extent that under hard sailing conditions head doors stick shut or won't close. Some older production boats--namely ones built in Florida-- are famous for those signs of flex; some of them even have lifted the decks off the hull flanges under extreme conditions. Maybe to Britton or you those are indicative of a strongly built boat. Not to me.

I don't own a Triton and probably shouldn't be contributing to a "Pearson Triton Specifics" forum group. However I don't think Tritons would flex the way it has been described in this thread. I do own a very similar boat to the Triton, just as you do Rachel; one that is built without a hull liner, one built of a solid glass hull, one that has all its interior cabinetry tabbed to its hull, etc. I can't speak for an Alberg 30 or for a Triton, nor was I. But I can speak for my boat. And Britton is mistaken if he thinks my boat also "flexes" or that it is not strongly built or seaworthy because it doesn't flex. That is total nonsence on his part.

As to your comments about chainplate attachment. You seem to think and myabe Britton does too that when chainplates are knee attached and pass thru the deck that the deck is somehow "floating" and not a part of the structure of either the knee or the hull. That is not the case: they are all interdependent. My remedy for leaking chainplates is to prevent the chainplate from torquing, make the slot the chainplate passes thru the deck as small and tight as possible, raise the base of the deck slot above standing water on deck and then use 5200 under the chainplate cover. This will prevent it from leaking on my boat. I think the same principle would prevent leaking on any boat where the chainplates pass thru the deck or bulkwarks. By no means am I suggesting that any of you good people follow the same procedure.

Frankly, I regret I ever mentioned a solution in the first place.

[Tim]

All right, enough of this thread. Good grief.