Chain plate leaks

[TonyMiles]

I have through-deck chain plates on my 1977 Trident Voyager 35 which are set well in from the gunwhale, and have had great difficulty in water proofing them. They are rectangular sectioned SS bars with a welded horizontal plate which now sits about 3mm clear of the deck surface.

I have removed them a few times and re-sealed with various sealants - silicon based and Sikaflex - and they all work for a while before starting to leak again.

Because of leaks over the years, some of the balsa core in the deck sandwich has crumbled around the chain plate holes, so I have tried to fill the resultant gap with epoxy resin filler to reduce the chance of the deck surface springing away from the plate, but they stil eventually leak.

Does anybody have any suggestions please?

 

[jfkal]

Sika should do the job. However you need to prime it properly. There is obviously movement between the chain plate and the deck. Unless you use the right primer for GRP, SS, wood (whatever material involved) , the flexing will break the bond after a short while. So clean (Sand, acetone, sika cleaner), prime (sika primer), wait until dry and then use Sika.

 

[PuffTheMagicDragon]

It seems to me that you have already identified your problem. There is no way that you'd get a 3mm gap simply by the Sika breaking bond. Not having seen the boat I would hazard a guess that you have, for all intents and purposes, 'lost the filling' from your sandwich deck.
I would suggest that, when you lay-up for winter, you remove the shroud from one plate and have a good look underneath (i.e. from inside the cabin) Prod rather heavily with a pointed spike or somesuch. If there is any suggestion of springing - or, worse, drops of moisture come out - then I'd say that the only solution would be to :
1. uncover the core by cutting away the inner skin.
2. remove damp core until you are well into the dry zone.
3. clean thoroughly and let dry over as long a period as possible.
4. fit as large a panel of marine ply (20-25mm thick) as possible into the space previously occupied by the core, bedding it well down into resin putty.
5. cover panel with at least 3 layers of CSM and 1 of woven.
Drill through from the deck and re-fit the chainplate, bedding down into Sika or similar. Leave overnight before tightening.
6 repeat for other side.

It might sound complicated but, once you get down to it, it's just a matter of slogging on, taking your time to get the job well done.
If you have any doubts you could always ask a second opinion from someone knowledgeable in your area.

Look on the bright side:- you now know how to occupy your winter weekends!

Good Luck!


Wally