Chainplate popped out when sailing - what's next?

[roverhi]

The problem with glassed in chain plates in most boats is crevice corrosion. Water leaks into an oxygen deprived environment and SS corrodes. Failure is usually the chain plate breaking at deck level or just below. This failure is relatively rare as the glass laminate actually pulled free from the hull. Reglassing it is chancy. The original had some chemical bonding to a freshly laid up hull that won't be there with the many years the hull has had to cure. Epoxy might help but I'd be leery of putting it back as contructed.

Because of the outboard nature of the chain plates you don't lose anything by going with external bolted chain plates. That would be my solution to the problem. If you didn't want exterior chain plates, they could be through bolted from the outside. Since the loads will be in shear, no great need for backing plates on the outside. Carriage bolts would probably work fine.

[Jim Cate]

As I read the last two pics you provided, the failed chainplate (and its mate presumably) were fixed to a thwartships bulkhead. Is that correct?

Sure looks like they were glassed to the inside of the hull, TP, not the bulkhead. I think you have that wrong.

And to me, this indicates that reglassing back in the original place is in order. Likely a good idea to do all of them prior to their following suit!

Jim

[teejayevans]

I would secure those wires better while you’re in there.

[gmakhs]

Originally Posted by Jim Cate

Sure looks like they were glassed to the inside of the hull, TP, not the bulkhead. I think you have that wrong.

And to me, this indicates that reglassing back in the original place is in order. Likely a good idea to do all of them prior to their following suit!

Jim

If he re-glass shouldn't he enlarge the chain plate area to spread the load.more ?

[Jim Cate]

Originally Posted by gmakhs

If he re-glass shouldn't he enlarge the chain plate area to spread the load.more ?

Well, it did last over 50 years with the original bonding! As i see it, it isn't the bond between glass and plate that takes the loads. Rather, it is the "T" shapes that would have to shear the glass or pull the glass from the hull that do the work.

If the plates are renewed, it would be easy enough to make the Ts wider, and I agree that it couldn't hurt. And also that use of Epoxy might be justified to improve chances of the new glass being well bonded to the hull. But, such repairs are quite commonly made and with general success. I wouldn't worry too much using the original dimensions and polyester if the work was done to normal professional standards.

Jim

[Fore and Aft]

I agree with you Jim, why reinvent the wheel. I would make all new stainless steel chain plates and glue/glass them in place with epoxy. I would use double bias glass with the last layer being peel ply so you do not have to sand the last layer of glass smooth. This is really an easy interesting job and the worst bit is going to be removing the old chain plates and grinding the old glass smooth.
I would also glue and glass those chain plates in place in one day. You can have all the fibreglass cloth cut and numbered ready to go. Then have a piece of plywood so you can wet out the glass before you stick it around the chain plates. I always use slow hardener for jobs like this just to give me the extra time.
Cheers

[Jim Cate]

Originally Posted by Fore and Aft

I agree with you Jim, why reinvent the wheel. I would make all new stainless steel chain plates and glue/glass them in place with epoxy. I would use double bias glass with the last layer being peel ply so you do not have to sand the last layer of glass smooth. This is really an easy interesting job and the worst bit is going to be removing the old chain plates and grinding the old glass smooth.
I would also glue and glass those chain plates in place in one day. You can have all the fibreglass cloth cut and numbered ready to go. Then have a piece of plywood so you can wet out the glass before you stick it around the chain plates. I always use slow hardener for jobs like this just to give me the extra time.
Cheers

good advice IMO!

Jim

[a64pilot]

For whatever it’s worth when I was looking at having mine replaced, I had our Engineer at work take a look at the design.
He had his FAA DER in structures, and is an avid sailor/racer.
In his opinion, the hull to deck joint at least on the IP design took the majority of the load, even though as you can see in my picture that about three ft of stranded glass was placed over each side of the “T”.

I think he needs to fix his deck of course, and reinstall the chainplate, after inspecting of course, and use stranded glass like in my picture.

We need to realize that this is a 1967 Boat and if you can probably easily exceed its value in repairs, but not increase its selling price by a nickel.

[boatpoker]

This happened on only your second sail ? This weak spot should have been obvious to your surveyor. What else did he miss ?

[Thumbs Up]

This boat is an excellent candidate for external chain plates. You would only lose an inch or so on sheeting angle. You could use part of the old chainplates as backing plates.

[petered]

Thanks again for all of your input, this community is very helpful.

Originally Posted by TrentePieds

As I read the last two pics you provided, the failed chainplate (and its mate presumably) were fixed to a thwartships bulkhead. Is that correct?
.

They were fixed to the hull, not a thwartship bulkhead, but I believe the rest of your advice still holds in this case.

Thank you a64pilot for the advice about the directional fiberglass (and for the very operating-room picture).

Originally Posted by cal40john

One issue is the chainplates are possibly in a wet low oxygen area so they potentially could be corroded and ready to fail.

The chainplates themselves looked ok to me but I'll take a closer look now that you mention this.

I will post an update once this job is completed.

[Adelie]

Originally Posted by Cheechako

I believe that chainplate was intended to be attached more to the hull sides than the deck. (?) Based on the T bottom. So... the deck may not actually be your biggest problem. Rather, the old fiberglass that attaches the T shaped plate to the hull has given out. I would remove all chainplates including the stern, inspect the SS plates, Grind to fresh glass and re glass them to the hull.
Or make new chainplates and devise bolting them through the hull.

+1.

Unless you have a very small boat the chainplates go thru the deck and attach to the hull or to a bulkhead.

I have a 20’ boat and on mine the shrouds attach to the deck and bear on it directly. In the long run I’m going to change this.

[MartinR]

It looks to me like the chainplate was actually attached to a bulkhead?

In this case, external chainplates will change the geometry of the rigging and effect sailing performance. How are the other chainplates attached?

And just for info, the cap shroud is basically taking all the load while sailing. The other shrouds are mostly to keep the mast in column.

[MartinR]

Soory, was wrong, it looks like it attaches to the hull.

[Ambler]

I reckon a stainless ring frame would be the best bet. Back in the 60's the boat builders weren't really on top of the limitations of fibreglass. Redirecting the rigging loads to the base of the king post will do your hull a big favour in my opinion.
Wayne