chainplate bushing

[gadangit]

My rigger tells me that I need a bushing for one of my chainplate holes. Apparently the hole has elongated due to an improper size pin in its past. He suggested drilling it out round, it looks like 3/4" will suffice and then put in a bushing for a 5/8" pin.

Questions:
1. What should the bushing material be made from?
2. How is it secured in the hole?

Any thoughts or suggestions?

Thanks!
Chris

 

[mherrcat]

Maybe the ears of the toggle that secures to the chainplate hold the bushing in place?

 

[Frank Langer]

I'm not sure that's a good idea, as most toggles are not a really tight fit against the chainplate. I think I would want a bushing pressed into the chainplate very tightly so it's not going to go anywhere given the movement of shrouds, toggles and clevis pins as the boat is sailing. Just my thoughts, and maybe I'm being too cautious, but I would want to be sure....

Frank

 

[Second Star]

I have had past experience with a hole in a plate (one of three lifting straps for a manned submersible) that became elongated, initially diagnosed as a too small diameter bolt in place, a similar fault to your chainplate problem. In fact, the plate had become stretched at the hole (the metal either side of the hole stretching) and ultimately resulted in the sub being dropped during a launch when the plate failed.

This leads me to consider a couple of things. Shrouds and stays aren't normally so loose that the pin will move about and wear the round hole into an oval so what has actually happened? Can you see similar wear on the pin and does the hole have little "turned up lips" at the point of the wear (the metal has to go somewhere). If so then a bushing seems a good idea if you don't want to go to the considerable trouble of replacing the plate. If the plate has stretched then putting a bushing in doesn't solve the inherent weakness induced by aplastic stretching of the plate at it's already weakest point and the plate should be changed.

A bit conservative but your problem got me thinking ....

 

[gadangit]

I had considered that

But haven't had a chance to look again. I have pictures of each chainplate, but it must be the deformation is slight enough that my camera angle can't catch it. I'll see if I can get a better picture this afternoon when I go to the boat and post it for everyone to get a look. FWIW the rigger didn't seem concerned about the chainplate, just the potential loose pin.

Chris

 

[tenders]

I'd drill it out and put in a 3/4" pin before I'd mess around with a bushing. If there are multiple pins, do it for as many as necessary so the stress is evenly distributed.

 

[AleksT]

Bronze is a good material for a bushing. You will need to cut the bushing in length to fit inside the toggle at the end of the rigging. The toggle itself will keep the bushing in place. Drilling out a chainplate will in most cases remove any distorted metal leaving the non stressed metal behind.
Drilling the chainplate and the toggle out for just a larger pin is a possibility. You may want to use a drill press to drill the toggle it will make it easier to get a straight hole through both sides of the toggle.

 

[Guy Stevens]

Time to replace the chain plate

If the hole has elongated the metal has also work hardened.

Most boats of our era need to have the chain plates replaced. They have crevice corrosion, and in cases like yours have worked hardened and no longer have the safety factor that they were designed with.

Chain plate failure is the number 1 cause of dismasting.

Thanks,
Guy

 

[Brass Dragon]

What material is your chainplate? Most are stainless but some models such as the 36C have aluminum chainplates. I would not put a bronze or any copper alloy bushing into an aluminum chainplate. The Bruce King drawing for the 36C shows a stainless bushing in the aluminum chainplate but apparently Ericson ignored this detail because mine does not have one.

Also, be careful not to drill out assuming you can size up on your pin. Rigging components are matched to pin sizes so you cant necessarily mix and match. Drilling to a larger pin may drive you to replace the complete shroud and have to over drill the fitting at the top to get all to match up. My brother ran into that when he wanted to up size his rigging. There may be ways around it but check that you have hardware to match before drilling.

 

[gadangit]

Aluminum Chainplate

I realize I should have included this minor detail: this is one of the aluminum chainplates that is glassed into the hull. Specifically, it is the heavier of the two aluminum chainplates and the one that the upper shroud attaches to. I've been thinking that one should be able to TIG weld on a new "tab" from below. I've got the headliner out and I'm working on recoring from below, so now is the time... Just a thought of course...

Chris

 

[tenders]

I don't know a ton about this but I have to say the thought of welding aluminum chainplates makes me really nervous.