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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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#2 ·
This is going to be some job.. I expect you'll need to get to the opposite side as well at some point?

Once you get the glass off the inside I suppose you're hoping to pull the chainplates out from inside? or are you going to have to cut them out?

I expect you'll find the external crazing is from corrosion swelling on the plates.
 
#3 ·
I'm confused, how are the chain plates fastened?
They can't just be glassed to the hull and that is all, can it?

Is their any chance that they keep going down and attach to something below the seat. I can't tell from the picture if they stop or keep going.

I notice that they are in the middle of a span not at a bulkhead.
That means that the compression force has to be handled by the deck, yes?

Is that a nut at the bottom end of the forward chain plate?

Nice pictures, thanks for that!!!
 
#5 ·
I see two, how is access to the forward most plates (forward lowers I'm assuming)

I'm confused, how are the chain plates fastened?
They can't just be glassed to the hull and that is all, can it?
These Irwin's have chainplates that are yes, simply glassed in. Its not that uncommon. Their are quite a few different boat builders that fastened chainplates this way on at least some of there models. Allied Luders 33, Hans Christian 33, Endurance 35 are just a few that come to mind.
 
#6 ·
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.
Chuck,

While you're in there you may want to add some through bolts to the hull/deck joint as opposed to just screw & glue....
 
#8 ·
David,

The nut at the bottom of the forward (actually the center) plate is used to fasten a ground wire, it goes from there to the keel.

The plates stop at the heavy glass strip, they do not go anywhere else.

I'm not an engineer, I don't know where the compression is going - I thought it was to the keel, the mast is deck stepped with a post directly under the mast that transfers the compression to at 3/4 plate 2 inches above the (encapsulated) keel.


Maine Sail, you betcha - some of those screws have got to be replaced by bolts, probably all of them that are for stanchions and jib tracks - if I can get to the bottoms.


I have to get tarps, plastic, vacuums, tyvek suits and all that. Then it's off to fiberglass dust hades for a couple weeks.

I'll shoot some pics on the way.
 
#9 · (Edited)
#10 ·
It is obviously OK as it has lasted a long time on a lot of different boats. I'm just trying to understand the loads.
The mast is pushing down that makes sense.
The chain-plates are pulling up.
Some portion of the load however is attempting to make the boat narrower.
I see a lot of boats that have the chain plates connected to a bulkhead.
The bulkhead is tabbed into the hull distributing the load.
The bulkhead often has a small beam that goes across the whole boat again distributing the load.

In this case the load attempting to make the boat narrower has to be taken by the deck.

I'm not saying it is a problem unless of course you had a soft deck.

I guess I find it hard to believe that a bandage of glass over the chain-plate on the hull is all their is to it.
Is it possible they are relying in part on 5200?
Does polyester resin stick that well to SS?

Did they do some tricks like put some holes in the stainless so the resin would form keys?

What I'm saying is that a SS bar bolted to a bulkhead makes sense to me. It is obviously strong.

This kind of construction has stood the test of time so must be pretty good, I'm just trying to understand it.
 
#16 · (Edited)
So the next question is how to put it back together again so they can be inspected easily and/or replaced?

Bolting right through the hull is the obvious solution.
External is another obvious solution.

I doubt if most owners would be willing to change the look of the boat that much.
It really looks pretty and is out of the way coming out of the cap rail like it does.

Of course the argument could be made that they lasted over 30 years so put back together with epoxy instead of polyester and call it good for another 30 years.

If a better mounting is impossible maybe this is the right place for titanium regardless the cost.
 
#18 ·
Simplest solution is on the outside of the hull. Without a bulkhead in each plate's location there are no other options I can see except the original method. That was probably the reason it was done this way to start with - without knees which would have been in the way of interior cabinetry or bulkheads at the right place it allows placement anywhere the builder wanted.
 
#28 ·
I would say the simplest solution would be to put them back where they were on the inside of the hull but bolt them through the hull rather than glassing them in place.

On that boat putting them on the outside would present big problems because of the heavy cap rail and rub rail.
 
#20 ·
Once you cut out the chain plates I would be interested in how thick that bandage of glass is covering them?
 
#22 ·
So if you look a a boat and see the chainplates topside and there is no way to see any attachment below is their any other way they could have been built that doesn't use a knee or bulkhead or exterior bolts through the hull and is NOT glassed in?

IOW is their any construction method where the chainplates are flush or nearly flush with the hull interior and still allows inspection.
 
#24 ·
I ground out my chainplates and re-glassed them in, after shortening them a little. I cut off the high stress area where it goes through the deck.

The crazing on your hull looks like water got in the chainplate pocket and froze, many years in a row. I have heard some folks drill a small hole in the pocket on the inside to allow water to drain out. The builder just glassed over the chainplate so there is plenty of room for water where the glass makes a radius over the edges of the steel chainplates. No way to know how it is in there unless you cut it out and inspect. It's perfect conditions for crevice corrosion.
 

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#26 ·
FWIW I spent a lot of time discussing the plates and how to fix or re=-install with both Maine Sail and Jeff_H, neither of which is a lightweight when it comes to stuff like this.

Neither of them had knowledge of the shape of the plates prior to today - all I could tell them was that a horizontal band/tab was involved, but no through bolts etc.

Titanium is one of the the things I'm looking at, the could be thinner in all dimensions.
Science has moved on since 1987, I have a LOT more options than "drill through the existing and bolt new ones on the outside" - that's the first and last option according to the Irwin 'expert' - a Mr. Gene Gammon.
I prefer taking advice from someone that does not tell me to leave the possibly rusting old ones in place as backing plates.

I'm still thinking- I might go with a hybrid inner/outer.
I have to rebuild the 'furniture', i.e. book shelves, I do not have to rebuild them they way they were.
 
#34 ·
FWIW I spent a lot of time discussing the plates and how to fix or re=-install with both Maine Sail and Jeff_H, neither of which is a lightweight when it comes to stuff like this.

Neither of them had knowledge of the shape of the plates prior to today - all I could tell them was that a horizontal band/tab was involved, but no through bolts etc.

Titanium is one of the the things I'm looking at, the could be thinner in all dimensions.
Science has moved on since 1987, I have a LOT more options than "drill through the existing and bolt new ones on the outside" - that's the first and last option according to the Irwin 'expert' - a Mr. Gene Gammon.
I prefer taking advice from someone that does not tell me to leave the possibly rusting old ones in place as backing plates.

I'm still thinking- I might go with a hybrid inner/outer.
I have to rebuild the 'furniture', i.e. book shelves, I do not have to rebuild them they way they were.
If you're going to replicate the original method, then titanium seems a good way to go.

AllThumbs had a good idea, about leaving weep holes. Not only would it prevent freeze damage, but it would also provide an indicator of trouble when you start seeing water stains.

People are also right when they point out that this system lasted 25 or 30 years. If you do it right, you'll probably never worry about it again in your lifetime.

I guess I kind of overreacted when I said to just bolt them to the hull.
 
#29 · (Edited)
I'm envisioning a way to make new chain plates that will be removable for inspection but be similar to the existing ones.

Let me see if I can explain in words what should be a drawing.

Glass with epoxy two or three horizontal stainless plates about the same way the current T crosses are glassed in.
The difference is that they are glassed in such a way so their is a slot left in the middle wide enough so the vertical chain plate can be slipped up under each horizontal strap and out through the slot in the cap rail.
Now just use flat head machine screws through the horizontal straps and tapped into the vertical chain plates.

The bottom of the chain plate can have a doubler piece welded on as a stop against the bottom horizontal piece.

The whole thing can have an inspection cover over it so it can be inspected.
The horizontal pieces glassed in should never get wet and last indefinitely.
The vertical piece can just be unscrewed and withdrawn and the critical part just below the cap rail inspected.

In any event even if water did get in it would not be trapped in a pocket.

Any concern about the strength of the machine screws can be engineered away by simply changing the size of the vertical member. It can be wider or thicker under the cap rail if you need more screw area and the existing width above the cap.

This would be a modest increase in cost mostly labor to deal with drilling and tapping a couple dozen screws rather than welding.

Do you think this would work?
 
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#31 ·
davidpm's solution sounds awfully good. It sounds like it puts the stresses pretty much where they were before, without embedding parts that get wet above deck and without messing with the outside of the hull or taking up huge amounts of interior.
 
#32 ·
David's idea is interesting but would not be as strong as the original. Instead of the large chainplate glassed in solidly the vertical plate's strength would only be as good as the bolts used. If you are going to put 4 or 5 large bolts through the hull to make it strong enough you may as well install the plate outside for easier inspection. This will also eliminate the hole through the deck that exists currently.
 
#37 · (Edited)
At the risk of starting something I'm not prepared to finish.:)

This is a little like the difference between some anchors. Some are welded some are bolted. As long as the numbers work out from a strength point of view it probably don't matter.

All you have to do is make sure the bolts are about 10 times stronger than the piece of wire connected to the plate and I suspect it doesn't matter any more.

My idea was that the bolts thread into the vertical plate and do not go through the hull.

The width and thickness of the plate below the cap rail, it can be doubled for more thickness and/or wider for more room to space bolts, can be adjusted until the strength and the number of bolts is as strong as needed.
 
#33 ·
With David's idea, I don't believe the bolts were going through the hull, just through the chainplate into the cross plates. Doesn't it pretty much always come down to the bolts? I guess it did with my last boat, a Pearson 28-2, where I believe the chainplates were fastened to a knee in the hull with 3 (I think) bolts.
 
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#36 ·
Let's see if I can describe this well - I don't have a good drawing tool that is easy to use.

1) make some knees out of g-10 - laminate to a 1 inch thickness. Put them in - one per plate with epoxy, fillets and heavy glass (maybe CF, double layer). Smooth, fair, paint.
2) turn the plates 90 degrees, bolt through the knees, backed on the other side.
3) build joinery back where and how I like.

I'd have inspectable plates, be able to see any leaks and rectify and I 'think' just as strong. The knees would run from the deck to the core area, really don't need to be much more than the width of the plate as it's more about spreading the load - and that's on the fillets and fiber glass tabs and tapes.

BTW - let's call the discussion on 'it's on the bolts' pretty much done. The bolts can pretty much hold the entire weight separately - look up the tensile and sheer strengths.
The shrouds are rated about 9k SWL - bolts pretty much better than that.
 
#38 ·
1) make some knees out of g-10 - laminate to a 1 inch thickness. Put them in - one per plate with epoxy, fillets and heavy glass (maybe CF, double layer). Smooth, fair, paint.
2) turn the plates 90 degrees, bolt through the knees, backed on the other side.
3) build joinery back where and how I like.

BTW - let's call the discussion on 'it's on the bolts' pretty much done. The bolts can pretty much hold the entire weight separately - look up the tensile and sheer strengths.
The shrouds are rated about 9k SWL - bolts pretty much better than that.
That would work strength wise but I was trying to save the guy the significant hassle of redoing the joinery.
 
#43 ·
I don't understand why the twist is necessary. The chainplates on my Pearson 28-2 with knees have no twist, the knees are U-shaped with clearance to access the bolt heads. I haven't looked my friend's Yankee 30 (which also uses knees) too closely but I think it worked the same way.

I do think that knees are the way to go.
 
#45 · (Edited)
I don't understand the comments about twisting the chains to mount them on a knee - a knee is just a mini-bulkhead so the chains will mount athwartships just like they would if mounted to a bulkhead. The slots in the deck would have to be filled & recut to change the orientation.

A really skookum setup would angle the knees for lower shrouds to put the chains in line with the angle the shrouds form with the mast - angled aft for the forward lowers and forward for the aft lowers.

I still say the simplest method would be to clean up the area where they currently sit to get a smooth mounting surface and bolt them through the hull - virtually a direct replacement for the existing setup and only a few S/S carriage bolt heads showing on the outside. Just as easy to remove for inspection as any other bolted setup too.
 
#46 ·
I still say the simplest method would be to clean up the area where they currently sit to get a smooth mounting surface and bolt them through the hull - virtually a direct replacement for the existing setup and only a few S/S carriage bolt heads showing on the outside. Just as easy to remove for inspection as any other bolted setup too.
That certainly sounds simple and would look OK for some people but fiberglass is brittle especially gel coat.
So exactly how much to you torque the bolts so the heads doesn't crack the gel coat. The obvious solution is to use a standard bolt with a washer. But now it doesn't look so good. Then the next option is a backing plate. The backing plate could come right up to under the cap and look ok for some folks but it is a different look for sure.

I'm pretty sure carriage bolts are best set into wood where it is expected that they will crush in a little as you tighten them.
 
#47 ·
Davidpm,

Not much I can't do with wood. I'm not a professional but I 'm a pretty fair amateur wood smith with both power and wood tools. I saved the old facing so I've got both ready at hand trim and bits for stain matching.

JonB - the 'twist' is because the plates are flush to the hull. Knees would by definition be perpendicular to the hull (at right angles). As I said in my response I'd probably just change the cap rail by re cutting a slot awarthship.
I'd repair the current slot with a dutchman, then cut the new.

Close up of the cap rail, just for entertainment purposes.

Before:


You can tell it's really 5 strips of teak. Anywhere it's joined it has a nice curved joint like it should be. This is with 1 coat of JD's Total Care, natural teak - no gloss / clear yet.


 
#48 · (Edited)
Knees don't need to be built in a way that requires a twist. This photo isn't mine (and isn't a Pearson 28-2), but closely resembles how they are done on my boat:


The knees don't need to be that deep if space is a concern. They only need to come in far enough for you to get a wrench around the back side of them.

Edit: one thing that isn't clear from this photo is how you access the back of the chainplate. On my Pearson there are cutouts in the knees to access the nuts on the backside. I'll take photos when I'm next at my boat (likely this afternoon).
 
#49 ·
I think through bolting would work. I doubt you could pull a carriage bolt head through the glass, and I expect you would use 2 or 3 on each chainplate. Also remember the stress is in shear, making it even more difficult to pull a carriage head through the hull.

Also, don't forget, at the mast the rig is usually fastened to a tang that is held on by 4 pop rivets. We get all anal about how the chainplates are fastened (and we should be) but it only needs to be stronger than the tang at the top.

No one has suggested just glassing in new plates. That's how it's been for 30 years, so no reason to think it's not adequate. Grind out the old ones, smooth everything with 30 grit on an angle grinder, and glass in new ones. On mine, I first filleted in the chainplate with thickened structural epoxy (after pushing the chainplate into a bed of same), then added 5 layers of 9 oz. cloth over them.

For sure you need to grind one out to have a look at what's going on. Can't really make any decisions until one is out.
 
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