chainplates

[sardinebreath]

Anyone have any experience replacing glassed in chainplates? I can't imagine how to even begin--other than just to put some new ones outboard. Anyone know why a designer would opt to have chainplates glassed?

[Kevin84]

Because you're not supposed to replace them. You're supposed to scrap the boat and buy a new one from the manufacturer! :-D

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[a64pilot]

You can go external as you suggest, or depending on the boat, it may not be that big a deal to replace them.
I'm sure glassing them in was for strength, a cost savings, or aesthetic reasons, or all of the above, who knows?
If kept completely sealed as in rebedded every year or two, glassed in chainplates can last a long time. There are disadvantages to every construction technique, or there would only be one way to do things.

[DeepFrz]

If kept completely sealed as in rebedded every year or two, glassed in chainplates can last a long time.

How can you be completely sure that absolutely no water has entered and that crevice corrosion isn't about to destroy your boat when the mast comes tumbling down?

[a64pilot]

Originally Posted by DeepFrz

How can you be completely sure that absolutely no water has entered and that crevice corrosion isn't about to destroy your boat when the mast comes tumbling down?

You can be as sure of that as you can be that there no inclusions in the metal of the chainplates you just put in new. Or that you are in the beginning phases of a terminal fast acting disease.


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[DeepFrz]

So, not sure at all. Glassing in chain plates is a very bad idea.

[Chasing Summer]

If you really think you have to inspect / replace your chainplates they have to be done from the inside. Remove the headliner or hull covering, and grind off the overlay. ... Mine are directly under the deck at the reinforced hull/deck joint and are plates with tabs that go through the deck. It would be a lot of grinding dust but it can be done. The other option is to perform an hydralic load test on them. This puts a strain on them where they are which is much more than the mast will ever have. It may cost a few buck, but if you're worried it's the way to go.

[73Islander36]

well in theory yes especially for stainless plates and especially 316....now having said that my one glassed in plate, actually its a stainless knee on my islander 36 is just fine and the ones that suffered were the bolted on ones, to bulkheads but that has more to do with stainless fatigue over the years and crevice corrosion than anything else

now...if DRY glassed in plates can last a looooooooooooong time...and nothing worng

the problem is accesing them to check on them requires glass work and most guys or boat owners dont want to do that just to check so they leave them be...

also if you arent recaulking or sealing the deck holes you are asking for it

a good way to check if you should is t drill a weep hole in the glass...at the lowest point if the structure...

good luck

if water seeps out and is even remotely rusty do yourself a favor and replace and rebuild the plates...

[model 10]

I'm surprised that the mobile testing services don't cater to sailboats. You can determine all these problems with the correct test. Easy if the part is in your hand, harder and more $$ if still in the boat. Maybe too much $$$ ?

[a64pilot]

Originally Posted by Guy

I'm surprised that the mobile testing services don't cater to sailboats. You can determine all these problems with the correct test. Easy if the part is in your hand, harder and more $$ if still in the boat. Maybe too much $$$ ?

I think maybe it's because chain plate failures are about as common as keel bolt failures, plus the most likely boats to need the service are older and therefore less expensive boats. Just exactly the ones that don't have lots of money laying around to spend on such inspections? Other than X-ray, how could you inspect?
X-ray is problematic in a public area to say the least.

[model 10]

Originally Posted by a64pilot

Other than X-ray, how could you inspect?
X-ray is problematic in a public area to say the least.

It's not like they bombard the whole boatyard with X rays. You have ultrasonic and eddy current testing also.
There are guy's in vans zooming around testing pipes and valves and wing spars and welds and all kinds of stuff, all over the place but not chain plates in boatyards. Free lunch at the yacht club might help.

[Fortytwo]

I am replacing my glassed in chainplates now and putting the new ones outboard. After removing the old bits, I epoxied a 4" wide strip of 1/2" G10 on the inside for a backing plate. I did have to notch out the rub rail on the outside to accommodate the new plates. I've seen people put the plates under the rub rail, but that seemed to be more work then it is worth. I didn't see any issue with the old 1/4" thick chainplates, although I am replacing them with 3/8" thick. The chainplate bolts were another matter...

[Cheechako]

Originally Posted by DeepFrz

How can you be completely sure that absolutely no water has entered and that crevice corrosion isn't about to destroy your boat when the mast comes tumbling down?

When you think about it...Even bolted external chainplates you are only 50% sure. You have no idea what is going on between the hull and the chainplate... which is where the crack crevice corrosion will happen. The bolts themselves are a perfect spot for water ingress as well as the top where the hull last touches the chainplate where it flexes...

Xray isn't the end all solution. From my time in aerospace, I learned you have to be able to shoot the xray image from just the right angle and side, or you cant tell anything much. You could see a large crack probably though.. but an old gouge/scratch in the material from frabrication will look very similar.

[Jim Cate]

Originally Posted by Cheechako

When you think about it...Even bolted external chainplates you are only 50% sure. You have no idea what is going on between the hull and the chainplate... which is where the crack crevice corrosion will happen. The bolts themselves are a perfect spot for water ingress as well as the top where the hull last touches the chainplate where it flexes...

Yes, but with external plates one can visually detect developing cracks before they reach failure level.

But, for many designs, having the chainplates outboard will have detrimental effects on windward performance, increase chafe issues, and look kinda agricultural (IMO).

Use of better alloys is a reasonable approach to increasing reliability of inboard plates if you do retrofit them. Our 2205 stainless plates were pristine when I pulled them for inspection last year... and they were 23 years and some 100,000 miles old at that time.

Cheers,

Jim

[sardinebreath]

Originally Posted by Fortytwo

I am replacing my glassed in chainplates now and putting the new ones outboard. After removing the old bits, I epoxied a 4" wide strip of 1/2" G10 on the inside for a backing plate. I did have to notch out the rub rail on the outside to accommodate the new plates. I've seen people put the plates under the rub rail, but that seemed to be more work then it is worth. I didn't see any issue with the old 1/4" thick chainplates, although I am replacing them with 3/8" thick. The chainplate bolts were another matter...

How did you go about removing the "old bits"? What is involved in exposing the glassed in bolts? Are you cutting or grinding or both?