Chain plate removal?

[BubbleheadMd]

I have a deck-stepped mast, with a compression bulkhead belowdecks (no compression post).

I am un-stepping the mast this winter to replace sheaves, etc.

With the mast down, is it correct to say that removing the chain plates should be as simple as unbolting them from the bulkheads and pulling them down into the cabin to remove them?

I have no evidence that anything is wrong with them, but if it's this simple, then it's worth inspecting them, and probably having new ones made.

In fact, what's the recommended material? SS or bronze?

The originals were bronze.

[zz4gta]

If it were me, I'd go stainless. How much bronze do you see going onto new boats?

And in my boat, it's very easy to get them out. Drop the rig, unbolt them, and slide em out through the bottom. Sometimes tap on em w/ a hammer.

[mitiempo]

With the rig down they should be easy to remove.

Bronze is as strong as stainless and not subject to crevice corrosion. I'd stick with bronze.

[BubbleheadMd]

I've just been offered some SS chain plates specifically for my boat, that were someone's spares.

I assume the only way I could ever really trust these, is to have them magnaflux'd by a machine shop?

[mitiempo]

It's not really the condition at install, but what happens to the stainless over time if they get damp (likely) without the presence of oxygen.

[jrd22]

If you use SS make sure it's 316 which is much more corrosion resistant than 304. Any machine shop should be able to magnaflux them for you and it shouldn't be expensive. SS plates should be polished to a mirror finish to reduce crevice corrosion. Getting them out can be easy or a major project depending on how they were installed and access to them. Some are glassed into the hull, some are bolted thru the hull, some are bolted thru knees glassed to the hull. I've seen some that would require destroying a considerable amount of the cabinetry just to get to.

[BubbleheadMd]

Originally Posted by mitiempo

It's not really the condition at install, but what happens to the stainless over time if they get damp (likely) without the presence of oxygen.

The ones I'm being offered were installed on a boat for an indefinite period of time, and subjected to unknown stresses.

My chain plates are easily accessible belowdecks. It appears that the only portion that is hidden, is the "ear" that protrudes through the deck that the shrouds attach to.

I'll probably buy these "spares", and have all 4 of them magnaflux'd and use the best ones.

[mitiempo]

That makes sense since they have been used.

[MacGyverRI]

Psst, you can't directly magnaflux Stainless unless it has a high Iron content <306 (cheap stuff) since it isn't magnetic.... If it's 316, 318+ grade like most boat/marine stuff, magnaflux is useless since the chromium and or Nickle content is too much.

Magnaflux works by finding another N/S magnetic pole (a crack) across a "magnetic" piece and the powder finds both sides of that crack or if there's no fracture, a solid/even powder dusting across the piece like you dropped whiskers from an electric shaver on a piece of paper.

You can also put a piece of stainless strip/plate etc. on a special steel plate w/ a mag unit under it, then you can mag that then drop the iron powder on top of that to see how it looks. Not as good as the next part;

FWIW, "Zyglo" testing (or other dye/blacklight methods) works best w/ any non-ferrite stainless, copper, brass etc..

You can buy Zyglo and a blacklight and check everything you want for cracks, it's a simple procedure

HTH!