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Unpaid Intern
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Discussion Starter #1
Hi all,
I need to rebed some chainplates on our "new" boat. I've done the procedure before on this boat, but the mast was out.

The part I need help with is the "mast up" thing. My shroud configuration is the standard single spread rig, with fore and aft lowers (3 chainplates each side). I've been told I can run the main halyard to the rail, then mark the turnbuckle position with tape, and remove the shroud to do the chainplate. This makes sense on the upper, but what about the lowers? Can I remove those (one at a time of course) without slacking the lowers on the opposite side? The main halyard will support the top of the mast, but not the middle where the lowers attach.

I just want to make sure that I can safely remove one shroud at a time, replacing before moving on. Or do I need to take some other precautions?

For what it's worth I'll be doing this at the slip on a calm day (it's well-protected where the boat is).

Thanks for any advice you may have on this.
-J
 

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Midwest Puddle Pirate
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2,160 Posts
Sounds like you're on the right track. This is exactly what I did 3 times before I discovered the wonders of butyl tape. Now go get busy.
 

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Not Finished Yet
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829 Posts
I would skip the halyard. I do it this way:

1) Loosen and then disconnect the uppers.
2) Rebed their chainplates.
3) Wait until the bedding cures (if you are using bedding that cures).
4) Reattach and tighten the uppers5) Loosen the lowers
6) Rebed their chainplates
7) Wait until the bedding cures (if you are using bedding that cures).
8) Reattach and tighten the lowers

You can do them all in 3 days (assuming a 24 hour cures). The stays + uppers is far more than what you need to support the mast at your slip. The same is true for stays + lowers.
 

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Unpaid Intern
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Discussion Starter #5
I would skip the halyard. I do it this way:

1) Loosen and then disconnect the uppers.
2) Rebed their chainplates.
3) Wait until the bedding cures (if you are using bedding that cures).
4) Reattach and tighten the uppers5) Loosen the lowers
6) Rebed their chainplates
7) Wait until the bedding cures (if you are using bedding that cures).
8) Reattach and tighten the lowers

You can do them all in 3 days (assuming a 24 hour cures). The stays + uppers is far more than what you need to support the mast at your slip. The same is true for stays + lowers.
Well, I am planning to use 3M101, which is what I've used before. Can't use butyl tape here because my chainplate covers are not through-bolted, so polysulfide is my preference. It cures over several weeks.

So my assumption was that I could just rebed one at a time, and put everything back together without waiting, since there's really no way to take the boat out of commission for weeks anyway.

Not sure I like the idea of loosening both sides without halyard reinforcement...makes me nervous, even if it does make sense.
-J
 

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Registered
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334 Posts
Have you tried Sikaflex 291?

All-purpose, polyurethane adhesive and sealant for use above or below the waterline. Elastic, sandable/paintable.
  • Formulation: One-part polyurethane adhesive/sealant
  • Recommended Usage: Humid climates, high temp., long assembly time; sealing wood hull seams, thru-hulls, bedding deck hardware
  • Material Incompatibilities: Acrylic plastics (ABS, Lexan)
  • Adhesion Rating: Tensile: 200 psi; elongation: 700%
  • Cure Time: Tack free: 3 to 5 hrs; complete cure: 3 to 14 days
My project Click here
 

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Not Finished Yet
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829 Posts
I did mine with 3M 4000 UV. I did the first chainplates and all the stancions on Saturday. On Sunday I reattached the lifelines and the upper shrouds and rebedded the lower shroud chainplates. Monday I just had to reattach the lower shrouds and tune the rig. 101 has a longer cure time than 5200. I would not want to load the rig until the sealant cures, but maybe I am just being superstitious.
 

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Don Radcliffe
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398 Posts
a typical mast will be fine supported only by the lowers or uppers, as long as the wind is less than hurricane strength.

My boat got a new (keel-stepped) mast because the yard disconnected ALL the shrouds and went home for the night. It then blew over 40 knots and folded the mast over onto the neighboring boats.
 

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Unpaid Intern
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992 Posts
Discussion Starter #9
a typical mast will be fine supported only by the lowers or uppers, as long as the wind is less than hurricane strength.

My boat got a new (keel-stepped) mast because the yard disconnected ALL the shrouds and went home for the night. It then blew over 40 knots and folded the mast over onto the neighboring boats.
I see your point that only the lowers or only the uppers would be OK.

My main question is, do I need to disconnect lowers on both sides evenly, or is it OK to leave them on one side, but disconnect the other to work on them? I wasn't sure if the lop-sided pull would be problematic, or OK for a few hours of work.

By the way, the stinks regarding your mast, but I'm glad to hear you got a new one out of it!
 

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Telstar 28
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1,000 Posts
Not a good choice. First, 5200 isn't elastic enough for the purpose, since the chainplates will move a bit. Second, removing the stuff in the event that they start leaking is going to be a royal nightmare. 5200 and silicone have very, very, few legitimate uses on a boat IMHO.
I did mine with 3M 5200 UV. I did the first chainplates and all the stancions on Saturday. On Sunday I reattached the lifelines and the upper shrouds and rebedded the lower shroud chainplates. Monday I just had to reattach the lower shrouds and tune the rig. 101 has a longer cure time than 5200. I would not want to load the rig until the sealant cures, but maybe I am just being superstitious.
 

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Telstar 28
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1,000 Posts
That's a different story. :) much better choice... :)
Sorry, I meant 3M 4000, not 3M 5200. I agree 5200 would be a very bad idea.
 

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My main question is, do I need to disconnect lowers on both sides evenly, or is it OK to leave them on one side, but disconnect the other to work on them? I wasn't sure if the lop-sided pull would be problematic, or OK for a few hours of work.
I would recommend first easing all the turnbuckles a few turns just to take the strain off. Then you will have no problem removing shrouds either in pairs or singly. Halyards aren't really necessary, but they sure can't hurt. Sometimes, you can hook the shrouds back up temporarily to the rail too. Just don't load em up.
 

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Unpaid Intern
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992 Posts
Discussion Starter #14
I did mine with 3M 4000 UV. I did the first chainplates and all the stancions on Saturday. On Sunday I reattached the lifelines and the upper shrouds and rebedded the lower shroud chainplates. Monday I just had to reattach the lower shrouds and tune the rig. 101 has a longer cure time than 5200. I would not want to load the rig until the sealant cures, but maybe I am just being superstitious.
I've been told before that with 3M 101, you want to load everything up before it cures anyway (just relaying info here). As one Sailnet member stated at the time, if you're chainplates are moving enough to break the seal, then you have bigger problems than choice of sealant.

I rebedded a very leaky chainplate with 3M 101 this spring, a few days before the mast was stepped. We sailed the boat offshore to get her home in pouring rain and waves, and have since had days on the Chesapeake, pounding to weather with green water over the decks. That chainplate still isn't leaking.

Of course, that's no scientific test--it was only been a few months, and I'm no expert here. But I'll try this again, and see how it goes. I'll report back if I run into problems down the line.

Sooo, any votes on whether I should remove the lowers on BOTH sides at the same time, or can I do one side at a time and leave the other side connected? Or does it matter?
 

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SD, How do you figure that 5200 isn't flexible enough to bed chainplates? How big a gap do you leave around them anyway? I'm holding a cured chunk in my hands right now. Squeezing it between the jaws of my Leatherman. The stuff feels like a piece of rubber.
If you have a gap of about a 32nd to an 1/8 of an inch around the plate, how could it not work?
 

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Telstar 28
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1,000 Posts
How old is that chunk, the stuff loses flexibility and elasticity as it cures and ages...
SD, How do you figure that 5200 isn't flexible enough to bed chainplates? How big a gap do you leave around them anyway? I'm holding a cured chunk in my hands right now. Squeezing it between the jaws of my Leatherman. The stuff feels like a piece of rubber.
If you have a gap of about a 32nd to an 1/8 of an inch around the plate, how could it not work?
 

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Registered
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I think the best reason not to use 5200 is that it's so adhesive, if you ever have to remove it (and you will eventually) that it will pull gelcoat off underlying glass structure. Sure you want the sealant to stick to what you're bedding, but not to that extent. 5200's 700 psi is not needed, 4000/4200's
300 psi is plenty.
Brian
 

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Telstar 28
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Exactly... and for something like chainplates, where the fit depends on the strength of the pieces, and does not rely on sealant for strength... butyl tape is an excellent choice, since it is very elastic and sticky, but not very strong.
I think the best reason not to use 5200 is that it's so adhesive, if you ever have to remove it (and you will eventually) that it will pull gelcoat off underlying glass structure. Sure you want the sealant to stick to what you're bedding, but not to that extent. 5200's 700 psi is not needed, 4000/4200's
300 psi is plenty.
Brian
 

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Midwest Puddle Pirate
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2,160 Posts
I tried several of the sealants mentioned in this thread. Butyl tape finally sealed it for good.
 
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