Chainplate replacement - Rotten and water soaked Knees under my chainplates

[alaskanviking]

Been Hard at work removing two of my chainplates in a Passport 42 cutter. worst thing
i have had to do to my boat yet. old chainplates are fiberglassed in
place in a kinda H shape. had to cut out the lovely teak backs, of the salon cabinets to access them. two plates on starboard were right at cabinet bulkheads. very depressing. used a Rigid Multitool to cut out the fiberglass covering. found that you
must use the metal and wood saws, as the wood only blades turn into
scraper blades far to quickly. while cutting out the chainplates i hit
3 pockets of water on the starboard plate, and 5 on the port. nasty
black ooze drained out. when i finally got the plates off the port
side the knee was all black on the bottom. tried to drill drainage
holes but the wood was way to spongy or rotten. even the wood that
initially looked ok on both sides was spongy, i could almost push the
drill bit in without pulling the trigger. i then cut one of the
fiberglass sides of the knee on both sides and they pretty much just
fell out. obviously these were not installed correctly and
fiberglassed on every side, one of the knees did not even go all the
way to the deck and had a gap of about 2". the wood looks like fir,
but its so bad i cant be sure.
its a simple job to replace them, but i need to know what wood i can
use to do so. should i go get some blocks of fir, Ironwood(IPE), Mahogany, or would
Oak be a better choice? what about replacing it all with a block of
G10 Fiberglass epoxied into place? i have a decent piece of oak that
may be about the right size. not sure which way to proceed here.

Thanks

Robert

[Brion Toss]

Hello,
And condolences on this mess. And congratulations on your standards and initiative. And curses on the people who installed those things, and the people who installed lots of others just as bad.
As for how to proceed, I'm sure that there will be some good suggestions showing up. Are you planning to glass in the new chainplates? If so, use grade 5 titanium, and leave lots of drainage holes and seal everything better. But this could be an opportunity to go with throughbolted chainplates. Is this an option?
As for materials, the G10 sounds best, but even plywood can be fine, so long as you epoxy-seal and -bush everything, so water can't get to it.
Good luck, and fair leads,
Brion Toss

[alaskanviking]

Thanks. Yes i am going to through bolt and use titanium chainplates and hardware from allied titanium, and use a sisterplate on the exterior. as the mast is still up i was going to do one or two at a time till its all done. the g10 looks very good, but its a bit spendy, epoxied plywood wouldnt be too hard. i was under the impression that a softer material like wood would have to be used. if not G10 fiberglass plate sounds like the perfect, never another problem fix that would pair well with titanium.

[Stumble]

Alaskan,

I would highly recommend going to http://www.boatdesign.net/forums/sailboats/ and asking there, include pictures, and a rough idea of what you are planning on doing. While this forum is great, boatdesign.net has a pretty high concentration of designers that are happy to help actually do load calculations. Pay particular attention to Par.

Without comment on them, you might also want to look into composite chainplates. They eliminate holes in the deck compleatly, which in my eyes is always a good thing.

[Ian McColgin]

Second the above. You need to know if this is a cored hull with a massive and dangerous structural problem or if this is localized wood that can be readily replaced.

It is possible to locally recore. Some work from the inside and some from the out, but whichever way you find easier it means taking the glass structure on one side away, googing out the soaked core, scarfing in new core, and then rebuilding the glass to original. Not by any means trivial as the problem can easily run well below the chainplates and can run fore and aft quite a way. But doable for those with the guts.

G'luck

[alaskanviking]

Thank you for all the help. i thought about composite chain plates, i really like the idea of no leaks and glassing directly to the hull and deck, however i believe that with design work and having someone else come in to install them it would be too cost prohibitive. i like the idea of sustainability, once i head out cruising. there is always a chance of something breaking, and composite chainplates and titanium are not in use extensively to 100% garuantee anything (althou i suspect its close). i like the idea that in the slim chance that something did break/crack/bend/get damaged/ect i could have bolt on spares or limp to the next port and have a temporary stainless or bronze chainplate made from drawings or cad file. or even have something shipped out if need be. while i would keep some mas or west system epoxy on board and i could technically make a repair if need be, i could no longer garauntee that the plate would be ok. to change it out id have to regrind everything out, which would be even more fun with the carbon. i am definately tempted, but that slight risk holds me back. the same would go with encapsilating titanium into place. while it is unlikely, anything is possible, and so i think i would prefer to bolt on. i believe that area is solid and not cored, i will be able to find out when i remove the rubrail and get the single bolt out. currently i am planning on continuing with g10 fiberglass plates glassed together for the knee, and internal titanium chainplates throu bolted to exterior sister plates. i believe that this may be my best solution while balancing corrosion and water resistance, cost, and sustainability/ease of repair. i am also posting this question to the boat design forum before i pull any trigger. ill forward any findings.

V/R

Robert

[rockfordwoods]

http://www.rodiponer.com/sail/001-Re...a_Passport_42/