Check Your Chain Plates

John · May 2, 2009

How would one go about checking for something like that? Are there any surface tell-tale signs or would you have to x-ray it or is it just a matter of replacing them every so often?

Ron20324 · May 2, 2009

Isn't there a standard-size u-bolt that will fit in?

Ross · May 2, 2009

For any material that is either notch sensitive or subject to stress corrosion cracking that design is subject to concern. Forming the shoulder can cause a crevasse at the shoulder that may take years to fail. I like a design that uses plates for chain plates. With multiple bolts, spread over a wide surface sudden failure of the complete system is not likely. It is still difficult to inspect without disassembly.

catsailor · May 2, 2009

That would be a tough one.

I do NDE testing as part of my living, and both x-ray and dye would be tough. Testers hate sharp corners, because they are hard to inspect and failure prone.

Why would he not consider going up a size with a u-bolt and skipping the shoulder, though what he has looks "neat?"

Ken Honeycutt · May 2, 2009

Might try rigright

Somewhere on the web I read about an Erickson restoration where the owner was able to get a broken chainplate (U - bollt) from rigrite...said it was pricey.
http://www.rigrite.com/Hardware/Chainplates_&_Stemheads/Chainplates&Stemheads.htm

I'll see if I can find his webpage.

Franklin · May 2, 2009

And they say Hunters are weak....my chain plate bolts are 1 1/2" each and the nuts are so big I couldn't find a wrench big enough so I had to use a pipe wrench.

Ross · May 2, 2009

Franklin said:
And they say Hunters are weak....my chain plate bolts are 1 1/2" each and the nuts are so big I couldn't find a wrench big enough so I had to use a pipe wrench.

What are they attached to?

Franklin · May 2, 2009

Ross said:
What are they attached to?

The hull + 1/2" extra fiberglass + 1/4" x 3" x 8" backing support (not sure what that material is) + 1/8" x 3" x 6" SS backing plate.

Roger Long · May 3, 2009

Maine Sail said:
One of the guys on the Ericson forums seems to think these were supplied to Ericson by Navtec.

Those have a very Navtec look about them; especially the bent toggle plates. The design strikes me as dumb. There are so many things wrong with that forged shoulder I won't even start.

If this were my boat, aside from the lateness of the refit season, I would design a new plate fitting and have the amazingly good welder on my wharf built replacements. This would require shortening the stays and swaging new ends on but that's not a bad thing to do anyway. The new ones might not be as neat looking but I would sail with more peace of mind.

Pulling my chainplates will definitely be on the list for next season.

Bob S · May 3, 2009

How often would you recommend checking your chain plates? I would have thought you'd pull them when you see evidence of leaks.

sailingdog · May 3, 2009

This is one reason I prefer stainless steel chain plates made from flat bar stock... finding replacements is very simple. Getting a replacement for a custom machined/forged u-bolt is going to be a gold-plated B****.

Stu Jackson · May 3, 2009

Bob S said:
How often would you recommend checking your chain plates? I would have thought you'd pull them when you see evidence of leaks.

Bob, it's like reefing. Most all of the Association websites have good chainplate replacement projects documented (here's ours: http://www.c34.org/wiki/index.php?title=Inspecting_and_Re-bedding_Chainplates) and they all recommend: do NOT caulk the inside! Then you can see if they are leaking.

Dawg - I think a lot of people with older boats think they need to find OEM parts, which gets difficult, if not impossible, for boat builders who are out of business, save, for instance Pearson where I understand there is a great business supporting parts for the boats. Good Old Boat magazine has made a nice business of documenting skipper's work supporting the theory that new parts can be fabricated for replacement that may be even better than OEM. It doesn't appear from his photo that that particular part would be difficult to replace with assistance from a good shop, and maybe even improved upon if flat stock could be employed.

The failure picture brings a new meaning to crevice corrosion!

catsailor · May 3, 2009

All true, and I know that the Stilettos that use u-bolts are prone to similare failure....

Maine Sail said:
I don't believe the Ericson chain plates are simple post formed stainless bar stock. They certainly appear to me from the photo to be forged, then machined, which should make them stronger than a basic mandrel bent u-bolt. The other problem is they are not U shaped but rather flat on top to accept the toggle. Because of this any bends would need to be 90 degrees which could significantly weaken the bar stock. A continuously curved U is probably a lot stronger than a flat bottomed U after being bent..

One of the guys on the Ericson forums seems to think these were supplied to Ericson by Navtec. I will relay back what ever supplier / source info I can find. If you guys know who originally made these please let me know..

Forging new ones is probably out of the question unless you could find the original dies..

Which leads owners to go up one size.

However, I wonder if replacing the toggle with a lashing would spread the load and eliminate the cracking issue. Wish I had thought of it when I still had my Stiletto!

This might be a good application for a high-tech lashing, if the correct fitting is not available.

Ross · May 3, 2009

Re: All true, and I know that the Stilettos that use u-bolts are prone to similare failure....

I wonder if the load was in line with the axis of the U-bolt? An off center load would concentrate the stress off center. One of the causes of bolt failure is non-parallel surfaces under the head and the nut.

48dodge · May 3, 2009

Some Odays have a similar ubolt, but without the toggle. You might want to check with Rudy at drmarine.com to see if he has something that has similar dimensions. I don't think oday's are forged, though.
http://www.drmarine.com/proddetail.asp?prod=DR23285

catsailor · May 3, 2009

You got it!! The deck is crowned outward.

Ross said:
I wonder if the load was in line with the axis of the U-bolt? An off center load would concentrate the stress off center. One of the causes of bolt failure is non-parallel surfaces under the head and the nut.

Up a size works. It needs to be far larger than called for, like triple. I went to 3/8" for the shrouds of a 1300# cat. 5/16" cracked. Cheap, still.

RichH · May 4, 2009

Maine,
Any chainplate that fails, and fails catastrophically such as in your pic, shouldnt be 'replaced in kind' or replaced with a duplicate; it should be either radicaly redesigned and/or radically 'beefed-up'. Chainplates that fail clearly show evidence that the plate was designed totaly ignoring the endurance limit of the base metal. The fatigue endurance limit for 300 series stainless is typically in the range of 30,000 psi (ultimate tensile 90,000 psi) .... plus the 'factor of safety', necessary for EVERY cyclically loaded structure needs to be increased.
If chainplates were properly designed, in the first place, one would RARELY see 'brittle failure' .... well maybe a few times in a hundred years.