Various types of chain plates

moonie5961 · #1 (**permalink**) 12-25-2009

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CalebD · #2 (**permalink**) 12-25-2009

Quote:

Originally Posted by moonie5961

In my aimless internet browsing, see several types of chain plates, and means of distributing the load of standing rigging.

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My own interest stems from the fact that I want to replace my own-belonging to my 1974 Contest 31. All of my standing rigging is original, stainless and I'm sure riddled with crevice corrosion. To augment the problem of my own situation, mine are glassed in from below deck to prevent moisture penetration into the cabin. To me, this is asking for maintenance neglect, and an eventual disaster. Luckily, my decks have no core material to worry about, as they are solid glass.

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Mine are like the stainless loopy ones on bottom, and they're what I will likely use to replace the current ones. Aside from being very expensive from the few places that I have seen them, what do you think of these?

Thanks, I look forward to hearing what you have to say.

Stainless steel will corrode in the presence of moisture and no air so glassing in any SS is basically a bad idea. I know this because the chain plates on my own boat were done that way back in 1967 and I have already replaced our aft chain plate. They built a knee wall consisting of a core of plywood which had the chain plate bolted to it and the whole thing was glassed over. Get a little water in the plywood and it turns to soil over time.
What some owners of the Tartan 27' have done is to rebuild the knee wall and put the chain plates outside the fiberglass so the bolts and plate can be inspected.

The 2 bottom photos look more like 'bow eyes' then chain plates to me. Usually your shrouds/stays will attach to the chain plate by using a clevis pin as in your first photo. Once you disencumber your chain plates from their fiberglass tomb you will likely see that they look more like the one in the attached pic.

mitiempo · #3 (**permalink**) 12-25-2009

I agree with caleb. They would have to be attached to something more solid than the deck. The four slot head machine screws are just holding the cover plate against the probably hardened sealant. The actual chainplate is a pretty beefy piece of stainless that goes through the deck and bolts to something I'm sure.
As far as the different types of chainplates the ones bolted through the topsides are the simplest but other types are, or can be just as strong. The kind in caleb's photo are probably the most common, either bolted to knees like his or to a main bulkhead like mine. If they are on the hull sides it doesn't let you sheet in the jib as close to the boat's center line as inboard chainplates so it effects your windward ability a bit.
The examples shown in your photos would probably work for a small boat like a 22' trailer cruiser but aren't anywhere near beefy enough for a boat like your Contest 31. The deck is not strong enough to support the rig at one spot. Do you have other chainplates through the deck near those? As far as I can tell you have an upper shroud and fore and aft lowers and they're pretty close to the hull/deck join. They could all be one piece below deck and glassed in. The Spencer 35 has the same arrangement and it works well. In the case of the Spencer it is about 3' fore and aft and heavily glassed in. To remove such a chainplate is major surgery but I think that's what you have as opposed to 3 separate plates if you don't have the arrangement in caleb's photo. If this is the case unless there is evidence of leaking I would leave them be and just remove the cover plates and rebed them. Hope this helps.

GaryHLucas · #4 (**permalink**) 12-25-2009

My boat has chainplates looking like the looped ones at the bottom. However the deck does NOT carry the load. There is a backing plate with two holes, that has a plate welded to it which attaches to a turnbuckle. A rod then goes down to an attachment on the hull.

It's kind of sad. Chainplates have turned more Good Old Boats into junk than any other device. Damn near all of them leak, and all for the same reason. A basic piece of boat physics is that EVERYTHING moves! Not providing for that motion is why chainplates leak.

In the top picture that chainplate could be 100% leak free. All it needed was for the cover plate to be left off, and the hole in the deck you be large enough to leave a gap about 3/8" wide all around. Fill that gap with the flexible sealant of your choice and it may never leak for the life of the fiberglass hull.

mitiempo · #5 (**permalink**) 12-25-2009

Gary
I agree the chainplate he has (top photo) could be leak free. As a matter of fact if it is as I described it can probably be more leak free than most. He says they are glassed in from below to prevent moisture penetration but that is not the case if I am correct. The cover plates, as you and I suggest, will prevent leaks. The glassing is for strength and is quite a good system. I wish mine were like that. I think if there is no evidence of corrosion they should be left alone as they are much more a part of the boat than most.
Merry Christmas

bluwateronly · #6 (**permalink**) 12-26-2009

I would not be suprised if the chainplates are not just glassed into the hull. They are probley in the shape of t's and fiberglassed into the hull so the Distribution of stress is spread out into the hull. If you see any brown streakes it's a for sure thing to grind them out and take the old ones to a shop and have some new ones made and glass them back in. I guess you could build a knee and use straight chainplates and bolt them to it but, if you do the glass work correctly and keep the topside sealed it would probley last as long as you do

I think if you are worried about it I would replace them and not have to stress about it, that nagging voice bugging you can be a real pain and worth the time and effort to shut up

mitiempo · #7 (**permalink**) 12-26-2009

I agree with bluwater. The chainplates can't be just attached to the deck, especially on a boat from Conyplex (Contest). While this one is older, they've always been solid boats. I couldn't find a pic of a Contest 31, only the 33 (moonie - get a new camera

) but it shows the chainplates coming through the deck very close to the hull. They are also in line. I would think they are either as I described or as bluwater suggested "T" shaped and glassed to the hull. A deck view of a 33 is below.

icerick · #8 (**permalink**) 05-09-2010

Quote:

Originally Posted by CalebD

Stainless steel will corrode in the presence of moisture and no air so glassing in any SS is basically a bad idea. I know this because the chain plates on my own boat were done that way back in 1967 and I have already replaced our aft chain plate. They built a knee wall consisting of a core of plywood which had the chain plate bolted to it and the whole thing was glassed over. Get a little water in the plywood and it turns to soil over time.
What some owners of the Tartan 27' have done is to rebuild the knee wall and put the chain plates outside the fiberglass so the bolts and plate can be inspected.

The 2 bottom photos look more like 'bow eyes' then chain plates to me. Usually your shrouds/stays will attach to the chain plate by using a clevis pin as in your first photo. Once you disencumber your chain plates from their fiberglass tomb you will likely see that they look more like the one in the attached pic.

I also have a Tartan 27 with weeping on the hull side of the encapsulated chain plate. You have a picture of a chain plate bolted to the existing knee wall butit appears to be further inboard of the existing attachment points for the rigging. I was thinking of sisterering a new stainless chainplate with a wood sandwich and then bolted and glassed to the existing knee wall. This would give two attachment tangs on deck that I would attach my turnbuckle to. I am not sure I want to dig the old chain plates out. Could you explain your chain plate fix a bit more?

CalebD · #9 (**permalink**) 05-09-2010

Icerick,
The photo I posted is not from my T27 but from another owners repair job. I borrowed the pic from a member on the yahoo group: T27Owners. Join up - it is free. Lots of discussion about chain plates and re-core issues.
I think you are going to have to take apart that knee wall as the wood in there has likely turned to mush. Believe me, I am not looking forward to doing this job either. I have only re-done the aft chain plate so far.

sailingdog · #10 (**permalink**) 05-09-2010

It sounds like the OP's chain plates are basically tied to the hull via tierods inside the boat.

I would recommend using butyl tape for the sealant, since it is the most flexible sealant.

I'd recommend that you listen to the others about crevice corrosion and not glass in the chain plates.