Sealing A Leaky Chain Plate

[Ghoster]

I have a stainless steel chain plate for a detachable inner fore-stay for setting a storm jib. The chain-plate is through bolted to the bulkhead at the back of the anchor locker with six s/s bolts. Rather inconveniently if the anchor locker fills with water then water was getting through the bolt holes for the chain-plate into the fore-cabin. I have removed the chain-plate and re-bedded it with silicone sealant but have not yet tested it. However, I am also wondering whether the chain-plate could be painted with epoxy or some other material to optimise sealing.

Does anyone have any thoughts or experience on this?

Many thanks

 

[Tranona]

Have you really used silicone? - not really suitable for the job as it does not seal well to either wood or Stainless. Reseal it with either a polyurethane or butyl sealant - might also be a good idea to seal the holes in the bulkhead with epoxy first. The stainless does not need any coating - that is why stainless is used.

 

[BarneysDad]

Reading a reputable American blogger a few days ago convinced me that silicone should never be allowed near a boat, though it's sold by most chandlers. I took out an aft cabin window last April; the previous owner had used silicone to seat the thing. The silicone had made a very poor, leaky sealing compound. So I scratched out the lot and replaced it with one of the Sikaflex compounds.

 

[macd]

I can only agree that silicone is absolutely the wrong stuff (for most things) and that butyl or a polyurethane sealant would be far better. The trouble now is that nothing will stick to the surface coated with silicone without a fairly severe mechanical scrubbing. Fortunately, since it's stainless steel, that should be straightforward. The other surface to which the silicone was applied (GRP?) should also be thoroughly attacked in the same way.

As well as bedding-down the body of the chainplate, if the bolts involved are countersunk, they're particularly easy to seal with butyl tape: simply form a butyl cone under each countersunk head and bolt down.

 

[Daydream believer]

I can only agree that silicone is absolutely the wrong stuff (for most things) and that butyl or a polyurethane sealant would be far better. The trouble now is that nothing will stick to the surface coated with silicone without a fairly severe mechanical scrubbing. Fortunately, since it's stainless steel, that should be straightforward. The other surface to which the silicone was applied (GRP?) should also be thoroughly attacked in the same way.

As well as bedding-down the body of the chainplate, if the bolts involved are countersunk, they're particularly easy to seal with butyl tape: simply form a butyl cone under each countersunk head and bolt down.

Would not butyl gradually extrude over time? Would it not be better to coat the hole & thread in a Sycaflex?

 

[macd]

Would not butyl gradually extrude over time? Would it not be better to coat the hole & thread in a Sycaflex?

It does slowly extrude, but never in my experience to the point where the seal is broken. Excellent stuff, and never sets, so the items sealed can always easily be dismantled.
Sycaflex is presumably the new green version of the well-known family of goo?

 

[Ghoster]

Very helpful replies. Thanks guys.

I previously thought that Sikaflex was synonymous with silicon - now I know better - my only problem is now I am not sure whether I in fact used used silicon or Sikaflex - hopefully the remains of the tube are in the locker.

 

[CAPTAIN FANTASTIC]

Clean the surfaces with Acetone and then use polyurethane sealant; it won't leak!!

 

[macd]

my only problem is now I am not sure whether I in fact used used silicon or Sikaflex - hopefully the remains of the tube are in the locker.

Whatever it was, it clearly didn't work and will need to be removed. However, unlike silicone, a small residue of any Sikalex probably won't prevent the adhesion of any new sealant applied.
Incidentally there's no more a substance called "Sikaflex" than there is one called "Heinz". It's a family of products with different chemistries and properties. If you use it, choose the right one for the job.

 

[vyv_cox]

Not quite the same job but may give you some idea of the steps necessary. http://coxeng.co.uk/sails-and-rig/sadler-34-lower-and-cap-chainplates/

 

[Kelpie]

Not quite the same job but may give you some idea of the steps necessary. http://coxeng.co.uk/sails-and-rig/sadler-34-lower-and-cap-chainplates/

Very thorough and useful as always.
I hadn't heard of Puraflex before. I've currently got most of my deck fittings off and will be re-bedding them, so am toying with various options such as CT1, butyl tape, or Sika.
My chainplates have only a small tufnol covering plate held down by self tappers, rather than a welded flange at deck level. So I am leaning towards CT1 as being the most bomb-proof option. Any shrinkage away from the stainless chainplate itself will cause a leak though, so maybe it would be better to use butyl and just check/renew regularly?

 

[doug748]

Very ..... I've currently got most of my deck fittings off and will be re-bedding them, so am toying with various options such as CT1, butyl tape, or Sika.
My chainplates have only a small tufnol covering plate held down by self tappers, rather than a welded flange at deck level. So I am leaning towards CT1 as being the most bomb-proof option. Any shrinkage away from the stainless chainplate itself will cause a leak though, so maybe it would be better to use butyl and just check/renew regularly?

I have tried butyl tape but am not totally convinced yet. Polywotsits I don,t fancy at all. Tom Cunliffe has similar chainplates to you and was singing the praises of this stuff:

https://www.sealantsdirect.co.uk/arbomast-br-grey-380ml.html

I will be trying it next time.

 

[Old Bumbulum]

I swear by CT1, it's never let me down so far.

 

[Tranona]

I have tried butyl tape but am not totally convinced yet. Polywotsits I don,t fancy at all. Tom Cunliffe has similar chainplates to you and was singing the praises of this stuff:

https://www.sealantsdirect.co.uk/arbomast-br-grey-380ml.html

I will be trying it next time.

Same sealant as the tape you used but in a different form. Equally good at sealing. big advantage over polyurethane is that it is non setting. Another alternative is polysulphide (also non setting) from the same manufacturer. Had better be good as I bedded my keel with it in 1995 - still no leaks!

 

[lw395]

In my view, the design of the joint and sealant interface is more important than the choice of sealant.
Whatever sealant you use, there will eventually be problems if it's squeezed down to zero thickness by the pressure on the joint.
You want something like a chamfer on the holes to provide some volume for the sealant.
So you have something like 2mm of sealant where it has to move with the parts. Silicone for example will stretch something like 100% before failure, 2mm of it will survive the joint being stressed, a micron-thin layer will only move a micron before failure.
Done properly silicone is a pretty good sealant. Others are better, but will still fail in a poor joint. Many have lower % strain to fail than silicone. Non-setting can move infinitely, but that's no good if it moves away from sealing the right bits....
I'd use polyurethane because it is easy to to a good job of priming and porous surfaces, using normal paint primer or even varnish.
With a chain plate, you need to be clear whether the bolts are supposed to be in shear or in tension, with the main load being friction between the plate and the substrate. A non-setting goo may allow all the tension to be lost....

 

[doug748]

Same sealant as the tape you used but in a different form.

Quite so, the link tells us what it is. I am suggesting the OP might try Cunliffe's suggestion because it is a different formulation

 

[johnalison]

My first thought, as a bodger rather than an engineer, was that the strength of the bulkhead at the join needs to be checked. If it is flexing or moving under strain, this might add to the problem and possibly some reinforcement at this point might assist.

 

[duncan99210]

If the problem is being caused by water sitting in th chain locker rather draining away before it has time to work through the seal, then perhaps improving the locker drainage arrangements might be a good idea?