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Go Back   SailNet Community > On Board > Gear & Maintenance > Chainplate reinforcement
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Thread: Chainplate reinforcement Reply to Thread
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Topic Review (Newest First)
01-16-2013 08:38 AM
vmaks
Re: Chainplate reinforcement vs beefing up the deck

My "new to me boat", 1983, 28 ft O'Day has a very similar problem to Tafa's posted pic, however, my boat DOES have a backing plate and I do not see any visual cracking in the glass from the inside. My boat does have the lower back shroud anchored with a rod through the boat to a bulkhead behind the settee. However, the lower front shroud is only thru-bolted to the top deck with a backing plate. When I bought the boat the captain I hired to transport the boat with me (a situation that allowed me to get familiar with my boat in big waters and a 200 nm trip) tightened the shrouds too tight and caused a "canning effect". Is the front shroud important enough to pay to have a "strapping" created, perhaps mounting an exterior strapping thru the hull or.....beefing up the top deck from the inside and increase the size of the backing plate? Thoughts? We want to be safe but we don't want this project to out-cost the cost of the re-sale of the boat in the future. Sorry, no pics, the boat is 5 hrs away, shrink wrapped with snow.
03-13-2012 11:32 PM
Tafa
Re: Chainplate reinforcement

Thank you very much everyone,

Yes the picture has taken from inside and crack is on the headliner. From outside there's no sight of crack, softening, delamination or damage on the hull.

I will definitely replace the chainplates (not a big ticket investment and really wise thing to do) and will use backing plates instead of washers.

About reinforcing, I will open the area first and do some damage control. Then proceed accordingly. Hopefully will post update with before/after pictures.

Thanks again for your advise.

Tafa
03-13-2012 09:32 PM
knothead
Re: Chainplate reinforcement

I pretty much agree with all the above.
Some good pictures would really help.
However, I would respectfully suggest that it still might be a good idea to pay a professional to take a look at it for you at the very least.
Even if you choose to do the work yourself, and I encourage you to, sometimes having someone that's done it before explain the process is really helpful.
If you are going to do the work in a DIY boatyard, they will probably have someone on staff that could advise you.
And there are almost always some pretty skilled boat owners hanging around in boatyards.

Just make sure you run any questionable advice by the SailNet crew before proceeding.
03-13-2012 07:31 PM
bwindrope
Re: Chainplate reinforcement

Thought I would add my experience of recently replacing my chainplates for precisely the reasons enumerated here. Here is my blog post: Stories of Aeolus- Our Gulf 32 Pilothouse: New Chainplates!''

Mine were original to the boat in 1988 and so 20+ years old, and like many boats, passed through the deck in a unseeable way. Sure am happy with my new, thicker, well sealed with butyl rubber new plates! It had been on my list, and now is fully off.
03-13-2012 02:45 PM
GeorgeB
Re: Chainplate reinforcement

Tafa, can you take a couple more pictures of your rigging? (From the topsides for example.) Am I’m looking at a lower shroud and that your cap shrouds are chainplated into a bulkhead, frame or hull? My guess is the crack you are seeing is from a molded-in headliner and that the problem is there is a gap between it and the deck proper and that tightening that one nut is the culprit and not a question of over tensioned wire. When you remove the topside “chainplate”, clean the bolt holes really good. Tape over the hole bottoms and pour in the epoxy to fill the gap and re-drill. You probably have wood core here and check to see if it is wet and rotted. That too will cause your problem. Mainesail has an excellent website that shows how to do these kinds of repairs. You will probably want to add a proper backing plate. You can fabricate one out of 1/8 inch stainless (polished) plate. However, this is expensive and requires cobalt drill bits and saw blades. Downscale, you can use 3/16 inch G-10 (Garolite). This is easier to work with but lacks the finished look of polished stainless. Are you missing lock washers on the those bolts or it the picture quality? You will want lock washers. If you use SS backing plates, all you will need are the locking washers and nuts (plus an acorn nut to finish it off). If using Garolite, then add a flat washer.
03-13-2012 02:30 PM
Faster
Re: Chainplate reinforcement

Is this the bottom of a lower shroud 'chain plate' connection? It doesn't look right for a cap shroud chain plate, they are usually attached to something more robust like a bulkhead or a knee..

Also is the crack in a liner molding or the deck structure itself??
03-13-2012 02:15 PM
jrd22
Re: Chainplate reinforcement

If that is the interior of the boat the way it looks (external chainplates?) then I would recommend a large SS backing plate and longer bolts.
03-13-2012 02:06 PM
MedSailor
Re: Chainplate reinforcement

Quote:
Originally Posted by Tafa View Post
Great point MedSailor... What do you think would cause the problem rust of metal exhaustion. If the main concern is rust, its easily inspect-able. Is there such concern as metal exhaustion on ss.

Thanks,

Tafa
Yes, the "metal exhaustion" you refer to is called "work hardening". When the stainless steel family of metals is flexed under load (anything other than a perfectly in-line load) it becomes more hard and brittle over time. It's a little counter-intuitive but it can actually become "stronger" with work-hardening but more brittle. Suffice to say the characteristics of the steel of your chainplates were selected for a reason at construction and hardening of them over time is bad. You don't want brittle metal with a shock load of a crash-jybe.

Reading on work-hardening here: Article: Mechanism and measurement of work hardening of austenitic stainless steels during plastic deformation

The type of corrosion that stainless suffers from is called "Crevice Corrosion" and it happens in an anaerobic environment. It's unavoidable with bedded stainless hardware. Silicone bronze (marine bronze) doesn't suffer from this problem but is more expensive and isn't "shiny" like stainless. Most of the time the corrosion appears as brown staining but unfortunately it's not always visible. Micro cracks on the surface can lead to destruction of the core of the chainplate with the only visible evidence being the (hard to find) micro-crack.

Reading on crevice corrosion here:http://soar.wichita.edu/dspace/bitst...pdf?sequence=1

Image of crevice corrosion on a chainplate:
03-13-2012 01:50 PM
Tafa
Re: Chainplate reinforcement

Quote:
Originally Posted by MedSailor View Post
Everybody replaces the rigging on some kind of schedule but often the plates are not replaced.

If you're going to all the labor to un-bed and remove and re-bed the plates, I'd recommend replacing them while you're at it.
MedSailor
Great point MedSailor... What do you think would cause the problem rust of metal exhaustion. If the main concern is rust, its easily inspect-able. Is there such concern as metal exhaustion on ss.

Thanks,

Tafa
03-13-2012 01:45 PM
Tafa
Re: Chainplate reinforcement

My bad..... You're right

She's a Nash 26
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