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Chainplate rebedding with mast up

13K views 31 replies 12 participants last post by  donlofland 
#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
 
#3 ·
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.
 
#5 ·
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
 
#6 ·
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
 
#7 · (Edited)
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.
 
#10 ·
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.
 
#8 ·
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.
 
#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!
 
#12 ·
That's a different story. :) much better choice... :)
 
#15 ·
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?
 
#17 ·
How old is that chunk, the stuff loses flexibility and elasticity as it cures and ages...
 
#18 ·
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
 
#19 ·
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.
 
#21 ·
Butyl tape is also my first choice as my boat (CS27) had most deck hardware and hull/deck joint sealed with butyl 32 years ago. The hull/deck joint butyl bedding is still flexible after this time and there are not too many other issues except those that are due to poor maintenance by previous owners. My second choice is Sikaflex 291 as I find that some items are not able to be tightened enough to fully squeeze out the butyl when installing such as access ports made of plastic.
Brian
 
#25 ·
Originally Posted by knothead
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.

Knothead,
You must be speaking of a keel stepped mast. Certainly a deck stepped mast will have to have something holding it up. On a deck stepped mast are halyards OK while the chainplates are rebed. My upper and lower both go to the same place and i need to rebed but am nervous about taking the shrouds loose
 
#26 ·
Knothead,
You must be speaking of a keel stepped mast. Certainly a deck stepped mast will have to have something holding it up. On a deck stepped mast are halyards OK while the chainplates are rebed. My upper and lower both go to the same place and i need to rebed but am nervous about taking the shrouds loose
Hi jackytdunaway, I certainly can't speak for knothead, but your question made me realize I should have specified that I have a keel-stepped mast. You're absolutely right that would make a huge difference.
 
#30 ·
In a case such as yours where there is only one chainplate you must use halyards to support the mast. It's either that or just unstep the mast.
What I do is hook up the halyards first. Then disconnect the upper shroud turnbuckle from the chainplate and hook it up temporarily to the toe rail, a midship cleat or something. It can even be lashed on. You don't want to load it up too much, but you don't need much just to hold the mast up. After you temporarily hook the upper back up, go ahead and remove the lower. :)
 
#32 ·
When I rebedded my lowers, I took them all off, one after another, did the "drill out the deck hole a size or two larger then fill the hole with epoxy and redrill it for the chainplate" thing, then rebedded each with 4200. I don't think it makes any difference if the (relatively flexible) mast is pulled a tad out of column as you loosen one lower shroud, then another, but you could always go around all the lowers loosening each turnbuckle a turn until they are all loose enough to disconnect. And counting the turns as you go would give you an idea where you want them when you put it all together again...

When I replaced the bulkhead to which the upper attaches, I first strung the halyard to the stanchion base near the upper shroud chainplate, then lossened and removed the shroud.
 
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