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Chainplate Crack Cause, Effect, Theory, RFP

ignacio

Member III
Blogs Author
But wouldn't a cascading BS adjuster be the preferred occupation over the cascading BS fabricator?
 

Emerald

Moderator
You would do much better to actually figure out the loads and the safety factor on the rig and the boat and make sure that you have the right rigging to support those loads.

I have seen way way too many boats that have rigs that are untunable, and or unsafe rigging from upsizing to a bigger wire.

This is not a simple solution that you can apply.

Guy
:)

With all due respect, I feel I must clarify that this was not a blind upgrade of upping one size to just go up one size. I will not try to describe the detail that led me reaching out to Mr. King for his assistance, and I am forever grateful for his time and attention he gave me on this, but I up-sized key pieces of the rigging based on the original design loads and differences in the strengths of the alloys, and I went back to the designer of the boat for his input to sort this out. I just feel it's important to clarify this wasn't some blind up-sizing. And again, I fully respect your knowledge and experience in the rigging industry, but I feel somehow what I posted must not have conveyed properly.
 

Guy Stevens

Moderator
Moderator
With all due respect, I feel I must clarify that this was not a blind upgrade of upping one size to just go up one size. I will not try to describe the detail that led me reaching out to Mr. King for his assistance, and I am forever grateful for his time and attention he gave me on this, but I up-sized key pieces of the rigging based on the original design loads and differences in the strengths of the alloys, and I went back to the designer of the boat for his input to sort this out. I just feel it's important to clarify this wasn't some blind up-sizing. And again, I fully respect your knowledge and experience in the rigging industry, but I feel somehow what I posted must not have conveyed properly.

The part that didn't work for me was the last bit of your post, this:
"so upsize it all. Lovely, ain't it?"

Which is not what you did, and not what either of us would advise. Especially since some of these old boats have been upsized by one or maybe even two owners already, with the old saw "that if you just upsize it you will be great". Don't "Just upsize it all". No one tells you to put bigger pistons in your engine if you are heading offshore, or to make sure that your oil sump is twice as big.......

Your last post is a better post, some things may need to be upsized when switching from 304 to 316, some may not. Some peoples boats may have come from the factory with 316 already and should not be upsized. It is more complex and the advice to just upsize everything has caused a lot of problems for a lot of owners. It isn't good general advice. It sounds like you approached it in a fashion that would result in a good result, getting the designer or a good rigger involved and making sure that things were correctly sized for their loads. Not just upsized. I just wanted to point out that everyone here on the forum shouldn't run out and get the next larger size wire for their rigging.

Guy
:)
 

Alan Gomes

Sustaining Partner
You would do much better to actually figure out the loads and the safety factor on the rig and the boat and make sure that you have the right rigging to support those loads.

I have seen way way too many boats that have rigs that are untunable, and or unsafe rigging from upsizing to a bigger wire.

This is not a simple solution that you can apply.

Guy
:)
Not doubting you, Guy, and maybe the answer to this is obvious, but could you please elucidate on how upsizing one's rigging can result in an untunable and/or unsafe rig? Is it because you'd want the rig to "blow" (kinda like a fuse) before other things rip apart? Or is there some other reasoning behind this?
 

Eddie 169

Junior Member
After I cleaned the rust from my transom chainplate E35-III I could see mine has a crack through the plate from the left edge of the plate to the second bolt from the top. I was planning a trip to Catalina when I discovered it. Should I cancel the trip? Is there anyone in the LA area with experience that would be available to assist me in removal and replacement?
 

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Puget sailor

Member II
My non professional opinion informed by some history owning Chinese sailboats with dubious metallurgical origins, this does not look like metal fatigue at all. I see crevis corrosion initiated from the back side where the plate is sealed to the transom to prevent leaks. Unfortunately that sealant prevents the availability of oxygen which is required for stainless to remain stainless, as I understand it. I would not be suspicious of the tightness of the fiberglass holes, the reason for all those screws is because the fiberglass is way weaker than the original strength of the chain plate, so it’s extremely unlikely a single fastener would have overstrained the chain plate vs just deforming the fiberglass.

Crevis corrosion on sailboats is insidious because it strikes exactly where you can’t see it. And it is basically, from what I’ve seen of several failed fittings, little more than veins of rust running through stainless metals like veins of gold in a mine. The rest of the stainless is fine, but once the crevis corrosion gets started, it takes off like a lightning bolt formation within the metal, and then the strength is compromised. The next step is, a stress crack forms because the general integrity of the metal is no longer sufficient, so it’s easy to assume the stress crack is related to the load, but it’s really related to the metal being microscopic Swiss cheese.

My advice as a non expert but with some experience, is to not worry about the holes, and just have the parts duplicated in 316 stainless, and expect them to last another 40 years without incident. 304 is not as resistant and these parts are not subject to that much fatigue.

As a side note, since many of us seem to have old navtec turnbuckles, there are early ones out there with the cross pin at the bottom pressed in tight so it can’t move, then the toggle wraps around it. Later versions have the pin captive, but floating so it can shift in the hole through the turnbuckle. I’ve had one of the older style on a forestay, and while testing it with my weight at the dock, it went BOING. I looked down and half of the pin had broken off and dropped in the water! I could see the crevis corrosion lightning bolt like structure in the face of the broken pin, about 1/3 of it was fresh metal, the rest looked like a rusty Hibachi. I suspect that’s why they changed the design, so that pin would have some oxygen around it. In fairness, it also allows the pin to self align so that the toggle loads are balanced across both ends in the case of slightly assymetrical toggles. So a double whammy, crevis corrosion and metal fatigue. I have no idea when Navtec made the shift, but I’m eager to slacken my backstay to find out where my 1985 boat stands.

Here’s some cocktail reading to strike fear in the hearts of those who dare to sail old boats:

 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
After I cleaned the rust from my transom chainplate E35-III I could see mine has a crack through the plate from the left edge of the plate to the second bolt from the top. I was planning a trip to Catalina when I discovered it. Should I cancel the trip? Is there anyone in the LA area with experience that would be available to assist me in removal and replacement?
I would advise replacing the bad ss piece ASAP. It might certainly hold for a while, but replacing a lost rig can top 25 or 30K. Not all owners are fully insured, and can be surprised to find that a replacement will allow their insurer to "insurance total" their boat.

I would guess that there are lots of shops in your area that can duplicate your old plate. In SoCal, I would first call Garhauer, since they probably know exactly what you have and what you need.
(When we took that same part off of our '88, as part of the prep for hull painting, we inspected it closely and were pleased to find it in as-new condition. I buffed it to a mirror shine, and no imperfections were found.)
 

Tin Kicker

Sustaining Member
Moderator
After I cleaned the rust from my transom chainplate E35-III I could see mine has a crack through the plate from the left edge of the plate to the second bolt from the top. I was planning a trip to Catalina when I discovered it. Should I cancel the trip? Is there anyone in the LA area with experience that would be available to assist me in removal and replacement?
I would definitely cancel the trip till that is replaced. I fellow at our marina just came back with a broken forestay on a different brand of boat and the break looked just like what you are showing. The only reason his rig didn't fall is that his boat runs two forestays.

On the upside, you are looking at a thousand dollar repair, not a $10-20,000 repair and possibly injuring somebody.
 
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