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jeffandlori · 18-03-2024, 09:31

I'm doing a refit of the mast on my '71 Morgan. One of the things I'm considering is replacing the various pins that hold the stays/shrouds. How paranoid should I be about crevice corrosion on these? The pins that hold the shroud tangs/plates are 1" for the lower and 5/8" for the upper. These go through an aluminum tube that is welded into the mast and the pins are corroded in place. I have every reason to assume that they are original, so 50+ years old. The visible surfaces don't look corroded. The pins for the fore and back stays are 1/2" and go through 1/2" aluminum plates, bridging about a 1" gap that the eye of the stay rides in.

Assuming I can/should get them out, is 316L the correct steel for these?

Benz · 20-03-2024, 03:16

Yes, get them out at any cost, and yes, use 316 and goop it up with plenty of Tef-gel.
Torch them, pound them, drill, cut, do whatever it takes.

thomm225 · 20-03-2024, 04:25

Odd that they are corroded.

I have replaced some of my pins but not all. None are corroded in place just old.

The boat is a 1974 Bristol 27.

The pins are twice the diameter of the rigging wire. My research showed these pins rarely fail, but again mine are not corroded.

I added a second backstay (miscommunication, long story) so the original is still up plus a new one. Added second chainplate. I set the new stay with slightly more tension than the old one.

Will replace all 4 lowers next. Already replaced all side chainplates with only one having a hairline crack. Bolts had surface rust but nothing more.

Boat is 50 years old in July. (according to the HIN)

Will either replace the uppers and furler later this year or have a rigging company do it. I may have the ancient Furlex 100 replaced.

jeffandlori · 20-03-2024, 04:26

Thanks for the reply. I'm down to just the upper shroud pin that is still not budging. Hopefully I can get it out today. I've had several people at the yard tell me it is a waste of time to replace it, but after finding crevice corrosion on one of the chainplate bolts I'm motivated.

jeffandlori · 20-03-2024, 04:33

Quote:

Originally Posted by thomm225

Odd that they are corroded.

I have replaced some of my pins but not all. None are corroded in place just old.

The boat is a 1974 Bristol 27.

The pins are twice the diameter of the rigging wire. My research showed these pins rarely fail, but again mine are not corroded.

I added a second backstay (miscommunication, long story) so the original is still up plus a new one. Added second chainplate.

Will replace all 4 lowers next. Already replaced all side chainplates with only one having a hairline crack. Bolts had surface rust but nothing more.

Boat is 50 years old in July. (according to the HIN)

The pins themselves don't appear corroded, but where they run through the aluminum mast there has been reactive corrosion that had them stuck in place. The shroud pins especially are run through a fairly tight tube in the mast, which seems like a textbook environment for crevice corrosion.

That said, I agree that chainplate failure seems way more common.

thomm225 · 20-03-2024, 04:42

I'm hoping since my boat is over built and has the 4 lowers it can go a bit longer with the old uppers and forestay under the furler.

I never met the PO but he left the boat near here in 2006 after a 2 years cruise from Massachusetts to Florida and the Bahamas.

So rigging is at least 20 years old but probably older.

Mast is only 30' or so ...... (seems higher when you are up there though especially when near 70 years old) so not a lot of load.

Original chainplates were over size so replacements are a bit smaller/thinner.

pcmm · 20-03-2024, 05:24

Quote:

Originally Posted by jeffandlori

I'm doing a refit of the mast on my '71 Morgan. One of the things I'm considering is replacing the various pins that hold the stays/shrouds. How paranoid should I be about crevice corrosion on these? The pins that hold the shroud tangs/plates are 1" for the lower and 5/8" for the upper. These go through an aluminum tube that is welded into the mast and the pins are corroded in place. I have every reason to assume that they are original, so 50+ years old. The visible surfaces don't look corroded. The pins for the fore and back stays are 1/2" and go through 1/2" aluminum plates, bridging about a 1" gap that the eye of the stay rides in.

Assuming I can/should get them out, is 316L the correct steel for these?

Odd that the rigging pins are that large. Would make it hard to find the correct size fittings. If they are corroded in place then its going to take a bit of work to free them. Also Odd that they are corroded in place as the riggin pins are usualy stainless steel going through stainless steel tangs and swage fittings.

When you replace the rigging, the fittings normally come with new pins so no need to worry about it.

My 78 morgan OI 41 doesn't have pins in this configuration. When I bought my boat the rig hand not been down for over a decade and I'm sure the rigging was original but we still had no issue pulling the pins and none of them were the size you are mentioning. Do you have pictures?

If you are talking about the tang bolts, then yes they usually get corroded into place. Its going to take a lot of work to free them in order to replace them. Heat, PB blaster, heat anmd beat. Its going to be a lot of work.

Bowdrie · 20-03-2024, 21:24

Quote:

Originally Posted by pcmm

If you are talking about the tang bolts

Yeah, I think that the OP is referring to "bolts", not "pins" that go thru tubes holding the tangs?

jeffandlori · 21-03-2024, 03:19

Quote:

Originally Posted by Bowdrie

Yeah, I think that the OP is referring to "bolts", not "pins" that go thru tubes holding the tangs?

They are pins with threads on the ends that have nuts holding the tangs on. Does that make them bolts? Too philosophical for me.

psk125 · 21-03-2024, 08:28

Bolts have threads. Pins (clevis pins) don't. Bolts are for holding things together and are designed for strength along their lengths. In your case they hold the tangs to the mast. Pins are designed and made for strength in cross-section. You would not want to put a bolt instead of a pin in the end toggles of a stay or shroud, even if it "fits". It might fail and bring the rig down. Try putting a bolt in a vise horizontally and hitting it with a hammer - it may crack in two. A pin might bend, but it will be almost impossible to break.

Cheechako · 21-03-2024, 08:46

Quote:

Originally Posted by jeffandlori

They are pins with threads on the ends that have nuts holding the tangs on. Does that make them bolts? Too philosophical for me.

If they have threads then yes, replace them. The thread root is the perfet spot for moisture build up and crevice corrosion. 316 SS would be best. It may be very difficult to get them out if they go through an aluminum tube in the mast. That white corrosion from the aluminum builds up terribly.

thomm225 · 21-03-2024, 16:18

Those tang bolts are pretty thick according to what you posted so it would take a while for rust to do much harm.

I was talked into replacing a shackle on my anchor rode a while back here on CF which I actually figured had another 10-15 years of life left in it.

It looked pretty bad, but I know rust as in the farm equipment I used as a teenager and the old boats I bought as a teen.

A plow blade would rust over totally during the Winter as our equipment was near the Atlantic Ocean (and Chesapeake Bay), but on the first furrow plowed the blade would be the shiniest chrome you ever saw.

I did replace the shackle since the PO was a pack rat and had several more on the boat.

After removal, I cut it with a hacksaw and there was maybe 1/16" of rust with the rest perfect.

This shackle and my rode and CQR anchor saved my boat countless times while anchored 50-70 yards off the beach with heavy onshore winds.

I picked some of the worst places to anchor when I first bought this boat having never had to anchor overnight on all my other boats.

But of course, when I did replaced the shackle along with the anchor, rode and chain, it did look a lot more reliable.

Benz · 22-03-2024, 03:14

^^^Thomm, we're talking two different metals here. Galvanized steel shackles like on your anchor tackle can rust halfway through and still have some strength. Stainless steel like the OP's rigging bolts is susceptible to crevice corrosion, which can cause a catastrophic failure even when no material is visibly lost. All metals corrode differently, with different failure modes. It's pretty well known that a stainless fitting more than 10 years old is at least worth replacing. It may not fail ever. It may fail tomorrow, with no discernible, visible reason beforehand. It's a toss of the dice to keep stainless past its replacement interval.

thomm225 · 22-03-2024, 03:45

Quote:

Originally Posted by Benz

^^^Thomm, we're talking two different metals here. Galvanized steel shackles like on your anchor tackle can rust halfway through and still have some strength. Stainless steel like the OP's rigging bolts is susceptible to crevice corrosion, which can cause a catastrophic failure even when no material is visibly lost. All metals corrode differently, with different failure modes. It's pretty well known that a stainless fitting more than 10 years old is at least worth replacing. It may not fail ever. It may fail tomorrow, with no discernible, visible reason beforehand. It's a toss of the dice to keep stainless past its replacement interval.

Okay.

Thanks for that info. I'm no metals expert. Just used to seeing rust on "metal" with the boats and farm equipment I was always around while growing up. There were few to no sailboats in the area as the water was too shallow in most places.

As far as rigging, I'm depending on my new forward lowers assisting my 20 year old forestay with furler for the next few years.

My rigging is at least 20 years old and may be older since I never met the PO.

I replaced the backstay and will be replacing the lowers within a few weeks.

Tang bolts for the lowers look good as far as I could tell yesterday but I didn't go up there.

When I added prebend a few years ago by increasing the pressure on the lowers and bowing out the forward center of the mast an inch or so I'm thinking that took at least some of the load off the forestay.

Also no broken strands on the forestay. Top is a swedge fitting bottom Sta-Lok it appears for the ancient furlex furler. I may replace that lower pin in the mean time.