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-   -   Chainplate rebedding with mast up (http://www.sailnet.com/forums/gear-maintenance/55683-chainplate-rebedding-mast-up.html)

josrulz 06-25-2009 11:15 PM

Chainplate rebedding with mast up
 
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

US27inKS 06-25-2009 11:29 PM

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.

RainDog 06-26-2009 12:23 AM

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.

jackytdunaway 06-26-2009 05:54 AM

What if the upper and lower tie into the same chain plate? You have to do the halyard thing then.

josrulz 06-26-2009 10:01 AM

Quote:

Originally Posted by RainDog (Post 500195)
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

gtod25 06-26-2009 10:16 AM

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

RainDog 06-26-2009 10:27 AM

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.

donradclife 06-26-2009 01:10 PM

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.

josrulz 06-26-2009 01:36 PM

Quote:

Originally Posted by donradclife (Post 500367)
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!

sailingdog 06-26-2009 01:39 PM

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.
Quote:

Originally Posted by RainDog (Post 500317)
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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