E38-200 replacement aft chainplate

[Kenneth K]

The chainplate has to line up naturally before holes are drilled, and I think Ericson was casual about that in my case. If slightly askew when bolted down the strain isn't even on the steel.

If re-locating the holes to "line up" the chainplate, it's probably a good idea to check the rigging first to ensure the top of the mast is where it's supposed to be.

Also, a note to the owner, Eric: It looks like the chainplate screw heads have been messed with a bit (post #14) and the original backstay has been altered (post #1) with a Sta-Lok fitting (vs the factory swaged fitting). Might be worth getting the rig checked out if a previous owner made changes to it.

 

[Pete the Cat]

I think the most important thing, when reinstalling, is to insert the lowest bolt first, then tension the backstay. Or maybe the top bolt first, not sure it matters.

The chainplate has to line up naturally before holes are drilled, and I think Ericson was casual about that in my case. If slightly askew when bolted down the strain isn't even on the steel.

Rather than worry about the type metals, I would likely fill all the current holes with hi density filler and possibly look at the backing plate situation for improvement while it is all apart, and then follow Christian's advice. This is not a great design from Ericson or King, but they built boats to a price they eventually could not afford. Ideally you would anchor the backstay like you do a staysail stay; there would be a straight shot to a small bulkhead glassed to the hull. But that would be very expensive to pull off. And many production boats have funky arrangements like this so I think it is something for all of us to watch. Appears to my untrained eye that there was a serious flaw in the original metal--that gap looks like more than a crevice.

 

[footrope]

I like the titanium idea, perhaps because I had my forestay chainplate duplicated (same thickness) in titanium back in 2017. No countersinks. It took a month, by Colligo Marine in Grover Beach, CA. Alignment, as mentioned in several posts, should be corrected if necessary.

Craig

 

[EricHasAnEricson]

@Kenneth K - the sta lok was me. I just replaced all the standing rigging.

Update on my situation: I found a local welder to shore up my existing chainplate in the meantime. Going to go the titanium route, it's not much more expensive, and I'm sold on the efficacy of grade 5 Ti vs 316L.

Looks terrible, but strong enough (for now). For the new chainplate I intend to take 5° off the bend - like others here, mine does not match the angle to the masthead. I'm also going to get rid of the countersunk holes, and use grade 5 Ti bolts with stainless nuts.

Thank you all for your ideas, recommendations, and feedback. I really appreciate it.

 

[Christian Williams]

Can someone explain to me the need for long chainplates, with six holes?

Does such a design actually spread a load?

What are the chances that all six bolts share equally the force upon the chainplate?

The design is traditional and ancient, I just don't get it. Would a chainplate twice as long be stronger? Would a chainplate half the length, with only three bolts, be significantly less strong?

 

[bgary]

Does such a design actually spread a load?

I wondered the same thing, and also while considering the "angle" question farther up-thread.

In particular, I wonder if there is some sort of engineering magic involved in *not* having the chainplate angle neatly line up with the load.

It might be that having the angle slightly beyond the line of the backstay creates some compression-load against the transom surface at the upper end, rather than straight line of pure tension-load along the line of fasteners.

....or, I might be giving Ericson too much credit, and they shipped several thousand boats will ill-designed backstay chainplates. Dunno.

 

[Pete the Cat]

Can someone explain to me the need for long chainplates, with six holes?

Does such a design actually spread a load?

What are the chances that all six bolts share equally the force upon the chainplate?

The design is traditional and ancient, I just don't get it. Would a chainplate twice as long be stronger? Would a chainplate half the length, with only three bolts, be significantly less strong?

I am no engineer, but I would suggest that the length and number of bolts is more related to spreading the load to the hidden backing plate, albeit unevenly. I also believe that the mainsheet, vang and aft lowers, mitigate some of the force on the back stay puts at this point, but it still seems like something to monitor.

 

[Kenneth K]

I am no engineer, but I would suggest that the length and number of bolts is more related to spreading the load to the hidden backing plate, albeit unevenly.

Yeah, I think the large number of bolts is due to the relatively weak fiberglass (versus steel) being the mating material. The steel strap doesn't need 6 bolts but the fiberglass hull does.

 

[Christian Williams]

That makes sense. Our forestay chainplates wrap around the bow and continue down the stem nearly two feet. That must be spread to the load over the hull, not the steel. Similarly, my model has long chainplates in the cabin, led up to rods through the hull. The chainplates are attached to mere plywood bulkheads less than half an inch thick. The length spreads the load on the plywood, not the stainless.

I feel better now. Yes, you may say, but there is still a long way to go.

 

[Drewm3i]

Indeed, that crack is across the top hole. On one side it has completely separated, on the other side the crack is just beginning...

The crack was not there when i replaced the standing rigging and tightened it all down. Not visible to me at least.

I crossed the sea of Cortez as a "shakedown" two days ago. We had about 20 knots on a deep broad reach. The boat behaved excellently, but I believe this is what aggravated the weakened chainplate. I did manage to average 7.3 knots, pressing the boat a bit.

Today I took tension off the backstay by loosening the turnbuckle. I set up both running backstays (my addition) as a backup as well.

I'm going to order a chainplate from rigging only, they supplied my new standing rigging and have one that looks like a close enough fit. I don't trust that the stainless I'll get around here in Mexico will be proper 316.

For now, I'm planning to jury rig a few reinforcements and then motor the rest of the way to La Paz.

There is a lesson here: always "shake down" a recently refit boat. I too broke a (u-bolt) chainplate on my Ericson 38-200 in similar conditions on the first passage. I also caught it before it fully separated and took the rig and sails with it.

Good job for catching it NOW, rather than after catastrophe!

 

[Drewm3i]

Thanks everyone for your thoughts and ideas. Here are some better photos of the damage.

It appears to me that the design of this chainplate places bending stress at the first bolt hole. Certainly the damage seems to back up that claim.

I can get a replacement made up locally out of 316L for $300. Grade 5 titanium is $520. Another idea is to redesign the plate to remove those bending stresses.

My favorite of these options is the titanium route. That's a "forever" solution assuming the bending stresses are low enough to not fatigue the material.

Lead time for titanium is 60 days. So I'd be welding together a temporary reinforcement in the meantime. I'm going to take the chainplate off when I arrive in port today and inspect. If the whole underside is a mess of crevice corrosion, then I won't risk a temporary fix and just get it done right here right now.


View attachment 51755View attachment 51756

I much prefer the E-34-2 backstay chainplate design over the E-38 (which always looked too flimsy to me--especially once fatigue and corrosion set in).

 

[ConchyDug]

38 chain plate looks flimsy?

Here is a photo of E38 hull #11's backstay chain plate. Apologies for the potato quality, I was trying to find a decent photo of it and had to zoom in. I knew mine didn't look the same. Either a previous owner beefed it up or Ericson got cheap with later models.

 

[EricHasAnEricson]

I much prefer the E-34-2 backstay chainplate design over the E-38 (which always looked too flimsy to me--especially once fatigue and corrosion set in).

Fully agree. I considered changing mine to a design like the E34-2, which would eliminate any torsion across the thin section of plate.

 

[Guy Stevens]

That isn't a stress fracture start for that failure it is standard crevice corrosion of Stainless Steel. You can look at this under a microscope and see it. (There are plenty of cheap over your phone microscopes that we use all the time for this purpose.)
This chainplate is canary in your coal mine.
Take the plate off and send it to John at Colligo marine, get a new one made from it as a pattern in certified Ti, which will outlast the boat. No crevice corrosion on Ti.
Also a good opportunity to remove all of the rest of them and replace them also. They will be suffering from the same amount or most likely more crevice corrosion.
Ti is a great chainplate material. SS a fairly poor one due to its failure methods, and suitability to crevice corrosion and anaerobic degradation where it passes through decks.