Replacing bulkhead bolted chainplates with deck bolted with a wire strut - Page 2 - SailNet Community

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  #11  
Old 07-03-2010
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The idea of attaching it to the hull directly is a little scary,especially if below the water line.Why not just replace is as originally builtmarc
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Old 07-03-2010
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MARC makes a good point as well. On boats I have seen with that type of chainplate (Peterson 34 being one) the attachment point on the hull is either a beam that ties into the keel structure or a fairly large stainless weldment that is incorporated into the hull during layup. Quite often spanning a distance of several feet fore and aft to spread the load. It does have to withstand a few thousand pounds of force. A secondary bond, even if using epoxy and expertly done, would not have the strength of original construction of this type of attachment. And that is why most builders and designers favor the attachment to either the main bulkhead or a secondary bulkhead wherever possible. The cap shroud when heeled in a good breeze exerts a lot of force on any chainplate attachment. If you wish a change best to consult a naval architect to make sure it will work.
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Old 07-03-2010
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Quote:
Originally Posted by sailingdog View Post
Well, I am guessing that the bulkhead is structural... it has to be if the chainplates are TIED TO IT. If the bulkhead isn't structural, they would never have tied the chainplates to it.

Again, it would help if you said what kind of boat you had, since there may be a known fix for the boat that other owners have come up with.
The bulkhead attaches to the molded interior via screws at the bottom and screws to a headboard that is not glassed in, it runs to the other bulkhead and connects with screws. The headboard is kinda just wedged in and screwed to the bulkheads. I already said that most of the glassing wasn't stuck to the bulkhead like not glassed on(not done by the manufacturer). Ive been sailing it like that for a year on the bay, some times in heavy winds with no reefs. so basically the only thing keeping the rig up was bulkheads attached with screws being pulled tight against the cabin top. When you said the bulkhead needs to be replaced before i can use the boat did you mean that the bulkhead does more the hold the chainplate? because i pretty much explained that its not glassed in at all. When I un-stepped the mast both bulkheads and headboard could be move back and forth freely by definition(permanently fixed) It is NOT STRUCTURAL. and originally(from the manufacturer) the chainplates were attached to the cabin top but someone beefed up the rig and decided to bolt new chainplates to the bulkheads, so you really jumped the gun on your I know everything and your a greenhorn speech, just because i just signed up on sailnet doesn't mean i don't know stem from stern only that i haven't owned a computer in a few years!!!
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Old 07-03-2010
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I do not know of any substantial boats with the chainplates attached only to the cabintop.

If you think you got an earfull here why don't you post here Boat Design Forums
and see what they have to say.
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Last edited by mitiempo; 07-03-2010 at 01:29 AM. Reason: add
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Quote:
Originally Posted by mitiempo View Post
Schaefer makes chainplates but they are all basic stainless chainplates and not what you are after. Here's the link to their chainplate page.
Schaefer Marine Hardware - Product Catalog

Harken is a very innovative company. But chainplates are not really an innovative type of product. They do not make them. Not in my catalog or their online catalog. They are also boat specific so the market would not be worthwhile. The chainplates that come with the boat will last decades if not the life of the boat. Every boat design has different requirements and other than a straight bar type of chainplate which Schaefer has there probably isn't one available to fit your needs. Every rig has different angles and hole sizes and every deck design is different as far as angle is concerned.

Your best bet is to draw exactly what you want, go to a good metal shop specializing in stainless steel and having them custom made. Use 316 and get them electro-polished for the best corrosion resistance. Anyone I know who has either built or restored a boat and needs chainplates, unless they are simple bar stock, gets them custom made as I have in the past.
I know Harken doesn't make them. just saying a reputable brand like Harken. Your right about every rig being different. I was already thinking 316 SS, Is Electro better than hand for corrosion resistance? What about a reputable shop that i could send specs and and orignals?
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Quote:
Originally Posted by mitiempo View Post
I do not know of any substantial boats with the chainplates attached only to the cabintop.

If you think you got an earfull here why don't you post here Boat Design Forums
and see what they have to say.
Now a days with fiberglass so thin its scary but in the late 60's when they were built like tanks......
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Yes electropolishing is better as it passivates the stainless and prevents corrosion. Every major area has a shop that works in stainless. I know a good one locally I have used for 20 years but there should be one close to you wherever you are.

I do not know of a current boat with the chainplates bolted to the cabintop. The Bayliner Bucaneers were done that way though in the 70s.
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Old 07-03-2010
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If the original chain plates only attached to the deck, then the bulkhead may not be structural, but the boat can't be all that big, and is poorly designed IMHO. If the chain plates had been attached to the bulkhead by the manufacturer, they would have to be structural. It is a pretty stupid idea to attach chainplates to the "lid" of a box rather than the bottom of the box. If there's a problem with the hull-deck join, the chainplates fail by default.

I'd note that you never said the chainplates had been modified and that the attachment to the bulkhead was done by the previous owner. Having chainplates attached to a bulkhead is a pretty standard thing and it is very unusual to have them only attached to the cabintop. Must be a pretty small POS boat to have them that way.
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Quote:
Originally Posted by sailingdog View Post
If the original chain plates only attached to the deck, then the bulkhead may not be structural, but the boat can't be all that big, and is poorly designed IMHO. If the chain plates had been attached to the bulkhead by the manufacturer, they would have to be structural. It is a pretty stupid idea to attach chainplates to the "lid" of a box rather than the bottom of the box. If there's a problem with the hull-deck join, the chainplates fail by default.

I'd note that you never said the chainplates had been modified and that the attachment to the bulkhead was done by the previous owner. Having chainplates attached to a bulkhead is a pretty standard thing and it is very unusual to have them only attached to the cabintop. Must be a pretty small POS boat to have them that way.
I confirmed with the group that the bulkheads were never glassed in only screwed in like I said. But the headboard attached to the horizontal compression post and the original chainplates attached to part of the headboard/compression post and part of the bulkhead. Its a Coronado 25 KIT boat that was built for racing from the start nothing special by most peoples standards. allot of modifications were put into it its been down the west coast and back a few times. I think it went to Hawaii which is where i wanna take it.
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If you want to take a boat like yours that is built for coastal at most to Hawaii the strongest solution would be to glass the bulkhead in and attach the chainplates to them or place the chainplates outboard on the hull and lose a bit of pointing ability. Nothing else you can do will be as strong.
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