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Embedded Chain plate maint/replacement

59K views 186 replies 36 participants last post by  Irwin54 
#1 ·
I promised in this thread to start a new thread on the steps going forward.
http://www.sailnet.com/forums/gear-maintenance/104260-chain-plate-impact.html
This is my attempt at doing so.

Last night I pulled the joinery off and took a look at what I'd be needing to do to replace the chain plates.
Just a reminder - 1987 Irwin 38 CC MkII, chain plates embedded in the fiberglass, the tab with the pin hole (for the shroud) goes through a 2 inch thick toe/cap rail.
Here's the overall view:


The issue that spring boarded this:


That area from the outside on a FLIR image

That area from the inside on a FLIR

That area eyeball view, obvious long term water leak (previous owner).


Okay, here's the big one. That area - no wood or joinery over it. Raw hull.


What you are seeing is two of the three chain plates (the forward one is on the other side of the bulkhead). The chain plates have two horizontal 'tabs' - like an inverted orthodox cross. I do not know how they are joined, no bolts are obvious so I assume a weld.
The obvious dirt is from long standing wet/rot over the years. I had no leaks at all until I removed the jelly fish/snot over the chain plate covers while doing the teak rails. It is all obviously years old.
Between the two horizontal tabs of the plates are some obviously well caulked screw pointy ends - they are what is holding the 2 inch thick, 3 inch wide rub rail on.

There is a heavy glass strip at the bottom of the plates, this folds horizontal over where the coring obviously starts (as well as the gel coat).
At the top there is a gel coat cover strip, up under that looks like this.


Those screws are bunged toe rail/cap rail, stanchion bases etc, going through the bases, teak, and folded 'shoebox' lips of the deck/hull.

Here's the underside showing a plate -


That's enough for now.
 
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#163 ·
the way my polisher explained it, the process removes all the free iron molecules from the outer surface - to a very thin depth, less than .001".

That leaves the outer surface only the chrome and other alloys that comprise S/S so it does stop the crevice corrosion process until that thin layer eventually wears or weathers through, at which point normal corrosion processes start - the exposed iron molecules being the path in for crevice corrosion.

Getting the e-polishing redone every few years would keep it immune, barring damage.

The chains and floors I had done still looked like new after 7 years.
 
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#164 ·
I had mine mirror polished...thats what they call it down here...its like glass...basically the top coat is melted down by buffing...you lose some thickness but because I had mine oversized to 3/8ths instead if 1/4 Im still way stronger

well see how long they last

even if its only 10 years Ill be happy for sure
 
#165 ·
Electropolishing is a process where the metal is submerged in an acid and an electric current is run thru the system. This causes the imperfections to be lifted from surface. Basically it is plating in reverse, but because of the way it works it takes high spots down faster than the bulk of the material. By removing the high spots and edges it also reduces the number of crevices that salt crystals can hide in, which reduces the speed with which crevice corrosion can occur.


Sloop,

What you are talking about is called pasivation. Which helps bring the chromium to the surface. Since this is what provided the corrosion protection in stainless, the more surface chromium there is again the slower corrosion occurs.


These processes are complimentary but very different.
 
#168 ·
I got two warm days in a row so I made some progress.
Using West 105/205 and 405 as structual filler I laid in filler in the center slot where there used to be an air gap that became a water gap.
Keep in mind that the on old plates which were flat the only portion of the plate that touched the hull was the bottom 1/4 of an inch. What I need to do is build out a 'landing' for the new plates that will fit the curve of the hull and be flat at the plate.
https://lh6.googleusercontent.com/-...AAAPCI/x0cGexsNduE/w1113-h835-no/P1010092.JPG

This is step one, in progress. Do some fill, then do some seal, then overcoat, and overcoat etc..
 
#170 ·
The quickest and easiest way to create the landing you need is to wrap the chains in packing tape, put a thick bed of thickened epoxy down where they will mount and put the chains in place.

Clean up the squeeze out and wait for the epoxy to kick. Then remove the chains, peel off the packing tape and you're ready to remount them.
 
#173 ·
I'm sure everyone will say it's a horrible idea but how about leaving the old chain plate in and bolt a new set through the old ones after cutting the stem that goes through the deck?

That way there is no need for the extensive surgery to take them out. One can grind slightly oversized holes through them and fill the area with epoxy before redrilling through for the bolts.

Wouldn't that work if the core of the chain plate is not completely compromised in compression?
 
#175 · (Edited)
I don't think it is a bad idea at all, and I have seen it done well - on a Pan Oceanic. I met the owners several years after they made the change. They loved the set up - citing peace of mind in finally being able to inspect the plates as a huge factor. I believe that the change they made gave them stronger and safer chainplates. I also know that the original plates were accessed and assessed to insure future integrity, the rails were capped and sealed permanently, and adjustments were made to allow for drainage and drying of the original plates/spaces. and that the change was conceived and completed by a boat builder and engineer. I know this because I was working for the company that did the job.

I worked for this shipwright company in the Caribbean for a couple of years - one of the jobs I did was a chainplate conversion. I think that your location can affect your opinion in this situation. The warmer the water/weather, the greater the corrosion and clingy critter count, the more likely you are to approve of copper bottom paint, to forgo water cooled refrigeration, and to desire the ability to visually inspect your chainplates. We recently bought a resto boat from MD USA. The locals there thought quite differently from the folks we met and worked with in el Carib - and they were also correct. Perspective changes with geography.

It may very well be that the designers of these old tubs had no idea how much we would fall in love with them and to what lengths we would go to keep them afloat 30, 40, 50 years later. Had they known, they might have chosen a different design. According to the riggers I worked with, chainplates can often be moved safely outboard, but I would not do it without consulting a rigger. Changing angles on the rigging changes stress loads/points.
 
#174 ·
Might make it a little easier but it's what the British call a "lash up".

Here we call it quick & dirty.

A big, expensive boat should have something as important as chainplates done properly - it's no place to be cutting corners.
 
#176 ·
ChucklesR,

I have an 89 Irwin CC38 and am both amazed and depressed by your detailed documentation as you move thru this process. I'd love any current info you're gathering re pix and updates, and also wondering about access to the forward port/stbd plates? Mine (like yours probably?) are buried behind the v-berth bulkhead and seem extremely difficult to access from inside. And also, now that you're on the hard, the bow/bobstay plate down at the waterline? This thread has been extremely informative for me, thanks so much, and hoping you are progressing and soon back in the water.
 
#177 ·
Hey Edakira,

Here's a pic of the 'hole's' fiberglassed over, ready for new plates to be installed.
It just so happens that today is the day the rigging company is measuring and fitting for where to drill the holes; they want to both space them out visually nice and be strong enough.

The forward lowers are indeed hard to get to. I'm not pulling them based on the condition of the four plates I did pull. Instead I'm going to drill a drain hole at the bottom of them, check the water out etc.. and make that a routine check.

The bobstay/dolphin striker plate is also fine, just rebedded. Aft stay is going to get a drain hole and inspection also. At some point I might do the forward lowers and aft stay simply by drilling through in place and bolting them similar to the new plates.

My interpretation of causal factors is: improperly maintained bedding of the chain plates allowed water to ingress into the cavities caused by less than stellar fiberglass embedding (lots of air gap). That water was pretty much in flow, i.e. not stagnant/oxygen depleted so the stainless was never compromised.
 
#179 ·
Just a thought, but you could leave the old chainplates where they are and rig new chainplates to the outside of the hull, or in the interior. Once you disconnect the shrouds from the chainplates, the old chainplates can stay where they are unless you are dead set on replicating the exact setup you currently have.
 
#181 ·
Speaking of the whole thread - sometime back I mentioned that I needed to build a platform for the plates because obviously the hull curves. The rigger said no, just a good flat surface and he'd bend the plates to the hull curve.

Guess what, now I need a platform/shim because a) bending 1/4 ss plate ain't so easy and b) doing so puts unacceptable pressure on my cap rail where the plate exits.

1 week to launch and all of it is raining.
 
#184 ·
An update from my end, ChucklesR. I just had my plates x-rayed (7 of 8 - they couldnt do forward bobstay down at waterline). An outfit that does oil and gas pipeline based in TX theyd never done a sailboat before. The images were very clear and revealing from top of plate down below "bastard" bar and below first of 3 cross bars. I had a local surveyor present to monitor and inspect images w the techs - who were all certified. We were very impressed and pleased w the results, and most importantly the plates all looked clean and free of cracks and corrosion. Cost me a hundred dollars per plate ($700) and makes me feel very confident moving forward w a Gulf crossing planned soon. I can upload a few images once I rcv from surveyor. So much gleaned from your in depth documentation of your own process and understanding exactly what we were looking for and exact plate shape etc. Here's a diagram of the forward bobstay FYI that I rcvd from Gene Gammon. Its from a bigger irwin but he said they were pretty consistent in style. Hope all goes well w your install. Obviously something I'll look forward to someday in the near future as I ponder the long term fix. --E
 

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#186 ·
Is there any posting on how this job turned out, in the end? I have a Cascade 36, similar arrangement but with a much heavier toe rail section and a good solid mahogany sheer clamp. I've religiously kept them sealed, but have no idea what the previous owners did. To mollify my nervousness, I was planning on cutting out the fiberglass "pockets" and making up new plates, with backing plates ( and carriage bolts) on the outside. The current plates are held in place with five, 3/8 dia, stubs, sticking thru the glass roving, welded to the plates.
Before I start cutting and grinding, I'd love to know how this project was completed.
 
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