Chain plate separating from deck

[FDL S2]

Looking for some advice and better ideas and holes shot in my plan.
Boat is an S2 7.3

Last night as I was leaving the boat I noticed that my starboard side chain plate was separating from the deck on the inboard side. I went out today to investigate it, first thing I did was run my main halyard to the toe rail and loosen the stays to take some tension off the plate. I can see the bolts inside the cabin, but I can't really get at the nut on the one that's pulling up (see pics), because it's recessed pretty far and it is right next to a bulkhead. It looks like there was a repair done in the past based on the epoxy that soaked the carpet on the ceiling and that the hole is recessed.
Here is what I'm thinking:
Cut off the bolt and push it through. Hopefully be able to unscrew the other bolt.
Cut the carpet out around the holes and clean everything up.
Assess damage and probably fill the holes with epoxy and cloth.
Drill new holes for bolts
Assemble with butyl tape and the biggest washers I can get inside the cabin.

What can possibly go wrong?

 

[jssailem]

First... Secure the mast.

1. Cut away the carpet so you can see the deck.
   
2. The bolts in the carpet are not securing the chainplate. The Chain plate is secured by the bolts going through the hull.
   
3. The 2 bolts through the deck are to pull the deck against the cover.
   
4. From the look of things, I would guess you have had water intrusion under the deck and perhaps some wet core or what ever the boats deck has sandwiched between the fiberglass skins.
   
5. Your going to have to pull the chainplates out and examine the area.(MARK ALL OF YOUR CHAINPLATES SO YOU KNOW WHICH ONE GOES WHERE AND HOW IT IS ORIENTED - and which edge faces the bow.)
   
6. If you find water or rotten core you will need to address that repair.
   
7. Next. It looks like the chainplate deck cover has been welded to the chainplate. My opinion, that is a weak design. Most plate covers slip over the chainplate. They serve to pull a sealant (i.e. butyl, or 4200 caulk down and around the chainplate to stop water intrusion. The flex of the deck and the welded chainplate cover did not play well together. This lead to breaking the seal of the caulk and water intrusion under your deck.
   
8. Check you chainplates for pit corrosion (they may have been sitting in the water that is beneath the deck skin). Stainless steel will corrode if oxygen is denied it's surface. Sitting in stagnant water is a good way to encourage corrosion of stainless steel.
   
9. Clean up if the plate is sound. If bad corrosion you will need to have new chainplates made. Take your plates to the metal shop to have an "EXACT" replacement made. This will give you the best chance at having the new plates fit and not having to drill new holes through your hull.

Big job I know. But you can do it. Take it one step at a time.

 

[LeeandRick]

FDLS2 Does the 7.3 have the small triangular mini bulkhead to attach the chainplate too like most S2s? If so I'm guessing you may have rot in that piece where the large bolts are going through. To lift like that would require the bolts (the ones that are double nutted with the acorn nut) to shift Also is the lifted side on the side away from the mast (outside edge of boat)? How about a picture of the whole chainplate.

 

[FDL S2]

Thank you for your response, the details and guidance really help. Marking and labeling the chainplates is something I would have for sure forgotten, so thank you putting that in bold.
After staring at it for a bit after I posted, I realized it is just a cover and yes, it is welded to the plate and this will cause flex and water intrusion. I haven't pulled it off yet, I'm thinking I can fasten the stays to the toe rail with either spare cable I have at home or some line. I have both halyards running to the toe rail on that side right now. I only had about an hour at the boat earlier so I didn't start hacking at anything-sometimes its good to step away and think before you act.
There is some mold on the carpet at the bottom of the bulkhead so I'm thinking there is some water intrusion that caused rot. The wood on either side above the bulkhead is solid, but I know that doesn't mean the wood directly under the cover is solid. My most recent thought is that the bulkhead might have some rot in it and is being pulled up or that the bolt holes in the bulkhead for the chainplate are ovaled causing the plate to pull up-this may be caused by rot. After I secure the mast I will pull these bolts out and cut the carpet away to take a look at the condition of the deck, bulkhead and chainplate then go from there.
I have done a fair amount of fiberglass work including replacing rotted floors and seat bases in a few powerboats, lots of work on my daysailer and replacing the rotted wood core in the transom of my old Coronado; so I'm not afraid of the work and I have some time this week to tackle it-I just really don't want to.

 

[FDL S2]

FDLS2 Does the 7.3 have the small triangular mini bulkhead to attach the chainplate too like most S2s? If so I'm guessing you may have rot in that piece where the large bolts are going through. To lift like that would require the bolts (the ones that are double nutted with the acorn nut) to shift Also is the lifted side on the side away from the mast (outside edge of boat)? How about a picture of the whole chainplate.

Yes, this is on the small triangular bulkhead. The lift is on the mast side of the chainplate. I'll pull the carpet off the bulkhead and get a pic of that. I'll also get a wider view pic of the cover.

 

[LeeandRick]

Looking at the welded cover, in your picture, made me run out and look at mine. I remembered it looking similar from afar, but it was just silver/gray caulk. One more thing to do before I put this project in the water this fall. Thanks jssailem for reminding me to pull the chainplates and check for corrosion.

 

[Mark Maulden]

Are you sure the cover plate is welded to the chainplate? If so, unweld it and clean it up. The chainplate will move slightly under loads which will want to make the cover plate move. The bolts for the cover plate should not be bolts but screws to just give the cover plate some compression. Someone overtightened the screws and they kept turning and just through bolted them. Also, put a washer under the coverplate screw on the smooth deck end. That will give the screw something to tighten against since the nonskid at the other end is higher. If you go back to screws, the holes will need to be filled and redrilled. Somebody really messed this up.

 

[mm2347]

Usually, a stained hull liner in that area is caused by water. You prob. have a deck with a rotten core in at least the chain plate area as well as rot in the bulkhead. (It is the bulkhead that carries the load) Also your chainplate deck cover should not be welded to the chainplate.
Good job on inspecting your boat!
There are many ways to repair depending on the extent of the damage. Often the rotten area of bulkhead can be cut out and replaced. Patch in new to old just like patching a fiberglass hull. Then laminate a number of layers of glass on each side to make an oversized backing plate for the chainplate. Stager each layer. Drill the mounting holes oversize and fill with milled fiber resin (2 at a time for alinement) and then redrill to the proper size. This not only spreads out stress but adds a compression post.
Next clean out the rotten core in the deck. Remove about a 1/8 inch from the top deck hole to aid in filling w/ resin. Wax your chain plate and mount. Tape the bottom to seal and the top around the edges to help with clean-up. Fill the void with resin mixed w/ milled fiber and cabosil. Remove chain plate after the resin has set. Then grind a small, shallow "V" into the c-plate hole at the top. (like countersinking a screw hole) Use butyl from Main Sail. Start packing w/ the c-plate about 3/4 in and try to push as much butyl into the area as possible as you slide the plate down. Do not try to seal the bottom. Then cover the area the size of cover plate w/ butyl, install the plate gradually tightening the screws allowing the excess to ozz out.

 

[FDL S2]

Are you sure the cover plate is welded to the chainplate? If so, unweld it and clean it up. The chainplate will move slightly under loads which will want to make the cover plate move. The bolts for the cover plate should not be bolts but screws to just give the cover plate some compression. Someone overtightened the screws and they kept turning and just through bolted them. Also, put a washer under the coverplate screw on the smooth deck end. That will give the screw something to tighten against since the nonskid at the other end is higher. If you go back to screws, the holes will need to be filled and redrilled. Somebody really messed this up.

I had a little time to kill between appointments today so I went to the boat. Port chainplate cover is through bolted to the deck too, so I'm pretty sure it was factory installed this way-it looks a lot alot better though (see pic). I pulled the bolts out that go through the bulkhead and took off the backing plate. I poked at the ceiling with a pick and didnt feel any soft spots, but I won't know anything until I get the carpet off it. I got the easy cover bolt out, and started working on the other one, but ran out of time. It just spins and I can't get anything on the nut to hold it.

 

[FDL S2]

Update:
I got the chainplate out with the help of an older gentleman walking through the harbor - the dock was a ghost town, none of the powerboaters on my dock who bother me when I'm working on the boat were there for the one time I could use their help. He turned the screw driver while I held the nut with a needle nose.
The chainplate is pristine (see pic #1).
Pulled the carpet off bulkhead and it has no rot or moisture.
I poked around the hole in the deck the chainplate passes through and deck wood above the bulkhead has some of that lovely mushy pulp that's good for making paper, but no good for providing structure in a boat (see pic#2 rot is at the end of the screwdriver).
I dug around the other side and there was at least 1/4" of caulk, silicone, whatever, but it definitely was not structural.
Log book says the side stays were replaced in 2000, so I'm thinking that was this half-a$$ed repair was done.
Plan for tomorrow is to cut out the wood from the deck 2" on either side of the bulkhead and see if the rot stops there. If not I will keep cutting in 2" increments until it stops. Then I will cut a piece of marine ply-it looks like 1/4" or 5/16"- to the right size (I have both in the garage from an earlier boat project), encapsulate it with resin and tab it in.
I'm thinking west system would be best, but the nearest West Marine is an hour away, can I get away with using good old fiberglass resin?
Thank you @jssailem, @Mark Maulden, @LeeandRick and @mm2347 for your help and advice.

 

[jssailem]

The chainplate is pristine (see pic #1).

You can tell better than I, but the two circled spots are what I would examine and buff out. Likely sound. If the spots grow as you buff the metal , then I would take the plates to a metal shop and have them put in an nitric acid bath to passivate the steel reducing the possibility of rust. (https://www.mmsonline.com/articles/how-to-passivate-stainless-steel-parts)

Did the Chainplate cover come loose or was it welded to the chainplate?

 

[FDL S2]

I will take a closer look at those spots tomorrow. They just looked like dings, but I will definitely buff them and see. Thank you for pointing that out.
Cover is welded to the chainplate on the top only (this pic is it upside down with the top between the boards in the dock), I'm thinking of grinding the weld off to make it free floating-but it just kinda hurts me to grind off a nice looking weld.... The port chainplate is also welded.
On a positive note the boom kicker I ordered 3 weeks ago finally showed up so that's a little more motivation to get this project finished quickly and right.

 

[jssailem]

the boom kicker I ordered 3 weeks ago finally showed up

That is good news. New additions are always fun.

kinda hurts me to grind off a nice looking weld.

The weld did look nice. But you will want the cover to properly cover and allow you to seal the opening.

 

[dlochner]

I'm thinking west system would be best, but the nearest West Marine is an hour away, can I get away with using good old fiberglass resin?

A good epoxy would be best. West System, System Three are a couple of the brands. Epoxy has better adhesive properties than polyester and you want good adhesion.

Epoxy will also penetrate the wood better leading to a better seal against moisture.

 

[FDL S2]

Today's progress.
Using a grinding bit on my dremel I started next to the bulkhead and plunged through the fiberglass into the wood looking for mush-i didn't use a drill because it's easier to stop the dremel and I didn't want to damage the deck fiberglass. I found rot about 4" on either side of the bulk head I then cut the glass another 1/2 inch out just to be safe. I peeled off as much of the glass as I could then started with a putty knife, hammer and screwdriver hacking out all the balsa core. The rot was only a total of about 4 sq in. But it had followed a path so it was spread out. The toughest part was above the bulkhead on the inboard side where someone had filled it with caulk, silicone, whatever-at least 3/4" on either side and it was a BBB (ball busting female dog) to get out. DO NOT EVER PUT THAT CRAP INTO ANYTHING STRUCTURAL!
I got it as smooth as I could with the tools at hand and wiped it with acetone to help dry out the areas that were still damp.
Tomorrow:
Sand the area to bare glass. Also sand on eitherside where the patch piece will be tabbed in.
Wipe everything with acetone.
Cut out two pieces of 1/4 plywood the fit the area I ground out-two pieces because it will be more flexible to fit the very gentle curve of the deck then ill coat them with resin and glass in the first piece and sandwich the second to it. Layer cloth on top of it and tab it the existing fiberglass.
1st pic is the area to be repaired cleaned of balsa core.
2nd pic is the wreckage and tools
3rd pic is my useless helper watching me the other day

 

[dlochner]

3rd pic is my useless helper watching me the other day

Everyone needs a support dog.

 

[jssailem]

Well you can see the confusion on the dogs face.
Looks like a solid plan.

 

[FDL S2]

He's good at that. Damn good bird dog, he grew up around the boat and thinks he should drive.

 

[shemandr]

Dog has a good heart. He'd help but he doesn't have thumbs. Best he can do is watch and offer support. Maybe bark a bit. That's it.
So all this because you noticed a screw pulling out of the deck. The smallest clues can lead to big projects. You know you have to do the other side - right?

 

[FDL S2]

Dog has a good heart. He'd help but he doesn't have thumbs. Best he can do is watch and offer support. Maybe bark a bit. That's it.
So all this because you noticed a screw pulling out of the deck. The smallest clues can lead to big projects. You know you have to do the other side - right?

Yes, I noticed a small issue that probably would have been fine if I hadn't noticed it or done anything about it, but the stays are not something to triffle with. This is a huge safety issue that I would have been uncomfortable with sailing knowing about-especially with guests.
The other side looks good. The chainplate cover isn't pulling up and there isn't any discolor on the carpet on the ceiling or the bulkhead. After this season I'm probably going to replace the carpet in the interior and I'll take a good close look at the port chainplate. So I guess we'll see (which usually means I will have to do the same thing on that side).
Also, he is the unofficial dock dog on my dock and everyone knows his name. When he's out there he greets everyone, but he has manners so he doesn't jump up-the only thing he will do is go on the pontoons to get affection and run up and down with other dogs that show up. My neighbors have treats just for him.